WHAT HAVE WE DONE TO THE WEATHER?

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.

“When people have a large computer,” he said, “and they gather up the world’s temperature records, they feel that because they have so many records, they can average all the temperatures together and come up with a monumental representation of the world’s true temperature. But they haven’t separated out the rural temperature stations from the urban stations.”

Watt, an outspoken opponent of the global warming theory, calls it “pure baloney. It’s a complete hoax, in my view. I would suggest that the perception that the world is getting warmer has been influenced by the fact that many of the thermometers that are being studied are in big cities and around airports. How you find the truth about global temperature is to look at what you find in the country.”

And, he said, the temperatures in the country--away from urban centers--have remained fairly constant, a condition that he claims debunks the global warming theory.

Still, Watt said, the urban heat island effect and the man-made factors that influence it are quite real.

What exactly have we done?

In Orange County, the effects of development and urbanization might be illustrated using a model of, say, an industrial park with a large housing tract on one side, a golf course on the other, and a freeway running past it all. Assume that the area was once a huge orange grove.

First, the trees were cleared and the ground leveled. And this alone, said Goodridge, was enough to affect the surrounding temperatures.

“In a modified climate where you don’t have the heat (from the sun) being converted to plant tissue growth, it goes to heating the outside air,” he said.

Also, said Watt, “the reason that the countryside is cool is that most of the cooling in the world is a result of converting liquid to gas and gas into liquid--because river and lake and stream and pond surfaces and surfaces of vegetation are converted to water vapor.”

Next in the evolution of the industrial/residential neighborhood were the structures themselves, houses and industrial buildings. Most of the industrial buildings were fitted with air-conditioning systems, and those that were not employed machines and other equipment that used a lot of energy--in the form of both fossil fuels and electricity--and therefore emitted a high concentration of waste heat and possibly air pollution.

And, with the coming of the reflective or heat-absorbing walls in place of the heat-converting trees, the temperature of the surrounding air went up another notch.

“All those buildings tend to generate heat, from food service, computers, lighting, air conditioning,” said Charles Pyke, a meteorologist for the U.S. Army Corps of Engineers in Los Angeles and president of a private weather research and forecasting business. “And there’s a certain amount of heat that escapes to the outside, through air-conditioning vents or through glass.”

The effects of this waste heat are felt most acutely at night, Pyke said. He estimates that in the highly urbanized areas of Los Angeles, the average nightly temperature has risen 12 to 13 degrees in the last century.

The houses near the industrial park produced less waste heat, but they, too, provided reflecting surfaces and--along with the golf course--added another dimension to the alteration of the local weather: higher humidity. Back-yard pools, lawns in both front and back yards, and other landscaping that requires frequent watering, along with the large expanse of golf course land that often is watered daily, supplanted the more natural surroundings that were watered less frequently.

Under such conditions, said Pyke, a higher “dew point”--a more accurate measure of moisture in the atmosphere than relative humidity--often results. He said that effect has been noticed fairly dramatically in places like Palm Springs, where the frequent irrigation of large tracts of man-made greenbelts and golf courses is felt in the form of more humid weather in the hotter months of the year.

Pyke estimates that the dew point since Orange County became more urbanized has risen two or three degrees, which would make for an increase in relative humidity of about 10%.

Finally, access streets were built, along with the freeway, and these also reflected or absorbed heat from the sun, adding to the rising temperatures. They also brought cars into the neighborhood, sometimes in large quantities. And the autos’ effects, scientists say, can be dramatic.

Tailpipe emissions help heat the air and, because they contain a component of water vapor, also add to the humidity, Pyke said.

“In places like Fairbanks, Alaska,” said Pyke, “you can actually get dense ice fogs forming because of too many cars on the roads.”

Of greater concern than any weather trends, however, said Pyke and others, are the effects of air pollution--even though on paper the figures show that the air quality in Orange County has improved in recent years, the result of more stringent controls on auto and industrial emissions.

The air may be cleaner in Orange County today than it was, say, 15 years ago, but this trend will probably evaporate in the face of the county’s ever-growing population and its need to travel by automobile, said David Rutherford, a spokesman for the South Coast Air Quality Management District.

“The air quality has gradually improved since the late ‘70s,” Rutherford said, “but it will be a challenge for us to continue that as the area grows, and, as a result, the carbon monoxide emissions from tailpipes increase. As the population grows, so will the demand for the use of the area’s thoroughfares. That is the No. 1 source of air pollution.”

But does air pollution affect the weather? If vegetation is considered a moderating influence on local weather, then the answer is yes, researchers say.

