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Global warming

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Global mean surface-temperature change from 1880 to 2018, relative to the 1951–1980 mean. The 1951–1980 mean is 14.2 °C (57.5 °F).[1][attribution needed] The black line is the global annual mean, and the red line is the five-year local regression line. The blue uncertainty bars show a 95% confidence interval.
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Average global temperatures from 2014 to 2018 compared to a baseline average from 1951 to 1980, according to NASA's Goddard Institute for Space Studies.

Global warming is a long-term rise in the average temperature of the Earth's climate system, an aspect of climate change shown by temperature measurements and by multiple effects of the warming.[2][3] Though earlier geological periods also experienced episodes of warming,[4] the term commonly refers to the observed and continuing increase in average air and ocean temperatures since 1900 caused mainly by emissions of greenhouse gases in the modern industrial economy.[5] In the modern context the terms global warming and climate change are commonly used interchangeably,[6] but climate change includes both global warming and its effects, such as changes to precipitation and impacts that differ by region.[7][8] Many of the observed changes in climate since the 1950s are unprecedented in the instrumental temperature record, and in historical and paleoclimate proxy records of climate change over thousands to millions of years.[9]

In 2013, the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report concluded, "It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century."[10] The largest human influence has been the emission of greenhouse gases such as carbon dioxide, methane, and nitrous oxide. Climate model projections summarized in the report indicated that during the 21st century, the global surface temperature is likely to rise a further 0.3 to 1.7 °C (0.5 to 3.1 °F) in a moderate scenario, or as much as 2.6 to 4.8 °C (4.7 to 8.6 °F) in an extreme scenario, depending on the rate of future greenhouse gas emissions and on climate feedback effects.[11] These findings have been recognized by the national science academies of the major industrialized nations[12][a] and are not disputed by any scientific body of national or international standing.[14][15]

Effects of global warming include rising sea levels, regional changes in precipitation, more frequent extreme weather events such as heat waves, and expansion of deserts.[16] Surface temperature increases are greatest in the Arctic, with the continuing retreat of glaciers, permafrost, and sea ice. Overall, higher temperatures bring more rain and snowfall, but for some regions droughts and wildfires increase instead.[17] Climate change impacts humans by, amongst other things, threatening food security from decreasing crop yields, and the abandonment of populated areas and damage to infrastructure due to rising sea levels.[18][19] Environmental impacts include the extinction or relocation of ecosystems as they adapt to climate change, with coral reefs,[20] mountain ecosystems, and Arctic ecosystems most immediately threatened.[21] Because the climate system has a large "inertia" and greenhouse gases will remain in the atmosphere for a long time, climatic changes and their effects will continue to become more pronounced for many centuries even if further increases to greenhouse gases stop.[22]

Globally, a majority of people consider global warming a serious or very serious issue.[23] Possible societal responses to global warming include mitigation by emissions reduction, adaptation to its effects, and possible future climate engineering. Every country in the world is a party to the United Nations Framework Convention on Climate Change (UNFCCC),[24] whose ultimate objective is to prevent dangerous anthropogenic climate change.[25] Parties to the UNFCCC have agreed that deep cuts in emissions are required[26] and that global warming should be limited to well below 2 °C (3.6 °F) compared to pre-industrial levels,[b] with efforts made to limit warming to 1.5 °C (2.7 °F).[28] Some scientists call into question climate adaptation feasibility, with higher emissions scenarios,[29] or the two degree temperature target[30]

Observed temperature changes

Annual (thin lines) and five-year lowess smooth (thick lines) for the temperature anomalies averaged over the Earth's land area (red line) and sea surface temperature anomalies (blue line) averaged over the part of the ocean that is free of ice at all times (open ocean).
Two millennia of mean surface temperatures according to different reconstructions from climate proxies, each smoothed on a decadal scale, with the instrumental temperature record overlaid in black.

Multiple independently produced datasets confirm that between 1880 and 2012, the global average (land and ocean) surface temperature increased by 0.85 [0.65 to 1.06] °C.[31] Currently, surface temperature rise with about 0.2 °C degrees per decade.[32] Since 1950, the number of cold days and nights have decreased, and the number of warm days and night have increased.[33] These trends can be compared to historical temperature trends: patterns of warming and cooling like the Medieval Climate Anomaly and the Little Ice Age were not as synchronous as current warming, but did reach temperatures as high as late-20th century regionally.[34]

Although the increase of the average near-surface atmospheric temperature is commonly used to track global warming, over 90% of the additional energy stored in the climate system over the last 50 years is in warmer ocean water.[35] The rest has melted ice and warmed the continents and the atmosphere.[36][c] The warming evident in the instrumental temperature record is consistent with a wide range of observations, documented by many independent scientific groups,[37] for example in most continental regions the frequency and intensity of heavy precipitation has increased.[38] Further examples include sea level rise,[39] widespread melting of snow and land ice,[40] increased heat content of the oceans,[37] increased humidity,[37] and the earlier timing of spring events,[41] such as the flowering of plants.[42]

Regional trends

Global warming refers to global averages, with the amount of warming varying by region. Since 1979, global average land temperatures have increased about twice as fast as global average ocean temperatures.[43][needs update?] This is due to the larger heat capacity of the oceans and because oceans lose more heat by evaporation.[44] Where greenhouse gas emissions occur does not impact the location of warming because the major greenhouse gases persist long enough to diffuse across the planet, although localized black carbon deposits on snow and ice do contribute to Arctic warming.[45]

The Northern Hemisphere and North Pole have heated much faster than the South Pole and Southern Hemisphere. The Northern Hemisphere not only has much more land, its arrangement around the Arctic Ocean has resulted in the maximum surface area flipping from reflective snow and ice cover to ocean and land surfaces that absorb more sunlight.[46] Arctic temperatures have increased and are predicted to continue to increase during this century at over twice the rate of the rest of the world.[47][needs update?] As the temperature difference between the Arctic and the equator decreases ocean currents that are driven by that temperature difference, like the Gulf Stream, are weakening.[48]

Short-term slowdowns and surges

Because the climate system has large thermal inertia, it can take centuries for the climate to fully adjust. While record-breaking years attract considerable public interest, individual years are less significant than the overall trend. Global surface temperature is subject to short-term fluctuations that overlay long-term trends, and can temporarily mask or magnify them.[49]

An example of such an episode is the slower rate of surface temperature increase from 1998 to 2012, which was dubbed the global warming hiatus by the media and some scientists.[50] Throughout this period ocean heat storage continued to progress steadily upwards, and in subsequent years surface temperatures have spiked upwards. The slower pace of warming can be attributed to heating and cooling in the Pacific Ocean from natural variability such as El Niño and La Nina events, reduced solar activity, and a number of volcanic eruptions that inserted sunlight-reflecting particles into the atmosphere.[51]

Physical drivers of climate change

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Contribution of natural factors and human activities to radiative forcing of climate change.[52] Radiative forcing values are for the year 2005, relative to the pre-industrial era (1750).[52] The contribution of solar irradiance to radiative forcing is 5% of the value of the combined radiative forcing due to increases in the atmospheric concentrations of carbon dioxide, methane and nitrous oxide.[53]

By itself, the climate system may generate changes in global temperatures for years (such as the El Niño–Southern Oscillation) to decades[54] or centuries[55] at a time. Other changes emanate from so-called external forcings. These forcings are "external" to the climate system, but not necessarily external to Earth.[56] Examples of external forcings include changes in the composition of the atmosphere (e.g., increased concentrations of greenhouse gases), solar luminosity, volcanic eruptions, and variations in Earth's orbit around the Sun.[57]

Attributing detected temperature changes and extreme events to man-made increases in greenhouse gases requires scientists to rule out known internal climate variability and natural external forcings. So a key approach is to use physical models of the climate system to determine unique fingerprints for all potential external forcings. By comparing these fingerprints with the observed pattern and evolution of the climate change, and the observed evolution of the forcings, the causes of the observed changes can be determined.[58]

Greenhouse gases

Greenhouse effect schematic showing energy flows between space, the atmosphere, and Earth's surface. Energy exchanges are expressed in watts per square meter (W/m2).
concentrations over the last 800,000 years as measured from ice cores (blue/green) and directly (black).

Greenhouse gases trap heat radiating from Earth to space.[59] This heat, in the form of infrared radiation, gets absorbed and emitted by these gases in the planet's atmosphere thus warming the lower atmosphere and the surface. On Earth, an atmosphere containing naturally occurring amounts of greenhouse gases causes air temperature near the surface to be warmer by about 33 °C (59 °F) than it would be in their absence.[60][d] Without the Earth's atmosphere, the Earth's average temperature would be well below the freezing temperature of water.[61] The major greenhouse gases are water vapour, which causes about 36–70% of the greenhouse effect; carbon dioxide (CO2), which causes 9–26%; methane (CH4), which causes 4–9%; and ozone (O3), which causes 3–7%.[62][63][64]

Human activity since the Industrial Revolution has increased the amount of greenhouse gases in the atmosphere, leading to increased radiative forcing from CO2, methane, tropospheric ozone, CFCs, and nitrous oxide. In 2011, the concentrations of CO2 and methane had increased by about 40% and 150% respectively since pre-industrial times,[65] with CO2 readings taken at the world's primary benchmark site in Mauna Loa surpassing 400 ppm in 2013 for the first time.[66] These levels are much higher than at any time during the last 800,000 years, the period for which reliable data has been extracted from ice cores.[67] Less direct geological evidence indicates that CO2 values haven't been this high for millions of years.[66]

Global anthropogenic greenhouse gas emissions in 2010 were 49 billion tonnes of carbon dioxide-equivalents per year (using the most recent global warming potentials over 100 years from the AR5 report). Of these emissions, 65% was carbon dioxide from fossil fuel burning and industry, 11% was carbon dioxide from land use change, which is primarily due to deforestation, 16% was methane, 6.2% was nitrous oxide, and 2.0% were fluorinated gases.[68] Using life-cycle assessment to estimate emissions relating to final consumption, the dominant sources of 2010 emissions were: food (26–30% of emissions);[69] washing, heating and lighting (26%); personal transport and freight (20%); and building construction (15%).[70]

Land use change

Changing the type of vegetation in a region impacts the local temperature by changing how much sunlight gets reflected back into space and how much heat is lost by evaporation. For instance, the change from a dark forest to grassland makes the surface lighter, and causes it to reflect more sunlight: an increase in albedo. Humans change the land surface mainly to create more agricultural land.[71] Since the pre-industrial era, albedo increased due to land use change, which has a cooling effect on the planet. Other processes linked to land use change however have had the opposite effect, so that the net effect remains unclear.[72]

Aerosols and soot

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Ship tracks can be seen as lines in these clouds over the Atlantic Ocean on the East Coast of the United States, an example of the Twomey effect.

