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Scientists Predict Droughts,
Rise in Temperatures, Sea Levels in Global Warming Report

Ioana Patringenaru | February 5, 2007

Temperatures will probably increase by 3.2 to 7.2 degrees Fahrenheit by 2100. Sea levels will rise by 7 to 23 inches. Many of the world’s most populated regions will face severe water shortages.

Tony Haymet (Photo / Victor W. Chen)
Tony Haymet, director of the Scripps Institution of Oceanography at UCSD
See a video clip of Haymet (Quicktime).

Scientists made these dire predictions in a report issued Friday in Paris by the Intergovernmental Panel on Climate Change. This was the IPCC’s fourth report since 1990. For the first time, it states with near-certainty that global warming is man-made.

“This morning, we received a sober assessment of the state of the planet’s climate,” said Tony Haymet, director of the Scripps Institution of Oceanography at UCSD, at a press conference at the Birch Aquarium Friday. “The planet is warming, land, atmosphere, ocean. This fact is unequivocal.”

IPCC findings are based on an extensive three-year review of climate change research, including complex computer simulations modeling the impact of global warming.

Some 600 scientists from 40 countries collaborated on the project. More than 620 experts and representatives from113 governments reviewed it. Scripps professor Richard Somerville and Mario Molina, a Nobel Prize winner and UCSD professor of chemistry and biochemistry, were two of the report’s drafting authors. Lynne Talley, a Scripps expert on oceanic and atmospheric conditions, was a lead author on one chapter. Scripps’ V. Ramanathan, an expert on climate, greenhouse gases and particulate pollutants, acted as a reviewer.

Lynne Talley and V. Ramanathan (Photo / Victor W. Chen)
Scripps researchers Lynne Talley and V. Ramanathan, who worked on the IPCC report.

Friday, Sommerville and Molina were in Paris. But Talley and Ramanathan, as well as other Scripps scientists, were on hand at the Scripps press conference to comment on the findings.

Report highlights include:

Temperatures could rise between 2 to 11.5 degrees Fahrenheit by the end of the century, depending on how much greenhouse gas emissions continue to rise. Scientists forecast temperatures are most likely to increase by 3.2 to 7.2 degrees Fahrenheit. By contrast, temperatures have risen 1.5 degrees in the last 100 years.

Sea levels are likely to increase anywhere from 7 to 23 inches, depending on how much the planet warms.

Semi-arid tropical regions will face more severe droughts, with a 20 percent drop in rainfall under the IPCC midrange forecast for a rise in greenhouse gas emissions.

Tim Barnett (Photo / VIctor W. Chen)
Scripps researcher Tim Barnett
See a video clip of Barnett (Quicktime).

Californians live in a semi-arid region where dry areas will probably get drier and wet areas wetter, Scripps researcher Talley said. “We may drown, but we’ll probably burn first here,” she joked.

Temperatures in California could rise anywhere from 3 to 7 degrees Fahrenheit by 2100, added Scripps meteorologist Dan Cayan. For example, ocean temperatures might warm by about 4 degrees at the coast, but that could mean 8-degree temperature increases in El Centro, he said.

The state’s water supply also is at risk, scientists warned. Between 40 to 80 percent of the Sierra Nevada snow pack could disappear, Cayan said. Water shortages will hit California in a few decades, predicted Tim Barnett, a Scripps marine geophysicist. Worldwide, shortages will get even worse, he said.

“Basically, what we’re headed for on a global basis is a catastrophe for water supplies,” he said.

What is causing dramatic shifts in the planet’s climate? Greenhouse gases, such as carbon dioxide, act like a blanket, trapping heat that would otherwise escape into space, said Ramanathan. The heat trapped is roughly equivalent to the heat generated by 25 trillion light bulbs burning constantly, he said. “Each one of us is burning 4000 light bulbs, every second, every day, every night,” he said.

Global Warming
Rising temperatures: click here to see a chart showing projected temperature changes from 2020 to 2099.

Carbon dioxide also has a long life, Ramanathan pointed out. About 30 percent of the gas that is around today will still be here 100 years from now. So even if greenhouse gas emissions stabilized at today’s level, the planet would continue to warm over the next 100 years, he said.

What can we do about it? Today’s concentration of CO2 is 379 parts per million, according to the IPCC report. We would have to cut fossil fuel emissions by as much as 70 to 80 percent over the next 50 years just to stabilize CO2 concentration to 450 to 550 parts per million, said Scripps global warming researcher Ralph Keeling.

Keeling and colleagues, including Somerville, published in Science Magazine Friday a score card for the IPCC report released in 2001. The organization got most of its predictions right, Keeling said. But it tended to be more conservative in some areas, including sea level rise, he added.

In fact, melting ice sheets in the planet’s polar regions remain a big question mark, scientists said. It’s not clear how quickly they deteriorate, Talley said. The last time polar regions were significantly warmer for a long period of time was 125,000 years ago, when sea levels were about 12 to 20 feet higher than today, according to the report.

“The science is really done now,” said Barnett. “We need to get on with mitigation.”

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