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What Have We Done To The Weather?

May 03, 1990|PATRICK MOTT | Patrick Mott is a regular contributor to Orange County Life.

Everbody talks about the weather, but nobody does anything about it.

Not any more. These days, we're doing plenty about it. All that's needed are a few thousand miles of blacktop, a few thousand fewer trees, a few hundred thousand garden hoses and sprinkler heads and a few big buildings. In short, a city.

And, before long, we're tinkering with the weather.

We may not notice it day to day, but in Orange County we're hotter and more humid than we used to be. In fact, the last decade was the hottest in Orange County history. It is, say weather researchers and meteorologists, the price of urbanization.

Forty years ago, the idea of slow-cooking the county would have seemed like science fiction. It was a time when Los Angeles was just beginning to discover smog and Orange County was still an agricultural backwater. Downtown Anaheim looked like a Norman Rockwell sketch. Disneyland was an orange grove. The South Coast Metro area was a series of bean fields. The total population of the county was 216,224.

And that's the way it was for decades. It all made for usually pleasant, consistent weather, with the trees and crops acting as natural air conditioners.

But when planners and developers started taking the oranges out of Orange County--along with thousands of acres of other vegetation--and adding people, buildings, industry, roads, freeways, cars and a penchant for energy consumption, they also took the lid off the thermometer.

According to statistics compiled by a former California state climatologist, the mean annual temperature in Santa Ana--near the geographic center of Orange County--rose from slightly below 61 degrees in 1910 to between 65 and 66 degrees in the last decade.

It's called the "urban heat island effect," and it occurs whenever an area becomes citified.

"The temperature at the core of cities has a very simple mathematical relationship to the population," said Kenneth Watt, a professor of zoology at UC Davis. "Civilization has manufactured an oven."

In Orange County, that oven has several components:

* Blacktopping. "If you blacktop something, as we all know from trying to walk on it, it absorbs all the (heat) radiation that hits it," said F. Sherwood Rowland, Bren professor of chemistry at UCI and a specialist in global atmospheric problems. This, he said, causes the air close to the ground to heat up. Also, because the heat is absorbed into the blacktop, it can continue to radiate out into the surrounding air even after the sun goes down.

* Concrete paving. Unlike blacktopping, white concrete paving reflects heat into the upper atmosphere or into lower altitudes where it is trapped by clouds.

* Large buildings. Depending on their color, these also serve as absorbers or reflectors of heat from the sun. In a larger sense, however, they warm the surrounding air as a result of what Ralph Cicerone, head of the UCI geosciences department, calls "waste heat." This heat, he said, is a byproduct of any machine: air conditioners, heaters, electric motors, gasoline engines.

* Homes. While they do not produce the high concentration of waste heat that large buildings or industrial sites do, each machine used at home--particularly the air conditioner--causes the local temperature to rise.

* Cars. That exhaust emissions produce ozone pollution is well-known. However, the engines also produce waste heat and water vapor.

* Lack of trees and other vegetation. Orange County is no longer primarily an agricultural region, and hundreds of square miles of open land have been cleared for development in recent decades. This, weather researchers say, not only removes natural windbreaks, but also eliminates a source of natural air conditioning.

Taken together, these elements account for a local heating trend that is likely to continue for as long as Orange County grows, scientists say.

But, said Jim Goodridge, a former California state climatologist who now studies rainfall and climatic variation full time, the urban heat island effect is not exactly novel. The effect, he said, was first described in 1811 by an English scientist named Luke Howard, who reported on the rising temperatures in London as a result of urbanization.

In more modern times, however, said Goodridge, the effect may be responsible for the birth--erroneously--of the global warming theory. Also called the greenhouse effect, the theory holds that atmospheric pollution from such sources as chlorofluorocarbons and carbon dioxide are stripping away the earth's protective shield of ozone and causing temperatures to rise around the globe.

But, said Goodridge, the global warming proponents' figures may be skewed because of unusually high temperatures in urban areas.

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