Taking the Temperature

A Freeze-Thaw Cycle?

Global warming may have picked up steam with the dawn of the Industrial Age 200 years ago, but humans began altering the global climate thousands of years earlier. So argues William F. Ruddiman, professor emeritus of environmental sciences, in his book, Plows, Plagues and Petroleum: How Humans Took Control of the Climate, citing evidence gleaned from three-kilometer-thick Antarctic ice cores. The book won the Phi Beta Kappa Society’s 2006 Science Award.

Ruddiman’s hypothesis—which he calls “provocative and controversial”—asserts that the Earth’s wobbly orbit causes predictable ice-age cycles. As the Earth cools toward an ice age, concentrations of certain greenhouse gases, like carbon dioxide and methane, decline. As it thaws, greenhouse gases increase. Historic levels of these concentrations can be measured in air bubbles trapped in Antarctic ice, and ice-core sampling confirms many of these freeze-thaw cycles.

The cycles indicate that the Earth should be in a cooling period now, with greenhouse gases declining. But Ruddiman found that although the gases began to decline on schedule, they abruptly reversed course.

Carbon dioxide levels stopped declining and began increasing about 7,500 years ago—about the same time that human agricultural activity spread from the Fertile Crescent to Europe. Clearing forests by burning, or simply leaving trees to rot, released a climatically significant amount of CO2 into the air, Ruddiman argues.

Similarly, methane levels stopped declining and began to increase about 5,000 years ago—about the same time that rice irrigation began in China. As the oxygen in water gets used up, he explains, carbon from rotting plant material is released as methane or “swamp gas.”

“Until I came up with this hypothesis, most people thought [global warming] started about the time that Jefferson was building the University,” Ruddiman says. He suggests that pre-Industrial Age warming may account for nearly half of the temperature rise seen since the warming trend began—and that had natural cycles not been interfered with, global temperatures would be lower by three to four degrees centigrade, with ice spreading over much of northeastern Canada.

Act Now

Systems ecologist H.H. “Hank” Shugart has studied environmental change on a global scale since 1984, when he wrote the first assessment of the effects of climate change on terrestrial ecosystems. His computer models predict effects on the world’s forests not only from climate change, but also from wildfires, land use and other factors.

Is there really a climate-change crisis? Not exactly, he says.

“The word ‘crisis’ implies a short-term, immediate problem that hopefully has some sort of short-term, immediate solution,” says Shugart, who directs UVA’s Center for Regional Environmental Studies.

But this problem is not limited to climate change, and solutions will require substantial changes in our economic, social and governmental structures, he warns. He is particularly concerned by the politicization of environmental research, which he calls “an unfortunate and worrisome trend.”

“We have substantively scaled down our national capability to understand how our planet works at the very time we should be learning more,” he says, citing in particular the possibility of abetting consequences that might be difficult to reverse, like altering ocean currents or melting permafrost. “The wisdom to manage a planet that we are now vicariously changing must be fed by knowledge. We really can’t afford to stick our heads in the sand when we know we are changing the Earth itself.”

His message, simply put: reduce our energy consumption now.

Pollution For Sale

Vivian Thomson, co-founder and director of UVA’s Environmental Thought and Practice program, spent part of 2006 in Europe monitoring the early phases of the European Union’s emissions trading program.

Theoretically, she says, it shows great promise.

Under the program, a country that seeks to cut total greenhouse gas emissions in its power industry by 10 percent a year, for example, would give each company in that industry annual emissions allowances, with the total of all allowances adding up to 90 percent of the previous year’s output. If Company A retools its power plants and achieves a 25 percent reduction, it can sell its extra allowances on an open market. There, they might be purchased by Company B, which opts not to install new equipment and is emitting 5 percent more pollution than the previous year. At the end of the year, each company’s emissions must match the allowances it holds. Thus, “the market will find a way to most efficiently reduce its emissions,” Thomson says.

Thorough monitoring is needed to discourage cheating, plus heavy penalties for violators. The EU program—modeled on a U.S. system for reducing sulfur dioxide allowances—appears to be effective in its early stages. While there are kinks to be worked out, the EU appears on its way to meeting its obligations under the 1997 Kyoto Protocol. “The level of commitment is very strong in both the public and private sectors,” she says. “I never once heard them say, ‘Do I have to do this?’”

Cap-and-trade programs are being proposed in the U.S., both on the state and federal levels. With economists asserting that prevention of global warming is cheaper than remediating its effects, “It’s not a question of whether it will happen here; it’s a question of when,” Thomson says.