First, Do No Harm

by James Morris

This month, world leaders are meeting in Paris to discuss climate change. This time, there is optimism that concrete measures will be adopted to do something about this planetary problem.

Sadly, debates about whether climate change is real have slowed attempts to do something about it. In his recent op-ed in The Boston Globe, Freeman Dyson, professor emeritus at the Institute of Advanced Study at Princeton, writes (stunningly) that “the main effect of carbon dioxide on the ecology of the planet has nothing to do with climate.”

It’s hard to know where to begin with statements like this. Carbon dioxide is a greenhouse gas. This is a well-known fact, and is not in any way controversial. Greenhouse gases let solar radiation through, but trap heat beneath them. In this way, they act like window panes in a greenhouse. In fact, without carbon dioxide and other greenhouse gases like methane and water vapor in the atmosphere, the Earth would be far colder than it is now. Life on Earth wouldn’t be possible without them.

Since the late 1800s, the amount of carbon dioxide in the atmosphere has been increasing. And the Earth’s temperature has risen as well, a predictable consequence of increased levels of this greenhouse gas.

So, to say that carbon dioxide has no effect on climate is simply incorrect. We can debate how warm the Earth will get over time. And we can debate what we should do about it. But facts are not up for debate: we know that carbon dioxide is a greenhouse gas and therefore affects climate. And we know that carbon dioxide levels in the atmosphere are increasing.

Dyson is a theoretical physicist with no expertise in climate science, as he has acknowledged himself. If you have a problem with your car, you turn to a car mechanic. If you are not feeling well, you go to a doctor. So why, in the case of climate, do we listen to people with no knowledge of the topic, rather than climate scientists?

Dyson also brings up uncertainty in climate modeling as part of his argument to do nothing about climate change. To be clear, there is no uncertainty that the climate is changing. What’s less certain is the timing and magnitude of the change.

All models come with some measure of uncertainty. Common sense (and basic tenets of risk management) teach us that in the face of uncertainty and great potential risks, it’s best to err on the side of caution. If the models are accurate or underestimate the risks, the consequences of inaction are dire: rising sea levels, severe storms and drought, loss of glaciers and the polar ice sheets, and flooding of coastal and other low-lying areas. Many of these changes will disproportionately affect developing countries.

What about the consequences of action if the models overestimate the risks? We have cleaner, renewable energy. We don’t have to turn to hydraulic fracturing (or “fracking”), with its potential to pollute the groundwater, for sources of energy. We don’t have to depend on fossil fuels, which are limited resources. Fossil fuels, after all, are the fossil remains of organisms that lived hundreds of millions of years ago – and they are neither renewable nor limitless.

Which would you choose?

In Harvard Square in Cambridge, Massachusetts, along Church Street close to where the movie theater used to be, there is a large mural by Be Sargent with the following title – “Indication of harm, not proof of harm, is our call to action.”

RachelCarsonThis “precautionary principle” applies whenever there are significant risks in the context of uncertainty. Rachel Carson invoked such a principle when she wrote about the devastating use of pesticides and their effects on the environment. At the time, it wasn’t certain that they caused harm. But the possibility of harm was enough for her to make a call to action. Climate change is similar.

Dyson also misses the point that uncertainty is part of the scientific process. Science really works by making observations, coming up with tentative explanations called hypotheses, doing experiments and making further observations to support or reject these hypotheses, and so on. Over time, we gain more confidence in our explanations and can explain a wider variety of observations, raising hypotheses to the level of theories. But science is at heart a humble enterprise, and we always recognize that our ideas can be modified as we learn more.

Just because there is some level of uncertainty, however, does not make all predictions the same or equally likely. As Mary Lefkowitz, another not-uncontroversial professor emerita, wrote, “…the absence of certainty does not mean that one interpretation is as valid as another. Probabilities and plausibilities matter, and when the evidence is less precise or less tangible than we would like it to be, some explanations are still more likely than others.”

© James Morris and Science Whys, 2015

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