think or thwim

I was surprised by the urgency of this article.

Jon Gertner interviewed water managers all over the southwestern United States for his article on the predicted water crisis. They used words like catastrophe and armageddon to describe the water shortages they see coming in their region.

That may sound over the top, but the area’s major reservoirs, Lake Powell and Lake Mead, are currently only about 50% full. Lake Mead was slightly lower in 1955 and 1964 (Powell wasn’t built until 1965), but the system is more stressed now. There are more people relying on that water, and the climate models indicate that there may not be enough rain to fill them. The Southern Nevada Water Authority is racing to install a lower water intake from Lake Mead before the lake level falls below the existing intakes that supply Las Vegas. Of course, the trend could reverse any time, but a lot of knowledgeable people are convinced that the current dry spell is the beginning of a permanent change.

From Gertner’s article:

Steven Chu, a Nobel laureate and the director of the Lawrence Berkeley National Laboratory, one of the United States government’s pre-eminent research facilities, remarked that diminished supplies of fresh water might prove a far more serious problem than slowly rising seas. When I met with Chu last summer in Berkeley, the snowpack in the Sierra Nevada, which provides most of the water for Northern California, was at its lowest level in 20 years. Chu noted that even the most optimistic climate models for the second half of this century suggest that 30 to 70 percent of the snowpack will disappear. “There’s a two-thirds chance there will be a disaster,” Chu said, “and that’s in the best scenario.”

The southeastern US is also in the middle of a severe drought, but the climate models aren’t predicting armageddon there. Texas seems to be the only place in the southern US with full lakes at the moment, but the aquifers are falling there too.

Read the rest of Jon Gertner’s article: The Future is Drying Up

It was in the 10/21/07 New York Times Magazine, but I’m linking to Truthout’s reprint to avoid the NYT’s ridiculous registration page.

climate change, rainfall, water, weather

This map from the Lamont-Doherty Earth Observatory shows the projected average precipitation over the next 50 years compared to the average precipitation over the last 50 years.

It’s going to get much dryer at the equator and wetter at the poles.

…nineteen different climate modeling groups around the world, using different climate models, show widespread agreement that Southwestern North America - and the subtropics in general - are on a trajectory to a climate even more arid than now.

I didn’t find a map, but the southern Europe/Mediterranean/Middle East region is also expected to dry significantly.

This graph from the original article in Science Magazine shows the results of all 19 models. This century is divided into five 20 year segments. Almost all of the predictions fall on the negative side of the line.

climate change, rainfall, weather

This map is from the lecture notes of Dr S.E Jones at The School of Ocean Sciences, University of Wales - Bangor. There is a link to it under 3) Patterns of Climate. It looks like a class I’d like to take.

Check out the green band that the circles the globe through South America, Africa, and Asia. I knew each of those places had high rainfall, but I’d never put them together before. From Jones’ notes:

Rainfall is highest near equator (rising air is warm so can store a lot of water vapour). Most tropical rainfall is convective: prolonged heavy showers and thunderstorms.

At high latitudes precipitation is low because the air is too cold to hold much water vapour. Subtropical high pressure belts have low rainfall (stable conditions due to high pressure) while northern mid-latitudes have moderate rainfall, much of it frontal, which diminishes into the interiors of North America and Asia.

He has another equally interesting animation showing temperature. I didn’t put it here because two animated gifs on one page is too many.

animated maps, climate, data visualization, maps, rainfall, temperature, weather