tiny compared to the radiative effects of the gases. Convection currents are blocked by the glass of greenhouses, but not by greenhouse gases. But CO2 does absorb some of the infrared radiation emitted from the planet. Absorbing an infrared photon puts a CO2 molecule into an excited state, and fairly quickly the molecule returns to its unexcited state by emitting a photon of the same energy. Some of those photons emitted by excited CO2 molecules head back toward Earth (the emission direction is random). So, the CO2 serves to trap energy in the Earth system, warming the planet so that it glows more brightly to shove infrared radiation past the CO2, achieving a new balance. Points Earned: 1/1 Correct Answer: D Your Response: D 11.The United Nations-sponsored Intergovernmental Panel on Climate Change shared the2007 Nobel Peace Prize. The information that the Panel has supplied to policymakers includes: A.The observed rise in atmospheric CO2levels has been caused primarily by a sudden increase in explosive volcanism, and is causing the climate to warm.B.The observed rise in atmospheric CO2levels has been caused primarily by human fossil-fuel burning, and very likely is causing warming of the climate that is unlikely to become much larger.C.
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