Solid and liquid particles known as aerosols – from volcanoes, plankton and human-made pollutants – reflect incoming sunlight,[73] cooling the climate.[74] From 1961 to 1990, a gradual reduction in the amount of sunlight reaching the Earth's surface was observed, a phenomenon popularly known as global dimming,[75] typically attributed to aerosols from biofuel and fossil fuel burning.[76][77] Aerosol removal by precipitation gives tropospheric aerosols an atmospheric lifetime of only about a week, while stratospheric aerosols can remain in the atmosphere for a few years.[78] Global aerosols have been declining since 1990, removing some of the masking of global warming that aerosols had been providing.[79][77]

In addition to their direct effect by scattering and absorbing solar radiation, aerosols have indirect effects on the Earth's radiation budget. Sulfate aerosols act as cloud condensation nuclei and thus lead to clouds that have more and smaller cloud droplets. These clouds reflect solar radiation more efficiently than clouds with fewer and larger droplets, a phenomenon known as the Twomey effect.[80] This effect also causes droplets to be of more uniform size, which reduces growth of raindrops and makes the cloud more reflective to incoming sunlight, known as the Albrecht effect.[81] Indirect effects of aerosols are the largest uncertainty in radiative forcing.[82][needs update]

While aerosols typically limit global warming by reflecting sunlight, if black carbon in soot falls on snow or ice, it can also increase global warming. Not only does it increase the absorption of sunlight, it also increases melting and sea level rise.[78][83] Limiting new black carbon deposits in the Arctic could reduce global warming by 0.2 degrees Celsius by 2050.[84] When soot is suspended in the atmosphere, it directly absorbs solar radiation, heating the atmosphere and cooling the surface. In areas with high soot production, such as rural India, as much as 50% of surface warming due to greenhouse gases may be masked by atmospheric brown clouds.[85] The influences of atmospheric particles, including black carbon, are most pronounced in the tropics and northern mid-latitudes, with the effects of greenhouse gases dominant in the other parts of the world.[86][87]

Incoming sunlight

As the Sun is Earth's primary energy source, changes in incoming sunlight directly affect the climate system.[88] Solar irradiance has been measured directly by satellites since 1978,[89] but indirect measurements are available beginning in the early 1600s.[88] There has been no upward trend in the amount of the Sun's energy reaching the Earth, so it cannot be responsible for the current warming.[90] Physical climate models are also unable to reproduce the rapid warming observed in recent decades when taking into account only variations in solar output and volcanic activity.[91]

Another line of evidence for the warming not being due to the Sun is the temperature changes at different levels in the Earth's atmosphere.[92] According to basic physical principles, the greenhouse effect produces warming of the lower atmosphere (the troposphere), but cooling of the upper atmosphere (the stratosphere).[93] If solar variations were responsible for the observed warming, warming of both the troposphere and the stratosphere would be expected, but that has not been the case.[94]

While variations in solar activity have not produced recent global warming, variations in solar output over geologic time (millions to billions of years ago) are believed to have caused major changes in the earth's climate.[95][not in citation given] The 11-year solar cycle of sunspot activity also introduces climate changes that have a small cyclical effect on annual global temperatures.[96] The tilt of the Earth's axis and the shape of its orbit around the Sun vary slowly over tens of thousands of years in a phenomenon known as the Milankovitch cycles. This changes climate by changing the seasonal and latitudinal distribution of incoming solar energy at the Earth's surface,[97] resulting in periodic glacial and interglacial periods over the last few million years.[98] During the last few thousand years, this phenomenon contributed to a slow cooling trend at high latitudes of the Northern Hemisphere during summer, a trend that was reversed by greenhouse-gas-induced warming during the 20th century.[99] Orbital cycles favourable for glaciation are not expected within the next 50,000 years.[100]

Climate change feedback

The dark ocean surface reflects only 6 percent of incoming solar radiation, whereas sea ice reflects 50 to 70 percent.[101]

The response of the climate system to an initial forcing is increased by positive feedbacks and reduced by negative feedbacks.[102] The main negative feedback to global temperature change is radiative cooling to space as infrared radiation, which increases strongly with increasing temperature.[103] The main positive feedbacks are the water vapour feedback, the ice–albedo feedback, and probably the net effect of clouds.[104] Uncertainty over feedbacks is the major reason why different climate models project different magnitudes of warming for a given amount of emissions.[105]

As air gets warmer, it can hold more moisture. After an initial warming due to emissions of greenhouse gases, the atmosphere will hold more water. As water is a potent greenhouse gas, this further heats the climate: the water vapour feedback.[104] The reduction of snow cover and sea ice in the Arctic reduces the albedo (reflectivity) of the Earth's surface.[106] More of the sun's energy is now absorbed in these regions, contributing to Arctic amplification, which has caused Arctic temperatures to increase at almost twice the rate of the rest of the world.[47] Arctic amplification also causes methane to be released as permafrost melts, which is expected to surpass land use changes as the second strongest anthropogenic source of greenhouse gases by the end of the century.[107]

Cloud cover may change in the future. To date, cloud changes have had a cooling effect, with NASA estimating that aerosols produced by the burning of hydrocarbons have limited warming by half from 1850 to 2010.[73] An analysis of satellite data between 1983 and 2009 reveals that cloud tops are reaching higher into the atmosphere and that cloudy storm tracks are shifting toward Earth's poles, suggesting clouds will be a positive feedback in the future.[108]

Carbon dioxide stimulates plant growth so the carbon cycle has been a negative feedback so far: roughly half of each year's CO2 emissions have been absorbed by plants on land and in oceans,[109] with an estimated 30% increase in plant growth from 2000 to 2017.[110] The limits and reversal point for this feedback are an area of uncertainty.[111] As more CO2 and heat are absorbed by the ocean it is acidifying and ocean circulation can change, changing the rate at which the ocean can absorb atmospheric carbon.[112] On land, greater plant growth will be constrained by nitrogen levels and can be reversed by plant heat stress, desertification, and the release of carbon from soil as the ground warms.[113]

A concern is that positive feedbacks will lead to a tipping point, where global temperatures transition to a hothouse climate state even if greenhouse gas emissions are reduced or eliminated. A 2018 study tried to identify such a planetary threshold for self-reinforcing feedbacks and found that even a 2 °C (3.6 °F) increase in temperature over pre-industrial levels, may be enough to trigger such a hothouse Earth scenario.[114]

Climate models

Future CO2 projections, including all forcing agents' atmospheric CO2-equivalent concentrations (in parts-per-million-by-volume (ppmv)) according to four RCPs (Representative Concentration Pathways).
Projected change in annual mean surface air temperature from the late 20th century to the middle 21st century, based on a medium emissions scenario (SRES A1B).[115] This scenario assumes that no future policies are adopted to limit greenhouse gas emissions. Image credit: NOAA GFDL.[116]

A climate model is a representation of the physical, chemical and biological processes that affect the climate system.[117] Computer models are run on supercomputers to reproduce and predict the circulation of the oceans, the annual cycle of the seasons, and the flows of carbon between the land surface and the atmosphere.[118] There are more than two dozen scientific institutions that develop climate models.[118] Model forecasts vary due to different greenhouse gas inputs and different assumptions about the impact of different feedbacks on climate sensitivity.

A subset of climate models add societal factors to a simple physical climate model. These models simulate how population, economic growth and energy use affect – and interact with – the physical climate. With this information, scientists can produce scenarios of how greenhouse gas emissions may vary in the future. Scientists can then run these scenarios through physical climate models to generate climate change projection.[118]

Climate models include different external forcings for their models. For different greenhouse gas inputs four RCPs (Representative Concentration Pathways) are used: "a stringent mitigation scenario (RCP2.6), two intermediate scenarios (RCP4.5 and RCP6.0) and one scenario with very high GHG emissions (RCP8.5).[119] Models also include changes in the Earth's orbit, historical changes in the sun's activity and volcanic forcing.[118] RCPs only look at concentrations of greenhouse gases, factoring out uncertainty as to whether the carbon cycle will continue to remove about half of the carbon dioxide from the atmosphere each year.[120]

The physical realism of models is tested by examining their ability to simulate contemporary or past climates.[121] Past models have underestimated the rate of Arctic shrinkage[122] and underestimated the rate of precipitation increase.[123] Sea level rise since 1990 was underestimated in older models, but now agrees well with observations.[124] The 2017 United States-published National Climate Assessment notes that "climate models may still be underestimating or missing relevant feedback processes".[125]


Historical sea level reconstruction and projections up to 2100 published in January 2017 by the U.S. Global Change Research Program for the Fourth National Climate Assessment.[126]
Map of the Earth with a six-meter sea level rise represented in red.

Physical environmental

The environmental effects of global warming are broad and far-reaching. They include the following diverse effects:

Arctic sea ice decline, sea level rise, retreat of glaciers: global warming has led to decades of shrinking and thinning of the Arctic sea ice, making it vulnerable to atmospheric anomalies.[127] Projections of declines in Arctic sea ice vary.[128][129] Recent projections suggest that Arctic summers could be ice-free (defined as an ice extent of less than 1 million square km) as early as 2025–2030.[130] Since 1993, sea level has on average risen with 3.1 ± 0.3 mm per year. Additionally, sea level rise has accelerated from 1993 to 2017.[131] Over the 21st century, the IPCC projects (for a high emissions scenario) that global mean sea level could rise by 52–98 cm.[132] The rate of ice loss from glaciers and ice sheets in the Antarctic is a key area of uncertainty since Antarctica contains 90% of potential sea level rise.[133] Polar amplification and increased ocean warmth are undermining and threatening to unplug Antarctic glacier outlets, potentially resulting in more rapid sea level rise.[134]

Extreme weather, extreme events, tropical cyclones: Data analysis of extreme events from 1960 until 2010 suggests that droughts and heat waves appear simultaneously with increased frequency.[135] Extremely wet or dry events within the monsoon period have increased since 1980.[136] Projections suggest a probable increase in the frequency and severity of some extreme weather events, such as heat waves.[137] Studies have also linked the rapidly warming Arctic to extreme weather in mid-latitudes as the jet stream becomes more erratic.[138] Maximum rainfall and wind speed from hurricanes and typhoons are likely increasing.[139]

Changes in ocean properties: increases in atmospheric CO2 concentrations have led to an increase in dissolved CO2 and as a consequence ocean acidity.[140] Furthermore, oxygen levels decrease because oxygen is less soluble in warmer water, an effect known as ocean deoxygenation.[141]

Long-term effects of global warming: On the timescale of centuries to millennia, the magnitude of global warming will be determined primarily by anthropogenic CO2 emissions.[142] This is due to carbon dioxide's very long lifetime in the atmosphere.[142] Long-term effects also include a response from the Earth's crust, due to ice melting and deglaciation, in a process called post-glacial rebound, when land masses are no longer depressed by the weight of ice. This could lead to landslides and increased seismic and volcanic activities. Tsunamis could be generated by submarine landslides caused by warmer ocean water thawing ocean-floor permafrost or releasing gas hydrates.[143] Sea level rise will continue over many centuries.[144]

Abrupt climate change, tipping points in the climate system: Climate change could result in global, large-scale changes.[145] Some large-scale changes could occur abruptly, i.e. over a short time period, and might also be irreversible. Examples of abrupt climate change are the rapid release of methane and carbon dioxide from permafrost, which would lead to amplified global warming. Another example is the possibility for the Atlantic Meridional Overturning Circulation to slow or to shut down (see also shutdown of thermohaline circulation).[146][147] This could trigger cooling in the North Atlantic, Europe, and North America.[148]


As the climate change melts sea ice, the U.S. Geological Survey projects that two-thirds of polar bears will disappear by 2050.[149]

Ecosystem changes: In terrestrial ecosystems, the earlier timing of spring events, as well as poleward and upward shifts in plant and animal ranges, have been linked with high confidence to recent warming.[150] It is expected that most ecosystems will be affected by higher atmospheric CO2 levels, combined with higher global temperatures.[151] Expansion of deserts in the subtropics is probably linked to global warming.[152] Ocean acidification threatens damage to coral reefs, fisheries, protected species, and other natural resources of value to society.[140][153] Without substantial actions to reduce the rate of global warming, land-based ecosystems are at risk of major ecological shifts, transforming composition and structure.[154]

Overall, it is expected that climate change will result in the extinction of many species and reduced diversity of ecosystems.[155] Rising temperatures have been found to push bees to their physiological limits, and could cause the extinction of bee populations.[156] Continued ocean uptake of CO2 may affect the brains and central nervous system of certain fish species, and that this impacts their ability to hear, smell, and evade predators.[157]

Impacts on humans

A helicopter drops water on a wildfire in California. Drought and higher temperatures linked to climate change are driving a trend towards larger fires.[158]

The effects of climate change on human systems, mostly due to warming or shifts in precipitation patterns, or both, have been detected worldwide. The future social impacts of climate change will be uneven across the world.[159] All regions are at risk of experiencing negative impacts,[160] with low-latitude, less developed areas facing the greatest risk.[161] Global warming has likely already increased global economic inequality, and is projected to do so in the future.[162] Regional impacts of climate change are now observable on all continents and across ocean regions.[163] The Arctic, Africa, small islands and Asian megadeltas are regions that are likely to be especially affected by future climate change.[164] Many risks increase with higher magnitudes of global warming.[165]

