High temperatures in the Central Valley are expected to last through the end of the week.

America’s heat wave has caught up with California — at least the inland areas.

Sacramento has had six consecutive days above 100 degrees; an excessive heat warning is in effect from Merced to Bakersfield; and on Saturday Modesto tied its record for highest temperature for the date, at 105 degrees.

“In general, we’re about ten-to-fifteen degrees above normal for this time of year,” Holly Osborne, a meteorologist with the National Weather Service in Sacramento told me. “Today will be our sixth day of 100 or above in Sacramento, and we’re looking at temperatures being 100 or above for the rest of the week.” Osborne expects things to cool off, “moving into the weekend.”

The record number of consecutive days over 100 degrees in Sacramento is eleven, set in 2006. If the current heat wave holds up, it could tie for the second longest stretch, at nine. Temperatures like this may become more common in the future. In the California climate assessment released by the California Energy Commission last month, one projected outcome of climate change is an increase in the number of “extremely hot” days. In Sacramento, the number of days hotter than 105 degrees could inch up from four or five, to about 20 every summer, if global emissions of warming gases continue on their present course.

Osborne says overnight lows in the Sacramento Valley have been closer to normal, which is important, because cooler nighttime temperatures give people a chance to cool off. The southern San Joaquin Valley hasn’t seen much relief, though, according to Kevin Durfee, a meteorologist with National Weather Service in San Joaquin Valley.

“Overnight lows in Fresno and Bakersfield have been staying above 80 since the weekend,” he said. “One reason why this weekend we had an excessive heat warning in effect for the San Joaquin Valley is, when nighttime lows do not get below 80 and daytime highs are well over 100, very close to records, that is pretty extreme.”

Cooling centers are open today in Kern County. They open when the temperature is predicted to be 105 degrees or higher. Different locations have different triggers for opening cooling centers. Sacramento County tracks nighttime lows, rather than daytime highs. If the temperature at night doesn’t dip below 75 degrees for three consecutive days, and if they’re hearing from area hospitals that people are coming in or calling in with heat-related issues, they’ll open cooling centers.

Chris Andis from the Sacramento County Office of Emergency Services says this week, they probably won’t (a local TV station points out that people tend to use shopping malls as informal cooling centers).

“We have hot weather. That’s what July and August are in Sacramento,” she said. But she also emphasized that it’s important in weather like this to keep an eye on others who may be feeling the heat. “Check on loved ones,” she said. “Especially people who are chronically ill, seniors and pets.”

And it’s not only living things that get hit by the heat. The California Independent System Operator, or Cal-ISO, which manages the state’s power grid, is asking customers to conserve electricity wherever possible until 6:00 p.m., and is issuing a Flex Alert for tomorrow.

Photo: Craig Miller

It reached 113 degrees in Los Angeles on Monday, a record. And while a string of hot days in California doesn’t signify climate change any more than do record snowstorms in Washington D.C., the summer of 2010 did set quite a few records for high temperatures and heat waves. Although for us here in California, this week notwithstanding, we’ve had a pretty cool summer.

But this week’s heat — especially in Southern California — is a reminder of the ripple effects that could become commonplace if predictions of more frequent and severe heat waves come to pass, with a changing climate. Utilities pleaded with customers to conserve power as temperatures triggered record spikes in the electricity load and subsequent strain on the electrical grid.

But as Jennifer Skene writes for the KQED’s Quest blog, research suggests that it won’t take much “global warming” to make heat waves a regular feature:

As heat waves become more and more frequent, will people see them as evidence that global warming is happening? Or will people just get accustomed to the hot weather? New York City had the hottest summer on record; Russia suffered through horrible heat and fires. Are all these heat waves the result of global warming?

Several climate studies have found that heat waves are likely to become more frequent — and hotter  — as the earth warms up. In a recent paper out of Stanford University, two researchers ran several different climate models to see how a one-degree Celsius increase in average global temperature would affect heat waves over the next 30 years. They found that even with this relatively optimistic increase in average temperature, heat waves are predicted to happen more frequently — especially here in California.

One event is just one data point. To know whether there is a trend, we have to look at a whole cloud of data: heat wave incidence across several years. But, 2010 is shaping up to be a really hot year. So far, heat records have been set in 17 countries since the start of 2010.

