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 anthropogenic (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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Glacier Mass Balance Map.png
Credit: Global Warming Art

The effective rate of change in glacier thickness, also known as the glaciological mass balance, is a measure of the average change in a glacier's thickness after correcting for changes in density associated with the compaction of snow and conversion to ice. The map shows the average annual rate of thinning since 1970 for the 173 glaciers that have been measured at least 5 times between 1970 and 2004. Larger changes are plotted as larger circles and towards the back.

All survey regions except Scandinavia show a net thinning. This widespread glacier retreat is generally regarded as a sign of global warming.

During this period, 83% of surveyed glaciers showed thinning with an average loss across all glaciers of 0.31 m/yr. The most rapidly growing glacier in the sample is Engabreen glacier in Norway with a thickening of 0.64 m/yr. The most rapidly shrinking was Ivory glacier in New Zealand which was thinning at 2.4 m/yr. Ivory glacier had totally disintegrated by circa 1988. [1]

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The Great Freeze refers to the winter of 1894-1895, especially in Florida where the brutally cold weather destroyed much of the nation's citrus crop.

There were actually twin freezes in Florida during this momentous season, the first in December 1894 and the second in February 1895. The first did not actually kill a lot of groves, but did cause them to produce new shoots. So, when the second, harder freeze came a few months later, the effects were even more devastating. All varieties of fruit (oranges, grapefruits, lemons, limes, etc.) blackened on the trees, and bark split from top to bottom. These effects were felt as far south as the Manatee River, below Tampa.

Up to 1895, the cheap abundance of semi-tropical citrus groves extended into northern Florida and were producing as much as 6 million boxes of fruit per year. After the Great Freeze, however, production plummeted to just 100,000 boxes and did not break the 1 million mark again until 1901. As a result, land values also dropped in the citrus growing areas from $1,000 per acre to as little as $10 per acre. Many compared the economic impact of the Great Freeze on Florida to the effects of the Great Fire on the city of Chicago.

In the wake of the Great Freeze, many planters simply abandoned their Florida groves in search of frost-free locations in places as far away as Cuba, Puerto Rico, and Jamaica. Others relocated to California, utilizing a seedless variety of grapefruit discovered by C.M. Marsh near Lakeland, Florida. Growers who were not able to abandon the region were forced to try their hands at growing other crops, which had the positive result of diversifying Florida's agriculture. For instance, Palatka became particularly well-known for its potato crop in the years following the Great Freeze; and Sanford was closely identified with celery.

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James E. Hansen (born March 29, 1941) heads the NASA Goddard Institute for Space Studies in New York City, a part of the Goddard Space Flight Center in Greenbelt, Maryland. He has held this position since 1981. He is also an adjunct professor in the Department of Earth and Environmental Sciences at Columbia University.

After graduate school, Hansen continued his work with radiative transfer models, attempting to understand the Venusian atmosphere. Later he applied and refined these models to understand the Earth's atmosphere, in particular, the effects that aerosols and trace gases have on Earth's climate. Hansen's development and use of global climate models has contributed to the further understanding of the Earth's climate.

Hansen has stated that one of his research interests is radiative transfer in planetary atmospheres, especially the interpretation of remote sensing of the Earth's atmosphere and surface from satellites. Because of the ability of satellites to monitor the entire globe, they may be one of the most effective ways to monitor and study global change. His other interests include the development of global circulation models to help understand the observed climate trends, and diagnosing human impacts on climate.

Hansen is best known for his research in the field of climatology, his testimony on climate change to congressional committees in 1988 that helped raise broad awareness of global warming, and his advocacy of action to avoid dangerous climate change. In recent years, Hansen has become an activist for action to mitigate the effects of climate change, which on a few occasions has led to his arrest. In 2009 his first book, Storms of My Grandchildren, was published.

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2007 Arctic Sea Ice.jpg
Credit: NASA

This image shows the Arctic as observed by the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) aboard NASA’s Aqua satellite on September 16, 2007. The image denotes a record sea ice minimum in the Arctic.

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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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