Food and water

Crop production will probably be negatively affected in low latitude countries, while effects at northern latitudes may be positive or negative.[166] Global warming of around 4 °C relative to late 20th century levels could pose a large risk to global and regional food security.[167] The impact of climate change on crop productivity for the four major crops was negative for wheat and maize, and neutral for soy and rice, in the years 1960–2013.[168] Climate variability and change is projected to severely compromise agricultural production, including access to food, across Africa.[169] By 2050, between 350 million and 600 million people are projected to experience increased water stress due to climate change in Africa.[169] Water availability will also become more limited in regions dependent on glacier water, regions with reductions in rainfall and small islands.[169]

Health and security

Aerial view over southern Bangladesh after the passage of cyclone Cyclone Sidr. A combination of sea level rise and increased rainfall from cyclones makes countries more vulnerable to floods, impacting people's livelihoods and health.[170]

Generally impacts on public health will be more negative than positive.[171] Impacts include the direct effects of extreme weather, leading to injury and loss of life;[172] and indirect effects, such as undernutrition brought on by crop failures.[173] There has been a shift from cold- to heat-related mortality in some regions as a result of warming.[163] Temperature rise has been connected to increased numbers of suicides.[174] Climate change has been linked to an increase in violent conflict by amplifying poverty and economic shocks, which are well-documented drivers of these conflicts.[175] Links have been made between a wide range of violent behaviour including fist fights, violent crimes, civil unrest, or wars.[176]

Livelihoods, industry and infrastructure

In small islands and mega deltas, inundation as a result of sea level rise is expected to threaten vital infrastructure and human settlements.[177][178] This could lead to issues of homelessness in countries with low-lying areas such as Bangladesh, as well as statelessness for populations in island nations, such as the Maldives and Tuvalu.[179] Climate change can be an important driver of migration, both within and between countries.[180][181]

Africa is one of the most vulnerable continents to climate variability and change because of multiple existing stresses and low adaptive capacity.[169] Existing stresses include poverty, political conflicts, and ecosystem degradation. Regions may even become uninhabitable, with humidity and temperature reaching levels too high for humans to survive.[182]


Mitigation of and adaptation to climate change are two complementary responses to global warming. Successful adaptation is easier in the case of substantial emission reduction.[183] Many of the countries that contributed least to global greenhouse gas emissions are most vulnerable to climate change, which raises questions about justice and fairness with regard to mitigation and adaptation.[183]


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The graph on the right shows three "pathways" to meet the UNFCCC's 2 °C target, labelled "global technology", "decentralized solutions", and "consumption change". Each pathway shows how various measures (e.g., improved energy efficiency, increased use of renewable energy) could contribute to emissions reductions. Image credit: PBL Netherlands Environmental Assessment Agency.[184]
Annual greenhouse gas emissions attributed to different sectors as of the year 2010. Emissions are given as a percentage share of total emissions, measured in carbon dioxide-equivalents, using global warming potentials from the IPCC fifth Assessment Report.

Mitigation of climate change is the reduction of greenhouse gas emissions, or the enhancement of the capacity of carbon sinks to absorb greenhouse gases from the atmosphere.[185] There is a large potential for future reductions in emissions by a combination of activities, including energy conservation and increased energy efficiency; the use of low-carbon energy technologies, such as renewable energy, nuclear energy, and carbon capture and storage;[186][187] decarbonizing buildings and transport; and enhancing carbon sinks through, for example, reforestation and preventing deforestation.[186]

[187] A 2015 report by Citibank concluded that transitioning to a low carbon economy would yield positive return on investments.[188]

Global carbon dioxide emissions by country in 2015

Drivers of greenhouse gas emissions

Over the last three decades of the twentieth century, gross domestic product per capita and population growth were the main drivers of increases in greenhouse gas emissions.[189] CO2 emissions are continuing to rise due to the burning of fossil fuels and land-use change.[190][191] Emissions can be attributed to different regions. Attribution of emissions due to land-use change are subject to considerable uncertainty.[192][193]

Emissions scenarios, estimates of changes in future emission levels of greenhouse gases, have been projected that depend upon uncertain economic, sociological, technological, and natural developments.[194] In most scenarios, emissions continue to rise over the century, while in a few, emissions are reduced.[195][196] Fossil fuel reserves are abundant, and will not limit carbon emissions in the 21st century.[197] Emission scenarios, combined with modelling of the carbon cycle, have been used to produce estimates of how atmospheric concentrations of greenhouse gases might change in the future.[198] Using the six IPCC SRES "marker" scenarios, models suggest that by the year 2100, the atmospheric concentration of CO2 could range between 541 and 970 ppm.[199]

Reducing greenhouse gases

Near- and long-term trends in the global energy system are inconsistent with limiting global warming at below 1.5 or 2 °C, relative to pre-industrial levels.[200] Current pledges made as part of the Paris Agreement would lead to about 3.0 °C of warming at the end of the 21st century, relative to pre-industrial levels.[201] In limiting warming at below 2 °C, more stringent emission reductions in the near-term would allow for less rapid reductions after 2030,[202] and be cheaper overall.[203] Many integrated models are unable to meet the 2 °C target if pessimistic assumptions are made about the availability of mitigation technologies.[204]

Co-benefits of climate change mitigation may help society and individuals more quickly. For example, cycling reduces greenhouse gas emissions[205] while reducing the effects of a sedentary lifestyle at the same time[206] The development and scaling-up of clean technology, such as cement that produces less CO2.[207] is critical to achieve sufficient emission reductions for the Paris agreement goals.[208]

The most effective and comprehensive policy to reduce carbon emissions is a carbon tax[209] or the closely related emissions trading.[210] The most significant action individuals could make to mitigate their own carbon footprint is to have fewer children, followed by living car-free, forgoing air travel, and adopting a plant-based diet.[211] Some argue that allocating emissions to one's ancestors is a category mistake and that children "embody a profound hope for the future", and that more emphasis should be placed on overconsumption, lifestyle choices of the world's wealthy, fossil fuel companies and government inaction.[212] Sill others, such as Mayer Hillman, contend that both individual action and political action by national governments will not be enough, and only a global transition to zero GHG emissions throughout the entire economy and a reduction in human population growth will be sufficient enough to mitigate global warming.[213]


Climate change adaptation is the process of adjusting to actual or expected climate and its effects.[214] Humans can strive to moderate or avoid harm due to climate change and exploit opportunities.[214] Examples of adaptation are improved coastline protection, better disaster management and the development of crops that are more resistant.[215] The adaptation may be planned, either in reaction to or anticipation of global warming, or spontaneous, i.e., without government intervention.[216]

The public section, private sector and communities are all gaining experience with adaptation and adaptation is becoming embedded within certain planning processes.[217] While some adaptation responses call for trade-offs, others bring synergies and co-benefits.[217] Environmental organizations and public figures have emphasized changes in the climate and the risks they entail, while promoting adaptation to changes in infrastructural needs and emissions reductions.[218]

Adaptation is especially important in developing countries since those countries are predicted to bear the brunt of the effects of global warming.[219] That is, the capacity and potential for humans to adapt, called adaptive capacity, is unevenly distributed across different regions and populations, and developing countries generally have less capacity to adapt.[220]

Climate engineering

Climate engineering (sometimes called geoengineering or climate intervention) is the deliberate modification of the climate. It has been investigated as a possible response to global warming, e.g. by NASA[221] and the Royal Society.[222] Techniques under research fall generally into the categories solar radiation management and carbon dioxide removal, although various other schemes have been suggested. A study from 2014 investigated the most common climate engineering methods and concluded they are either ineffective or have potentially severe side effects and cannot be stopped without causing rapid climate change.[223][224]

Society and culture

Political response

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Article 2 of the UN Framework Convention refers explicitly to "stabilization of greenhouse gas concentrations".[225] To stabilize the atmospheric concentration of CO
, emissions worldwide would need to be dramatically reduced from their present level.[226]

As of 2019 all countries in the world are parties to the United Nations Framework Convention on Climate Change (UNFCCC), but 12 countries have not ratified it,[227] which means they are not legally bound by the agreement.[228] The ultimate objective of the Convention is to prevent dangerous human interference to the climate system.[229] As stated in the Convention, this requires that greenhouse gas concentrations are stabilized in the atmosphere at a level where ecosystems can adapt naturally to climate change, food production is not threatened, and economic development can be sustained.[230] The Framework Convention was agreed on in 1992, but global emissions have risen since then.[231] Its yearly conferences are the stage of global negotiations.[232]

During these negotiations, the G77 (a lobbying group in the United Nations representing developing countries)[233] pushed for a mandate requiring developed countries to "[take] the lead" in reducing their emissions.[234] This was justified on the basis that the developed countries' emissions had contributed most to the accumulation of greenhouse gases in the atmosphere, per-capita emissions (i.e., emissions per head of population) were still relatively low in developing countries, and the emissions of developing countries would grow to meet their development needs.[235]

This mandate was sustained in the 2005 Kyoto Protocol to the Framework Convention.[235][236] In ratifying the Kyoto Protocol, most developed countries accepted legally binding commitments to limit their emissions. These first-round commitments expired in 2012.[236] United States President George W. Bush rejected the treaty on the basis that "it exempts 80% of the world, including major population centres such as China and India, from compliance, and would cause serious harm to the US economy".[237]

In 2009 several UNFCCC Parties produced the Copenhagen Accord,[238][239] which has been widely portrayed as disappointing because of its low goals, leading poor nations to reject it.[240][241] Parties associated with the Accord aim to limit the future increase in global mean temperature to below 2 °C.[242] In 2015 all UN countries negotiated the Paris Agreement, which aims to keep climate change well below 2 °C. The agreement replaced the Kyoto protocol. Unlike Kyoto, no binding emission targets are set in the Paris agreement. Instead, the procedure of regularly setting ever more ambitious goals and reevaluating these goals every five years has been made binding.[243][244] The Paris agreement reiterated that developing countries must be financially supported.[243]

Scientific discussion

In the scientific literature, there is an overwhelming consensus that global surface temperatures have increased in recent decades and that the trend is caused mainly by human-induced emissions of greenhouse gases.[245] No scientific body of national or international standing disagrees with this view.[190][246][247] Scientific discussion takes place in journal articles that are peer-reviewed, which scientists subject to assessment every couple of years in the Intergovernmental Panel on Climate Change reports.[248] The scientific consensus as of 2013 stated in the IPCC Fifth Assessment Report is that it "is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century".[249]

National science academies have called on world leaders for policies to cut global emissions.[250] In November 2017, a second warning to humanity signed by 15,364 scientists from 184 countries stated that "the current trajectory of potentially catastrophic climate change due to rising greenhouse gases from burning fossil fuels, deforestation, and agricultural production – particularly from farming ruminants for meat consumption" is "especially troubling".[251] In 2018 the IPCC published a Special Report on Global Warming of 1.5 °C which warned that, if the current rate of greenhouse gas emissions is not mitigated, global warming is likely to reach 1.5 °C (2.7 °F) between 2030 and 2052 causing major crises. The report said that preventing such crises will require a swift transformation of the global economy that has "no documented historic precedent".[252]

Position of oil and gas companies

In the 20th century and early 2000s some companies, such as ExxonMobil, challenged IPCC climate change scenarios, funded scientists who disagreed with the scientific consensus, and provided their own projections of the economic cost of stricter controls.[253] In general, since the 2010s, global oil companies do not dispute that climate change exists and is caused by the burning of fossil fuels.[254] As of 2019, however, some are lobbying against a carbon tax and plan to increase production of oil and gas[255] but others are in favour of a carbon tax in exchange for immunity from lawsuits which seek climate change compensation.[256]

