CONTRA COSTA TIMES
(Walnut Creek, CA)
July 28, 2006, n.p.

© 2006, McClatchy-Tribune Information Services.

Heat Waves to Rise in Number and Intensity, Scientists Say

By Betsy Mason and Mike Taugher
Contra Costa Times (MCT)

     WALNUT CREEK, Calif.--Searing heat waves cannot be directly attributed to global warming, but scientists say the sweltering hot spell is no surprise.

     Like the intense hurricanes of 2005, there is no way for scientists to pin one season's weather anomalies onto a warming climate. But scientists say hurricanes and heat waves are now more likely to be more intense and frequent.

     "I think you cannot attribute a single heat wave to global warming," said climate scientist Inez Fung, director of the University of California-Berkeley's Center for Atmospheric Sciences. "But in the future there will be more of these heat waves because of global warming."

     Scientists compare the situation to a pair of loaded dice. Even if the dice have been weighted to favor ones, there is no way to tell if any given pair of snake eyes is a result of the weight or just chance.

     Similarly, global warming has increased the odds of intense heat waves.

     "If we're even in the ballpark, then there is a link between human activity, a change in the climate and these kinds of heat waves," said atmospheric scientist Ben Santer of Lawrence Livermore Laboratory. "And that's bad news."

     Climate scientists almost universally agree that the Earth is warming and that the trend is due at least in part to human activity. The warming is caused by gases, including carbon dioxide, that trap heat in the atmosphere.

     The world is on average 1.4 degrees Fahrenheit warmer now than in 1900, and that warming trend has increased since the 1970s. The five warmest years in the past 100 all have occurred since 1998, according to NASA's Goddard Institute for Space Studies.

     And the first six months of 2006 were the hottest in the continental United States since recordkeeping began in 1895, according to the National Oceanic and Atmospheric Administration.

     "It's definitely true in the last few years we have seen more of these (heat waves), and this makes sense because as the climate warms it's going to be more likely that (temperature) deviations upward are going to be more extreme," said Claudia Tebaldi, a statistician who studies climate change at the National Center for Atmospheric Research in Boulder, Colo.

     "The western United States is going to be much more affected by this warming" than some other regions, including the southeastern United States, she added.

     Although the latest heat wave broke several individual day temperature records, it was not unprecedented. National Weather Service regional science officer Warren Blier said it was probably the type of heat wave that might occur once every 20 years.

     San Francisco did not break 100 degrees, as it has in past heat waves, and some temperature records are still standing.

     Still, Blier said there were several extraordinary measurements taken in the past week. One reliable weather station in southern Monterey County, Calif., recorded an astonishing 120 degree high temperature last Saturday.

     Livermore hit 113 degrees, just 2 degrees shy of that city's record high of 115, recorded in June 1961 and again in September 1950. Blier said the Livermore records for which he has access go back to 1930.

     And two weather stations in Mount Diablo's foothills recorded overnight lows of 91 degrees over the weekend.

     "That's an extraordinarily high low temperature," Blier said. "To my mind, this was a significant event."

     In Pleasanton, which was hit with five days of more than 100-degree weather in the past week, residents agree that this heat wave seems unusual.

     "It's lasting too long," said Dave Thompson, outside a downtown coffee shop with fellow regular Richard Lovoi. "I'm not used to it lasting so long. Three times this year we had to sit inside."

     "It's never been that hot out here," agreed Lovoi, a 30-year Pleasanton resident.

     Both northern and southern California have been hit simultaneously, which is unusual. The East Coast has had its share of heat this summer, and Europe is also in the grip of a major heat wave.

     "This one heat event is pretty extreme," said climate scientist Ken Caldeira of the Carnegie Institution at Stanford University. "It's part of a pattern that is consistent with global warming."

     After a monster heat wave hit Europe in 2003, killing more than 20,000 people, scientists at the Hadley Center for Climate Prediction and Research in England used their climate model to see if they could expect more killer weather in the future.

     Adding human activity such as carbon dioxide emissions to the model, they determined the chance of a similar heat wave increased by a factor of four, from once every 1,000 years to once every 250 years.

     "By large-scale warming of the planet we do indeed increase the risk of these types of events," said Lawrence Livermore's Santer.

     That might already be evident: Earth's 15 hottest years on record have occurred in the last two decades.

     California could be hit especially hard, said Amy Luers, climate impact scientist for the Union of Concerned Scientists. She participated in an analysis of potential impacts on California for the governor's Climate Action Team.

     "If emissions continue unabated, by the end of the century we could see three to four times as many heat waves in major urban centers in California as we see today," she said.

     Philip Duffy at Lawrence Livermore agreed that climate change will affect people.

     "What that means in the broader context is that there is a cost to global warming," said Duffy. "People are dying because of this heat."

     While scientists aren't willing to definitively pin this particular heat wave in California on global warming, many California residents are.

     "I think (global warming) does have something to do with it just because it's just as hot in England as it is here. It seems unusual," said Bea Miller who recently moved to Dublin, Calif., to escape Utah's desert heat.

     "I would have to say I do think global warming has something to do with it," Mike LaMarche said as he filled up his Prius at a downtown Pleasanton, Calif., gas station. "I've been here 13 years and I've never seen it so hot that I've had to keep the air conditioning running all night before. A few of my neighbors said the same thing."