Overture

Recent investigations suggest that current atmospheric models underestimate future global warming. The Intergovernmental Panel on Climate Change estimates that the global average temperature could increase as much as 5.8°C by the end of the 21st century. But these estimates don't factor in some feedback mechanisms that may be triggered by rising temperatures. For instance, accelerated decomposition in soils and changes in ocean chemistry may add considerably to greenhouse gases and further intensify warming (http://sciencenow.sciencemag. org/cgi/content/full/2006/526/1?rss=1).

The current warming trends in the Arctic may shove the Arctic system into a seasonally ice-free state not seen for more than 1 million years. The melting is accelerating, and researchers were unable to identify natural processes that might slow the deicing of the Arctic. Such substantial additional melting of Arctic and Antarctic glaciers and ice sheets would raise the sea level worldwide, flooding the coastal areas where many of the world's population lives. Studies, led by scientists at the National Center for Atmospheric Research (NCAR) and the University of Arizona, show that greenhouse gas increases over the next century could warm the Arctic by 3–5°C in summertime. Thus, Arctic summers by 2100 may be as warm as they were nearly 130,000 years ago, when sea levels eventually rose up to 6 m higher than today (http://www.ucar.edu/news/releases/2006/melting.shtml).