Public opinion and disputes

Global warming was the cover story in this 2007 issue of Ms. magazine

The global warming problem came to international public attention in the late 1980s and polling groups began to track opinions on the subject.[257] The longest consistent polling, by Gallup in the US, found relatively small deviations of 10% or so from 1998 to 2015 in opinion on the seriousness of global warming, but with increasing polarization between those concerned and those unconcerned.[258] By 2010 in the US, just a little over half the population (53%) viewed it as a serious concern for either themselves or their families. Latin America and developed Asia saw themselves most at risk at 73% and 74%.[259] In the assessed 111 countries, people were more likely to attribute global warming to human activities than to natural causes, except in the US where nearly half (47%) of the population attributed global warming to natural causes.[260] Public reactions to global warming and concern about its effects have been increasing, while many perceiving it as the worst global threat.[261] A 2015 global survey showed that a median of 54% of respondents consider it "a very serious problem", with significant regional differences: Americans and Chinese (whose economies are responsible for the greatest annual CO2 emissions) are among the least concerned.[23]

From about 1990 onward, American conservative think tanks had begun challenging the legitimacy of global warming as a social problem. They challenged the scientific evidence, argued that global warming would have benefits, and asserted that proposed solutions would do more harm than good.[262] Organizations such as the libertarian Competitive Enterprise Institute, conservative commentators have challenged IPCC climate change scenarios, funded scientists who disagree with the scientific consensus, and provided their own projections of the economic cost of stricter controls.[263]

Global warming has been the subject of controversy, substantially more pronounced in the popular media than in the scientific literature,[264][265] with disputes regarding the nature, causes, and consequences of global warming. The disputed issues include the causes of increased global average air temperature, especially since the mid-20th century, whether this warming trend is unprecedented or within normal climatic variations, whether humankind has contributed significantly to it, and whether the increase is completely or partially an artifact of poor measurements. Additional disputes concern estimates of climate sensitivity, predictions of additional warming, what the consequences of global warming will be, and what to do about it.[266]

Due to confusing media coverage in the early 1990s, issues such as ozone depletion and climate change were often mixed up, affecting public understanding of these issues.[267] According to a 2010 survey of Americans, a majority thought that the ozone layer and spray cans contribute to global warming.[268] Although there are a few areas of linkage, the relationship between the two is not strong. Reduced stratospheric ozone has had a slight cooling influence on surface temperatures, while increased tropospheric ozone has had a somewhat larger warming effect.[269][needs update] However, chemicals causing ozone depletion are also powerful greenhouse gases, and as such the Montreal protocol against their emissions may have done more than any other measure to mitigate climate change.[270]

In a response to perceived inaction on climate change, a climate movement is protesting in various ways, such as fossil fuel divestment,[271] worldwide demonstrations[272] and the school strike for climate.[273]


Scientific American description of 1856 Eunice Newton Foote's experiments which found that carbonic acid (CO2) causes warming.

The history of climate change science began in the early 19th century when ice ages and other natural changes in paleoclimate were first suspected and the natural greenhouse effect first identified.[274] In the late 19th century, scientists first argued that human emissions of greenhouse gases could change the climate. In the 1960s, the warming effect of carbon dioxide gas became increasingly convincing.[275] By the 1990s, as a result of improving fidelity of computer models and observational work confirming the Milankovitch theory of the ice ages, a consensus position formed: greenhouse gases were deeply involved in most climate changes, and human-caused emissions were bringing discernible global warming. Since then, scientific research on climate change has expanded.[276] The Intergovernmental Panel on Climate Change, set up in the 1990s to provide formal advice the world's governments, spurred unprecedented levels of exchange between different scientific disciplines.[277]

The greenhouse effect was proposed by Joseph Fourier in 1824, discovered in 1856 by Eunice Newton Foote,[278][279] expanded upon by John Tyndall,[280] investigated quantitatively by Svante Arrhenius in 1896,[274] and the hypothesis was reported in the popular press as early as 1912.[281][282] The scientific description of global warming was further developed in the 1930s through the 1960s by Guy Stewart Callendar.[283][284]


Research in the 1950s suggested increasing temperatures, and a 1952 newspaper reported "climate change". This phrase next appeared in a November 1957 report in The Hammond Times which described Roger Revelle's research into the effects of increasing human-caused CO
emissions on the greenhouse effect "a large scale global warming, with radical climate changes may result". Both phrases were used only occasionally until 1975, when Wallace Smith Broecker published a scientific paper on the topic, "Climatic Change: Are We on the Brink of a Pronounced Global Warming?" The phrase began to come into common use, and in 1976 Mikhail Budyko's statement that "a global warming up has started" was widely reported.[275] Other studies, such as a 1971 MIT report, referred to the human impact as "inadvertent climate modification", but an influential 1979 National Academy of Sciences study headed by Jule Charney followed Broecker in using global warming to refer to rising surface temperatures, while describing the wider effects of increased CO
as climate change.[285]

In 1986 and November 1987, NASA climate scientist James Hansen gave testimony to Congress on global warming. There were increasing heatwaves and drought problems in the summer of 1988, and when Hansen testified in the Senate on 23 June he sparked worldwide interest.[276] He said "global warming has reached a level such that we can ascribe with a high degree of confidence a cause and effect relationship between the greenhouse effect and the observed warming".[286] Public attention increased over the summer, and global warming became the dominant popular term, commonly used both by the press and in public discourse.[285]

Since 2018 terms such as global heating, the climate crisis, and climate emergency are increasingly being used instead of global warming or climate change, in order to emphasis its seriousness and urgency.[287]

See also


  1. ^ The 2001 joint statement was signed by the national academies of science of Australia, Belgium, Brazil, Canada, the Caribbean, the People's Republic of China, France, Germany, India, Indonesia, Ireland, Italy, Malaysia, New Zealand, Sweden, and the UK.[13] The 2005 statement added Japan, Russia, and the US. The 2007 statement added Mexico and South Africa. The Network of African Science Academies and the Polish Academy of Sciences have issued separate statements. Professional scientific societies include American Astronomical Society, American Chemical Society, American Geophysical Union, American Institute of Physics, American Meteorological Society, American Physical Society, American Quaternary Association, Australian Meteorological and Oceanographic Society, Canadian Foundation for Climate and Atmospheric Sciences, Canadian Meteorological and Oceanographic Society, European Academy of Sciences and Arts, European Geosciences Union, European Science Foundation, Geological Society of America, Geological Society of Australia, Geological Society of London-Stratigraphy Commission, InterAcademy Council, International Union of Geodesy and Geophysics, International Union for Quaternary Research, National Association of Geoscience Teachers, National Research Council (US), Royal Meteorological Society, and World Meteorological Organization.
  2. ^ Earth has already experienced almost 1/2 of the 2.0 °C (3.6 °F) described in the Cancún Agreement. In the last 100 years, Earth's average surface temperature increased by about 0.8 °C (1.4 °F) with about two-thirds of the increase occurring over just the last three decades. [27]
  3. ^ Scientific journals use "global warming" to describe an increasing global average temperature just at earth's surface, and most of these authorities further limit "global warming" to such increases caused by human activities or increasing greenhouse gases.
  4. ^ The greenhouse effect produces an average worldwide temperature increase of about 33 °C (59 °F) compared to black body predictions without the greenhouse effect, not an average surface temperature of 33 °C (91 °F). The average worldwide surface temperature is about 14 °C (57 °F).

