Trump administration predicts a 7-degree global temperature rise.

Last month, deep in a 500-page environmental impact statement, the Trump administration made a startling assumption: On its current course, the planet will warm a disastrous 7 degrees by the end of this century.

A rise of 7 degrees Fahrenheit, or about 4 degrees Celsius, compared with pre-industrial levels would be catastrophic, according to scientists. Many coral reefs would dissolve in increasingly acidic oceans. Parts of Manhattan and Miami would be under water without costly coastal defenses. Extreme heat waves would routinely smother large parts of the globe.

David Pettit, a senior attorney at the Natural Resources Defense Council who testified against Trump's freeze of car mileage standard Monday in Fresno, California, said his organization is prepared to use the administration's own numbers to challenge their regulatory rollbacks. He noted that NHTSA document projects that if the world takes no action to curb emissions, current atmospheric concentrations of carbon dioxide would rise from 410 parts per million to 789 ppm by 2100.