2.14.14 | By Carolyn Lochhead:
White House science adviser John Holdren, a Stanford-trained physicist who taught at UC Berkeley and has studied the effects of environmental change for much of his career, says President Obama will address climate change in his visit to Fresno on Friday.
“You can certainly expect that the president will talk about the connection between the increasing frequency and intensity of droughts and climate change,” Holdren said Thursday in a conference call with reporters.
Although droughts are common in the West, California’s current episode is among the strongest of the past 500 years, according to paleo-climate records, and the worst since record-keeping began a century ago, Holdren said. He is director of the White House Office of Science and Technology Policy and co-chair of the President’s Council of Advisers on Science and Technology.
California isn’t the only place in the West experiencing an unusually severe drought, Holdren said. A long dry spell in the Colorado River Basin “is probably one of the strongest droughts in that area in the last 1,000 years,” he said.
While no specific episode of extreme weather can be linked to climate change, Holdren said, the link between droughts and a warming climate is one of the best understood.
The global climate “has now been so extensively impacted by the human-caused buildup of greenhouse gases that weather practically everywhere is being influenced by climate change,” Holdren said. That means droughts are becoming more frequent, more severe and are lasting longer, he said.
Holdren listed three ways climate change places stress on water supplies and the environment:
- A larger share of rainfall occurs as extreme downpours, meaning more rain is lost to storm runoff and less soaks into the ground.
- More precipitation in the mountains occurs as rain instead of snow. Snow stores water and releases it gradually into rivers through the spring and summer, whereas rain runs off immediately.
- Warmer temperatures increase evaporation from soil and reservoirs.
Although farm groups are clamoring for the administration to help build more reservoirs, Holdren said reservoirs are not the problem.
“The problem in California is not that we don’t have enough reservoirs,” Holdren said. “The problem is that there’s not enough water in them.”
He ticked off statistics showing major reservoirs running at 18 percent to 37 percent of capacity. “We just haven’t had enough water flowing into those reservoirs,” he said. “It wouldn’t help to build any more.”
http://blog.sfgate.com/nov05election/2014/02/14/obama-to-stress-climate-change-in-fresno/
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