  1. ^ "Land and Ocean Summary". Berkeley Earth. 18 February 2019. Archived from the original on 3 September 2018. Retrieved 2 September 2018.
  2. ^ IPCC AR5 WG1 Summary for Policymakers 2013, p. 4: "Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased."
  3. ^ "Myths vs. Facts: Denial of Petitions for Reconsideration of the Endangerment and Cause or Contribute Findings for Greenhouse Gases under Section 202(a) of the Clean Air Act". U.S. Environmental Protection Agency. Archived from the original on 7 August 2017. Retrieved 7 August 2017. "The U.S. Global Change Research Program, the National Academy of Sciences, and the Intergovernmental Panel on Climate Change (IPCC) have each independently concluded that warming of the climate system in recent decades is "unequivocal". This conclusion is not drawn from any one source of data but is based on multiple lines of evidence, including three worldwide temperature datasets showing nearly identical warming trends as well as numerous other independent indicators of global warming (e.g., rising sea levels, shrinking Arctic sea ice)."
  4. ^ Masson-Delmotte et al. 2013, pp. 389, 399–400: "The PETM [around 55.5–55.3 million years ago] was marked by ... global warming of 4°C to 7°C ..... Deglacial global warming occurred in two main steps from 17.5 to 14.5 ka [thousand years ago] and 13.0 to 10.0 ka."
  5. ^ Mach, Serge & von Stechow 2014, p. 124: "Global warming refers to the gradual increase, observed or projected, in global surface temperature, as one of the consequences of radiative forcing caused by anthropogenic emissions."
  6. ^ Shaftel 2016: "'Climate change' and 'global warming' are often used interchangeably but have distinct meanings. .... Global warming refers to the upward temperature trend across the entire Earth since the early 20th century .... Climate change refers to a broad range of global phenomena ...[which] include the increased temperature trends described by global warming."
  7. ^ "What's the difference between global warming and climate change?". NOAA 17 June 2015. Archived from the original on 7 November 2018. Retrieved 15 October 2018. Global warming refers only to the Earth's rising surface temperature, while climate change includes warming and the 'side effects' of warming—like melting glaciers, heavier rainstorms, or more frequent drought. Said another way, global warming is one symptom of the much larger problem of human-caused climate change.
  8. ^ Mach, Serge & von Stechow 2014, p. 120: Climate change refers to a change in the state of the climate that can be identified (e.g., by using statistical tests) by changes in the mean and/or the variability of its properties and that persists for an extended period, typically decades or longer. Climate change may be due to natural internal processes or external forcings such as modulations of the solar cycles, volcanic eruptions and persistent anthropogenic changes in the composition of the atmosphere or in land use. .... {WGI, II, III}"
  9. ^ IPCC AR5 WG1 Summary for Policymakers 2013, p. 4.
  10. ^ IPCC AR5 WG1 Summary for Policymakers 2013, p. 17: "It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century."
  11. ^ IPCC AR5 WG1 Technical Summary 2013, p. 57.
  12. ^ "Joint Science Academies' Statement" (PDF). Archived (PDF) from the original on 9 September 2013. Retrieved 6 January 2014.
  13. ^ Kirby 2001.
  14. ^ "Scientific consensus: Earth's climate is warming". Climate Change: Vital Signs of the Planet. NASA. Archived from the original on 28 June 2018. Retrieved 7 August 2017.
  15. ^ "List of Organizations". The Governor's Office of Planning & Research, State of California. Archived from the original on 7 August 2017. Retrieved 7 August 2017.
  16. ^ Field et al. 2014, pp. 44–46; D'Odorico et al. 2013
  17. ^ National Geographic 2019; NPR 2010
  18. ^ Campbella et al. 2016.
  19. ^ US NRC 2012, pp. 26–27
  20. ^ Knowlton 2001.
  21. ^ EPA (19 January 2017). "Climate Impacts on Ecosystems". Archived from the original on 27 January 2018. Retrieved 5 February 2019.
  22. ^ Clark et al. 2016.
  23. ^ a b Stokes, Wike & Carle 2015.
  24. ^ "Status of Ratification of the Convention". United Nations Framework Convention on Climate Change. 2019. Retrieved 19 May 2019. As of May 2019 12 parties have not ratified the convention. Non-ratification means they are not legally bound by it.
  25. ^ "First steps to a safer future: Introducing The United Nations Framework Convention on Climate Change". United Nations Framework Convention on Climate Change. Archived from the original on 8 January 2014. Retrieved 7 August 2017. Preventing "dangerous" human interference with the climate system is the ultimate aim of the UNFCCC.
  26. ^ "Conference of the Parties – Sixteenth Session: Decision 1/CP.16: The Cancun Agreements: Outcome of the work of the Ad Hoc Working Group on Long-term Cooperative Action under the Convention (English): Paragraph 4" (PDF). UNFCCC Secretariat: Bonn, Germany: United Nations Framework Convention on Climate Change. 2011. p. 3. Archived (PDF) from the original on 17 November 2011. Retrieved 28 October 2011. (...) deep cuts in global greenhouse gas emissions are required according to science, and as documented in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, with a view to reducing global greenhouse gas emissions so as to hold the increase in global average temperature below 2 °C above preindustrial levels
  27. ^ National Research Council (2011). America's Climate Choices. Washington, DC: The National Academies Press. p. 15. ISBN 978-0-309-14585-5. Archived from the original on 21 July 2015. Retrieved 28 January 2019. The average temperature of the Earth's surface increased by about 1.4 °F (0.8 °C) over the past 100 years, with about 1.0 °F (0.6 °C) of this warming occurring over just the past three decades.
  28. ^ CNN, 12 December 2015; Vaughan 2015.
  29. ^ Hansen et al. 2013.
  30. ^ Steffen et al. 2018
  31. ^ IPCC AR5 WG1 Summary for Policymakers 2013, p. 5.
  32. ^ IPCC SR15 Ch1 2018, p. 81
  33. ^ Hartmann et al. 2013, p. 162
  34. ^ Masson-Delmotte et al. 2013, p. 386
  35. ^ "Climate Change: Ocean Heat Content". NOAA. 2018. Archived from the original on 12 February 2019. Retrieved 20 February 2019.
  36. ^ Rhein et al. 2013, p. 257: "Ocean warming dominates the global energy change inventory. Warming of the ocean accounts for about 93% of the increase in the Earth's energy inventory between 1971 and 2010 (high confidence), with warming of the upper (0 to 700 m) ocean accounting for about 64% of the total. Melting ice (including Arctic sea ice, ice sheets and glaciers) and warming of the continents and atmosphere account for the remainder of the change in energy."
  37. ^ a b c Kennedy et al. 2010
  38. ^ USGCRP Chapter 1 2017, p. 35
  39. ^ Kennedy, C. (10 July 2012). "ClimateWatch Magazine >> State of the Climate: 2011 Global Sea Level". NOAA Climate Services Portal. Archived from the original on 12 May 2013. Retrieved 1 October 2012.
  40. ^ "Summary for Policymakers". Direct Observations of Recent Climate Change. Archived from the original on 23 December 2018. Retrieved 22 December 2018., in IPCC AR4 WG1 2007
  41. ^ "Summary for Policymakers". B. Current knowledge about observed impacts of climate change on the natural and human environment. Archived from the original on 23 December 2018. Retrieved 22 December 2018., in IPCC AR4 WG2 2007
  42. ^ Rosenzweig, C.; et al. "Ch 1: Assessment of Observed Changes and Responses in Natural and Managed Systems". Sec Changes in phenology. Archived from the original on 23 December 2018. Retrieved 22 December 2018., in IPCC AR4 WG2 2007, p. 99
  43. ^ Trenberth et al., Chap 3, Observations: Atmospheric Surface and Climate Change Archived 23 December 2018 at the Wayback Machine, Executive Summary Archived 22 December 2018 at the Wayback Machine, p. 237 Archived 23 December 2018 at the Wayback Machine, in IPCC AR4 WG1 2007.
  44. ^ Sutton, Dong & Gregory 2007.
  45. ^ EPA (2016). Methane and Black Carbon Impacts on the Arctic: Communicating the Science (Report). Archived from the original on 6 September 2017. Retrieved 27 February 2019. "Black carbon that is deposited on snow and ice darkens those surfaces and decreases their reflectivity (albedo). This is known as the snow/ice albedo effect. This effect results in the increased absorption of radiation that accelerates melting."[page needed]
  46. ^ NOAA (10 July 2011). "Polar Opposites: the Arctic and Antarctic". Archived from the original on 22 February 2019. Retrieved 20 February 2019.
  47. ^ a b "TS.3.1.2 Spatial Distribution of Changes in Temperature, Circulation and Related Variables – AR4 WGI Technical Summary". Archived from the original on 23 December 2018. Retrieved 22 December 2018.
  48. ^ NASA, 12 September 2018: "We are seeing a major shift in the circulation in the North Atlantic, likely related to a weakening Atlantic Meridional Overturning Circulation (AMOC)", said Pershing. "One of the side effects of a weaker AMOC is that the Gulf Stream shifts northward and the cold current flowing into the Gulf of Maine gets weaker. This means we get more warmer water pushing into the Gulf."
  49. ^ Sévellec & Drijfhout 2018; Mooney 2018
  50. ^ England et al. 2014; Knight et al. 2009.
  51. ^ Lindsey 2018.
  52. ^ a b IPCC, Summary for Policymakers Archived 23 December 2018 at the Wayback Machine, Human and Natural Drivers of Climate Change Archived 22 December 2018 at the Wayback Machine, Figure SPM.2, in IPCC AR4 WG1 2007.
  53. ^ "3.2.2 Solar Irradiance". Volume 3: Attribution of Observed Climate Change. Endangerment and Cause or Contribute Findings for Greenhouse Gases under Section 202(a) of the Clean Air Act. EPA's Response to Public Comments. US Environmental Protection Agency. 2009. Archived from the original on 16 June 2011. Retrieved 23 June 2011.
  54. ^ Delworth & Mann 2000, p. 661
  55. ^ Delworth & Zeng 2012, p. 5
  56. ^ US NRC 2012, p. 9
  57. ^ Hegerl et al. 2007, p. 690: "Recent estimates indicate a relatively small combined effect of natural forcings on the global mean temperature evolution of the second half of the 20th century, with a small net cooling from the combined effects of solar and volcanic forcings."
  58. ^ Knutson 2017, p. 443; Bindoff et al. 2013, pp. 875–876
  59. ^ NASA. "The Causes of Climate Change". Climate Change: Vital Signs of the Planet. Retrieved 8 May 2019.
  60. ^ Le Treut et al. 2007, FAQ1.1: "To emit 240 W m–2, a surface would have to have a temperature of around −19 °C. This is much colder than the conditions that actually exist at the Earth's surface (the global mean surface temperature is about 14 °C). Instead, the necessary −19 °C is found at an altitude about 5 km above the surface." Le Treut, H.; Somerville, R.; Cubasch, U.; Ding, Y.; et al. (2007). "Chapter 1: Historical Overview of Climate Change Science" (PDF). In IPCC AR4 WG1 2007. Archived (PDF) from the original on 23 December 2018.
  61. ^ ACS. "What Is the Greenhouse Effect?". Retrieved 26 May 2019.
  62. ^ Kiehl & Trenberth 1997
  63. ^ Schmidt, Gavin (6 April 2005). "Water vapour: feedback or forcing?". RealClimate. Archived from the original on 18 April 2009. Retrieved 21 April 2009.
  64. ^ Russell, Randy (16 May 2007). "The Greenhouse Effect & Greenhouse Gases". University Corporation for Atmospheric Research Windows to the Universe. Archived from the original on 28 March 2010. Retrieved 27 December 2009.
  65. ^ IPCC AR5 WG1 Summary for Policymakers 2013, p. 11.
  66. ^ a b Amos 2013; Schiermeier 2015.
  67. ^ Siegenthaler et al. 2005; Lüthi et al. 2008
  68. ^ IPCC AR5 WG3 SPM 2014, pp. 6–7
  69. ^ Poore & Nemecek 2018
  70. ^ Bajzelj, Allwood & Cullen 2013
  71. ^ Duveiller, Hooker & Cescatti 2018
  72. ^ Andrews et al. 2016; IPCC AR5 WG1 Technical Summary 2013
  73. ^ a b Jenkins, Amber (7 December 2009). "Just 5 questions: Aerosols". NASA/Jet Propulsion Laboratory. Archived from the original on 14 February 2019. Retrieved 15 February 2019. Using climate models, we estimate that aerosols have masked about 50 percent of the warming that would otherwise have been caused by greenhouse gases trapping heat near the surface of the Earth. Without the presence of these aerosols in the air, our models suggest that the planet would be about 1 °C (1.8 °F) hotter.
  74. ^ Haywood, Jim (2016). "Chapter 27 - Atmospheric Aerosols and Their Role in Climate Change". In Letcher, Trevor M. (ed.). Climate Change: Observed Impacts on Planet Earth. Elsevier. p. 456. ISBN 9780444635242.
  75. ^ Hartmann et al. 2013, p. 183
  76. ^ He et al. 2018
  77. ^ a b Storelvmo, T.; Phillips, P. C. B.; Lohmann, U.; Leirvik, T.; Wild, M. (2016). "Disentangling greenhouse warming and aerosol cooling to reveal Earth's climate sensitivity". Nature Geoscience. 9 (4): 286–289. doi:10.1038/ngeo2670. ISSN 1752-0908.
  78. ^ a b Ramanathan & Carmichael 2008
  79. ^ Wild et al. 2005; Pinker, Zhang & Dutton 2005
  80. ^ Twomey 1977
  81. ^ Albrecht 1989
  82. ^ IPCC, "Aerosols, their Direct and Indirect Effects Archived 23 December 2018 at the Wayback Machine", pp. 291–292 in IPCC TAR WG1 2001.
  83. ^ Documentary Sea Blind (Dutch Television) (in Dutch). RIVM: Netherlands National Institute for Public Health and the Environment. 11 October 2016. Archived from the original on 17 August 2018. Retrieved 26 February 2019.
  84. ^ Sand et al. 2015
  85. ^ Ramanathan et al. 2008; Ramanathan et al. 2005
  86. ^ Ramanathan, V.; et al. (2008). "Part III: Global and Future Implications" (PDF). Atmospheric Brown Clouds: Regional Assessment Report with Focus on Asia. United Nations Environment Programme. Archived from the original (PDF) on 18 July 2011.
  87. ^ Wang & Xie 2016; Zhang et al. 2019; Yuan et al. 2019
  88. ^ a b USGCRP Chapter 2 2017, p. 78
  89. ^ US NRC 2008, p. 6
  90. ^ "Is the Sun causing global warming?". Climate Change: Vital Signs of the Planet. Retrieved 10 May 2019.
  91. ^ Schmidt, Shindell & Tsigaridis 2014; Fyfe et al. 2016
  92. ^ Hegerl et al. 2007, pp. 702–703
  93. ^ Hegerl et al. 2007, pp. 702–703; Randel et al. 2009
  94. ^ USGCRP 2009, p. 20
  95. ^ Hegerl et al. 2007, pp. 665–666
  96. ^ "Do Variations in the Solar Cycle Affect Our Climate System?". Archived from the original on 4 February 2019. Retrieved 21 February 2019.
  97. ^ Bradley, R. S.; Briffa, K. R.; Cole, J.; Hughes, M. K.; et al. (2003). "The climate of the last millennium". In Alverson, K. D.; Bradley, R. S.; Pederson, T. F. (eds.). Paleoclimate, global change and the future (PDF). Springer. pp. 105–141. ISBN 3-540-42402-4. Archived (PDF) from the original on 29 March 2017.
  98. ^ "Arctic Warming Overtakes 2,000 Years of Natural Cooling". Brown University. 26 January 2017. Archived from the original on 17 February 2019. Retrieved 16 February 2019.
