Portal:Global warming

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Global warming

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Global warming is the increase in the average temperature of the Earth's near-surface air and the oceans since the mid-twentieth century and its projected continuation. Global surface temperature increased 0.74 ± 0.18 °C (1.33 ± 0.32 °F) during the 100 years ending in 2005. The Intergovernmental Panel on Climate Change (IPCC) concludes that human-sourced greenhouse gases are responsible for most of the observed temperature increase since the middle of the twentieth century, and natural phenomena such as solar variation and volcanoes probably had a small warming effect from pre-industrial times to 1950 and a small cooling effect from 1950 onward. These basic conclusions have been endorsed by more than 40 scientific societies and academies of science, including all of the national academies of science of the major industrialized countries.

Climate model projections summarized in the latest IPCC report indicate that global surface temperature will probably rise a further 1.1 to 6.4 °C (2.0 to 11.5 °F) during the twenty-first century. The uncertainty in this estimate arises from the use of models with differing climate sensitivity, and the use of differing estimates of future greenhouse gas emissions. Some other uncertainties include how warming and related changes will vary from region to region around the globe. Although most studies focus on the period up to 2100, warming is expected to continue beyond 2100, even if emissions have stopped, because of the large heat capacity of the oceans and the lifespan of carbon dioxide in the atmosphere.

Pictured left: 1999-2008 Mean temperatures: This figure shows the difference in instrumentally determined surface temperatures between the period January 1999 through December 2008 and "normal" temperatures at the same locations, defined to be the average over the interval January 1940 to December 1980. The average increase on this graph is 0.48 °C, and the widespread temperature increases are considered to be an aspect of global warming. Source: NASA

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Arctic sea ice loss animation.gif
Credit: NASA

This time series, based on satellite data, shows the annual Arctic sea ice minimum since 1979. The September 2010 extent was the third lowest in the satellite record.

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2000 Year Temperature Comparison.png
Pictured left: Two millennia of mean surface temperatures according to different reconstructions, each smoothed on a decadal scale. The unsmoothed, annual value for 2004 is also plotted for reference.

Global temperatures have increased by 0.75 °C (1.35 °F) relative to the period 1860–1900, according to the instrumental temperature record. This measured temperature increase is not significantly affected by the urban heat island effect. Since 1979, land temperatures have increased about twice as fast as ocean temperatures (0.25 °C per decade against 0.13 °C per decade). Temperatures in the lower troposphere have increased between 0.12 and 0.22 °C (0.22 and 0.4 °F) per decade since 1979, according to satellite temperature measurements. Temperature is believed to have been relatively stable over the one or two thousand years before 1850, with possibly regional fluctuations such as the Medieval Warm Period or the Little Ice Age.

Deriving a reliable global temperature from the instrument data is not easy because the instruments are not evenly distributed across the planet, the hardware and observing locations have changed over the years, and there has been extensive land use change (such as urbanization) around some of the sites. The calculation needs to filter out the changes that have occurred over time that are not climate related (e.g. urban heat islands), then interpolate across regions where instrument data has historically been sparse (e.g. in the southern hemisphere and at sea), before an average can be taken.


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Al gore presentation.jpg
Pictured left: Al Gore's speech on Global Warming at the University of Miami BankUnited Center, February 28, 2007.

Albert Arnold "Al" Gore, Jr. (born March 31, 1948) served as the 45th Vice President of the United States (1993–2001), under President Bill Clinton. He was the Democratic Party's nominee for President in the 2000 U.S. presidential election. Gore is currently an author and environmental activist. He has founded a number of non-profit organizations, including the Alliance for Climate Protection, and has received a Nobel Peace Prize for his work in climate change activism.

In his senior year at Harvard University, he took a class with oceanographer and global warming theorist Roger Revelle, who sparked Gore's interest in global warming and other environmental issues. After joining the U.S. House of Representatives, Gore held the first congressional hearings on the climate change, and co-sponsor[ed] hearings on toxic waste and global warming. Gore was known as one of the Atari Democrats, later called the "Democrats' Greens: politicians who see issues like clean air, clean water and global warming as the key to future victories for their party.

Gore wrote the book An Inconvenient Truth: The Planetary Emergency of Global Warming and What We Can Do About It, which won a Grammy Award for Best Spoken Word Album in 2009. An Inconvenient Truth is a 2006 documentary film directed by Davis Guggenheim about Al Gore's campaign to educate citizens about global warming via a comprehensive slide show that, by his own estimate, Gore has given more than a thousand times. Our Choice is a 2009 book written by Gore, originally titled, which followed the An Inconvenient Truth... (book). All profits of the book (printed on 100% recycled paper) go to the Alliance for Climate Protection, which Gore founded in 2006.


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Antarctica temps2 1957-2006.jpg
Credit: NASA

Image showing the temperature trend in Antarctica between 1957 and 2006

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...that global warming millions of years ago put seas in a spin? The circulation of the deep oceans reversed abruptly some 55 million years ago, according to a study of fossilized sea creatures. This rings alarm bells about today's climate change, because the reversal coincided with a period of global warming driven by greenhouse gases." Article on Nature News
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