Sea lions are shown July 8, 2006, at the Farallon National Wildlife Refuge, Calif. As the global climate warms, the state's upwelling season, a time when nutrient rich deep waters are pushed to the surface, feeding the marine food chain, could become weaker, affecting sea lions and other marine mammals.

Los Angeles ? California is defined by its scenery, from the mountains that enchanted John Muir to the wine country and beaches that define its culture around the world.

But as scientists try to forecast how global warming might affect the nation’s most geographically diverse state, they envision a landscape that could look quite different by the end of this century, if not sooner.

Where celebrities, surfers and wannabes mingle on Malibu’s world-famous beaches, there may be only sea walls defending fading mansions from the encroaching Pacific. In Northern California, tourists could have to drive farther north or to the cool edge of the Pacific to find what is left of the region’s signature wine country.

“We need to be attentive to the fact that changes are going to occur, whether it’s sea level rising or increased temperatures, droughts and potentially increased fires,” said Lisa Sloan, a scientist who directs the Climate Change and Impacts Laboratory at the University of California, Santa Cruz. “These things are going to be happening.”

Among the earliest and most noticeable casualties is expected to be California’s ski season.

Snow is expected to fall for a shorter period and melt more quickly. It may shorten the ski season by a month in wetter areas and end it in others.

Predicting the future

Because California has myriad microclimates, covering an area a third larger than Italy, predicting what will happen by the end of the century is a challenge.

But through a series of interviews with scientists who are studying the phenomenon, a general description of the state’s future emerges.

By the end of the century, temperatures are predicted to increase by 3 to 10 degrees Fahrenheit statewide. That could translate into even less rainfall across the southern half of the state, already under pressure from the increased frequency of wildfires and relentless population growth.

Small mammals, reptiles and colonies of wildflowers in the deserts east of Los Angeles are accustomed to periodic three-year dry spells. But they might not be able to withstand the 10-year drought cycles that could become commonplace as the planet warms.

Scientists already are considering relocating Joshua tree seedlings to areas where the plants, a hallmark of the high desert and namesake of a national park, might survive climate change.

“They could be wiped out of California depending on how quickly the change happens,” said Cameron Barrows, who studies the effects of climate change for the Center for Conservation Biology in Riverside.

Farther north, where wet, cold winters are crucial for the water supply of the entire state, warmer temperatures will lead to more rain than snow in the Sierra Nevada and faster melting in the spring.

In the central and southern Sierra, the giant sequoias that are among the biggest living things on Earth might be imperiled.

“I suspect as things get warmer, we’ll start seeing sequoias just die on their feet where their foliage turns brown,” said Nate Stephenson, a U.S. Geological Survey ecologist who is studying the effects of climate change in the Sierra Nevada. “Even if they don’t die of drought stress, just think of the wildfires. If you dry out that vegetation, they’re going to be so much more flammable.”

Among the more sobering projections is what is in store for marine life.

The upwelling season, the time when nutrient-rich water is brought from the ocean’s depths to the surface, nourishes one of the world’s richest marine environments.

That period, from late spring until early fall, is expected to become weaker earlier in the season and more intense later. Upwelling along the Southern California coast will become weaker overall.

As a result, sea lions, blue whales and other marine mammals that follow these systems up and down the coast are expected to decline.