“In the Colorado floods of 2013, we got a sobering glimpse of a future that will only worsen if we don’t act now,” Susan Secord of Citizens’ Climate Lobby in Boulder said in a Dec. 27 op-ed in The Denver Post. “A planned, orderly economic adjustment now will save us from having to make very expensive and chaotic adjustments later.”
The floods along the Front Range also have become a campaign issue in this year’s tight U.S. Senate race. The liberal environmental group NextGen Climate, founded by billionaire Tom Steyer, has cited the floods as an example of climate change devastation in campaign materials attacking Rep. Cory Gardner, a Republican who is running against Democratic Sen. Mark Udall.
Warmer surface temperatures trigger moisture in the atmosphere, which tends to cause heavy rains, but the study said that was not what prompted the floods last year. A slow-moving, wet air mass, possibly the remnant of a tropical system, pushed up against Boulder’s steep mountains and was trapped, producing five straight days of rain, researchers concluded.
In fact, the scientists behind the study added that the probability of such an event “has likely decreased due to climate change.” They noted that similar systems hit the Front Range long before the advent of elevated carbon dioxide levels in the atmosphere.
“From an observational perspective, analogous events have occurred before in the Front Range, perhaps most strikingly similar in September 1938, long before appreciable climate change,” the study said.
In analyzing the 16 extreme weather events, the studies found that last year’s heat waves — in Australia, Asia and Europe — were more likely to be linked to changes in the climate than other disasters, such as droughts, storms and hurricanes, “indicating that natural variability likely played a much larger role in these extremes.”
In fact, the report included three studies on the California drought, but none of those could find a definitive link between climate change and the state’s long-standing below-average rainfall.
“The comparison of the three studies for the same extreme event, each using different methods and metrics, revealed sources of uncertainty,” the report says.
Stanford University researchers issued a study Monday — the same day as the release of the American Meteorological Society report — saying that the high-pressure system blocking California rains is “very likely” connected to human-caused climate change.