Global-warming skeptics: Might warming be 'normal'?

Some say that today's climate change is merely part of a natural cycle.

from the September 20, 2007 edition

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James Wang, a scientist in the climate and air program at Environmental Defense in New York, points out the close correlation between computer model predictions of how much heat has been trapped by greenhouse gases with measurements of how much heat has been stored in the global oceans over the past few decades.

"The earth has gotten warmer over the past 30 years, and a lot of that additional heat has gone into the oceans," Dr. Wang says. "We find that none of the natural factors, such as sunlight and volcanoes, can explain the warming that has occurred over the past 30 years or so."

Electricity, cars, and cement's effect

In a recent report, Wang and colleague Bill Chameides, chief scientist at Environmental Defense, write:

"Independent measurements demonstrate that the increased CO2 in the atmosphere comes from burning fossil fuels and forests. The isotopic composition of carbon from these sources contains a unique 'fingerprint.' The only quantitative and internally consistent explanation for the recent global warming includes the intensified greenhouse effect caused by the increase in CO2 and other greenhouse gases."

This is essentially what the United Nations Intergovernmental Panel on Climate Change (IPCC) concluded in its most recent report issued earlier this year. The report notes that concentrations of CO2 and of methane (another major greenhouse gas) today are "both very likely much higher than anytime in at least 650,000 years."

Burning fossil fuels to heat and light homes and offices, power vehicles, and even to manufacture cement (which releases high amounts of CO2) accounts for more than 75 percent of the increase in CO2 concentration during the industrial age, according to the IPCC, with the rest attributable to such land use changes as deforestation and biomass burning.

The type of CO2 in the atmosphere today, "in particular the ratio of its heavy to light carbon atoms," identifies it as having come from the burning of fossil fuels, the report says.

Climate change skeptics aren't convinced. Neither Taylor nor Meyer deny that ocean temperatures have been rising. But they say the picture is more complicated and inconclusive than Drs. Wang and Chameides do.

Looking at the data on temperature predictions from the IPCC, Meyer of the "Skeptical Layman's Guide" concludes that "if anything, the United Nations is overstating it. Even taking the worst it could be, it's not going to be that bad," he says, referring to what he sees as alarmist forecasts by Mr. Gore and others. "Therefore under no circumstances should we be doing things [to combat climate change] that are extraordinarily intrusive."

We'd like to hear from you. Do you think climate change skeptics are raising persuasive points or ignoring strong scientific evidence? Write to us at oped@csmonitor.com

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