  99. ^ Kaufman et al. 2009; Scientific American, 4 September 2009; Mann et al. 2008
  100. ^ Berger & Loutre 2002; Masson-Delmotte et al. 2013, p. 435
  101. ^ "Thermodynamics: Albedo". NSIDC. Archived from the original on 11 October 2017. Retrieved 10 October 2017.
  102. ^ "The study of Earth as an integrated system". Earth Science Communications Team at NASA's Jet Propulsion Laboratory / California Institute of Technology. 2013. Archived from the original on 26 February 2019.
  103. ^ Lindsey, R. (14 January 2009). "Earth's Energy Budget, in: Climate and Earth's Energy Budget: Feature Articles". Earth Observatory, part of the EOS Project Science Office, located at NASA Goddard Space Flight Center. Archived from the original on 2 September 2018. The amount of heat a surface radiates is proportional to the fourth power of its temperature (in Kelvin).
  104. ^ a b Met Office 2016
  105. ^ Wolff et al. 2015: "the nature and magnitude of these feedbacks are the principal cause of uncertainty in the response of Earth's climate (over multi-decadal and longer periods) to a particular emissions scenario or greenhouse gas concentration pathway."
  106. ^ "Arctic amplification". NASA. 2013. Archived from the original on 31 July 2018.
  107. ^ Gray, Ellen (20 August 2018). "Unexpected future boost of methane possible from Arctic permafrost". NASA's Earth Science News Team. Archived from the original on 31 March 2019.
  108. ^ Nature, 11 July 2016: "By 2009, the team found that there were fewer clouds over the mid-latitudes than there had been in 1983. That finding meshes with climate predictions that dry zones will expand out of the subtropics and push storms towards the poles. The team also found that cloud tops rose higher in the atmosphere by the end of the 2000s, again as predicted for a warming atmosphere."
  109. ^ Riebeek, H. (16 June 2011). "The Carbon Cycle: Feature Articles: Effects of Changing the Carbon Cycle". Earth Observatory, part of the EOS Project Science Office located at NASA Goddard Space Flight Center. Archived from the original on 6 February 2013. Retrieved 4 February 2013. So far, land plants and the ocean have taken up about 55 percent of the extra carbon people have put into the atmosphere while about 45 percent has stayed in the atmosphere. Eventually, the land and oceans will take up most of the extra carbon dioxide, but as much as 20 percent may remain in the atmosphere for many thousands of years.
  110. ^ "Study: Global plant growth surging alongside carbon dioxide". National Oceanic and Atmospheric Administration. 20 April 2017. Archived from the original on 2 March 2019. A new study published in the April 6 edition of the journal Nature concludes that as emissions of carbon dioxide from burning fossil fuels have increased since the start of the 20th century, plants around the world are utilizing 30 percent more carbon dioxide (CO2), spurring plant growth.
  111. ^ Scientific American, 23 January 2018: "Climate change's negative effects on plants will likely outweigh any gains from elevated atmospheric carbon dioxide levels"
  112. ^ "How the oceans absorb carbon dioxide is critical for predicting climate change". Archived from the original on 29 March 2019. Retrieved 24 February 2019. increasing CO2 modifies the climate which in turn impacts ocean circulation and therefore ocean CO2 uptake. Changes in marine ecosystems resulting from rising CO2 and/or changing climate can also result in changes in air-sea CO2 exchange. These feedbacks can change the role of the oceans in taking up atmospheric CO2 making it very difficult to predict how the ocean carbon cycle will operate in the future.
  113. ^ Melillo et al. 2017: "Our first-order estimate of a warming-induced loss of 190 Pg of soil carbon over the 21st century is equivalent to the past two decades of carbon emissions from fossil fuel burning and is comparable in magnitude to the cumulative carbon losses to the atmosphere due to human-driven land use change during the past two centuries."
  114. ^ &, 6 August 2018: "Hothouse Earth is likely to be uncontrollable and dangerous to many ... global average temperatures would exceed those of any interglacial period—meaning warmer eras that come in between Ice Ages—of the past 1.2 million years."; Steffen et al. 2018: "A Hothouse Earth trajectory would almost certainly flood deltaic environments, increase the risk of damage from coastal storms, and eliminate coral reefs (and all of the benefits that they provide for societies) by the end of this century or earlier".; The Guardian, 7 August 2018
  115. ^ "Patterns of greenhouse warming" (PDF). GFDL Climate Modeling Research Highlights. Princeton, New Jersey: The National Oceanic and Atmospheric Administration (NOAA) Geophysical Fluid Dynamics Laboratory (GFDL). 1 (6). January 2007. Archived from the original (PDF) on 14 October 2012. Retrieved 1 December 2012.
  116. ^ "NOAA GFDL Climate Research Highlights Image Gallery: Patterns of Greenhouse Warming". NOAA Geophysical Fluid Dynamics Laboratory (GFDL). 9 October 2012. Archived from the original on 14 October 2012. Retrieved 1 December 2012.
  117. ^ IPCC, Glossary A–D Archived 23 December 2018 at the Wayback Machine: "Climate Model", in IPCC AR4 SYR 2007.
  118. ^ a b c d "Q&A: How do climate models work?". Carbon Brief. 15 January 2018. Archived from the original on 5 March 2019. Retrieved 2 March 2019.
  119. ^ IPCC AR5 SYR Summary for Policymakers 2014, Sec. 2.1.
  120. ^ IPCC AR5 WG1 Technical Summary 2013.
  121. ^ Randall et al., Chapter 8, Climate Models and Their Evaluation Archived 23 December 2018 at the Wayback Machine, Sec. FAQ 8.1 in IPCC AR4 WG1 2007.
  122. ^ Stroeve et al. 2007.
  123. ^ Liepert & Previdi 2009.
  124. ^ Rahmstorf et al. 2007; Mitchum et al. 2018.
  125. ^ Kopp, R. E.; Hayhoe, K.; Easterling, D.R.; Hall, T.; et al. (2017). "Chapter 15: Potential Surprises: Compound Extremes and Tipping Elements". In USGCRP 2017. US National Climate Assessment. Archived from the original on 20 August 2018.
  126. ^ "January 2017 analysis from NOAA: Global and Regional Sea Level Rise Scenarios for the United States" (PDF). Archived (PDF) from the original on 18 December 2017. Retrieved 7 February 2019.
  127. ^ Zhang et al. 2008
  128. ^ Meehl, G. A.; et al. "Ch 10: Global Climate Projections". Sec Changes in Sea Ice Cover. Archived from the original on 23 December 2018. Retrieved 22 December 2018., in IPCC AR4 WG1 2007, p. 770
  129. ^ Wang & Overland 2009
  130. ^ "Arctic sea ice 2012". Exeter, UK: Met Office. Archived from the original on 15 May 2013. Retrieved 29 March 2013.
  131. ^ WCRP Global Sea Level Budget Group 2018
  132. ^ Church, John; Clark, Peter. "Chapter 13: Sea Level Change – Final Draft Underlying Scientific-Technical Assessment" (PDF). IPCC Working Group I. Archived (PDF) from the original on 16 November 2014. Retrieved 21 January 2015.
  133. ^ Perlman, Howard (18 June 2018). "Ice, Snow, and Glaciers: The Water Cycle". U.S. Department of the Interior, U.S. Geological Survey. Archived from the original on 28 February 2019. Retrieved 27 February 2019.
  134. ^ NOAA. "Climate Change: Global Sea Level". Archived from the original on 28 February 2019. Retrieved 27 February 2019. In 2017, global mean sea level was 3 inches (77 millimeters) above the 1993 average—the highest annual average in the satellite record (1993–present). It was the sixth consecutive year, and the 22nd out of the last 24 years in which global mean sea level increased relative to the previous year.
  135. ^ Bell, Brian (31 August 2015). "UCI study finds dramatic increase in concurrent droughts, heat waves". University of California, Irvine. Archived from the original on 3 July 2018.
  136. ^ Scientific American, 29 April 2014
  137. ^ IPCC SREX Summary for Policymakers 2012, section D ("Future Climate Extremes, Impacts, and Disaster Losses"), pp. 9-13.
  138. ^ Francis & Vavrus 2012
  139. ^ USGCRP Chapter 9 2017, p. 260
  140. ^ a b Ocean Acidification, in: Ch. 2. Our Changing Climate Archived 11 September 2013 at the Wayback Machine, in NCADAC 2013, pp. 69–70
  141. ^ Deutsch et al. 2011
  142. ^ a b *"Summary". In National Research Council 2011. pp. 14–19. Archived from the original on 11 December 2013.; Collins et al. 2013, pp. 88-89, FAQ 12.3
  143. ^ McGuire 2010
  144. ^ Smith et al. 2009
  145. ^ Smith, J. B.; et al. "Ch. 19. Vulnerability to Climate Change and Reasons for Concern: A Synthesis". Sec 19.6. Extreme and Irreversible Effects. Archived from the original on 25 September 2012. Retrieved 4 February 2013., in IPCC TAR WG2 2001
  146. ^ Clark, P. U.; Weaver, A.J.; Brook, E.; Cook, E.R.; et al. (December 2008). "Executive Summary". In: Abrupt Climate Change. A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research. Reston, VA: U.S. Geological Survey. Archived from the original on 4 May 2013.
  147. ^ BBC, 22 February 2013
  148. ^ ScienceDaily, 20 December 2004; Liu et al. 2017
  149. ^ "Global Warming and Polar Bears – National Wildlife Federation". Archived from the original on 17 October 2017. Retrieved 16 October 2017. As climate change melts sea ice, the U.S. Geological Survey projects that two thirds of polar bears will disappear by 2050.Amstrup, Marcot & Douglas 2013, p. 213
  150. ^ IPCC, Synthesis Report Summary for Policymakers Archived 23 December 2018 at the Wayback Machine, Section 1: Observed changes in climate and their effects Archived 23 December 2018 at the Wayback Machine, in IPCC AR4 SYR 2007.
  151. ^ Fischlin, et al., Chapter 4: Ecosystems, their Properties, Goods and Services Archived 23 December 2018 at the Wayback Machine, Executive Summary, p. 213 Archived 23 December 2018 at the Wayback Machine, in IPCC AR4 WG2 2007. Executive summary not present in on-line text; see pdf.
  152. ^ Zeng & Yoon 2009
  153. ^ * UNEP 2010
  154. ^ The Washington Post, 30 August 2018
  155. ^ Schneider et al., Chapter 19: Assessing Key Vulnerabilities and the Risk from Climate Change Archived 23 December 2018 at the Wayback Machine, Section 19.3.4: Ecosystems and biodiversity Archived 23 December 2018 at the Wayback Machine, in IPCC AR4 WG2 2007.
  156. ^ ScienceDaily, 28 June 2018
  157. ^ ScienceDaily, 21 January 2012
  158. ^ National Geographic 15 November 2018; Barbero et al. 2015
  159. ^ FAQ 7 and 8, in: Volume-wide Frequently Asked Questions (FAQs) (archived 8 July 2014), pp. 2–3, in IPCC AR5 WG2 A 2014
  160. ^ Field, C., et al., B-3: Regional Risks and Potential for Adaptation, in: Technical Summary (archived 8 July 2014), pp. 27–30, in IPCC AR5 WG2 A 2014
  161. ^ IPCC WG2 Ch19 2014, p. 1077
  162. ^ Diffenbaugh & Burke 2019; The Guardian, 26 January 2015; Burke, Davis & Diffenbaugh 2018
  163. ^ a b IPCC WG2 Ch18 2014, p. 983
  164. ^ Core Writing Team; et al., eds. (2007d). "3.3.3 Especially affected systems, sectors and regions". Synthesis report. Climate Change 2007: Synthesis Report. A Contribution of Working Groups I, II, and III to the Fourth Assessment Report of the Integovernmental Panel on Climate Change (IPCC). Geneva, Switzerland: Intergovernmental Panel on Climate Change. Archived from the original on 23 December 2018. Retrieved 15 September 2011.
  165. ^ IPCC WG2 Ch19 2014, pp. 1073-1080
  166. ^ Porter et al. 2014, p. 488
  167. ^ IPCC AR5 WG2 SPM 2014, p. 18
  168. ^ Porter et al. 2014, pp. 491–492
  169. ^ a b c d  This article incorporates public domain material from the US Environmental Protection Agency document: International Impacts & Adaptation: Climate Change: US EPA. US Environmental Protection Agency. 14 June 2012. Archived from the original on 29 August 2015. Retrieved 18 May 2018.
  170. ^ Kabir et al. 2016
  171. ^ Smith et al. 2014, p. 742; Costello et al. 2009; Watts et al. 2015
  172. ^ Smith et al. 2014, pp. 720-723
  173. ^ Costello et al. 2009; Watts et al. 2015; Smith et al. 2014, p. 713
  174. ^ USA Today, 13 July 2018
  175. ^ IPCC AR5 WG2 SPM 2014, p. 20
  176. ^ The Washington Post, 22 October 2014; Ranson 2014; Marshall, Hsiang & Edward 2014; National Review, 27 February 2014
  177. ^ IPCC AR4 SYR 2007. 3.3.3 Especially affected systems, sectors and regions. Synthesis report. Archived from the original on 23 December 2018. Retrieved 22 December 2018.
  178. ^ Mimura, N.; et al. (2007). "Executive summary". In Parry, M. L.; et al. (eds.). Chapter 16: Small Islands. Climate change 2007: impacts, adaptation and vulnerability: contribution of Working Group II to the fourth assessment report of the Intergovernmental Panel on Climate Change (IPCC). Cambridge University Press (CUP): Cambridge: Print version: CUP. This version: IPCC website. ISBN 0-521-88010-6. Archived from the original on 23 December 2018. Retrieved 15 September 2011.
  179. ^ Park, Susin (May 2011). "Climate Change and the Risk of Statelessness: The Situation of Low-lying Island States" (PDF). United Nations High Commissioner for Refugees. Archived (PDF) from the original on 2 May 2013. Retrieved 13 April 2012.
  180. ^ "Curbing environmentally unsafe, irregular and disorderly migration". UN Environment. 25 October 2018. Retrieved 18 April 2019.
  181. ^ "Climate Change Is A Key Driver of Migration and Food Insecurity". UNFCCC. 17 October 2017. Retrieved 18 April 2019.
  182. ^ Sherwood & Huber 2010
  183. ^ a b IPPC SYR SPM 2013 Section 3, p.17
  184. ^ PBL Netherlands Environment Agency (15 June 2012). "Figure 6.14, in: Chapter 6: The energy and climate challenge". In van Vuuren, D.; Kok, M. (eds.). Roads from Rio+20 (PDF). ISBN 978-90-78645-98-6. Archived (PDF) from the original on 15 May 2013. Retrieved 30 May 2013., p. 177, Report no: 500062001. Report website. Archived 1 June 2013 at the Wayback Machine
  185. ^ Mitigation Archived 21 January 2015 at the Wayback Machine, in USGCRP 2015.
  186. ^ a b IPCC, Synthesis Report Summary for Policymakers Archived 23 December 2018 at the Wayback Machine, Section 4: Adaptation and mitigation options Archived 1 May 2010 at the Wayback Machine, in IPCC AR4 SYR 2007.
  187. ^ a b Table TS.3, in IPCC AR5 WG3 Technical Summary 2014, p. 68.
  188. ^ The Guardian, 31 August 2015.
  189. ^ Rogner, H.-H., et al., Chap. 1, Introduction Archived 23 December 2018 at the Wayback Machine, Section Intensities Archived 23 December 2018 at the Wayback Machine, in IPCC AR4 WG3 2007.
  190. ^ a b NRC (2008). "Understanding and Responding to Climate Change" (PDF). Board on Atmospheric Sciences and Climate, US National Academy of Sciences. p. 2. Archived (PDF) from the original on 11 October 2017. Retrieved 9 November 2010.
  191. ^ World Bank 2010, p. 71.
  192. ^ Banuri et al., Chapter 3: Equity and Social Considerations, Section 3.3.3: Patterns of greenhouse gas emissions, and Box 3.1, pp. 92–93 Archived 23 December 2018 at the Wayback Machine in IPCC SAR WG3 1996.
  193. ^ Liverman 2009, p. 289.
