Climate change

Global warming is an increase over time of the average temperature of Earth's atmosphere. Many are afraid that this will lead to a worldwide harm to the environment and damage to agriculture (see global warming hypothesis), so the issue has become a matter of public policy. Not all global warming is attributed to the action of humans; global warming that is attributed to such causes is called anthropogenic global warming (see also greenhouse gases).

Researchers disagree on whether the effects of global warming will be beneficial or detrimental. Some researchers feel that up to 1.5 degrees Centrigade of warming would increase crop yields and stablize weather. Many researchers, especially those associated with the UN's Intergovernmental Panel on Climate Change (IPCC) predict disastrous consequences for such a warming; moreover, they predict warming of 2 to 5 times that amount.

There is also some disagreement on the historical temperature record. Depending on what direct measurements and proxies are accepted, researchers have presented various scenarios: stable temperature followed by a sudden, steady rise in the 20th century vs. fluctuations of 1 or 2 degrees Centigrade, with near-stable temperature since 1940.

Advocates of the global warming hypothesis who predict adverse consequences from as little as 1.5 degrees Centigrade of warming nearly all support the Kyoto Protocol as a countermeasure. Some researchers, politicians and businesses oppose it.

Historical temperature record

Climate scientists generally agree that Earth has undergone several cycles of global warming and global cooling in the last 20 thousand years, with the average air temparature fluctuating within a range of about 3 Celsius degrees (5 Fahrenheit degrees), over this time period. During the Medieval Warm Period, for example, Vikings colonized Greenland, but the colonies were abandoned during the Little Ice Age that followed.

Evidence for a current warming period

According to the IPCC, Earth has seen a significant increase in average global surface temperature over the last 150 years.

The main evidence for global warming comes from thermometer measurements from land stations since 1860. The data from these stations, particularly those located outside of the United States, show an average surface temperature increase of 0.4 to 0.8 Celsius degrees during the 20th century. Most of the warming occurred during two periods: 1910 to 1945 and 1976 to 2000. (Source: Intergovernmental Panel on Climate Change, the IPCC).

Secondary evidence comes from observed variations in the snow cover and ice extent, global average sea level, precipitation, cloud cover, El Niño and extreme weather events during the 20th century.

For example, satellite data shows a 10% decrease of snow cover since the late 1960s, and the Northern Hemisphere spring and summer sea-ice extent has decreased by about 10% to 15% since the 1950s and there has been a widespread retreat of mountain glaciers in non-polar regions throughout the 20th century. (Source: IPCC).

Evidence against a current warming period

In January 2002, scientists released data showing that the Antarctic ice cap had grown about 25%, which contradicts the prediction of rising temperatures causing the ice cap to shrink.

Weather balloons and satellites measuring the temperature of the atmosphere above the earth's surface show no warming trend. (Source: NASA)

Climate models

Climate simulations show that the warming that occurred from 1910 to 1945 can be explained by variation in solar radiation (internal and natural forcing) only (see climate change). The models are used to estimate the relative importance of the various factors mentioned above. Most models show that warming occurring from 1976 to 2000 needs anthropogenic greenhouse gas emissions to be explained.

The IPCC (see below), a United Nations science and public policy organization, published a report saying that scientists believe that anthropogenic greenhouse gases "play an important role in global warming."

This conclusion depends on the accuracy of the models used and on the correct estimation of the external factors. The majority of scientists agree that important climate features are incorrectly accounted for by the climate models but don't think that better models would change the conclusion. (Source: IPCC)

Critics point out that there are flaws in the models and external factors not taken into consideration that could change the conclusion above. Some critics say that the climate simulations are unable to model the cooling effects of the particles, fitting the water vapor feedback, and handling clouds. Critics also point out that the Sun may have a share of responsibility for the observed global warming greater than now thought by the majority of the scientific community. Some indirect solar effects may be very important and are not accounted for by the models. So, they argue, the share of global warming caused by anthropogenic greenhouse gases may be lower than thought. (Source: The Skeptical Environmentalist)

Potential Effects

Many public policy organizations and government officials are concerned that the current warming has the potential for harm to the environment and agriculture. This is a matter of considerable controversy, with environmentalist groups typically emphasizing the possible dangers and groups close to industry questioning the climate models and consequences of global warming.

