Ever heard of the Dunning-Kruger Effect? Back in 1999, a couple of researchers in Cornell University’s psychology department, Justin Kruger and David Dunning, published a paper in the Journal of Personality and Social Psychology. It carried the provocative title, Unskilled and Unaware of It: How Difficulties in Recognizing One’s Incompetence Lead to Inflated Self Assessments. The gist of Dunning’s and Kruger’s paper was that people unskilled in areas of intellectual inquiry tend to overstate their abilities in those areas. Worse, in addition to jumping to erroneous conclusions, they don’t realize they’ve jumped to erroneous conclusions.

For example, the skills enabling you to solve a math problem are the same skills needed for recognizing when the problem has been solved correctly and when it hasn’t. If you don’t know enough to solve the math problem, you won’t know enough to recognize when it’s been solved correctly and when it hasn’t, the Dunning-Kruger Effect tells us.

Donald Rumsfeld had a phrase for this cognitive sand trap: We don’t know what we don’t know. Back in the day, reporters made fun of Rumsfeld when, in the middle of some convoluted statement, he would use that phrase. For all his circumlocutions, the former defense secretary had it right.

The Dunning-Kruger Effect is a significant reason why climate change debates are so vexatious. People with all manner of opinions about climate change are susceptible to the phenomenon.

Here is one example of how the Dunning-Kruger Effect plays out: Climate scientists and those who accept their conclusions that human activities are changing the climate often are confronted with a contemptuous question, to the effect: “Don’t scientists realize that climate changed naturally in the past, before there were people building coal plants and driving SUVs?”

The short answer is, yes, scientists do know about past climate change episodes that had perfectly natural causes. They study them for clues on how the global climate system reacts to “forcing” events that can shift it into a different state.

Take, for example, the Paleocene-Eocene Thermal Maximum. Sounds like a heavy-metal rock band, but it’s sci-speak for a serious warming episode that took place some 55 million years ago, long before hominids showed up on the African savanna. The PETM, as climatologists refer to it, has been scrutinized for the insights that it might offer on how the current CO2 buildup in the atmosphere affects global temperatures.

While there is more to learn about past climate change episodes, they are part of the body of evidence that the climate system is sensitive to CO2 accumulation in the atmosphere.

Overcoming the Dunning-Kruger Effect requires some conscious effort. If something seems puzzling or odd about what a scientist says about climate change, it’s best not to assume that the scientist is a dummy who overlooked something obvious or a mendacious conspirator out to hoodwink the public. You know what can happen when you assume. Do some digging, find out what’s known with a high degree of confidence about how the climate works, and understand the range of impacts that climate change could have, and the odds of those impacts coming true.

There’s no shame in understanding the limits of one’s own knowledge. In honor of Donald Rumsfeld’s contributions to public discourse, remember one of his great musings in that regard: “As we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say, we know there are some things we do not know. But there are also unknown unknowns – the ones we don’t know we don’t know.”