For Roofs, White Is the New Cool

Officials at the US Department of Energy are checking their roofs for some of that “low hanging fruit” available to increase energy efficiency in buildings. A study released this week by Lawrence Berkeley National Laboratory suggests that “cool roofs” have the potential to offset up to two years worth of worldwide CO2 emissions and reduce the effects of urban “heat islands.” If that’s the case, increasing the albedo, or reflectivity, of roofs and pavements might be the solution to hotter days in the city.

Flying over most California cities reveals relatively few white roofs (Photo: Craig Miller)

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More Heat Waves and Health Problems Ahead

A backyard thermometer in upstate New York (Photo: Craig Miller)

I wore a wool coat to work today.  And I’m ashamed to say that last night I turned the heat on in my apartment.  San Francisco is obviously a special place, particularly in July.  And by “special,” I mean foggy, windy, and cold. says that it was in the 50’s last night and this morning, but I have trouble believing that.

So I found it a little bit hard to relate this morning on a conference call with journalists and scientists talking about climate change, heat waves, and public health.   It seems that much of the world beyond San Francisco has been experiencing some unprecedented heat lately.  According to NOAA, global combined surface and ocean temperatures for January through May 2010 are the warmest on record.   But in California, according to Tom Evans of the National Weather Service (NWS), so far this summer we’ve experienced pretty normal average temperatures, and that’s what the NWS Climate Prediction Center is forecasting for the rest of the summer for most of the state, he said, although the southeastern portion of the state may be in for some hotter-than-normal weather in the coming months.

On the call this morning, which was put together by the Union of Concerned Scientists, the speakers were careful to point out that one or two heat waves cannot be considered evidence for global warming, just at the snowstorms on the East Coast this winter couldn’t be used to refute it.  (This recent article in the Christian Science Monitor has more about the heat waves and changing attitudes about climate change.)

However, said NOAA climatologist David Easterling, “Warming temperatures increase the probability of heatwaves.  By the end of the century, what we currently consider a heat wave, or an extremely hot day, might become the norm.”

Warming temperatures can impact public health in a number of ways, said Michael McGeehin, director of the National Center for Environmental Health at the Center for Disease Control.

“Climate scientists predict that the U.S. will see an increase in the duration, intensity, and frequency of heat waves, and we know that heat waves are a public health disaster,” he said.  “They kill.”

And they could kill in large numbers in the centuries to come, according to a recent paper by Matt Huber of the Climate Change Research Center at Purdue.  Huber was on the call this morning to discuss his analysis, which found that if CO2 levels continue to rise over the next 200 years, hotter temperatures could make areas that are home to 50% of the world’s population uninhabitable during heat waves in the the centuries after 2100.  Problems start happening when the heat index is about 130, he said.  (A temperature of 105 degrees F with a humidity level of 50% has a heat index of 134.)

“I personally think that we’ve already committed to at least 2 degrees (Celsius) of warming, but the kind of warming we’re talking about here, which is on the order of at least 10 degrees Fahrenheit, maybe more like 15 degrees Fahrenheit, that’s something that we can still decide to avoid,” he said.  “And from our calculations it looks like we should really try and avoid that.”

And it looks like that potential warming could be becoming reality faster than some expected.  A new study out of Stanford announced today finds that “exceptionally long heat waves” could become commonplace in the United States in the next 30 years, particularly in the western US.  The study, headed up by Noah Diffenbaugh of the Woods Institute, used climate models to analyze what might happen if global temperatures rise two degrees C above pre-industrial levels by 2039. (An increase of two degrees Celsius is the limit agreed upon in the non-binding  2009 Copenhagen Climate Accord (PDF).)

The Stanford researchers found that “an intense heat wave – equal to the longest on record from 1951 to 1999 – is likely to occur as many as five times between 2020 and 2029 over areas of the western and central U.S.”

The analysis predicts during the 2030s the worst heat waves maybe be even more frequent.

It’s 57 degrees in San Francisco this afternoon, and I am wearing a winter scarf at my desk.  Despite all these grim predictions, right now it’s hard not to think that a little extra heat might be nice.

Fire Data: Dry Winters Mean More Charred Acres

Tim Walton

Photo: Tim Walton

Last year around this time, I asked some state fire officials what to expect in terms of the fire season and got a definite “It depends.” On the one hand, scant precipitation over the winter had left behind a dry landscape. On the other hand, spring rains had given a boost to rebounding vegetation, providing more fuel for later in the season. I was reminded of the old joke about politicians searching for a “one-handed economist” and found myself wishing for a one-handed forester.

Whether a good spring dousing is more likely to inhibit wildfires or feed them is a common source of confusion, which San Jose Mercury News writer Paul Rogers has sought to extinguish. By dipping into four decades of fire data, Rogers and his researchers at the Merc conclude that dry winters generally make for more intense fire seasons in California.

Rogers writes that “the worst fire seasons come after dry winters, not wetter ones like the one we’ve just had.” That would seem to bear out a conversation I had in 2007 with Crawford Tuttle, Chief Deputy Director at CalFire, fire protection arm of the state’s department of forestry. Walking through the burn zone of a Sierra wildfire that broke out in May of that year, Tuttle said that early-season fire was “a great demonstration of how (the) fire regime–fire severity is expanding in California.” Tuttle told me that when moisture levels in the air, vegetation and soil are lower, earlier in the season, it’s likely that the fire season will be intense.

The preceding winter had been dry by historical standards, with just over half the normal amount of precipitation and indeed, wildfires went on to char almost a million acres in the state that year.

The Rain in May Falls Mainly Near the Mean

Rainbow following late spring rains in Vallejo. Photo: Craig Miller

Rainbow following late spring rains in Vallejo. Photo: Craig Miller

Just a passing admonishment from meteorologist Jan Null, who keeps meticulous, often eye-opening records of weather patterns in northern California: We can stop talking about the “unusual weather” we’ve been having.

