No Room to Run

Hunched against the elements, ecologist Bill Fraser counts Adélie penguins. This colony dwindled from 320 breeding pairs to 54 between 1990 and 2004. Average winter temperatures here have increased nearly 9 degrees Fahrenheit over five decades, and sea ice has retreated by a fifth since the mid-1970s, depriving Adélies of an important feeding platform from which they hunt krill. "The Adélies are the canaries in the coal mine of climate change in the Antarctic," says Fraser.

Source :
environment.nationalgeographic.com

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Temperature Changes in The World

Based on estimates by NASA's Goddard Institute for Space Studies, 2005 was the warmest year since reliable, widespread instrumental measurements became available in the late 1800s, exceeding the previous record set in 1998 by a few hundredths of a degree. Estimates prepared by the World Meteorological Organization and the Climatic Research Unit show 2005 as the second warmest year, behind 1998. Temperatures in 1998 were unusually warm because the strongest El Niño in the past century occurred during that year. Global temperature is subject to short-term fluctuations that overlay long term trends and can temporarily mask them. The relative stability in temperature from 1999 to 2009 is consistent with such an episode.

Temperature changes vary over the globe. Since 1979, land temperatures have increased about twice as fast as ocean temperatures (0.25 °C per decade against 0.13 °C per decade). Ocean temperatures increase more slowly than land temperatures because of the larger effective heat capacity of the oceans and because the ocean loses more heat by evaporation.[18] The Northern Hemisphere warms faster than the Southern Hemisphere because it has more land and because it has extensive areas of seasonal snow and sea-ice cover subject to ice-albedo feedback. Although more greenhouse gases are emitted in the Northern than Southern Hemisphere this does not contribute to the difference in warming because the major greenhouse gases persist long enough to mix between hemispheres.

The thermal inertia of the oceans and slow responses of other indirect effects mean that climate can take centuries or longer to adjust to changes in forcing. Climate commitment studies indicate that even if greenhouse gases were stabilized at 2000 levels, a further warming of about 0.5 °C (0.9 °F) would still occur.

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Warmer Seas, Wetter Air Make Harder Rains

Storms will dump heavier rain and snow around the world as Earth's climate warms over the coming century, according to several leading computer models. Now a study by scientists at the National Center for Atmospheric Research (NCAR) explains how and where warmer oceans and atmosphere will produce more intense precipitation. The findings recently appeared in Geophysical Research Letters, a publication of the American Geophysical Union.
See Also:
Earth & Climate

* Pollution
* Air Pollution
* Environmental Issues
* Air Quality
* Geography
* Snow and Avalanches

Reference

* Precipitation (meteorology)
* Rain
* Winter storm
* Lake effect snow

The greatest increases will occur over land in the tropics, according to the study. Heavier rain or snow will also fall in northwestern and northeastern North America, northern Europe, northern Asia, the east coast of Asia, southwestern Australia, and parts of south-central South America during the 21st century.

"The models show most areas around the world will experience more intense precipitation for a given storm during this century," says lead author Gerald Meehl. "Information on which areas will be most affected could help communities to better manage water resources and anticipate possible flooding."

NCAR authors Meehl, Julie Arblaster, and Claudia Tebaldi analyzed the results of nine atmosphere-ocean global climate models to explain the physical mechanisms involved as intensity increased. Precipitation intensity refers to the amount of rain or snow that falls on a single stormy day.

Both the oceans and the atmosphere are warming as greenhouse gases build in the atmosphere. Warmer sea surfaces boost evaporation, while warmer air holds more moisture. As this soggy air moves from the oceans to the land, it dumps extra rain per storm.

Though water vapor increases the most in the tropics, it also plays a role in the midlatitudes, according to the study. Combined with changes in sea-level pressure and winds, the extra moisture produces heavier rain or snow in areas where moist air converges.

In the Mediterranean and the U.S. Southwest, even though intensity increases, average precipitation decreases. The authors attribute the decrease to longer periods of dry days between wet ones. The heavier rain and snow will most likely fall in late autumn, winter, and early spring, while warmer months may still bring a greater risk of drought.

Source : sciencedaily.com

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Stop Global Warming

Global warming is the increase in the average temperature of Earth's near-surface air and oceans since the mid-20th century and its projected continuation. Global surface temperature increased 0.74 ± 0.18 °C (1.33 ± 0.32 °F) between the start and the end of the 20th century. The Intergovernmental Panel on Climate Change (IPCC) has concluded that most of the observed increase in average global temperatures since the middle of the 20th century is very likely (>90% probability of occurrence) caused by increasing concentrations of greenhouse gases resulting from human activity such as fossil fuel burning and deforestation. The IPCC has also concluded that variations in natural phenomena such as solar radiation and volcanism had a small cooling effect after 1950.[3] These basic conclusions have been endorsed by more than 40 scientific societies and academies of science,[B] including all of the national academies of science of the major industrialized countries.

Climate model projections summarized in the latest IPCC report indicate that the global surface temperature is likely to rise a further 1.1 to 6.4 °C (2.0 to 11.5 °F) during the 21st century. The uncertainty in this estimate arises from the use of models with differing sensitivity to greenhouse gas concentrations and the use of differing estimates of future greenhouse gas emissions. Most studies focus on the period up to the year 2100. However, warming is expected to continue beyond 2100 even if emissions stop, because of the large heat capacity of the oceans and the long lifetime of carbon dioxide in the atmosphere.


An increase in global temperature will cause sea levels to rise and will change the amount and pattern of precipitation, probably including expansion of subtropical deserts.Warming is expected to be strongest in the Arctic and would be associated with continuing retreat of glaciers, permafrost and sea ice. Other likely effects include increases in the intensity of extreme weather events, species extinctions, and changes in agricultural yields. Warming and related changes will vary from region to region around the globe, though the nature of these regional variations are uncertain.

Political and public debate continues regarding global warming, and what actions (if any) to take in response. The available options are mitigation to reduce further emissions; adaptation to reduce the damage caused by warming; and, more speculatively, geoengineering to reverse global warming. Most national governments have signed and ratified the Kyoto Protocol aimed at reducing greenhouse gas emissions.

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