Heat waves have some serious consequences. Heat stresses and kills organisms. Its effects in the marine intertidal zone have been particularly well documented, affecting seaweed, mussels, barnacles, and more. Heat can make trees drop their leaves, and can damage and kill crops, creating economic havoc. And people, particularly the elderly, can perish, as a result of dehydration and hypothermia.

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By David Lobell

The heat wave in Russia has captured international media attention, breaking temperature records left and right (see figure below). It has also captured the attention of commodity traders. In a typical year Russia produces about as much wheat as the United States, and is among the top exporters of wheat flour in the world. But this year, wheat has been decimated in the areas around Moscow, with yield expected to be 30 percent or so below normal. This week Russia announced they are banning all exports of wheat from August 15 through the end of the year. Since late June, wheat prices on the Chicago Board of Trade have risen by 50 percent, to more than $7 a bushel.

It is, and always will be, impossible to say whether a single event is caused by climate change. But we can ask, is this the type of thing we expect to be more common? In terms of warming, we can say with little doubt that heat waves like this will become more common with global warming. Exactly how much more common is tough to say, but it is likely that the average summer in 2050 will be as warm as the warmest summer in the 20th century. I am not aware of anyone who has done the calculation of exactly how common the type of heat experienced this year will be, but based on projections in the UN Intergovernmental Panel on Climate Change (IPCC) reports one can suspect this type of heat wave will be relatively common in Russia in a few decades.

[Ed. Note: Compounding the misery, Russia is also enduring catastrophic wildfires, which have enshrouded Moscow in a dangerous smog. More intense wildfires are another predicted outcome from climate change. -- CM]

Land Surface Temperature Departures from Average, Early July 2010.
Credit: NASA Earth Observatiory

What about the impacts on agriculture — will the types of price spikes induced by this heat wave also be more common in the future? This is a much more complicated question (not that the first was simple!), because it involves decisions about what crops are being grown, where and how they are being cultivated, and how global markets are structured. It has been common in some circles to dismiss impacts on agriculture as easy to adapt to, whereas others prefer to assume more pessimistic views.

The reality will likely be somewhere in between, but exactly where is still very difficult to say. This is partly because there is so little evidence on how well farmers and the companies that service them are adapting to current changes. After the dust has settled in Russia, will farmers start to rethink what seeds they grow and how they manage the land, or will they chalk it up to bad luck and hope for the best next year? This is a story playing out throughout the world, but it’s a lot more difficult to observe and understand than something like temperature change.

Even if people are galvanized to adapt, there remains the question of how much adaptation is truly possible. Can wheat, a crop that prefers cooler climates, be modified to better withstand extremely high temperatures? To some degree the answer is surely yes, but how much and where is not clear. So while efforts to adapt are needed, there are big risks in relying on that and ignoring the need to reduce emissions of greenhouse gases. A recent National Academy of Sciences report I participated in explains exactly what’s at stake if we don’t begin to reign in emissions.

In short, it would be similar to a global game of Russian roulette.

The Silver Lining

The news is not all bad. For one, there are winners in this story, just like there will be winners from climate change. Consider a wheat farmer in the US, who expects good yields this year and will greatly benefit from higher international prices. Of course, next year it could be the US’s turn for a major drought or heat wave in the Plains, but for now they will gain.

More importantly, each major event raises the possibility that more people will raise their head out of the sand and understand that climate is changing. Although a single event can only advance science a small amount (which is why scientists rely on many, many observations and models), public perception is a different animal. As noted by Simon Shuster in Time, Russian President Dmitri Medvedev has been a critic of any action on global warming, and recently described it as “some kind of tricky campaign made up by some commercial structures to promote their business projects.” But in a recent statement during the heat wave, Medvedev struck a very different note: “What’s happening with the planet’s climate right now needs to be a wake-up call to all of us, meaning all heads of state, all heads of social organizations, in order to take a more energetic approach to countering the global changes to the climate.” Such words are encouraging, for the sooner people can stop denying the science, the sooner the public and policy makers can have an honest debate about tradeoffs and acceptable risks and policy options. The choices won’t be easy, but neither is growing wheat in 100˚F heat.

David Lobell is an Assistant Professor at Stanford University in Environmental Earth System Science, and a Center Fellow in Stanford’s Program on Food Security and the Environment. His research focuses on identifying opportunities to raise crop yields in major agricultural regions, with a particular emphasis on adaptation to climate change. His current projects span Africa, South Asia, Mexico, and the United States, and involve a range of tools including remote sensing, GIS, and crop and climate models.