In California’s Mediterranean climate, precipitation tapers off to virtually nothing between June and October. So any rain this close to the end of “the rainy season” tends to create some buzz.

But Null, a former forecaster with the National Weather Service and founder of his own weather consulting firm, pointed out in an email this week that “the amount and number of days (with rain) so far in May are right near the 30-year normals for San Francisco and San Jose.” Null confirmed for me this morning that:

“So far in May, San Francisco has had three days of rain for a total of 0.44 inches.  The May normal is 3.3 days of rain for a total of 0.54 inches.  Last year, there were 5 days of rain for a total of 0.80 inches.  Even if there is a little more rain (this week), it will be pretty close to a normal May.

Similarly in San Jose the normal is 0.44 inches in 3.0 days. So far in May 2010 there have been three days of rain totaling 0.19 inches.  Last year San Jose had 0.09 inches over three days.”

By George, I think we’ve got it.

The Bay Area’s weather has been unusually cool, however. Null says the April-May period could end with “dramatic cool averages.” He says average daily highs for the two months could be “on the order of three to five degrees below normal.”

Null regularly updates local weather statistics on his website.

California Storms: A Dent in the Drought

Spillway at Alpine Lake on Mt. Tamalpais. File photo: Marin Municipal Water District

Spillway at Alpine Lake on Mt. Tamalpais. File photo: Marin Municipal Water District

A version of this post also appears on Dan Brekke’s personal blog, Infospigot. Also see our updated map of reservoir conditions at the end of this post.

By Dan Brekke

Is California’s drought over? OK, let’s take a step back. Yes, I realize one could debate whether the last three years in California actually constitute a drought. But that’s a discussion for another time. For now, I think everyone can agree that we’ve had lower-than-average precipitation for the past three years.

The only reason to ask the question is that, after the first half of the wet season delivered only spotty rain, we’ve had a pretty solid week of downpours. Water is sluicing into our reservoirs, and the hills are greening up. Some counties, like Marin, have water tumbling down the spillways. All of that is a sign of what we think winter should be here.

My favorite water statistic from last week: when the storms were at their heaviest around Lake Shasta, California’s biggest reservoir, water was flowing into the lake at about 500,000 gallons per second. That’s 1.5 acre feet, or about enough for two-to-three “average” households for a year, every second.*

Amazing numbers like that aside, the people who get paid to think about whether the drought is over say “not yet.” Last week, Quest managing editor Paul Rogers wrote a good summary of the situation, for The San Jose Mercury News.

Rogers’ story does contain one bit of quirky California thinking about rain and water, though. He quotes a well established local meteorologist, Jan Null, about where we stand in terms of normal rainfall, saying: “This is a great start, but we need to keep it going.”

Of course, Null recognizes better than most that the amount of rain we get and when we get it is out of anyone’s control. But once you understand the importance of water in California, once you get how crucial the winter rains are, there’s a score-keeping aspect to weather-watching here. It becomes second nature to study the rain gauge and the seasonal precipitation table as an index of performance, a reflection on whether a great collective goal is being attained. Lots of rain means we’re doing well (and that we can put the complexities of water supply out of our minds). A dry spell means we’re failing (and the prospect of hell to pay, or at least the strong possibility of stringent conservation measures).

But in reality, there’s no performance going on. The rain is the rain, and the climate is the climate. California’s rainfall is famously variable. Dry spells can be counted on and the current run of dry years is the third we’ve had since I arrived in Berkeley in the 1970s.

My first California winter, 1976-’77, was bone-dry and was in fact the second year of the driest two-year period ever recorded here. A decade later, from roughly 1986 through 1992, we had another run of dry years. And if our winter rains were to stop now, we’d be in the fourth year of drier-than-normal years. In between these periods we’ve had average years and very wet years and years that didn’t quite hit the average. That might not be too different from anywhere else. The reason it’s a bigger deal here than it might be in, say, Wisconsin, is that we have a six-month dry season. We need to store water to get through that. We have 37 million people and millions and millions acres of farmland that need water, whether it’s falling from the sky or not. Thus the need to believe we can wish the rain to keep going during the wet season and the tendency to feel disappointment when the winter turns into a string of dry, sunny days.

*500,000 gallons per second. Here’s the arithmetic: California Department of Water Resources figures show that in the hour between noon and 1 p.m. on Tuesday, January 19, net inflow into the lake was 66,288 cubic feet per second. That’s the highest inflow figure for any single hour that week. One cubic foot equals 7.48 gallons. 66,288*7.48 = 495,834.24 gallons. One acre-foot = 325,851 gallons. And 495,834.24/325,851 = 1.52 acre-feet. Per second. For the entire 24 hours of the 19th, Lake Shasta’s inflow averaged just over 1 acre-foot a second.

View KQED: California Reservoir Watch in a larger map

Methane Sources and the “Dark Side” of Solar

plants.jpgPlants don’t produce methane after all, a new study out of the UK contends.  The results refute a 2006 report that suggested plants could account for almost half the world’s production of this potent greenhouse gas. But according to authors of the latest study, plants are more like little methane pipelines; they convey methane from the soil to the air, but they don’t actually produce it.

No one said that climate change was simple.

Neither are the solutions, apparently.  An article in the LA Times reports on the “dark side” of solar, outlining the toxic materials used in cells, the difficulty of recycling some components, and the fossil fuels burned in the production and transportation process of cells and panels.

And don’t let this weird weather confuse you either.  As the Thin Green Line reports, this week’s freezing temperatures in the Midwest don’t mean climate change isn’t happening.