As a physician you have to develop a certain comfort level with uncertainty. The simple fact is – we don’t know everything. The human body is extremely complex, and there are over 7 billion people on the planet representing a great deal of variation. Our data is incomplete and largely statistical, and we have to apply that to specific decisions about an individual patient. This means we have to make the best recommendations we can with the information we have, be honest about our level of uncertainty, and convey the range of possible outcomes based on various decisions.

It’s often helpful to think in terms of “clinical pathways,” – what are the different possible paths an illness can take, given what we know and what we don’t know, and how will our diagnostic and therapeutic interventions alter those possible pathways?

Perhaps because I live this every day, I find it easy to accept the logic of action on climate change. We don’t know exactly what will happen. The climate system is complex, and there are known unknowns. One of the big ones is climate sensitivity – what is the precise relationship between the level of CO2 in the atmosphere and the degree of warming. The lower the climate sensitivity the better, in terms of how much warming will result from the CO2 we have and are releasing.

But there are other variables as well, including human action. We don’t know how stable the Greenland and Antarctic iceshelves really are, for example. There are multiple feedback loops and tipping points, and the potential for cascading effects. So yes – climate models are just that, models. They are not a crystal ball that will tell us what will happen. They are our best guess at what might happen.

Global warming deniers use this uncertainty as an excuse to do nothing (doing nothing always seems to be their goal, regardless of the justification). As a physician, that logic is painful. If I am not sure that my patient has a serious condition, that is not a reason to do nothing, it creates an imperative to do something. The specific intervention is then based largely on a risk vs benefit analysis. And often, as with global warming, acting early is key. You definitely want to find that tumor when it is small and before it has metastasized.

A recent study published in Nature Climate Change takes a similar approach by looking at many (literally millions) different pathways the climate might take between now and 2100 based upon all the variables that affect climate and various actions we might take. Just as I often do with my patients, they ask, “Is there a potential pathway to an acceptable outcome?” The more time we waste, the more our options are limited, and the more the potential pathways close in on us.

The lead author states:

“Despite massive uncertainties in a multitude of sectors, human actions are still the driving factor in determining the long-term climate. Uncertainty is sometimes interpreted as an excuse for delaying action. Our research shows that uncertainty can be a solid reason to take immediate action,” said Lamontagne.

Exactly right. I make this exact point to my students – your uncertainty is not a justification for doing nothing. It’s the opposite – uncertainty means we need to be more careful, consider all possibilities, and make sure we are covering the worst outcomes.

The big unknown in the model used by the authors is climate sensitivity. They say, if climate sensitivity is toward the lower end of the range of possibilities, then it will be easier to stay below 2 degrees C post-industrial warming. As climate sensitivity increases the window closes, possible pathways become progressively limited, and at the upper end of the range it is already too late to avoid 2 C.

Climate change deniers often explicitly argue that we should assume that climate sensitivity it toward the lower end of the possible range. To put it bluntly – this is nuts. That’s like assuming a patient doesn’t have a tumor. Let’s wait so that if they do have a tumor, it will be untreatable by the time we are certain.

Another layer to this is the fact that you need to do a risk vs benefit analysis not just of any specific proposed intervention, but of every pathway you might take, including doing nothing. Again, as I tell my students (and as I was taught when I was a student), doing nothing is also a choice with its own risks vs benefits. So on climate change, what is the risk vs benefit of mitigating strategies, and what is the risk vs benefit of essentially doing nothing? This paper shows that doing little or nothing has massive risk.

The debate should no longer be about whether or not global warming is happening or whether or not humans are contributing. The answer to both is probably yes, with a level of uncertainty. (And to be clear – absolutely continue to do research to lower those levels of uncertainty.) Deniers have tried to frame the debate, however, as if anything less than certainty is a justification for doing nothing, and we will never have certainty, at least not before it is way too late to do anything. This paper reframes the discussion as – what can we do with what range of outcomes given the uncertainty?

I have written about and discussed global warming several times recently, and I always get a lot of e-mail in response (as well as comments). The recent batch of feedback I have received is less doubting about the reality of climate change, and focuses more on the proposed solutions.  This is where the debate should be – let’s discuss the range of possible mitigating actions, their cost, their potential efficacy, and potential outcomes. Let’s do the risk vs benefit analysis and start taking action.

Unfortunately, in the political and public arenas, I find the debate to be mostly counterproductive. Often proponents of either side focus on the most radical position of the other, as if that’s the only thing on the table. The reality is that there are a number of practical solutions that are actually a win-win for society. The best solutions involve increasing investment into clean technologies that have a range of benefits. If we play our cards right, no one will have to sacrifice anything. We can get cheaper energy, reduced pollution, better health, and greater energy independence all at the same time.

What is often frustrating is that we actually have the technology right now to do what we need to do. All we really need is the political will. Build more nuclear plants, expand renewable energy, update the grid and add more storage, create incentives for greater efficiency and electric vehicles, and don’t let industry externalize the costs of pollution.

All of this is going to happen anyway. These are the technologies of the future. We might as well try to get ahead of the curve and become leaders rather than followers. Our economy will actually benefit from taking this path, and it is extremely cost effective to mitigate climate change rather than pay for the consequences. Really, it’s just political stubbornness at this point, and an industry that does not want to adapt.

The cancer is already advanced, but is not yet terminal. Now is the time to act.