While the good news is that the U.S. Geological Survey (USGS) report issued last week finds that "abrupt" climate change is unlikely in the 21st century, the bad news is that such "abrupt" changes are possible and present models cannot even predict some of the potential changes.
Among the conclusions contained in the report are: (1) there will be "rapid and sustained arctic September sea ice loss", (2) the potential for sustained drought in the southwestern United States has increased, (3) there will likely be a decrease in the northward flow of warm water in the upper layers of the Atlantic Ocean and (4) there will likely be an increase in the release of methane gas deposits from the earth.
As reported in the Washington Post, perhaps one of the most disturbing conclusions is the possibility of an even greater rise in sea level by the year 2100 than was previously predicted. The original projection was for a 1.5 foot increase in sea level by the next century, but observations over the last two years demonstrate that major ice sheets are melting more rapidly than originally thought. Therefore, the rise in sea level may actually be as much as four feet. The USGS has created a Website which addresses issues relating to glaciers and climate change.