Greenhouse gases rise from a coal-burning plant in Gelsenkirchen, Germany, contributing to warming. Photo: Martin Meissner, Associated Press
Washington -- In his inaugural address last Monday, President Obama made climate change a priority of his second term. It might be too late.
Within the lifetimes of today's children, scientists say, the climate could reach a state unknown in civilization.
In that time, global carbon dioxide emissions from burning fossil fuels are on track to exceed the limits that scientists believe could prevent catastrophic warming. CO2 levels are higher than they have been in 15 million years.
The Arctic, melting rapidly and probably irreversibly, has reached a state that the Vikings would not recognize.
"We are poised right at the edge of some very major changes on Earth," said Anthony Barnosky, a UC Berkeley professor of biology who studies the interaction of climate change with population growth and land use. "We really are a geological force that's changing the planet."
Wholesale shift needed
The Arctic melt is occurring as the planet is just 1.4 degrees Fahrenheit (0.8 degree Celsius) warmer than it was in preindustrial times.
At current trends, the Earth could warm by 4 degrees Celsius in 50 years, according to a November World Bank report.
The coolest summer months would be much warmer than today's hottest summer months, the report said. "The last time Earth was 4 degrees warmer than it is now was about 14 million years ago," Barnosky said.
Experts said it is technically feasible to halt such changes by nearly ending the use of fossil fuels. It would require a wholesale shift to renewable fuels that the United States, let alone China and other developing countries, appears unlikely to make, given that many Americans do not believe humans are changing the climate.
"Science is not opinion, it's not what we want it to be," said Katharine Hayhoe, an evangelical Christian and climatologist at Texas Tech University who was lead author of a draft report on U.S. climate change issued this month by the National Climate Assessment and Development Advisory Committee, which was created by the federal government.
"You can't make a thermometer tell you it's hotter than it is," said Hayhoe, who with her husband, a linguist and West Texas pastor, has written a book on climate change addressed to evangelicals.
"And it's not just about thermometers or satellite instruments," she said. "It's about looking in our own backyards, when the trees are flowering now compared to 30 years ago, what types of birds and butterflies and bugs that ... used to be further south."
Robins are arriving two weeks early in Colorado. Frogs are calling sooner in Ithaca, NY. The Sierra Nevada snowpack is melting earlier. Cold snaps, like the one gripping the East, still happen, but less often. The frost-free season has lengthened 21 days in California, 9 days in Texas and 10 in Connecticut, according to the draft climate report.
Extreme weather
Scientists are loath to pin a specific event, such as Hurricane Sandy, to global warming.
But "the risk of certain extreme events, such as the 2003 European heat wave, the 2010 Russian heat wave and fires, and the 2011 Texas heat wave and drought has ... doubled or more," said Michael Wehner, a staff scientist at Lawrence Berkeley National Laboratory and co-author of the climate report.
"Some of the changes that have occurred are permanent on human time scales."
Last year, the continental United States was the hottest it has ever been in the 118 years that records have been kept. Globally, each of the first 12 years of the 21st century were among the 14 warmest ever.
Connecticut was 7.2 degrees Fahrenheit (4 degrees Celsius) warmer than the 20th century average. At current rates of CO2 emissions, scientists expect New England to have summers resembling the Deep South within decades.
The pine bark beetle, held in check by winter freezes, is epidemic over millions of acres of forests from California to South Dakota.
Oceans, which absorb CO2, have increased in acidity, damaging coral reefs, shellfish and organisms at the bottom of the food chain. Washington state shellfish growers have seen major failures in oyster hatcheries because the larvae don't form shells.
A report this month by the National Research Council, a public policy branch of the National Academies, said such changes in ocean chemistry in the geologic past were accompanied by "mass extinctions of ocean or terrestrial life or both."
Tipping point
A key question is when greenhouse gas emissions might reach a point where changes become self-reinforcing and out of human control.
Arctic sea ice reflects the sun. As it melts, the dark ocean absorbs more solar heat, raising temperatures. Similarly, the Greenland ice sheet is melting rapidly, reducing reflectivity and heating the Earth faster, possibly speeding up the melting of the West Antarctic ice sheet.
The northern permafrost is thawing, with the potential to release methane, a potent greenhouse gas, and CO2 stored in soils. These can produce sudden changes that are hard to predict.
"We could be at a tipping point where the climate just abruptly warms," said Mark Z. Jacobson, director of Stanford University's atmosphere/energy program.
Changes over time
UC Berkeley's Barnosky said tipping points could come earlier than anticipated when factoring in population growth and land use. More than 40% of the Earth's land surface has been covered by farms and cities. Much of the rest is cut by roads. By 2025, that footprint could reach 50 percent, a level that on smaller scales has led to ecological crashes, such as a fisheries collapse or an ocean dead zone.
"It's just sort of simple math: The more people, the more footprint," Barnosky said. "If we're still on a fossil fuel economy in 50 years, there is no hope for doing anything about climate change. It will be here in such a dramatic way that we won't recognize the planet we're on."
Not all climate scientists are so gloomy. Ashley Ballantyne, a bioclimatologist at the University of Montana who studies paleoclimate records, said the climate has always changed, with ice ages, warmings and mass extinctions. At current CO2 concentrations, the Arctic and Greenland are likely to become ice free, as they were 4 million years ago, he said.
Polar bears are poorly adapted to such conditions, he said, "but it wasn't bad for boreal trees. They were quite happy."
An international political consensus set as a danger zone a global temperature increase of 3.6 degrees Fahrenheit (2 degrees Celsius), which is expected in 25 years based on current trends and when atmospheric concentration of CO2 reaches 450 parts per million. It is now almost 400 parts per million. [CO2 equivalents are much higher than 400.]
Two degrees Celsius is "an arbitrary number," said Alan Robock, director of the Center for Environmental Prediction at Rutgers University. "On our current path, we will go zooming way past that."
Climatologist James Hansen, head of NASA's Goddard Institute for Space Studies, and activist Bill McKibben, founder of 350.org, believe the only way to preserve the Holocene climate humans are used to is to cut CO2 concentrations to 350 parts per million, last seen around 1988. [Actually, 350 ppm is not considered safe anymore -- better to get lower than 300 ppm.]
Ballantyne dismissed the 350 goal: "That's like a 70-year-old alcoholic saying, 'I'm going quit drinking when I'm 60 years old.' "
McKibben and Hansen propose a tax on fossil fuels at their source, to be reimbursed to all U.S. residents, as Sen. Bernie Sanders, independent-Vt., plans to propose in a "fee and dividend" scheme modeled on Alaska's oil royalty rebates to state residents.
Carbon tax unlikely
White House press secretary Jay Carney, asked Wednesday about the Sanders bill, said: "We have not proposed and have no intention of proposing a carbon tax."
It would have to be a big tax, McKibben said, "that drives up the price quickly. Maybe you go to the pump someday and you're paying what people in Europe pay for gasoline, which is good, because then it reminds you every time you go to the pump that you don't really need a semi-military vehicle to go to the grocery store."
Stanford's Jacobson maintains that wind and solar could power the world many times over. He calculated that the world would need to install 1.7 billion solar rooftops and 4 million wind turbines.
Jane Long, chair of the California Council on Science and Technology, said any such conversion would be costly and difficult at best. Still, she said, "one way to get out of the hole is to stop digging."
Carolyn Lochhead is The San Francisco Chronicle's Washington correspondent. E-mail: clochhead@sfchronicle.com
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