Colorado flood not linked to climate change, federal scientists say

Last September’s heavy rainfall and flooding in and around Boulder, Colo., were not likely caused by climate change, government scientists concluded.

Climate researchers from the National Oceanic and Atmospheric Administration (NOAA) said in a Thursday report that a warming climate does put more moisture into the atmosphere.


“The model results confirmed that warming has increased the amount of ‘precipitable water’ — the amount of moisture available to be rained out of the atmosphere,” the agency said. “But the increase did not translate into more frequent or stronger September rains.”

In fact, comparing records from the late 19th century with recent years shows that while the climate is warming, heavy rain events in that area are becoming less frequent.

But Klaus Wolter, a University of Colorado-Boulder meteorologist who works with NOAA, said increased atmospheric moisture is not the only factor that could increase flooding.

Boulder’s flooding was related to the remnants of a tropical system, NOAA said.

Wolter and others are still studying whether increased atmospheric moisture from climate change could increase flooding.

“This [decrease in heavy rain frequency] is a regional trend … not a national or global one, and our study only applies to September,” NOAA wrote, quoting Wolter. “We would want to repeat this analysis for different times of year, especially the late spring, which are our wettest months.”

Despite the Boulder flooding, climate change is generally increasing heavy rain events in the United States, NOAA said.