Due to potential effects on human health, the economy and the environment, global warming is the cause of great concern. Some important environmental changes have been observed and linked to global warming. The examples of secondary evidence cited above (lessened snow cover, rising sea levels, weather changes) are examples of consequences of global warming that may influence not only human activities but also the ecosystems. Increasing global temperature means that ecosystems may change; some species may be forced out of their habitats (possibly to extinction) because of changing conditions, while others may spread.

Another cause of great concern is sea level rise. Sea levels are rising 1 to 2 centimetres (around half an inch) per decade, and some small countries in the Pacific Ocean are expressing concerns that if this rise in sea level continues, they soon will be entirely under water. Global warming causes the sea level to rise mainly because sea water expands as it warms, but some scientists are concerned that in the future, the polar ice caps and glaciers may melt. As a consequence, the sea level could rise several metres. At the moment, scientists are not expecting any major ice melting in the next 100 years. (Sources: IPCC for the data and the mass media for the general perception that climate change is important.) Some researchers have found a negative correlation between sea level rise and average global temperature; water evaporates more quickly than it expands. (Source: Science and Environmental Policy Project)

As the climate gets hotter, evaporation will increase. This will cause heavier rainfall and more erosion. Many people think that it could result in more extreme weather as global warming progresses.

Global warming can also have other, less obvious effects. The North Atlantic drift, for instance, is driven by temperature changes. It seems as though it is diminishing as the climate grows warmer, and this means that areas like Scandinavia and Britain that are warmed by the drift might face a colder climate in spite of the general global warming.

However, global warming can also have positive effects, since higher temperatures and higher CO₂ concentrations improve the ecosystems' productivity. Satellite data shows that the productivity of the Northern Hemisphere has increased since 1982. On the other hand, an increase in the total amount of biomass produced is not necessarily all good, since biodiversity can still decrease even though a small number of species are flourishing. Similarly, from the human economic viewpoint, an increase in total biomass but a decrease in crop harvests would be a net disadvantage.

The Intergovernmental Panel on Climate Change

Since it is such an important issue, governments need predictions of future trends in global change so they can take political decisions to avoid undesired impacts. Global warming is being studied by the Intergovernmental Panel on Climate Change (IPCC). In its last report, the IPCC made some predictions about future climate change. These predictions are the basis for current political and scientific discussion.

IPCC predictions are based on the same models used to establish the importance of the different factors in global warming. These models need data about anthropogenic emissions of greenhouse gases and aerosols. These data are predicted from economic models based on 35 different scenarios. Scenarios go from pessimistic to optimistic, and predictions of global warming depend on the kind of scenario considered. None of these scenarios consider any kind of measures to avoid global warming.

The models used are primarily based on surface temperature measurements but attempt to predict the temperature of the entire troposphere, not just surface temperatures.

However, a NASA report challenges the success of these models: "The IPCC's 1995 estimate of average global warming at the surface until the year 2100 is +0.18 °C/decade. Climate models suggest that the deep layer measured by the satellite and weather balloons should be warming about 30% faster than the surface (+0.23 °C/decade). None of the satellite or weather balloon estimates are near this value." (Source: NASA Science News 14 August 1998.) Note that "deep layer" refers to the entire troposphere, rather than just the surface.

Nevertheless, proponents of the IPCC assessment say that the current climate models are good in predicting surface temperatures and that this is significant. They furthermore argue that it is surface temperatures that will have the greatest and most direct effect on the environment, agriculture and the stability of polar ice.

The IPCC says that it has corrected the land station data to account for the urban heat island effect. To do: find and summarize their correction technique.

In its last report, IPCC stated that average surface temperature is projected to increase by 1.4 to 5.8 Celsius degrees over the period 1990 to 2100, and the sea level is projected to rise by 0.1 to 0.9 metres over the same period.

IPCC predictions are supposedly the best predictions available but are nevertheless under strong scientific scrutiny. The IPCC concedes that there is a need for better models and better scientific understanding of some climate phenomena, as well as the uncertainties involved. Critics point out that the available data is not sufficient to determine the real importance of greenhouse gases in climate change. Sensitivity of climate to greenhouse gases may be overestimated because of some flaws in the models and because the importance of some external factors may be underestimated.

On the other hand, predictions are based on scenarios, and the IPCC did not assign any probability to the 35 scenarios used. Critics charge that some of the scenarios that predict the largest impacts are not realistic because they contradict basic economic reasoning.

