UN report warns of extreme heat and deluges

A United Nations report this week outlined the water scarcity, flooding and extreme heat risks possible within decades due to global warming. Though the U.N. Intergovernmental Panel on Climate Change focused on “rapid, far-reaching” actions needed to avert calamity the world over, it spelled out specific dangers for North America. Heavy rainfall, extreme heat and economic fallout could worsen in North America if the atmosphere rises another degree Celsius above preindustrial levels, the report said. The Earth already is 1 degree Celsius (1.8 degrees Fahrenheit) above, and whether it jumps to 1.5 or 2 degrees C (2.7 to 3.6 F) in coming years could make a big difference. Extreme heat gets worse: The highest levels of warming for extremely hot days would occur in the eastern and central USA – from the Dakotas south to Texas and toward the East – as well as parts of Asia, Africa, Europe and the Mediterranean. Soil in those regions tends to dry out. The Earth's surface uses available water to cool off, just like humans do with sweat, said Natalie Mahowald, a Cornell University climate scientist who helped author the report. “If there is no water to evaporate, then there is more increase in temperature, since the surface can't cool by evaporating water,” she said. Heavy rain more likely: Topping 2 degrees Celsius would risk increasing heavy rainfall from Ohio to Georgia and toward the East, one of several regions where the largest increases in extreme rain and snow would occur. Economic tolls: A study led by Solomon Hsiang at the University of California-Berkeley said America's economic damage equates to about 1.2 percent of the U.S. gross domestic product for every 1 degree increase in warming.