Global Warming

Abstract

The fourth report of the United Nations’ Intergovernmental Panel on Climate Change (IPCC, 2007), published in 2007, tells us that:

• Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.

• Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in man-made greenhouse gas concentrations.

• It is very likely that hot extremes, heat waves and heavy precipitation events will continue to become more frequent.

• Continued greenhouse gas emissions at or above current rates would cause further warming and induce many changes in the global climate system during the 21st century that would very likely be larger than those observed during the 20th century.

• Sea ice is projected to shrink in both the Arctic and the Antarctic under all emission scenarios. In some projections, arctic late-summer sea ice disappears almost entirely by the latter part of the 21st century.