NASA - Climate Approaching 'Dangerous' Point
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 authors use the model for climate simulations of the 21st century using both ‘business-as-usual’ growth of greenhouse gas emissions and an ‘alternative scenario’ in which emissions decrease slowly in the next few decades and then rapidly to achieve stabilization of atmospheric CO2 amount by the end of the century. 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.”