“Without significant [greenhouse gas emission] reductions, annual average global temperatures could increase by 9°F (5°C) or more by the end of this century compared to pre-industrial temperatures.” The increasingly dire effects will be sea-level rise, fires, floods, droughts, heat waves, ocean acidification, shrinking glaciers, disappearing Arctic sea ice, “growing challenges to human health and safety, quality of life, air quality, and the transmission of disease through insects and pests, food, and water and the rate of economic growth,” and “challenges to livestock health, declines in crop yields and quality, and changes in extreme events in the United States and abroad threaten rural livelihoods, sustainable food security, and price stability.” In short, an unspeakable planetary calamity “could” be coming.

The mainstream news media’s coverage of the report was predictably contrived to induce panic. The media featured the report’s recurring statement that the dominant cause (Washington Post: “almost entirely”) of its projected grim consequences is human action. Announced CBS News: “Mass deaths and mayhem: National Climate Assessment’s most shocking warnings — billions of hours in productivity will be lost. Hundreds of billions of dollars will be wiped from the economy. Tens of thousands of people will die each year.”

But what’s new here? The report, relying on passive constructions such as “is projected to be,” seems to collect all of the contentions made by climate alarmists over the past 30 years, and announce them again with a redoubled sense of urgency.

The “projections” are founded on computer models that, over the same period, have seriously overestimated the observed increase in global temperature. The report repeatedly tells us that somebody, unnamed, has “very high confidence” in certain of their own projections.

One critic has described the output as “an assembly of prophecies,” made by prophets whose careers in government-funded agencies will assuredly diminish if they don’t contribute to the correct planetary disaster narrative.

Equilibrium Climate Sensitivity is defined as the temperature increase that will result from a doubling of atmospheric carbon dioxide (now 410 ppmv). For 30 years, the ”official” ECS has been estimated as 1.5 to 4.5°C, average 3.0, an extraordinarily broad range.

Climatologist Judith Curry (Georgia Tech) writes that “Climate sensitivity and estimates of its uncertainty are key inputs into the economic models that drive cost-benefit analyses and estimates of the social cost of carbon. Continuing to rely on climate-model warming projections based on high, model-derived values of climate sensitivity skews the cost-benefit analyses and estimates of the social cost of carbon.”

At least four recent scientific papers, including hers, have concluded that the ECS is more like 1.6° C. If so, even with continuing greenhouse gas emissions, warming will be gradual, comfortable and probably net beneficial.

The tangible benefits from a warming planet are not conceded in the report. Since the present warming — not caused by humans — began around 1850, living on Earth has become a much happier experience. We have longer growing seasons, fewer crop-destroying cold snaps, greater food production, fewer deaths from cold, less need for heating fuels and less costly winter highway maintenance.

What of the report’s supposed 4-percent (+/-2 percent) reduction in global GDP resulting from a purely conjectural 9°F global average temperature increase by 2090? New York University physics professor Stephen Koonin, who was an Obama appointment as undersecretary of energy for science, puts that claim in perspective. Assuming a very conservative 2-percent annual global GDP growth rate, “the U.S. economy in 2090 would be no more than two years behind where it would have been absent man-made climate change.” (WSJ 11/27/18).

Yes, climate is changing, and human activity, notably land-use changes and fossil-fuel combustion, is, in part, responsible. Whether human activity is the “dominant” cause remains debatable. Debatable, too, is whether the cost of reducing global fossil-fuel combustion to non-threatening (to climate activists) levels demands too great a price in prosperity and human well-being.

Rational people are right to harbor serious doubts about this report’s dire and highly speculative projections.

John McClaughry is Ethan Allen Institute vice president.