The dramatic fall of Poyang Lake in landlocked southeastern Jiangxi Province had otherwise cut off irrigation canals to nearby farmland. Crews, using backhoes to dig trenches, work only after dark due to extreme heat during the day, the official Xinhua news agency reported. A severe heat wave is wreaking havoc across much of southern China. High temperatures have fueled mountain fires that have forced the evacuation of 1,500 people in the southwest and factories have been ordered to cut output as hydro plants reduce output amid drought conditions. Extreme heat and drought have withered crops and shrunk rivers, including the giant Yangtze, disrupting cargo traffic. Fed by China’s major rivers, Poyang Lake averages about 3,500 square kilometers (1,400 sq mi) in the high season, but has shrunk to just 737 square kilometers (285 sq mi) in the recent drought. As determined by the water level, the lake officially entered this year’s dry season on August 6, earlier than at any time since records began in 1951. Hydrological surveys prior to that time are incomplete, although it appears that the lake it may be at or near its lowest level in recent history. Along with providing water for agriculture and other uses, the lake is an important stopover for migratory birds heading south for the winter. A wide swath of western and central China saw days of temperatures exceeding 40 degrees Celsius (104 Fahrenheit) in heat waves that started earlier and lasted longer than usual. The heat is likely linked to human-caused climate change, although scientists have yet to do the complex calculations and computer simulations to say that for sure. “The heat is certainly on record and is certainly being exacerbated by human-caused climate change,” said Maarten van Aalst, director of the Red Cross Red Crescent Climate Center in the Netherlands. “Drought is always a little more complicated.” The “really shocking temperatures that are baking China” are linked to a stuck jet stream — the river of air that moves weather systems around the world — said Jennifer Francis, a climatologist at the Woodwell Climate Research Center in Falmouth, Massachusetts. He said an elongated area of relatively high atmospheric pressure parked over western Russia was responsible for both China’s and Europe’s heat waves this year. In the case of China, high pressure prevents cool air masses and precipitation from entering the region. “When hot, dry conditions stick, the soil dries out and heats up more easily, enhancing the heat dome even more,” Francis said. In the hard-hit city of Chongqing, some malls have been told to open only from 4 to 9 p.m. to save energy. Residents seek respite in air raid shelters dating back to World War II. This reflects the situation in Europe and elsewhere in the northern hemisphere, with high temperatures affecting public health, food production and the environment.
Associated Press science writer Seth Borenstein in Washington, DC, contributed.
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