The United Nations Framework Convention on Climate Change and the Kyoto Protocol

Even if there are some doubts about its importance, global warming is perceived by the general public, by many scientists, and by some political leaders as a potential threat to human health and economic prosperity. Reductions of the emissions of greenhouse gases by developed countries was proposed, with developing countries such as India and China being exempted from reductions. Since this problem is like the tragedy of the commons, only an international agreement could reduce the emissions of greenhouse gases; voluntary reductions would be avoided by individual countries. In light of this expectation, the global warming treaty will not take effect unless enough countries ratify it.

The United Nations Framework Convention on Climate Change (UNFCCC) establishes a process for developing an international response to the perceived global warming problem. Most of the countries in the world are parties to the UNFCCC, including all the major industrial nations. The UNFCCC, however, does not provide any binding emission targets.

Most of the parties to the UNFCCC, including all the major industrial nations, are party to the Kyoto Protocol to the UNFCCC, which proposes binding greenhouse gas limits for developed countries (developing countries are not subject to limits under the Protocol). The limits are based on the level of their emissions in 1990; most developed countries would be required to limit their emissions to a level below the 1990 level, although a few, such as Iceland, would be permitted to limit their emissions to a level higher than what they emitted in 1990.

The United States, responsible for one-third of the world-wide emissions of greenhouse gases, has signed but not ratified the Kyoto Protocol. During the Presidential administration of Bill Clinton, the United States Senate voted on a resolution against ratifying the protocol, with not a single Democratic Senator voting in favor of it. The current President, George W. Bush, has indicated that he does not intend to submit the treaty for ratification. This decision has resulted in internal and international controversy with major political and ideological ramifications.

To evaluate the effectiveness of the Kyoto protocol, it is necessary to compare global warming with and without the agreement. Several independent authors agree that the impact of the Kyoto protocol on global warming is very small (a reduction of 0.15 Celsius degrees by 2100, out of a projected total change of 2 Celsius degrees). Even some defenders of the Kyoto Protocol agree that the impact of it is small, but they view it as a first step, with more political than practical importance, for future reductions. At the moment, an analysis made by the IPCC is needed to clarify this issue.

The Kyoto Protocol can also be evaluated by comparing costs and gains. Several economical analyses were made that show that the Kyoto Protocol is more expensive than the global warming that it avoids. Defenders of the Kyoto Protocol argue however that while the initial greenhouse gas cuts may have little effect, they set the political precedent for bigger (and more effective) cuts in the future.

References

Every source has a point of view or a sponsor which might be a source of bias. If you discover evidence for bias or a major source of its funding, please include it in the site's description.

Scientific websites:

United Nations websites:

http://www.ipcc.ch -- the Intergovernmental Panel on Climate Change (IPCC), established by WMO and UNEP (below) in 1988
http://www.wmo.ch -- the World Meteorological Organization (WMO)
http://www.unep.org/ -- the United Nations Environment Programme
http://unfccc.int/ -- the United Nations Framework Convention for Climate Change (UNFCCC)
IPCC report: summary for policy makers, (2001) (pdf file)
IPCC report: Climate Change 2001: The Scientific Basis -- Technical Summaries (pdf file)

Environmentalist websites:

http://www.greenpeace.org/ -- Greenpeace
http://www.earthisland.org/eijournal/spring98/sp98a_fe.htm -- [Earth Island]]
http://www.panda.org/climate/ -- the Worldwide Wildlife Fund (WWF)
http://www.worldwatch.org/about -- Worldwatch Institute

Industry-sponsored (even in part):

http://www.cei.org -- the Competitive Enterprise Institute
Access to Energy
CO₂ science magazine
http://www.junkscience.com -- PR Watch says, "Steven Milloy's website is actually a good example of junk science itself, heaping adolescent insults on any and all scientists (ranging from Samuel Epstein to the New England Journal of Medicine) who fail to defend the corporate, anti-environmentalist worldview." (Source: [1])

Independent (or receives too little support to constitute "sponsorship"):

Bjorn Lomborg, author of The Skeptical environmentalist, (2001) ISBN 0521010683
"The PR Plot to Overheat the Earth", analysis by Bob Burton and Sheldon Rampton
Testimony of Richard S. Lindzen before the Senate Environment and Public Works Committee on 2 May 2001 -- Lindzen is a professor at MIT
http://www.sepp.org/ -- the Science and Environmental Policy Project (SEPP)

Other websites (viewpoint or sponsorship unknown):

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