Major Changes in State Climate Are Predicted

Widespread changes in California’s natural resources--from major shifts in ocean life to a higher sea level that could intensify coastal flooding--are highly certain over the next 100 years because global warming is expected to cause temperatures to rise by several degrees statewide, a team of seven scientific experts predicted in a report to be released today.

An increase in some of the most dramatic events feared by disaster-weary Californians--wildfires, landslides, droughts and severe El Nino storms--is considered likely too, although the scientists reported them as less certain.

The findings are based on a 1995 prediction from a United Nations panel of climate experts that global temperatures will rise by 2 to 6 degrees Fahrenheit in the next century. In California, climate modelers have predicted that winters will be 5 to 6 degrees warmer and summers one to two degrees hotter.

Many scientists believe the cause of the warming of the global climate is greenhouse gases released by the burning of oil, coal and gasoline as well as other human activities. The gases trap solar energy and increase surface temperatures. Others note, however, that natural fluctuations in climate cannot be ruled out as a cause.

In the new report, which acknowledges many uncertainties, the seven scientists, mostly from Stanford University and UC Santa Barbara, described the probable scenario in California as wetter, warmer winters and drier, hotter summers. They also reported the possibility of an amplified version of El Nino, the wintertime phenomenon of warm ocean currents that hits California with severe storms.

Some changes “could shape the overall experience of living in California--enough to have a significant impact,” said Christopher Field, a Stanford professor and Carnegie Institution of Washington plant biologist who specializes in global warming and served as lead author of the report. “It would not be fair to say that we saw evidence of impending total disaster. But the climate changes are important and worth thinking about and planning for.”

Convened to assess the ecological impacts that projected rates of global warming could have on California, the scientists were commissioned by two science-based interest groups: the Union of Concerned Scientists and the Ecological Society of America. Their work was reviewed by a steering committee of seven other scientists.

Most climate experts agree that global warming is occurring--they estimate surface temperatures have risen 1 degree over the past century--but the potential impact and pace remain extremely controversial. There is considerable uncertainty about computer models that predict changes in specific regions, as the California team has attempted to do.

“The regional impacts are just beyond the ability [of computer models]. Everything is speculation,” said Russell Jones, director of climate issues at the American Petroleum Institute, which represents oil companies. “Even if there is climate change, it’s hard to ferret out what are the benefits and what are the damages. It’s a terribly complicated subject.”

One climate expert on the team’s steering committee, Steven Schneider of Stanford, called the report “an antidote to the shrill pronouncements of those who claim either certain catastrophe or no big deal” from global climate change.

Also, Nobel laureate Mario Molina of the Massachusetts Institute of Technology, an atmospheric chemist, said in a statement that the study “adds to the growing evidence that climate change will bring serious impacts to some parts of the United States.”

Because California’s ecosystems are highly dependent on water, the report says “changes in the timing or amount of precipitation over the next century are likely to have a greater impact than changes in temperature.”

When it comes to global warming, Field said, “California’s environment has a couple points of special vulnerability and those are points related to water resources and wildfire.”

One of the most disturbing impacts, he said, could be increased scarcity of water--already a resource that invokes intense battles in California between agricultural, urban and environmental interests.

Warmer temperatures are likely to mean that more winter precipitation will fall as rain rather than snow, decreasing the Sierra snowpack that stores water, on which Californians rely year-round. Also, warmer temperatures in summer could aggravate the water losses by increasing evaporation, Field said.

The team reported that the largest ecological changes could come in the ocean, because California’s marine ecosystems are more sensitive to climate change than terrestrial ones. Ocean temperature and circulation can dramatically alter the food web, from plankton and invertebrates to fish, sea birds and mammals.

Field said scientists have already documented “dramatic changes in marine communities all along the California Coast” that could be linked to global warming. Warm-water fish that used to be found off Southern California 50 years ago now are found in Monterey Bay, while colder-water species have declined there. Kelp forests off Southern California are now dominated by warmer-water fish from farther south. The birds and mammals that depend on them could be shifting north too.

The team also foresees a cascading series of ecological events on land--grasslands expanding into foothills that are now lined with shrubs, and in turn, the shrub lands moving to higher elevations, replacing forests. As the vegetation changes, so do the animals that depend on it.

The shifts could be devastating for California’s endangered species, the report says. Protected areas for rare animals and plants are so small that the species could become extinct.

Another predicted consequence, an 8- to 12-inch rise in sea level, will worsen flooding from storms in coastal cities and add stress on levees in the Sacramento-San Joaquin Delta, the scientists say.

Also, if warming is accompanied by increased drought as expected, the state’s No. 1 industry, agriculture, would suffer. The report says the cost of growing food could rise, and water-intensive crops such as alfalfa, cotton and grapes could decline or even disappear.

The research team kept many predictions intentionally vague, because precisely how climate alters ecology varies widely in a state with such a diverse range of weather conditions and natural resources.

“We’re highly confident of changes in climate and we’re highly confident that some of the large suite of changes will occur, but we’re less confident about which specific changes, and which specific locations, and which specific times,” Field said.

Seven trends were assigned “high certainty” because they have been predicted by more than five computer models and scientists have observed them already occurring in some areas:

* More increases in warming in winter than summer.

* Higher sea level.

* Decreased stream flow in summer.

* Increased competition for water among urban, farm and natural uses.

* Northward shifts in fish and other marine life.

* Decreased habitat for many land animals and plants, including endangered species.

* Increased salinity in San Francisco Bay in summer.

Several other trends were assigned “medium certainty”--increased summer drought, less snow and more winter runoff, and shifts of some land species to the north and to higher elevations. Several models and direct observations have predicted these trends.

The scientists reported a level of “lower certainty” about increases in California’s extreme weather-related events--wildfires, floods, landslides and thunderstorms. The scientists said the term does not imply that these changes are unlikely, it only shows that knowledge is “too limited for us to be confident about the magnitude of changes.”

For example, “most fires in California occur under extreme rather than average weather and climate conditions, and climate models do poorly at predicting extreme events such as Santa Ana winds,” the report says.

Greenhouse gases from industrialized nations are supposed to drop 6% over 15 years under a global climate treaty signed in 1997. Solutions include improved energy conservation and use of alternative fuels. Government ministers are convening in Germany this week to work out details.

“We haven’t passed the point of no return,” Field said. “Ecosystems have substantial abilities to cope with changes, especially if they’re given time to do that, and there is an opportunity for humans to take action. We would like to see this report become a foundation for a dialogue about what steps Californians should take.”

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Changing Seasons

A group of seven scientists predicts that California’s ecology--from its giant redwoods to its popular beaches--will be altered by global warming. Climate models for California project that within 50 years, winters could warm by 5 or 6 degrees while summers could warm by 1 or 2 degrees.

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Source: The Union of Concerned Scientists and the Ecological Society of America