Earth's 'Tipping Points': How Close Are We?
Abrupt changes in climate are now an established phenomenon in Earth's history, and there is growing concern that our planet may be at a "tipping point" of dramatic climate change, this time due to human factors. Scientists from across different disciplines are now looking at many parts of the Earth system for signs of such pivotal shifts either already underway or likely to happen in this century.
This briefing will present the latest results from the perspective of global climate as well as potential impacts on three key regions of the globe. James Hansen discusses the "unrealized" global warming of Earth's climate system and the resulting need for urgent action to cut emissions beyond carbon dioxide. Richard Alley discusses the possibility that sustained warming of a few decades could produce major ice sheet losses that would last centuries. Peter Webster reports on a societal tipping point along three heavily populated Asian river basins when climate-induced changes to river flows collide with population growth. Joey Comiso reports that this year's large Arctic sea ice decline may be the tipping point for perennial ice and a recovery may no longer possible in the foreseeable future.