  194. ^ Fisher et al., Chapter 3: Issues related to mitigation in the long-term context Archived 23 December 2018 at the Wayback Machine, Section 3.1: Emissions scenarios: Issues related to mitigation in the long term context Archived 23 December 2018 at the Wayback Machine in IPCC AR4 WG3 2007.
  195. ^ Morita, Chapter 2: Greenhouse Gas Emission Mitigation Scenarios and Implications Archived 6 July 2013 at the Wayback Machine, Section Emissions and Other Results of the SRES Scenarios Archived 2 June 2016 at the Wayback Machine, in IPCC TAR WG3 2001.
  196. ^ Rogner et al., Ch. 1: Introduction Archived 23 December 2018 at the Wayback Machine, Figure 1.7 Archived 23 December 2018 at the Wayback Machine, in IPCC AR4 WG3 2007.
  197. ^ IPCC, Summary for Policymakers Archived 17 January 2012 at the Wayback Machine, Introduction, paragraph 6 Archived 11 March 2006 at the Wayback Machine, in IPCC TAR WG3 2001.
  198. ^ "Study: Global plant growth surging alongside carbon dioxide". National Oceanic and Atmospheric Administration. 20 April 2017. Archived from the original on 2 March 2019. Retrieved 27 February 2019. A new study published in the April 6 edition of the journal Nature concludes that as emissions of carbon dioxide from burning fossil fuels have increased since the start of the 20th century, plants around the world are utilizing 30 percent more carbon dioxide (CO2), spurring plant growth.
  199. ^ Prentence et al., Chapter 3: The Carbon Cycle and Atmospheric Carbon Dioxide Archived 24 December 2011 at the Wayback Machine Executive Summary Archived 7 December 2009 at the Wayback Machine, in IPCC TAR WG1 2001.
  200. ^ Clarke et al. 2014, p. 418; IPCC AR5 WG3 Summary for Policymakers 2014, pp. 10-13.
  201. ^ "The CAT Thermometer". Climate Action Tracker. 11 December 2018. Retrieved 14 April 2019.
  202. ^ IPCC AR5 WG3 Technical Summary 2014, pp. 55-56.
  203. ^ UNFCCC SYN 2016 p.10-11
  204. ^ IPCC AR5 WG3 Technical Summary 2014, p. 58.
  205. ^ Blondel, Benoît; Mispelon, Chloé; Ferguson, Julian (November 2011). Cycle more Often 2 cool down the planet (PDF). European Cyclists' Federation. Retrieved 16 April 2019.
  206. ^ "Cycling - health benefits". Better Health Channel. November 2013. Retrieved 16 April 2019.
  207. ^ Rodgers, Lucy (17 December 2018). "Climate change: The massive CO2 emitter you may not know about". BBC. Archived from the original on 17 December 2018.
  208. ^ United Nations Development Program. "Reducing emissions, promoting clean energy and protecting forests". Retrieved 17 April 2019.
  209. ^ The Economist, 7 February 2019.
  210. ^ Hagmann, Ho & Loewenstein 2019.
  211. ^ Science, 11 July 2017; Wynes & Nicholas 2017.
  212. ^ The Guardian, 27 February 2019; Vox, 15 October 2018.
  213. ^ The Guardian, 26 April 2018.
  214. ^ a b IPCC WG2 Summary for Policymakers 2014, p. 5
  215. ^ NASA's Global Climate Change. "Global climate change adaptation and mitigation". Climate Change: Vital Signs of the Planet. Archived from the original on 3 April 2019. Retrieved 12 April 2019.
  216. ^ Smit et al., Chapter 18: Adaptation to Climate Change in the Context of Sustainable Development and Equity Archived 17 January 2012 at the Wayback Machine, Section 18.2.3: Adaptation Types and Forms Archived 12 December 2009 at the Wayback Machine, in IPCC TAR WG2 2001.
  217. ^ a b IPPC SYR SPM 2013 Section 4, p. 26
  218. ^ "New Report Provides Authoritative Assessment of National, Regional Impacts of Global Climate Change" (Press release). U.S. Global Change Research Program. 16 June 2009. Archived from the original on 13 April 2016. Retrieved 14 January 2016.
  219. ^ Cole 2008
  220. ^ Schneider, S. H.; Semenov, S.; Patwardhan, A.; Burton, I.; Magadza, C. H. D.; Oppenheimer, M.; Pittock, A. B.; Rahman, A.; Smith, J. B.; Suarez, A.; Yamin, F. (2007). Parry, M. L.; Canziani, O. F.; Palutikof, J. P.; van der Linden, P. J.; Hanson, C. E. (eds.). Executive summary. In (book chapter): Chapter 19: Assessing Key Vulnerabilities and the Risk from Climate Change. In: Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge: Print version: Cambridge University Press,. ISBN 978-0-521-88010-7. Archived from the original on 2 May 2010. Retrieved 6 April 2010.
  221. ^ Lane, Lee; Caldeira, Ken (April 2007). Workshop on managing solar radiation (PDF) (Report). NASA. Archived from the original (PDF) on 31 May 2009. Retrieved 23 May 2009.
  222. ^ "Stop emitting CO2 or geoengineering could be our only hope" (Press release). The Royal Society. 28 August 2009. Archived from the original on 24 June 2011. Retrieved 14 June 2011.
  223. ^ Keller, Feng & Oschlies 2014We find that even when applied continuously and at scales as large as currently deemed possible, all methods are, individually, either relatively ineffective with limited (<8%) warming reductions, or they have potentially severe side effects and cannot be stopped without causing rapid climate change.
  224. ^ Bourbaki, Nicolas (1900). Reference test.
  225. ^ Quoted in IPCC SAR SYR 1996, "Synthesis of Scientific-Technical Information Relevant to Interpreting Article 2 of the UN Framework Convention on Climate Change", paragraph 4.1, p. 8 (pdf p. 18 Archived 23 December 2018 at the Wayback Machine.)
  226. ^ Morgan, M. Granger; Dowlatabadi, Hadi; Henrion, Max; Keith, David; Lempert, Robert; McBride, Sandra; Small, Mitchell; Wilbanks, Thomas (2009). "Non-Technical Summary: BOX NT.1 Summary of Climate Change Basics". Synthesis and Assessment Product 5.2: Best practice approaches for characterizing, communicating, and incorporating scientific uncertainty in decision making. A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research (PDF). Washington, D.C.: National Oceanic and Atmospheric Administration. p. 11. Archived (PDF) from the original on 15 August 2011. Retrieved 1 June 2011.
  227. ^ "Paris Agreement - Status of Ratification". United Nations Framework Convention on Climate Change. n.d. Retrieved 18 May 2019.
  228. ^ "Ratification Tracker". Retrieved 19 May 2019.
  229. ^ "Full text of the Convention, Article 2". United Nations Framework Convention on Climate Change. n.d. Archived from the original on 28 October 2005. Retrieved 18 May 2010.
  230. ^ Rogner et al., Chapter 1: Introduction Archived 23 December 2018 at the Wayback Machine, Executive summary Archived 23 December 2018 at the Wayback Machine, in IPCC AR4 WG3 2007.
  231. ^ US EPA (12 January 2016). "Global Greenhouse Gas Emissions Data". Archived from the original on 20 March 2019. Retrieved 12 April 2019.
  232. ^ UNFCCC. "What are United Nations Climate Change Conferences?". Retrieved 12 May 2019.
  233. ^ Dessai 2001, p. 4
  234. ^ Grubb 2003
  235. ^ a b Liverman 2009, p. 290
  236. ^ a b "Kyoto Protocol". United Nations Framework Convention on Climate Change. n.d. Archived from the original on 16 May 2011. Retrieved 21 May 2011.
  237. ^ Dessai 2001, p. 5
  238. ^ Müller, Benito (February 2010). Copenhagen 2009: Failure or final wake-up call for our leaders? EV 49 (PDF). Oxford Institute for Energy Studies. p. i. ISBN 978-1-907555-04-6. Archived (PDF) from the original on 10 July 2017. Retrieved 18 May 2010.
  239. ^ The New York Times, 25 May 2015
  240. ^ "Copenhagen: a successful failure". openDemocracy. 12 January 2010. Archived from the original on 12 April 2019. Retrieved 12 April 2019.
  241. ^ "Copenhagen failure 'disappointing', 'shameful'". 20 December 2009. Archived from the original on 12 April 2019. Retrieved 12 April 2019.
  242. ^ "Decision 2/CP. 15 Copenhagen Accord. In: Report of the Conference of the Parties on its fifteenth session, held in Copenhagen from 7 to 19 December 2009. Addendum. Part Two: Action taken by the Conference of the Parties at its fifteenth session" (PDF). United Nations Framework Convention on Climate Change. 30 March 2010. p. 5. Archived from the original on 30 April 2010. Retrieved 17 May 2010.
  243. ^ a b "The Paris Agreement: Summary. Climate Focus Client Brief on the Paris Agreement III" (PDF). Climate Focus. December 2015. Archived (PDF) from the original on 5 October 2018. Retrieved 12 April 2019.
  244. ^ Trouw, 12 December 2015
  245. ^ Cook et al. 2016
  246. ^ DiMento, Joseph F. C.; Doughman, Pamela M. (2007). Climate Change: What It Means for Us, Our Children, and Our Grandchildren. The MIT Press. p. 68. ISBN 978-0-262-54193-0.
  247. ^ Brigham-Grette et al. 2006: "The AAPG stands alone among scientific societies in its denial of human-induced effects on global warming."
  248. ^ Royal Society (13 April 2005). Economic Affairs – Written Evidence. The Economics of Climate Change, the Second Report of the 2005–2006 session, produced by the UK Parliament House of Lords Economics Affairs Select Committee. UK Parliament. Archived from the original on 13 November 2011. Retrieved 9 July 2011.
  249. ^ "Summary for Policymakers". Detection and Attribution of Climate Change. IPCC. "It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century" (page 15) and "In this Summary for Policymakers, the following terms have been used to indicate the assessed likelihood of an outcome or a result: (...) extremely likely: 95–100%" (page 2)., in IPCC AR5 WG1 2013.
  250. ^ Academia Brasileira de Ciéncias (Brazil); Royal Society of Canada; Chinese Academy of Sciences; Académie des Sciences (France); Deutsche Akademie der Naturforscher Leopoldina (Germany); Indian National Science Academy; Accademia Nazionale dei Lincei (Italy); Science Council of Japan, Academia Mexicana de Ciencias; Russian Academy of Sciences; Academy of Science of South Africa; Royal Society (United Kingdom); National Academy of Sciences (United States of America) (May 2009). "G8+5 Academies' joint statement: Climate change and the transformation of energy technologies for a low carbon future" (PDF). The National Academies of Sciences, Engineering, and Medicine. Archived (PDF) from the original on 15 February 2010. Retrieved 5 May 2010.
  251. ^ Ripple et al. 2017
  252. ^ The New York Times, 7 October 2018
  253. ^ Newsweek, 13 August 2007; Adams 2006; MSNBC, 12 January 2007; ABC, 3 January 2007.
  254. ^ "Oil Company Positions on the Reality and Risk of Climate Change". Environmental Studies, University of Oshkosh – Wisconsin. Archived from the original on 16 April 2016. Retrieved 27 March 2016.
  255. ^ The Economist, 9 February 2009
  256. ^ Milman 2019
  257. ^ Weart, S. (February 2015). "The Public and Climate Change (cont. – since 1980). Section: after 1988". American Institute of Physics. Archived from the original on 11 November 2016. Retrieved 18 August 2015.
  258. ^ "Environment". Gallup. 2015. Archived from the original on 16 August 2015. Retrieved 18 August 2015.
  259. ^ Pugliese, Anita (20 April 2011). "Fewer Americans, Europeans View Global Warming as a Threat". Gallup. Archived from the original on 24 April 2011. Retrieved 22 April 2011.
  260. ^ Ray, Julie; Pugliese, Anita (22 April 2011). "Worldwide, Blame for Climate Change Falls on Humans". Gallup.Com. Archived from the original on 4 May 2011. Retrieved 3 May 2011. People nearly everywhere, including majorities in developed Asia and Latin America, are more likely to attribute global warming to human activities rather than natural causes. The U.S. is the exception, with nearly half (47%) – and the largest percentage in the world – attributing global warming to natural causes.
  261. ^ "Climate Change and Financial Instability Seen as Top Global Threats". Pew Research Center for the People & the Press. 24 June 2013. Archived from the original on 4 October 2013.
  262. ^ McCright & Dunlap 2000
  263. ^ Newsweek, 13 August 2007
  264. ^ Boykoff & Boykoff 2004
  265. ^ Oreskes, Naomi; Conway, Erik (25 May 2010). Merchants of Doubt: How a Handful of Scientists Obscured the Truth on Issues from Tobacco Smoke to Global Warming (first ed.). Bloomsbury Press. ISBN 978-1-59691-610-4.
  266. ^ Poortinga et al. 2018, p. 15.
  267. ^ Newell, Peter (14 December 2006). Climate for Change: Non-State Actors and the Global Politics of the Greenhouse. Cambridge University Press. p. 80. Bibcode:2001AgFM..109...75B. doi:10.1016/S0168-1923(01)00246-5. ISBN 978-0-521-02123-4. Retrieved 30 July 2018.
  268. ^ Peach, Sara (2 November 2010). "Yale Researcher Anthony Leiserowitz On Studying, Communicating with American Public". Yale Climate Connections. Archived from the original on 7 February 2019. Retrieved 30 July 2018.
  269. ^ Shindell et al. 2006
  270. ^ "The Montreal Protocol: triumph by treaty". UN Environment. 20 November 2017. Archived from the original on 12 April 2019. Retrieved 12 April 2019.
  271. ^ Gunningham 2018
  272. ^ & The New York Times, 29 April 2017
  273. ^ & The Guardian, 19 March 2019
  274. ^ a b Weart, Spencer (2008). "The Carbon Dioxide Greenhouse Effect". The Discovery of Global Warming. American Institute of Physics. Archived from the original on 11 November 2016. Retrieved 21 April 2009.
  275. ^ a b Weart, Spencer R. (February 2014). "The Discovery of Global Warming; The Public and Climate Change: Suspicions of a Human-Caused Greenhouse (1956–1969)". American Institute of Physics. Archived from the original on 11 November 2016. Retrieved 12 May 2015. Also footnote 27 Archived 16 May 2015 at the Wayback Machine
  276. ^ a b Weart, Spencer R. (February 2014). "The Discovery of Global Warming; The Public and Climate Change: The Summer of 1988". American Institute of Physics. Archived from the original on 11 November 2016. Retrieved 12 May 2015.
  277. ^ Weart 2013
  278. ^ Sorenson, Raymond (11 January 2011). "Eunice Foote's Pioneering Research On CO2 And Climate Warming" (PDF). Search and Discovery. Retrieved 31 January 2016.
  279. ^ Foote, Eunice (November 1856). Circumstances affecting the Heat of the Sun's Rays. The American Journal of Science and Arts. 22. pp. 382–383. Retrieved 31 January 2016.
  280. ^ Tyndall 1861
  281. ^ Molina, Francis (March 1912). "Remarkable Weather of 1911: The Effect of Combustion of Coal on Climate – What Scientists Predict for the Future". Popular Mechanics. pp. 339–342. Retrieved 13 October 2018.
  282. ^ "Coal Consumption Affecting Climate". The Braidwood Dispatch and Mining Journal (New South Wales). 17 July 1912. p. 4. Archived from the original on 14 October 2018. Retrieved 13 October 2018.
  283. ^ Callendar 1938
  284. ^ Fleming, James Rodger (2007). The Callendar Effect: the life and work of Guy Stewart Callendar (1898–1964). Boston: American Meteorological Society. ISBN 978-1-878220-76-9.
  285. ^ a b Conway, Erik M. (5 December 2008). "What's in a Name? Global Warming vs. Climate Change". NASA. Archived from the original on 9 August 2010.
  286. ^ U.S. Senate, Committee on Energy and Natural Resources, 100th Cong. 1st sess. (23 June 1988). Greenhouse Effect and Global Climate Change, part 2. p. 44.
  287. ^ The Guardian, 17 May 2019


