NASA and Columbia University Earth Institute research finds that human-made greenhouse gases have brought the Earth’s climate close to critical tipping points, with potentially dangerous consequences for the planet.
From a combination of climate models, satellite data, and paleoclimate records the scientists conclude that the West Antarctic ice sheet, Arctic ice cover, and regions providing fresh water sources and species habitat are under threat from continued global warming. The research appears in the current issue of Atmospheric Chemistry and Physics.
Tipping points can occur during climate change when the climate reaches a state such that strong amplifying feedbacks are activated by only moderate additional warming. This study finds that global warming of 0.6ºC in the past 30 years has been driven mainly by increasing greenhouse gases, and only moderate additional climate forcing is likely to set in motion disintegration of the West Antarctic ice sheet and Arctic sea ice. Amplifying feedbacks include increased absorption of sunlight as melting exposes darker surfaces and speedup of iceberg discharge as the warming ocean melts ice shelves that otherwise inhibit ice flow.
The researchers used data on earlier warm periods in Earth’s history to estimate climate impacts as a function of global temperature, climate models to simulate global warming, and satellite data to verify ongoing changes. Lead author James Hansen, NASA Goddard Institute for Space Studies, New York, concludes: “If global emissions of carbon dioxide continue to rise at the rate of the past decade, this research shows that there will be disastrous effects, including increasingly rapid sea level rise, increased frequency of droughts and floods, and increased stress on wildlife and plants due to rapidly shifting climate zones.” ... Climate changes are so large with ‘business-as-usual’, with additional global warming of 2-3ºC (3.6-5.4ºF) that Hansen concludes “‘business-as-usual’ would be a guarantee of global and regional disasters.”
However, the study finds much less severe climate change – one-quarter to one-third that of the "business-as-usual" scenario – when greenhouse gas emissions follow the alternative scenario. “Climate effects may still be substantial in the 'alternative scenario’, but there is a better chance to adapt to the changes and find other ways to further reduce the climate change,” said Sato.
While the researchers say it is still possible to achieve the “alternative scenario,” they note that significant actions will be required to do so.
">http://www.nasa.gov/centers/goddard/news/topstory/2007/danger_point.html] FEATURE Research Finds That Earth's Climate is Approaching 'Dangerous' Point