The heat is on.

• Author: Florence, Joseph
• Position: EYE ON ECOLOGY - Reports on global temperature

THE YEAR 2005 WAS THE HOTTEST on record. The average global surface temperature of 58.6[degrees]F was the highest since such data has been kept, beginning in 1880. January, April, September, and October of 2005 were the hottest of those months on record, while March, June, and November were the second warmest ever. In fact, the six hottest years all have occurred in the last eight years. These readings, which come from the series maintained by NASA's Goddard Institute for Space Studies, continue a trend of higher global temperatures. During the past century, temperatures rose 1.44[degrees]F 0.6[degrees] of which occurred during the last three decades, a rate unprecedented in the last millennium.

Elevated temperatures primarily are due to the buildup of greenhouse gases in the atmosphere, particularly carbon dioxide (C[O.sub.2]) from the burning of fossil fuels. Once released, C[O.sub.2] traps heat that would otherwise escape back into space--and these carbon dioxide emissions have been on the rise since the start of the Industrial Revolution in 1760.

Two recent reports demonstrate the exceptional levels of current global temperature and atmospheric C[O.sub.2]. Using records stored in ice, tree rings, and fossils, scientists have estimated that the Northern Hemisphere is warmer now than at any time in the past 1,200 years. Another study revealed that atmospheric levels of C[O.sub.2] and methane, yet a different greenhouse gas, are higher today than at any time in the A last 650,000 years.

As greenhouse gas emissions continue to build up, so, too, will the pace of climate change. By 2100, the average global temperature is projected to rise 1.4[degrees] to 5.8[degrees]C relative to the 1990 level, according to the Intergovernmental Panel on Climate Change, a global body of more than 1,500 scientists. There is little question that a global temperature increase in the upper range of predictions would be highly disruptive. As temperatures rise, so, too, do the health risks from heat waves, failing crops, infectious diseases, and other environmental changes. People already facing food insecurity particularly could be distressed because with each 1[degrees]C jump in temperature above optimal levels, wheat, rice, and corn yields fall by 10%. Even at the lowest projected temperature increases, climate change models predict more frequent and more severe storms, floods, heat waves, and droughts--all of which would affect biodiversity, human health, and...