When you hear politicians speak (the president or members of Congress) and they tell you that the science or facts are settled, do you tend to believe them or treat their comments with skepticism? Those who survey such things show that faith in government and politicians has fallen to record lows. But many other professions have also seen a decline in public trust.

The government produces a “food pyramid” and dietary guidelines telling us what is good for us to eat and what is not. But it keeps changing — eggs and whole milk were bad, and now they are good. The “settled science” that eating foods high in cholesterol would increase an individual’s cholesterol turned out to be not necessarily true.

The global warming alarmists keep telling us the science is settled — but doomsday keeps being pushed back. Not one of the major global warming models predicted the recent 18-year pause in global warming. We were supposed to have more intense storms, floods and droughts. It didn’t happen. In fact, Florida has just set a record for the amount of time without a hurricane hitting. The Arctic Ocean was supposed to be largely free of ice by 2009, as I recall Al Gore saying, making it open to shipping. Didn’t happen, the Arctic ice is still there. And the Antarctic sea ice has increased in area, and the land-based ice is increasing, according to a new NASA study. The president, we are told, is frustrated because fewer and fewer believe him when he says global warming is the world’s greatest threat — but he has been telling us for years that it may be too late to take action — and, if so, why should we saddle ourselves with massive energy costs and other expenses? (Wasn’t it Michael Mann, the author of the famous “hockey stick” environmental scenario back in the 1990s, who told us if we did not act by 2003, it would be too late?) The president argues that it is those stupid Republicans who fail to see the crisis the way he does — so why is it that rich liberals keep buying low-lying waterfront property if it is all going to soon disappear? Clearly, they do not expect sea levels to rise at a much more rapid rate then they have in recent centuries.

The eminent biochemist, Bruce Ames, who developed an inexpensive way of determining potential carcinogens — the Ames test for cancer-causing agents — was a hero of the environmentalists. But Mr. Ames soon became a critic of the misuse of his test in that too few were looking at relative risks, and overestimating the real likelihood that many pesticides and other chemicals would cause cancer, while ignoring the great benefits to overall nutrition by using such chemicals. For example, the chemical Alar enables apple growers to produce better and cheaper apples that are good for you. After ill-informed attacks on Alar, it was banned, even though subsequent tests showed one would have to drink about 5,000 gallons of apple juice per day to be at significant risk.

Many blame gun violence and terrorist acts on the availability of guns. It seems logical — no guns, no gun violence. The number of guns in the United States has been growing rapidly. Various estimates put the number of guns to well over 300 million, or more than one gun per person. Yet despite all of the news hype, the number of gun deaths has been falling, not rising. Economist John Lott has done considerable serious work on gun crime and violence, and is the author of “More Guns, Less Crime” and other books and academic articles on crime and guns. Mr. Lott argues that some of the safest places in America are places where legal gun ownership is very high and vice versa. The “science” of the value of gun restriction is certainly not settled. There is also the inconvenient fact that guns can be easily obtained almost anywhere on the planet, despite gun bans — Paris, for instance. Crude guns are easy to make, and now they can even be made on 3D printers.

A couple of days ago, a trusted colleague informed me about an interesting website, retractionwatch.com, which reports on all recalled scientific papers that were found to be incorrect. The percentage of recalled papers, even in the major science journals, is uncomfortably high. There is always the big press release about the new blockbuster scientific or medical breakthrough, but the later retractions tend to get buried.

Politicians have always been prone to whoppers: “You can keep your doctor”; “there were no classified emails on my server”; “I did not have sex with that woman.” But the apparent rise of those in public life, including scientists and economists, making “settled science” statements, (which they may actually believe) when the science is far from settled, is doing as much as the “whoppers” to undermine public confidence. The great economist-philosopher, F.A. Hayek, in his essay on the limits to knowledge, warned us to be modest in what we claim to know for certain. That’s good advice.