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The Intergovernmental Panel on Climate Change, an international body comprising dozens of countries and thousands of scientists, released a long-awaited report today that confirms human beings are “very likely” causing global warming.

The United Nations-sponsored report effectively concludes the debate about whether humans are causing global warming and comes as the United States’ reluctance to address the issue with federal policy begins to wane.

“There’s now no doubt on the science,” said Tony Haymet, director of Scripps Institution of Oceanography. “The planet is warming: land, atmosphere, oceans.”

Here are the major points of the IPCC report, the fourth released since 1988:

  • The climate’s warming is unequivocal, which is evident in increases in global average air and ocean temperatures, widespread snow- and ice-melt and rising sea levels.
  • Several long-term climate changes are occurring: Widespread changes in rainfall amounts, ocean salinity, wind patterns and aspects of extreme weather including droughts, heavy precipitation, heat waves and the intensity of hurricanes.
  • The last 50 years have been warmer than any similar period in at least 1,300 years.
  • Warming will continue for centuries, even if greenhouse gas emissions are stabilized.

The report highlights the role San Diego has had both in diagnosing global warming and in studying its varied impacts. Charles David Keeling, a now-deceased Scripps Institution of Oceanography professor, was the first scientist to document the steady decades-long increase in the atmosphere’s carbon dioxide levels. Four Scripps professors — Mario Molina, Lynne Talley, Veerabhadran Ramanathan and Richard Somerville — contributed to the latest IPCC report, which will be issued in its full 1,644-page form in May.

The report synthesizes hundreds of published research papers. It provides the consensus on the past, present and future of climate change: how much warming is expected in the next century, what’s causing it, what its impacts will be. Think of it as the periodic census of climate science.

“It’s a start. But the real progress is going to be made when people start worrying about the regional impacts,” said Tim Barnett, a Scripps marine physicist who has contributed to previous IPCC reports. “Until we translate this to the regional, my-backyard scale, we’re not going to get movement.”

At a midday press conference, Dan Cayan, a Scripps research meteorologist, said San Diego could expect an average 4-degree Fahrenheit temperature increase by 2100 — tempered because of its proximity to the ocean. Further inland near El Centro, the increase may be as high as 8 degrees Fahrenheit.

California’s springtime snow melt and plant blooms are already occurring a week earlier, Cayan said. “The alarming thing, this is just a taste of what is probably going to happen,” he said.

The Sierra Nevada range — a major California drinking water source — will lose 40 percent of its springtime snow pack in best-case scenarios, Cayan said. At worst, it will lose 80 percent.

We have previously examined the impacts global warming can have on our water supply and sea levels.

ROB DAVIS

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