The balance of the scientific evidence supports the claim that man-made climate change is happening. That being said, there are many uncertainties with regard to how fast the climate might warm over the course of this century, how much it might warm, how fast sea level will rise, and so forth.
Climate scientists try to get a handle on the trajectory of climate change using computer climate models. When compared to observational temperature trends, the models' outputs have been somewhat less than robust. University of Alabama at Huntsville climatologist John Christy, who is a long-time skeptic of projections of future catastrophic warming, finds that computer model temperature increases average about 3 times greater than the actual temperature trends. A January 2017 paper in the Journal of Climate by researchers who unquestionably represent mainstream climate science corrected for satellite data trends and the inclusion of stratospheric cooling and also found that the models are warming 1.7 times faster than the observational temperatures.
In his column "Climate of Complete Certainty," New York Times opinion writer Bret Stephens sought to account for the skepticism of high percentage of Americans toward the dire warnings from environmentalists about impending catastrophic climate change. Stephens accepts that man-made warming is real; however, he observes that much else is still a matter of probabilities. From his column:
That's especially true of the sophisticated but fallible models and simulations by which scientists attempt to peer into the climate future. To say this isn't to deny science. It's to acknowledge it honestly....
Claiming total certainty about the science traduces the spirit of science and creates openings for doubt whenever a climate claim proves wrong. Demanding abrupt and expensive changes in public policy raises fair questions about ideological intentions. Censoriously asserting one's moral superiority and treating skeptics as imbeciles and deplorables wins few converts.
None of this is to deny climate change or the possible severity of its consequences. But ordinary citizens also have a right to be skeptical of an overweening scientism. They know—as all environmentalists should—that history is littered with the human wreckage of scientific errors married to political power.
As it happens, hundreds of thousands of climate activists this past weekend participated in the Peoples Climate March in Washington, D.C., along with subsidiary marches in 300 other cities. It is evident that many progressive marchers would eschew Stephens' warning against marrying uncertain science to political power and are entirely certain that climate change requires the complete transformation of the U.S. economy and society along more communitarian lines. It is not too much to say that environmentalists' apocalyptic climate rhetoric helped elect our current president.
The New York Post is reporting the nasty progressive backlash against Stephens who aim to get him fired from the Times.
For more background on the human wreckage of scientific errors made by political environmentalists see my book, The End of Doom: Environmental Renewal in the 21st Century. I also reprise failed predictions of impending environmental catastrophe from the first Earth Day in 1970.