American economist Jeffrey Sachs has attacked what he calls “right-wing” and “ideological” “conservatives” and “religious fundamentalists” allegedly funded by the coal-owning Koch brothers for having “mounted a fruitless protest” outside a meeting of “scientists” about climate change at the Pontifical Academy of Sciences at the end of April. The meeting is significant because the Academy provides advice to Pope Francis, who is expected to release an encyclical on the environment this month.

As one who witnessed the meeting and presented at the fruitful press conferences (not “fruitless” and not “protests”) held at a hotel facing St. Peter’s, may I reply to Mr. Sach’s charges?

First, the Koch brothers did not fund our visit to Rome, either in whole or in part. Mr. Sachs simply made that up. None of us were paid a dime to be there. How would Mr. Sachs like it if we called him “left-wing” and “Marxist” and “ideological” and “atheistic” and “taxpayer-funded”? A more mature approach is called for.

Something like 50,000 times as much is spent on promoting the pandemic of panic about our impact on the climate as is spent on pointing out that the predictions on which that panic was unsoundly founded have — to date at any rate — proven to be prodigious exaggerations.

Despite this egregious disparity in funding, we who dare to question the Party Line to which Mr. Sachs so unswervingly adheres have the evidence on our side. We were in Rome for one reason and one reason only: to point out that the science behind the climate scare, though strongly supported by a narrow political faction, is not supported by real-world measurement.

Mr. Sachs cites two opinion surveys as demonstrating that most Americans think manmade climate change is a problem. But both surveys are misleading. They were conducted by or on behalf of groups known to be parti pris in the climate debate. One was worded in a manner calculated to obtain the desired answer by inviting interviewees to assume from the outset that our influence on climate was causing global warming. The other was a notoriously unreliable Internet survey, with an error margin so wide as to vitiate the results on which Mr. Sachs relied.

Gallup, which knows how to do polling properly and is careful not to bias the results, has been conducting a major annual survey on attitudes to global warming since the late 1980s. In 2014 its survey showed global warming as second to bottom among voters’ concerns. This year, global warming is at the bottom even of Americans’ environmental concerns, attracting its lowest level of support since 1989.

In any case, grown-ups do not obtain scientific results by public opinion. Aristotle, 2,350 years ago, classified the head-count fallacy, which the medieval schoolmen later categorized as the argumentum ad populum, one of the commonest forms of bogus argument. Opinion polls are irrelevant to determining the truth of a scientific proposition.

The cleverer way to make the argumentum ad populum, of course, is to invoke a supposed scientific “consensus” in favour of climate catastrophe. It’s still a fallacy. Science should follow the evidence, not the majority opinion of scientists. For the record, though, only 0.3% of 11,944 climate-related papers in the reviewed journals from 1991-2011 even went so far as to say that most of the tiny warming since 1950 was manmade. How the UN’s Intergovernmental Panel on Climate Change (IPCC) turned this result into “95% confidence” that recent warming was mostly manmade is a mystery.

Mr. Sachs speaks of “the risk to our planet” posed by “global warming.” Yet thermometers show the Earth’s surface warming at a rate of one-twentieth of a degree per decade over the 11 years 2004-2014; bathythermographs show the upper mile and a half of the ocean warming at one-fortieth of a degree per decade over the same period; and satellites show the lower mile and a half of the atmosphere not warming at all for 18 years 5 months — indeed, they show no significant warming for a quarter of a century.

Models did not predict this near-total absence of recent global warming. Recently Dr. John Christy of the University of Alabama at Huntsville testified before Congress that the outputs of 102 climate models has exaggerated global warming compared with the measured outturn. And Dr. Held, an IPCC author, says 20 years without warming will settle the debate.

Yet there have been record increases in CO2 concentration. Though the rate at which man emits CO2 exceeds the IPCC’s 1990 business-as-usual prediction, the rate of global warming since then has fallen well below the entire range of the models’ predictions. It is exactly half of their then central estimate.

Besides, what is the ideal global mean surface temperature? Mr. Sachs does not tell us. Instead, he says we “reject earth science entirely, believing the world to be newly created.” Not one of us who went to Rome believes anything of the kind. Mr. Sachs made that up.

He went on: “The scientists at the Vatican meeting took extra care to emphasize that climate science and policy reflect fundamental principles of physics, chemistry, geology, astronomy, engineering, economics, and sociology, key parts of which have been well understood for more than 100 years.”

True, the existence of the greenhouse effect was posited 200 years ago, demonstrated empirically 150 years ago, and explained theoretically 50 years ago. Yet the amount of warming our enrichment of the atmosphere with CO2 may cause is not known and is, therefore, a matter of legitimate scientific debate. The lack of any recent warming strongly suggests catastrophe is not imminent.

In considering these matters, Pope Francis would do well to prefer real-world temperature measurements to Mr. Sachs’s opinion.