Experts say warmer atmosphere increases chances for extreme precipitation events
By Summit Voice
SUMMIT COUNTY — This week’s news that average global temperatures set a new record in May also triggered some discussion among climate scientists and journalists whether it’s time to start discussing extreme weather events in the context of global warming. The recent floods in Tennessee and Oklahoma were singled out as examples.
At best, the researchers gave a proceed-with-caution message, warning that a direct linkage between global climate change and localized events is hard to pinpoint. Reporting those events as being caused by climate change could be perceived as alarmist.
On the other hand, simply ignoring scientific evidence that global warming does produce changes consistent with extreme weather events is also not accurate. Reporting such events without at least placing them in the context of a changing climate misses an opportunity to inform the public about the potential impacts of global warming in a real-time, meaningful way, rather than as an abstract scientific context, said Andrew Freedman, writing in the Washington Post — in other words, “guilty by the sin of omission.”
Freedman says the media barely raised the issue of climate change in reporting on the Tennessee floods. That made the reporting inconsistent with scientific evidence showing that warmer temperatures result in more water vapor in the air, and thus, the potential for more precipitation.
Because of simple physics (warm air can hold more moisture than cold air) the bottom line is that warmer temperatures do cause an increased chance of heavy precipitation events. In his well-respected weatherblog, Dr. Jeff Masters, of Weather Underground has this to say:
- “… it is likely that the flooding in some of this year’s U.S. flooding disasters were significantly enhanced by the presence of more water vapor in the air due to global warming. We can expect a large increase in flooding disasters in the U.S. and worldwide if the climate continues to warm as expected.”
Masters also points out that the recent major flooding events in the U.S. were all associated with air masses that brought record-breaking high temperatures along with the rain. Preceding the June 11 Arkansas flood, more than 50 weather stations in the region reported record temperatures for the date. Similarly, the air mass that spawned the Oklahoma City floods set record warm minimum temperatures at 22 airports across the central and Eastern portions of the U.S.
And climate scientist Kevin Trenberth had this to say in an interview with New York Times climate reporter Andrew Revkin:
- “The way I think about is that for precipitation there is a shift in distribution caused by increased water vapor. So everything we see has an element of global warming but is dominated by weather/natural variability. At the low or middle range, a small shift still makes everything well within the normal distribution from the past but at the top end, the shift pushed events into new records and extremes. Even in cases where it is cold or where SSTs [sea surface temperatures] are cold, or where water vapor is low, they are still warmer/moister than they would have been without the global warming. The climate change acts in background in all these cases and is a pervasive influence.”
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