Editorial – The New York Times
The recent heat wave that has fried much of the country, ruined crops and led to heat-related deaths has again raised the question of whether this and other extreme weather events can be attributed to human-induced climate change. The answer, increasingly, is a qualified yes.
Mainstream scientists have always been cautious about drawing a causal link between global warming and any specific weather event; the world has experienced calamitous heat waves, droughts, wildfires and floods throughout its history. But they also agree that without sustained efforts to reduce greenhouse gases, dangerous heat waves are very likely to become more common, as will prolonged droughts and coastal flooding.
Many politicians and a vocal minority of scientists dispute such predictions as alarmist. What they cannot dispute are the numbers. According to the National Oceanic and Atmospheric Administration, the 11 years from 2001-11 rank among the 13 warmest globally since record-keeping began 132 years ago. The average temperature in the contiguous United States for the first six months of this year, the National Climatic Data Center reported on Monday, were the hottest recorded since 1895.
The Intergovernmental Panel on Climate Change, the United Nations body that examines climate change with help from thousands of scientists around the world, says that more frequent and potentially more damaging extreme weather events lie ahead. In a report last November assessing weather extremes, the panel said that “it is virtually certain that increases in the frequency and magnitude of warm daily temperature extremes and decreases in cold extremes will occur in the 21st century on the global scale.” If greenhouse gases continue unabated, it said, heat waves that now occur once every 20 years will be occurring every two years by the end of the century.
The climate panel is a judicious group, and it warned that against premature judgments. Following Hurricane Katrina, for instance, some climate experts suggested that rising global temperatures would produce more intense hurricanes. The panel said it did not have the evidence to establish such a link.
On the whole, however, its findings support the evidence presented by the basic science: warmer air makes heat waves and droughts more intense; warmer air also holds more water vapor, which increases the risk of destructive floods.
As Michael Oppenheimer, a Princeton University climate scientist and the lead author of the report, said: “A hotter, moister atmosphere is an atmosphere primed to trigger disasters.”
History is full of sad stories of humanity’s inability to see the writing on the wall — overplowing that helped produce the Dust Bowl, overfishing that has depopulated the oceans. The heat wave is merely the latest of many weather-related messages that should be easy to read. July 11,2012