Global warming to blame for Boulder floods? Yes and no.

Left Hand Canyon Drive was destroyed.
Photo by Stephen Hayes

This story is part of Our Road to Recovery, our coverage of the 2013 Boulder County floods.

A local scientist says the conditions that led to days of constant rain and devastating floods in Boulder County last week were not directly caused by climate change, but the amount of precipitation is a symptom of warmer atmospheric temperatures.

Dave Gochis, a hydrometeorologist at the National Center for Atmospheric Research in Boulder, says that any single weather event is a combination of very specific features interacting at a particular time, and the question to ask regarding climate change is whether global warming is conducive to such events.

“It’s really difficult to say, at this point,” he says, adding that while climate change is not going to increase the likelihood of those exact conditions reoccurring, “in general, a warmer atmosphere holds more moisture, so that when we get the right combination of events, there is a greater likelihood that more moisture will be involved.”

So he says the bottom line is that while global warming may not set up the rainclouds to do what they did, when that situation does reoccur, those clouds are likely to have more water in them than if the atmosphere were cooler.

“This atmosphere was really juicy, and when you push it up over the mountains, it gets rung out,” Gochis says.

Water content in the atmosphere varies widely depending on the temperature, he explains, so while some have speculated that if this storm had happened in the winter it would have generated as many feet of snow as it did inches of rain, that is false because a cold atmosphere carries much less moisture.

“Would we have gotten 16 feet of snow out of this?” Gochis asks. “The answer is no. It’s impossible.”


This story is part of Our Road to Recovery, our coverage of the 2013 Boulder County floods.