“The key thing for any plant is photosynthesis,” said Dave Tingey, a researcher at the Environmental Protection Agency research laboratory in Corvallis, Ore. Tingey is leading a team that is studying the effects of ozone pollution on crops and forest vegetation. “(Ozone pollution) suppresses the rate of photosynthesis and affects the way the plant processes the photosynthesis. It also shortens the life of any given leaf, and the leaf is the (photosynthetic) factory of the plant. It also directly affects the pollination process. It inhibits the germination of pollen grains on the female portion of the flower.”

It all adds up to reduced plant growth and a greater susceptibility to disease in the plant, he said.

“The trees can be killed by a secondary infection. It’s like in humans when something else gets you, but pneumonia kills you,” Tingey said.

The bad news: it isn’t going to get any better. Orange County continues to boom and, according to researchers--and the population/temperature equation--that means the county will probably get hotter as long as development goes on. How bad it can get can be illustrated by the world’s most populous city, Goodridge said.

“You should see the temperature curve for Tokyo,” he said. “It goes straight up. The temperature each year is higher than the one before.”

The good news: “It won’t continue indefinitely,” said Gunnar Roden, a research professor at the school of oceanography at the University of Washington in Seattle. “I would expect the temperature rise to stop when you reach a city growth plateau.”

When that plateau--or saturation point--is reached depends on how much discomfort in the form of higher temperatures and humidity and pollution Orange County residents are willing to live with, weather specialists say.

One palliative measure, Goodridge said, is to plant more trees. But, said Rowland--an advocate of the global warming theory--”it’s not sufficient to plant a seedling to make up for a 300-year-old tree.” On a global scale, he said, “we’d need to plant an area the size of Australia because that’s how many trees have been cut down around the world.”

In the end, he said, it may come down to money versus nature.

“When it becomes more and more to people’s economic advantage to become energy efficient,” said Rowland, “they will do it more quickly.”

HOW WE CHANGE THE CLIMATE

Several related causes, some seemingly insignificant, add up to long-term weather variations.

Deforestation: Vegetation, particularly trees, reduces heat. Trees use solar energy for plant tissue growth, and when they disappear, their moderating effect on the surrounding temperature disappears with them.

Energy use: Any source of energy--fossil fuels, electricity, air conditioners--emits heat. The more sources of energy, the more heat, particularly when industry or large buildings are the source.

Blacktoping/Paving: When an area formerly covered with soil, plants and trees is paved, the pavement either reflects or absorbs heat. White concrete reflects heat into the upper air; blacktop absorbs it and radiates it out into the air closer to the ground.

Emissions: Cars and industrial emissions create air pollution, which affects plant growth and the ability to cool the surrounding air. Water vapor produced from auto tailpipes also causes the humidity to rise.

Development: Man-made lakes artificially watered grass in yards, parks and golf courses, as well as residential swimming pools, cause a rise in humidity. Air conditioners also contribute.

POPULATION

More people equals more heat. The more Orange County grows, the hotter it’s going to get. And the temperature likely will continue to rise until we reach the population/development saturation point. 1980: 1.9 million 1990 (Estimate): 2.3 million 2000 (Estimate): 2.6 million

AIR POLLUTION’S IMPACT ON THE CLIMATE

Air pollution affects the climate by damaging crops and plants that in turn affect the weather.

Ozone and other harmful pollutants are released into the air from cars and factories. These emissions reach trees, crops and other plants we depend on for natural air conditioning.

HOW OZONE AFFECTS PHOTOSYNTHESIS IN PLANTS:

Normally, carbon dioxide is absorbed into the plant through leaf cells called stomates, where it is eventually converted into plant tissue and oxygen. When ozone invades the plant, the stomates respond to the attack by one of two ways. If they stay open, the leaf cell membranes are permeated and damaged by the ozone. The leaf’s heat-absorbing capability is diminished. If the stomates close in response to the ozone--as they do in some plants--life-giving carbon dioxide can’t get in. In either case, if the ozone is heavy enough, photosythesis stops and the plant dies.

CROP DAMAGE

Crops can be damaged or have their yields lowered by smog. One experiment at UC Riverside found that among varieties of sweet corn that were usually susceptible to damage from smog, the damage was even greater when the temperature rose.

AREA MOST AFFECTED BY CHANGE

While Orange County has yet to experience the degree of weather change felt by cities like Los Angeles (heat) and Palm Springs (humidity), there is a trend here toward higher temperatures and humidity.

Urban areas with large concentrations of buildings experience the most change. Inland cities like Anaheim, Santa Ana and Orange, where trees have been replaced by concrete surfaces, tend to be hotter than coastal cities.