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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Plant Productivity in a Warming World: The past decade is the warmest on record since instrumental measurements began in the 1880s. Previous research suggested that in the '80s and '90s, warmer global temperatures and higher levels of precipitation—factors associated with climate change—were generally good for plant productivity. An updated analysis published this week in Science indicates that as temperatures have continued to rise, the benefits to plants are now overwhelmed by longer and more frequent droughts. High-resolution data from the Moderate-Resolution Imaging Spectroradiometer, or MODIS, indicate a net decrease in net primary production (NPP) from 2000-2009, as compared to the previous two decades. This narrated video gives an overview of NPP and the carbon cycle.

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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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Larsen B collapse.jpg
Credit: NASA

The collapse of Larsen B Ice Shelf, showing the diminishing extent of the shelf from 1998 to 2002

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...Arctic haze contributes to global warming, raising temperatures by up to 5.4°F (3°C) during the arctic winter? A major distinguishing factor of Arctic haze is the ability of its chemical ingredients to persist in the atmosphere for an extended period of time compared to other pollutants.
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