Unsettled: What Climate Science Tells Us, What It Doesn’t, and Why It Matters

by Steven E. Koonin

Computer modeling is central to climate science. The models help us understand how the climate system works, why it has changed in the past, and—most importantly—how it might change in the future.

But remember: Climate is not weather. Rather, it’s the average of weather over decades, and that is what climate models try to describe.

And since different modelers will make different assumptions, results can vary widely among models. This is not at all an unimportant detail, since ordinary fluctuations in the height and coverage of clouds can have as much of an impact on flows of sunlight and heat as do human influences. In fact, the greatest uncertainty in climate modeling stems from the treatment of clouds.

For example, as the globe gets warmer, there’ll be less snow and ice on the surface, which decreases the planet’s albedo. The less reflective earth will then absorb more sunlight, causing even more warming. Another example of a feedback is that as the atmosphere warms, it will hold more water vapor, which further enhances its heat-intercepting ability.

The failure of even the latest models to warm rapidly enough in the early twentieth century suggests that it’s possible, even likely, that internal variability—the natural ebbs and flows of the climate system—has contributed significantly to the warming of recent decades.20 That the models can’t reproduce the past is a big red flag—it erodes confidence in their projections of future climates. In particular, it greatly complicates sorting out the relative roles of natural variability and human influences in the warming that has occurred since 1980. FIGURE 4.5 Global mean surface temperature anomalies from twenty-six CMIP6 models. Individual model runs are shown as light gray traces, while the dark lines are three different observational data sets. Anomalies are relative to an 1880–1910 baseline, and the curves are smoothed over eleven-year intervals.19

In other words, the researchers tuned their model to make its sensitivity to greenhouse gases what they thought it should be. Talk about cooking the books.

The uncertainties in modeling of both climate change and the consequences of future greenhouse gas emissions make it impossible today to provide reliable, quantitative statements about relative risks and consequences and benefits of rising greenhouse gases to the Earth system as a whole, let alone to specific regions of the planet.

In short, the general lack of knowledge of what the science actually says, the drama of extreme weather events and their heart-rending impact on people, and pressures within the industry all work against balanced coverage in the popular media.

It is time to return to the ethics and norms of science so that the political process may go on with greater confidence. The public may wonder why we do not already know that which appears vital to decision—but science will retain its place in public esteem only if we steadfastly admit the magnitude of our uncertainties and then assert the need for further research. And we shall lose that place if we dissemble or if we argue as if all necessary information and understanding were in hand. Scientists best serve public policy by living within the ethics of science, not those of politics.11

The most difficult subjects can be explained to the most slow-witted man if he has not formed any idea of them already; but the simplest thing cannot be made clear to the most intelligent man if he is firmly persuaded that he knows already, without a shadow of doubt, what is laid before him.

Crichton’s conversations with Caltech professor Murray Gell-Mann (the Nobel prize–winning physicist who was one of the first researchers to hypothesize quarks) led him to describe the “Gell-Mann Amnesia” effect: You open the newspaper to an article on some subject you know well. In Murray’s case, physics. In mine, show business . . . In any case, you read with exasperation or amusement the multiple errors in a story, and then turn the page to national or international affairs, and read as if the rest of the newspaper was somehow more accurate about Palestine than the baloney you just read. You turn the page, and forget what you know.18

Any appeal to the alleged “97 percent consensus” among scientists is another red flag. The study that produced that number has been convincingly debunked.8 And in any event, nobody has ever specified exactly what those 97 percent of scientists are supposed to be agreed upon. That the climate is changing? Sure, count me in! That humans are influencing the climate? Absolutely, I’m there! That we’re already seeing disastrous weather impacts and face an even more catastrophic future? Not at all obvious (for reasons I hope you understand, having read this far).

Confusing weather and climate is another danger sign. One year’s bad weather does not make for a changing climate; climate is determined over decades. And a headline might say “Most active storm season in thirty years!” . . . but if it happened before, when human influences were much weaker, natural variability must play a major role.

Economists have known for 150 years about “rebound”—that is, that efficiency improvements often lead to less conservation than might be expected. For example, you might keep your lights on more if you know they’re using less electricity. Or you might tend to drive an energy-efficient car more than a gas-guzzler. In my opinion, the only sure ways to promote conservation are through regulation or price increases.