A rise of 7 degrees Fahrenheit, or about 4 degrees Celsius, compared with preindustrial levels would be catastrophic, according to scientists. Many coral reefs would dissolve in increasingly acidic oceans. Parts of Manhattan and Miami would be underwater without costly coastal defenses. Extreme heat waves would routinely smother large parts of the globe.
But the administration did not offer this dire forecast as part of an argument to combat climate change. Just the opposite: The analysis assumes the planet’s fate is already sealed.The statement was part of an effort to justify freezing federal fuel efficiency standards for cars and light trucks built after 2020. Although the policy change would increase greenhouse gas emissions, the impact statement says, that policy would make little difference in temperatures.