Friday, August 19, 2011

Texas Drought Now Equals Worst in History

Back in the spring I wrote a couple of posts arguing that some of the rhetoric at the time about the Texas drought seemed overwrought relative to what the data showed. This morning a reader emails me a link to the latest data for July PDSI:

NOAA's graph software is a bit buggy as the July 2011 bar doesn't show full width, but if you look closely you can see that there's a trace of color all the way down to -7.25 which is the worst July in the historical record.  So the drought has continued and intensified and is now up there amongst the worst. It's not yet the worst month ever - that honor seems to belong to September 1956 when the PDSI reached -7.8.  However, as the map up top makes clear, the drought is not over yet and it could well be the worst Texas drought ever before it's done.

I don't think we have license to attribute it to climate change yet, however, since there's no overall trend in the Texas PDSI data (in contrast to California) and the drought is not yet bad enough to argue that we've crossed some kind of threshold into an ahistorical climate state.


Joseph said...

"I don't think we have license to attribute it to climate change yet"

And there's the rub: by the time we do have "license," it will probably be too late to do anything for the Lone Star State.

Or for New Mexico, as well, as the Southwest moves into a new climate era. With accelerating climate change, we may no longer be able to "assign" climates to areas, as the shift continues.

But we can say some things: West Texas in particular is probably not a place where one would want to lend money in the form of a 30 year mortgage-- no good way of being sure that the land or improvements will be worth anything at the end of the term.

Stuart Staniford said...

There's a very nice discussion of the summer's weather patterns here

Kobayashi said...

Don't forget that Texas (NM etc.) are roughly on the same latitude as Algeria, Marocco, Lybia etc. or in other words the Sahara region.

Texas and other SW, drier states are just too dry. Of course this wasn't a problem until you could AC everyting as much as you wanted and irrigate and sprinkle away everything with precious groundwater.

But as the groundwater levels are dropping and energy prices are increasing this lifestyle will be unsustainable.

Good luck for them.

Alexander Ac said...


we are not sure to attribute *any* weather event to climate change, so we do not need to reduce CO2 (yet).

That is great news for endless economic growth and also Paul Krugman who thinks only alien invasion can help US economy:

Robert said...

One of my very earliest childhood memories. Caught in a dust storm during a Sunday drive out of Amarillo. A neighbor ( google H H Finnell) was a leader in designing practices to help eliminate these storms.

Hypnos said...

I think it is irresponsible not to mention Climate Change in a discussion over climate extremes. This is exactly what the theory says: global warming will bring more intense weather phenomena, including temperatures extremes, drought, and storms.

The global climate is hotter and wetter; there is more energy floating around. No single event can be attributed to climate change, and every climate event will continue to have a normal - but stronger - signature. Is El Nino increasing in intensity a natural phenomenon, or due to climate change? It's both.

Trends will start to build up. Some already have. But it must be made clear to the public consciousness that this is what climate change is about, and that there will never be a moment where you can say "This is 100% climate change caused".

Stuart Staniford said...


If the null hypothesis is "climate change is having no effect on droughts in Texas" then the data are perfectly consistent with that hypothesis - there is no trend in the data and the current event is not outside the envelope of historical events back when climate forcings where a lot smaller.

Therefore you cannot use droughts in Texas as any kind of evidence that climate change is happening or is bad. This is quite apart from the fact that any single event is hard to use as evidence - there simply is no trend, suggesting that Texas droughts are not sensitive indicators of climate change (in contrast say to Antarctic glaciers or polar ice sheets or probably even droughts in California all of which evince clear change in the climate-change-expected direction that cannot be explained by the respective null hypotheses).

Stuart Staniford said...

(I should add that this could of course change if the drought goes on and on and gets worse and worse - there will come some point at which it's sufficiently anomalous that it would provide evidence of something new happening - but of course it would be evidence of some kind of non-linear change in regime since there's no prior trend).

Fixed Carbon said...

While Texas doesn't have a time series signal of increasing Palmer DSI, Arizona does appears to have a trend to drier. That huge California, ranging across multiple climate zones is trending, is fascinating. Breaking down California geographically would be fun.

Robert said...

One of the Woody Guthrie dust bowl songs

Michael Cain said...

While the current drought may not be indicative of anything, this whole year might be considered something of a live demonstration of what the models are predicting for the US West: drier across the southern tier of states (plus the corresponding portions of California and Nevada); wetter winters and springs across the norther tiers.

Flooding along most of the Missouri; California reservoirs that haven't been near full for decades filled to the brim; so much water in the Pacific NW that they had to back off wind and fossil fuel electricity production to allow release of enough water to protect the dams. This year's problem from California to Nebraska wasn't too little water, it was too little storage.

One of the Senators from South Dakota wants to change the Army Corps of Engineers' policy for the Missouri to pure flood control, which would generally require that the reservoirs be drawn down to near empty at the end of each year. I'm waiting for Texas to suggest an aqueduct that would dwarf the Central Arizona Project to bring "excess" water from South Dakota to West Texas.

rsg said...

Oct 25: Texas Climate News (new to me) reporting that 2011 drought equaled only once in nearly 500 years of tree ring data.

"Texas’ average PDSI this past summer (June through August) was -5.37 – the lowest, indicating the most severe drought conditions, since the start of the instrumental record in 1895.

And according to the federal government’s National Climatic Data Center, there was apparently only one other year during the last 461 years when Texas had a drought so severe."