You state in this article that “an increase in the atmospheric concentration of carbon dioxide, not an increase in solar radiation” is responsible for current global warming. What is the scientific—not political—basis for that remark?

Warren Finley
Laguna Beach, Calif.

Increasing solar radiation doesn’t affect climate change? Doesn’t changing the thermostat change the temperature in a room?

Sean Walton
Orem, Utah.

In February, the Intergovernmental Panel on Climate Change acknowledged that an increase in solar radiation had generated a slight warming of Earth since 1750 ( SN: 2/10/07, p. 83 ). Over that same interval, however, the IPCC reports that warming attributed to human-caused emissions of greenhouse gases such as carbon dioxide and methane has been about 20 times greater.—S. Perkins

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