This section is being reorganized; many sources are not yet where they belong, and at times maybe out of order.

Reports by The Intergovernmental Panel on Climate Change

AR4 Working Group I Report
AR4 Working Group II Report
AR4 Working Group III Report
AR4 Synthesis Report

AR5 Working Group I Report
  • IPCC (2013). Stocker, T. F.; Qin, D .; Plattner, G.-K.; et al. (eds.). Climate Change 2014: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, United Kingdom and New York, NY, USA: Cambridge University Press. ISBN 978-1-107-05799-9. (pb: 978-1-107-66182-0).
  • Stocker, T. F.; Qin, D.; Plattner, G.-K.; Alexander, L. V.; et al. (2013). "Technical Summary". IPCC AR5 WG1 2013.
AR5 Working Group II Report
  • IPCC (2014). Field, C.B.; Barros, V.R.; Dokken, D.J.; et al. (eds.). Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part A: Global and Sectoral Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press. ISBN 978-1-107-05807-1. (pb: 978-1-107-64165-5). Chapters 1–20, SPM, and Technical Summary.
  • IPCC (2014). Barros, V.R.; Field, C.B.; Dokken, D.J.; et al. (eds.). Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part B: Regional Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press. ISBN 978-1-107-05816-3. (pb: 978-1-107-68386-0). Chapters 21–30, Annexes, and Index.
AR5 Working Group III Report
  • IPCC (2014). Edenhofer, O.; Pichs-Madruga, R.; Sokona, Y.; et al. (eds.). Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, United Kingdom and New York, NY, USA: Cambridge University Press. ISBN 978-1-107-05821-7. (pb: 978-1-107-65481-5).
AR5 Synthesis Report

Special Report: SREX
Special Report: SR15
  • IPCC (2018). Masson-Delmotte, V.; Zhai, P.; Pörtner, H. O.; Roberts, D.; et al. (eds.). Global Warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty. In Press.
  • IPCC (2018). Summary for Policymakers. Geneva, Switzerland: World Meteorological Organization. IPCC SR15 SPM as printed by the WMO.

Other peer-reviewed sources

Editors: "o" marks citations to be deleted pending verification that any short-cites link to the replacement citation (above).

  • Liu, Wei; Xie, Shang-Ping; Liu, Zhengyu; Zhu, Jiang (2017). "Overlooked possibility of a collapsed Atlantic Meridional Overturning Circulation in warming climate". Science advances. 3 (1). doi:10.1126/sciadv.1601666.
  • o Mach, Katharine J.; Serge, Planton; von Stechow, Christoph (2014). "Annex II Glossary" (PDF). IPCC SYR AR5 (Report).
  • Sévellec, Florian; Drijfhout, Sybren S. (2018). "A novel probabilistic forecast system predicting anomalously warm 2018–2022 reinforcing the long-term global warming trend". Nature Communications. doi:10.1038/s41467-018-05442-8.
  • Ramanathan, V.; Agrawal, M.; Akimoto, H.; Aufhamer, M.; et al. (2008). Report Summary (PDF). Atmospheric Brown Clouds: Regional Assessment Report with Focus on Asia (Report). United Nations Environment Programme. Archived from the original (PDF) on 18 July 2011.
  • UNFCCC secretariat (2016). Synthesis report on the aggregate effect of the intended nationally determined contributions (INDCs).
  • Wuebbles, D. J.; Easterling, D. R.; Hayhoe, K.; Knutson, T.; Kopp, R. E.; Kossin, J. P.; Kunkel, K. E.; LeGran-de; A. N.; Mears, C.; Sweet, W. V.; Taylor, P. C.; Vose, R. S.; Wehne, M. F. (2017). "Chapter 1: Our Globally Changing Climate" (PDF). In USGCRP2017 (Report).

Non-technical sources

External links