Yes, consensus is a thing in science. And we’ve settled the issue of what’s causing climate change.

This is a letter in response to an Op-Ed by Teresa Keegan in The Denver Post on May 5, 2017 titled “There’s no such thing as settled science, and that’s a fact.” You can read the original Op-Ed  here.

Dear Teresa Keegan and those who hold similar beliefs about science,

As one devoted to teaching the nature of science to young minds, I applaud your recognition that science is an ongoing process, where new evidence can shift and improve our understanding of how the natural world works at any time. You seem as if you’ve read a few quotes about science, yet failed to grasp the deeper meaning, however.

While science is always changing, it does not change randomly nor completely start from scratch every time experimental results are published. Science is a process of learning about and coming to understand how the natural world works. So, while we may refine our ideas over time, we don’t simply throw out previous observations because our knowledge has improved. That would be like junking a car because you had a flat tire, rather than simply repairing the damaged tire. Our ideas improve constantly.

A few examples come readily to mind: we’ve improved our estimate of the age of the universe from 13.7 to 13.82 billion years old, we’ve learned that Newton’s Law of Gravity does not explain the behavior of quantum particles, that convection forces in the asthenosphere don’t entirely account for all tectonic plate movement, that any amount of lead in the body is unsafe, that smoking and fine particulates of all kinds are averse to health. Just because we’ve improved our confidence, knowledge, and *gasp* established a scientific consensus behind these issues does not mean we threw out the Big Bang Theory, the Law of Gravity, the Theory of Plate Tectonics, or began adding lead back into gasoline and telling kids it’s okay to smoke. Quite the opposite — our observations were consistent with previous ideas, but newer findings and studies refined and improved upon older ones.

What disturbed me is your claim that climate science it too complicated for common people to understand. As a science educator, my students seem to grasp the simple physics behind greenhouse gases’ impact on Earth’s climate easily. That science was worked out in 1824 by French scientist Joseph Fourier who realized that Earth is much warmer than it should be given our distance from the sun. The moon’s temperature is right around zero degrees Fahrenheit (F), but Earth’s average surface temperature is 59 deg F. From that information, Fourier hypothesized there must be something in Earth’s atmosphere (which the moon has very little of) that accounted for the extra heat.

By the 1850s, another scientist Eunice Foote discovered that carbon dioxide was one of the gases in Earth’s atmosphere which trapped more heat than did regular air, inferring that an atmosphere of carbon dioxide would give the Earth a warm temperature. Her work was replicated by John Tyndall three years later (and is easy to do yourself — no fancy equipment needed). As early as 1896 with the work of Swedish chemist Svante Arrhenius, scientists predicted that burning fossil fuels (which releases carbon dioxide) could lead to increases in temperature. The simple explanation is, the more greenhouse gases you have, the slower heat escapes the Earth, hence the warmer the temperature becomes. Think of greenhouse gases like layers of clothing you wear on a sunny day; the more layers of clothing you have, the slower your body will lose heat and the warmer you will become.

So while the physics is simple, your larger message was about scientific consensus. In the past nearly 200 years, there have been no observations that greenhouse gases do anything but trap heat. And our ability to detect greenhouse gases, their heat-trapping capacity, and even their source using isotopes of carbon, tells us with confidence the impact they are having on Earth’s temperature, and even where the carbon came from, and where it is being absorbed. Consensus is when every scientist has done her best to disprove a hypothesis and invalidate previous findings, thus securing a well-known reputation in her field. Yet, for 200 years scientists have been unable to find any alternative explanation for what’s warming our climate. They’ve ruled out volcanic eruptions, variations in solar output (actually in decline since the 1970s), and Earth’s wobble. All other factors point to people and the burning of fossil fuels.

That doesn’t mean the science behind climate change is over. As you grasped, science is never over. There is still much to learn about how the global change will affect specific regions of the world; some places will be warmer, others may even be cooler, some wetter, others drier — and predicting those localized effects is complicated, much more so than basic physics. Yet scientists openly state that this is an active area of research; I’ve not heard anyone claim we know with certainty how specific parts of the world will be different in 100 years, other than to say generally warmer than today. We don’t need specific predictions to take action, though. We’re already seeing the consequences of our fossil fuel consumption. For example, in the past decade the northeastern US has already seen 71% increase in heavy precipitation events since the beginning of the 20th century.

What scientists do say, however, is that there are tipping points — points beyond which we will not be able to reverse changes — and we are approaching them. We’ll unlock great stores of carbon that are currently frozen in tundra if the tundra continues to thaw and we’ll loosen vast ice sheets in the Antarctic that will slide into the ocean, causing dramatic sea-level rise, swallowing the coastal cities that house more than 1 billion people worldwide, including half of the US population. These are changes predicted within the next 50–150 years. Do we know the year the ice sheets will take their oceanic dive? No. Do we know precisely how much more greenhouse gases we can add to the atmosphere before we reach the point of no return? No. But do we know we will reach that point if we continue our present course? Yes.

Scientists don’t advocate for specific policies or ways to change civilization. That is the job of politicians and community leaders. You’ve juxtaposed the role of scientific consensus with political consensus — and the two are not equatable. Our understanding of the science behind climate change and how we know humans are the main cause is well-established, dare I say “settled”. For the past 200 years, all our evidence points to the same uncomfortable explanation.

What people are so frustrated about is that instead of taking the knowledge that we have and DOING SOMETHING about it, we’re still debating whether more layers of clothing make your body temperature rise, and how do we know who put all those clothes on in the first place. Meanwhile, there are real consequences for our inaction, and any chance we have at avoiding those tipping points become smaller and smaller.

You’ve fundamentally misunderstood science, despite reading Michael Crichton. And you’ve fundamentally misunderstood why so many are so upset about our inaction on climate change. We need debate, we need dialogue, we need political discussion. But we don’t need dialogue on whether the science is settled or whether science works; we need that dialogue on how are we going to rise to the occasion and change in response to that information.

Admitting you’re wrong is hard. Change is hard. What made Galileo the first great scientist was not that he could turn a tool used to spot ships towards the sky (though that was brilliant), but that he was the first documented individual to modify his beliefs based on evidence. Even more than 400 years later, with wildly improved technology and systems of collecting and sharing data, humans still struggle to do that simple scientific act: base beliefs on observations of the natural world rather than faith, ideals, or preferences

Science is that very difficult process of constant revision, but it is a revision, not a start from scratch do-over. Is science a perfect process? No. But it’s the best tool humans have ever used to acquire new knowledge about the wondrous universe we inhabit. This process of basing ideas on repeated observations works; that’s why there is consensus in science, and that’s why our conversation must shift from whether science can be trusted to: what will we do now that we know?