Drought, then and now

I am just back from a week in California, which is experiencing a brutal, historic drought.

As I flew there and back, the lakes, reservoirs and dams all looked like this photo: drained and still-dwindling.

Running out of water is a chilling prospect, as some well-users there are already experiencing.

Really, this is the stuff of nightmares. When you get right down to basics, water probably comes right after air as something we simply cannot live without – no ifs, ands or “should haves”.

And while California is the hapless poster child for water shortages, much of the west is hurting too.

Why is this happening? Experts weighing that question derive some conclusions from the “Dust Bowl” experienced in the 1930s. A new NASA study puts the historical record in perspective:

Using a tree-ring-based drought record from the years 1000 to 2005 and modern records, scientists from NASA and Lamont-Doherty Earth Observatory found the 1934 drought was 30 percent more severe than the runner-up drought (in 1580) and extended across 71.6 percent of western North America. For comparison, the average extent of the 2012 drought was 59.7 percent.

In the U.S., debate about things like global warming and this recent drought tends to argue about natural or human causes. This NASA study finds both were in play:

Two sets of conditions led to the severity and extent of the 1934 drought. First, a high-pressure system in winter sat over the west coast of the United States and turned away wet weather – a pattern similar to that which occurred in the winter of 2013-14. Second, the spring of 1934 saw dust storms, caused by poor land management practices, suppress rainfall.

“In combination then, these two different phenomena managed to bring almost the entire nation into a drought at that time,” said co-author Richard Seager, professor at the Lamont-Doherty Earth Observatory of Columbia University in New York. “The fact that it was the worst of the millennium was probably in part because of the human role.”

The high-pressure ridge that effectively blocks wet weather may be beyond human control. But there’s hope better land use practices to combat erosion will help this time around.

Dust clouds reflect sunlight and block solar energy from reaching the surface. That prevents evaporation that would otherwise help form rain clouds, meaning that the presence of the dust clouds themselves leads to less rain, Cook said.

“Previous work and this work offers some evidence that you need this dust feedback to explain the real anomalous nature of the Dust Bowl drought in 1934,” Cook said.

Still, it’s best to not rest on those laurels.

…agricultural producers need to pay attention to the changing climate and adapt accordingly, not forgetting the lessons of the past, said Seager. “The risk of severe mid-continental droughts is expected to go up over time, not down,” he said.

If we’re lucky, then, the weather ridge could shift to allow rain and snow pack back to the parched west. And while these explanations are helpful, there may be more to the story as well.

It’s just scary, damned scary, to see what too little water can mean.

Tags: California, drought, dust bowl, environment, NASA, water, weather