Before seeing that amazing story, I was all set to lead with the “unprecedented” rains soaking the Washington, DC area:
“I can’t recall flooding like this. This is unprecedented,” [Virginia Department of Transportation spokesman] Morris said.
The unrelenting rains, sometimes falling at four inches an hour….
Capital Weather Gang’s Jason Samenow points me to this post, which has more details on our deluge:
Fort Belvoir, Va., recorded at least (last ob with rain total was 7:55 p.m.) an incredible 8.82” with as much as 7.03” coming during a three-hour stretch during the evening. It has received a stunning 13.52” since Monday.
And let’s not forget Irene’s recent devastating 1-in-100 year deluge, which was “the most devastating weather event ever to hit the region” where I grew up near the Catskill Mountains of New York state. It also set “the greatest single-day rainfall in Vermont’s history” by over an inch.
What’s going on?
Well, a very basic prediction of climate science is that as you warm the planet you get more water vapor in the atmosphere and more rain comes down in extreme deluges. Observations reveal that is already happening, and the recent scientific literature has said that is extremely likely that human emissions are the cause of this increase in precipitation intensity. Climate Progress ran through the recent literature in this February post, “Two seminal Nature papers join growing body of evidence that human emissions fuel extreme weather, flooding that harm humans and the environment.”
In a new report by by the scientific group Climate Communication, “Current Extreme Weather and Climate Change” report, top climatologists scientists spell out how human-caused global warming is loading the dice for the extreme weather seen in the past year. You can listen to a press conference held Wednesday by Jeff Masters and Jerry Meehl and Kevin Trenberth and Richard Somerville here.
Trenberth, of the National Center for Atmospheric Research, explained the deluge-warming connection in an interview with Climate Progress last year:
I find it systematically tends to get underplayed and it often gets underplayed by my fellow scientists. Because one of the opening statements, which I’m sure you’ve probably heard is “Well you can’t attribute a single event to climate change.” But there is a systematic influence on all of these weather events now-a-days because of the fact that there is this extra water vapor lurking around in the atmosphere than there used to be say 30 years ago. It’s about a 4% extra amount, it invigorates the storms, it provides plenty of moisture for these storms and it’s unfortunate that the public is not associating these with the fact that this is one manifestation of climate change. And the prospects are that these kinds of things will only get bigger and worse in the future.
I also recommend his 2011 review paper, “Changes in precipitation with climate change,” which elaborates on this with extensive citations of the scientific literature. The abstract begins:
There is a direct influence of global warming on precipitation. Increased heating leads to greater evaporation and thus surface drying, thereby increasing the intensity and duration of drought. However, the water holding capacity of air increases by about 7% per 1°C warming, which leads to increased water vapor in the atmosphere. Hence, storms, whether individual thunderstorms, extratropical rain or snow storms, or tropical cyclones, supplied with increased moisture, produce more intense precipitation events. Such events are observed to be widely occurring, even where total precipitation is decreasing: ‘it never rains but it pours!’ This increases the risk of flooding.
The atmospheric and surface energy budget plays a critical role in the hydrological cycle, and also in the slower rate of change that occurs in total precipitation than total column water vapor. With modest changes in winds, patterns of precipitation do not change much, but result in dry areas becoming drier (generally throughout the subtropics) and wet areas becoming wetter, especially in the mid- to high latitudes: the ‘rich get richer and the poor get poorer’. This pattern is simulated by climate mod- els and is projected to continue into the future
Dry areas get drier, wet areas get wetter. Hell and High Water. And you ain’t seen nothing yet since we may see another 5°C warming this century!
- Last year, we had Tennessee’s 1000-year deluge aka Nashville’s ‘Katrina’.
- Coastal North Carolina’s suffered its second 500-year rainfall in 11 years.
- Craig Fugate, who heads the U.S. Federal Emergency Management Agency, said in December, “The term ’100-year event’ really lost its meaning this year” (see Munich Re: “The only plausible explanation for the rise in weather-related catastrophes is climate change”).
- Northern Territory Chief Minister on Carlos’s deluge: “So a really one in 500 year event; nobody’s experienced anything like this before”
- High Water: Aussie inland tsunami labelled 1-in-370 year event
- In other UK news: “Rain like this happens once every 1,000 years”
- Yes, “human-induced increases in greenhouse gases have contributed to the observed intensification of heavy precipitation events” over much of the NH