Must-Read on 2011’s Unprecedented Rains and Wet-Dry Extremes, Just What You’d Expect From Global Warming

by Jeff Masters, cross-posted from the WunderBlog.

Rains unprecedented in 117 years of record keeping set new yearly precipitation totals in seven states during 2011, NOAA’s National Climatic Data Center revealed in its preliminary year-end report for 2011.

An extraordinary twenty major U.S. cities had their wettest year on record during 2011. This smashes the previous record of ten cities with a wettest year, set in 1996, according to a comprehensive data base of 303 U.S. cities that have 90% of the U.S. population, maintained by Wunderground’s weather historian Christopher C. Burt. Despite the remarkable number of new wettest year records set, precipitation averaged across the contiguous U.S. during 2011 was near-average, ranking as the 45th driest year in the 117-year record. This occurred because of unprecedented dry conditions across much of the South, where Texas had its driest year on record.

2011 sets a new U.S. record for combined wet and dry extremes [see top graph]If you weren’t washing away in a flood during 2011, you were probably baking in a drought. The fraction of the contiguous U.S. covered by extremely wet conditions (top 10% historically) was 33% during 2011, ranking as the 2nd highest such coverage in the past 100 years. At the same time, extremely dry conditions (top 10% historically) covered 25% of the nation, ranking 6th highest in the past 100 years. The combined fraction of the country experiencing either severe drought or extremely wet conditions was 58% — the highest in a century of record keeping. Climate change science predicts that if the Earth continues to warm as expected, wet areas will tend to get wetter, and dry areas will tend to get drier — so 2011’s side-by-side extremes of very wet and very dry conditions should grow increasingly common in the coming decades.


23rd warmest year on record, and 2nd hottest summer for the U.S.The year 2011 ranked as the 23rd warmest in U.S. history, with sixteen states recording a top-ten warmest year on record. Delaware had its warmest year on record, and Texas its second warmest. However, these statistics don’t convey the extremity of the summer of 2011 — the hottest U.S. summer in 75 years. The only hotter summer — and by only 0.1° — was the Dust Bowl summer of 1936, when poor farming practices had turned much of the Midwest into a parking lot for generating extreme heat. The June — August 2011 average temperatures in Texas and Oklahoma were a remarkable 1.6°F and 1.3°F warmer than the previous hottest summer for a U.S. state — the summer of 1934 in Oklahoma. The U.S. Climate Extremes Index (CEI), which is sensitive to climate extremes in temperature, rainfall, dry streaks, and drought, indicated that an area nearly four times the average value was affected by extreme climate conditions during summer 2011. This is the third largest summer value of record, and came on the heels a spring season that was the most extreme on record. When averaged over the entire year, 2011 ranked as the 8th most extreme in U.S. history, since the fall weather was near-average for extremes. The CEI goes back to 1910.

Wunderground’s weather historian Christopher C. Burt has a more detailed look at the U.S. extremes observed during 2011 in his latest post. His selection for the most remarkable yearly record set during 2011:

Perhaps, most astonishing is the total annual rainfall of just 1.06” at Pecos, Texas (normal annual precipitation is 11.61”). If confirmed this would be a Texas state record for least amount of precipitation ever recorded in a calendar year, the current record stands at 1.64” at Presidio in 1956. — Jeff Masters is co-founder of the Weather Underground. This piece was originally published Masters’ WunderBlog.

For background on the science of extreme weather with links, see these Climate Progress posts:

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.