Was the extreme heat and dryness of the summer of 2012 the result of climate change?

“It’s the old problem of saying any one event is the result of climate change.” That’s James McCarthy, professor of biological oceanography at Harvard and current president of the board of the Union of Concerned Scientists, speaking September 21st in New York City at an event hosted by the Union.

“We have been locked in a two year now strong La Nina cycle. The La Nina cycle brings more aridity to the center of continents. Would it have been, from previous La Ninas, likely to be as dry as it is now, setting record after record of number of days over 100 degrees, number of days without rain?

“This year we actually hit a point where there were 400 parts per million of CO2 in the atmosphere. If it was more like 350 or maybe 280, which is what it was in the middle of the 19th century, would this have been as likely? And we’d say no, the odds of this would have been far less likely. It could have still occurred, but it would have been an extremely rare event. And as we look forward, this is going to be more common.”

—Steve Mirsky

[The above text is a transcript of this podcast.]