Jumping the gun

‘If I hear one more person say, ‘So much for global warming ….’”

A colleague uttered those words recently and the exasperation was all too familiar. A tiny shift in weather is regularly taken as meaningful when it’s not.

For instance, on Feb. 16, 1990, in the middle of a multiyear drought, western Nevada was hit with a major snowfall. It was followed immediately by premature “Is the drought over?” news stories.

It is akin to a comment Donald Trump made in a New York Times interview during the campaign—“You know the hottest day ever was in 1890-something. Ninety-eight.”—as though it had meaning. He never provided any verification for that bit of trivia, but even if what he had said was true, scientists and fact-checkers quickly pointed out that one point in time is not a trend. It may, indeed, be an exception or anomaly.

Far from the snowfalls this year disproving climate change, University of Nevada, Reno, scientist Glenn Miller said they are exactly “what you would expect to happen” with warming.

“This is one of the symptoms of global warming,” he said. “If you have a lot more water evaporate, that water is going to come down at some point. This is exactly consistent with global warming. You have more extreme events happening.”

Thus, hotter summers, colder winters. “Stronger events” also are a cause of shorter autumns and springs.

The Union of Concerned Scientists, a nonprofit science advocacy organization, has said extreme events like flooding, heavy snowfalls and downpours can all be signs of global warming. Of course, it is possible to assess this year’s heavy precipitation without reading more into it than there is. Some have been trying to do that.

Heather Emmons, spokeswoman for the Natural Resources Conservation Service, an agency of the U.S. Department of Agriculture, issued a statement that said what is significant about this winter is its resemblance to 1983.

“Nineteen-eighty-three is a winter talked about with awe and reverence by snow surveyors and water managers in the Western United States,” the statement said. “Putting it in the same sentence as 2017 indicates that we have a real heavy hitter at bat this winter.”

The numbers across the Western United States are impressive. In the Northern Sierra alone, precipitation this past January and February was nearly 300 percent of normal, according to the state Department of Water Resources’ California Data Exchange Center.

Another place where there could be a jump to conclusions is in the Western drought. There have been a lot of headlines: “California snowpack could bring five-year drought to its knees” and “Drought finally over in nearly every part of California.”

But no scientist has called an end to the drought. After all, an extreme winter could easily be followed by an extreme summer that undoes a lot of the gains.

At Nevada’s Lake Mead, where the “bathtub ring” and the lake’s dramatic fall have been used incessantly to illustrate the drought, the winter has raised the lake a bit, but Bureau of Reclamation spokeswoman Rose Davis still told KLAS News, “It’s a very important concept to remember that nobody’s out of drought. … I mean, regardless of what you’re seeing on the flooding in California and other places, one year doesn’t undo drought.”

And amid all the snow, the journal Water Resources Research last month issued a study that said, in part, “Fifteen years into the 21st century, the emerging reality is that climate change is already depleting the Colorado River water supplies at the upper end of the range suggested by previously published projections. Record-setting temperatures are an important and underappreciated component of the flow reductions now being observed.”

The study was done by hydrology researchers Brad Udall of Colorado State University and Jonathan Overpeck of the University of Arizona. Forty million people rely on the Colorado’s water, and its volume is down 19 percent as a result of the drought.

In a Wired essay, hydroclimatologist Peter Gleick wrote that there are two kinds of drought.

“But another key variable is temperature. Temperature determines, among other things, the demand for water by crops, vegetation and people, and especially the ratio of snow to rain that falls in the mountains. The past five years were by far the driest and hottest in more than a century of record-keeping—in part because of human-caused climate change—and those high temperatures played a key role on worsening the scarcity of water and devastating the snowpack.

“This combination of hot and dry led to massive groundwater overdraft, cutbacks to farmers, loss of snow storage in the mountains, reductions in hydropower production, and a range of voluntary and mandatory restrictions on urban water use. And while the wet year may end the ‘precipitation drought,’ higher and higher temperatures and a persistent ‘snow drought’ are here to stay.”