Are Humans to Blame for Global Warming?

Global warming is an environmental, economic, scientific, and political problem of the first order, and one doubly difficult to address because its dangers lie decades in the future. So if we are to act now to head it off, we must first scrutinize what is known about the nature of the threat. Should we place our faith in the Kyoto Treaty, which sets firm limits on human emissions of so-called greenhouse gases? Or is the US administration right to reject the Kyoto Treaty, because targeting emissions is based on "bad science"?

Circumstantial evidence does indeed point to our profligate burning of fossil fuels and perhaps also to its impact on global warming. Since 1900 the global temperature of the Earth's atmosphere and ocean surface waters has risen by 0.5-1 degree Celsius, and the prime suspect is atmospheric carbon dioxide, CO2, which is second only to water vapor in its greenhouse effect. Since 1860, when the industrial revolution and soaring population growth led to widespread consumption of fossil fuels, the volume of atmospheric CO2 has increased by about 28%.

The increase began slowly, rising from 290 parts per million in 1860 to 295 ppm in 1900. But it then accelerated rapidly, reaching 310 ppm in 1950 and 370 ppm in 2000, with half of the total gain of 80 ppm occurring just since 1975. Numerical global climate models suggest that a doubling of the current atmospheric accumulation of CO2 will produce further warming of 3-5 degrees Celsius, perhaps as soon as 2050.

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