The President has made further, and grander, promises of future U.S. carbon cuts, but these are only vaguely outlined. In the unlikely event that all of these extra cuts also happen, and are adhered to throughout the rest of the century, the combined reduction in temperatures would be 0.057 degrees.
To put it another way, if the U.S. delivers for the whole century on the President's very ambitious rhetoric, it would postpone global warming by about eight months at the end of the century.
Now let's add in the rest of the world's Paris promises. If we generously assume that the promised carbon cuts for 2030 are not only met (which itself would be a U.N. first), but sustained, throughout the rest of the century, temperatures in 2100 would drop by 0.3 degrees – the equivalent of postponing warming by less than four years. Again, that's using the UN's own climate prediction model.
But here's the biggest problem: These miniscule benefits do not come free; quite the contrary.
The cost of the Paris climate pact is likely to run to 1 to 2 trillion dollars every year, based on estimates produced by the Stanford Energy Modeling Forum and the Asia Modeling Exercise. In other words, we will spend at least one hundred trillion dollars in order to reduce the temperature, by the end of the century, by a grand total of three tenths of one degree.
Some Paris Agreement supporters defend it by claiming that its real impact on temperatures will be much more significant than the U.N. model predicts. But this requires mental gymnastics and heroic assumptions.
The Climate Action Tracker, widely cited by Paris Agreement fans, predicts a temperature reduction of 1.6 degrees Fahrenheit by the end of the century. But this prediction is based very heavily on the assumption that even stronger climate policies will be adopted in the future. Actually, 98% of the assumed reductions will come only after 2030, which is what the current Paris agreement covers. And even such wishful thinking won't achieve anything close to the 2 degrees Celsius reduction that has become the somewhat arbitrary, but widely adopted, benchmark to avoid the worst effects of global warming. The actual promised emission reductions under the Paris agreement literally get us just 1 percent of the way to the 2 degrees target. 99 percent of what would be required is put off until after 2030.
