@RichardAEpstein: President Pittsburgh rejects President Paris. @HooverInst
Photo: Global warming is a slow, steady rise in Earth's surface temperature. Temperatures today are 0.74° C (1.33° F) higher than 150 years ago. Many scientists say that in the next 100–200 years, temperatures might be up to 6° C (11° F) higher than they were before the effects of global warming were discovered. Of the greenhouse gases, the basic cause seems to be a rise in atmospheric carbon dioxide concentration, as predicted by Svante Arrhenius a hundred years ago. When people use fossil fuels like coal and oil, this adds carbon dioxide to the air. When people cut down many trees (deforestation), this means less carbon dioxide is taken out of the atmosphere by those plants.
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