Uncertainty in Climate Science Cuts Both Ways

By Thomas H. Pritchett

Recently, the argument is being made that the U.S. should take no action on climate change because of the uncertainty in the science.  Although, multiple lobbyists and politicians have been heard to make this argument, it was probably best articulated by Bret Stephens in his April 28 opinion in the New York Times.  .   I would like to address that argument here.  

Yes, there is indeed still considerable uncertainty in science on climate change, particularly in terms of the prediction of ultimate impacts.  But here is what is not uncertain: 1) the Earth is absorbing more heat from the Sun than it radiating back into space; 2) the primary cause of this energy imbalance is the increased levels of greenhouse gasses with the primary source of these gasses being the increased use of fossil fuels by mankind; 3) this imbalance has resulted in the warming of our oceans (over 90% of the excess heat is being trapped here) and freshwater lakes worldwide, the increase of average world air temperatures in the lower troposphere (the air we breathe), and the increased melting of ice sheets and glaciers; and 4) this changing of the energy balance between the oceans and the atmosphere is having effects on our overall climate.  In addition, the increase in carbon dioxide concentrations in the air have resulted directly in increasing the acidity of the oceans.  These are givens that the vast majority of climate scientists, as well as the National Academy of Sciences of almost, if not, all every major industrialized country agree upon.   In fact, the National Research Council of the National Academy of Sciences has specifically affirmed the first two givens twice in detailed reports with the first being as early as 1979.

There is very little uncertainty on whether or not the above are happening, but there is indeed uncertainty in scale, magnitude or amount, that each is occurring.   There is also uncertainty in just how long the lag time is in our climate system (i.e., if our carbon emissions magically dropped to zero overnight, how long it would take before the Earth warmed to the point that it was now radiating back to space as much energy it was receiving from the Sun and the Earth stopped warming).  Most scientists believe this lag time could range from just a few decades to a century or longer.  In addition, there is scientific uncertainty in how long it would take the greenhouse gas levels to return to what they were at the middle of the 20th Century and our climate to respond accordingly after our emissions did drop to zero.  Again, the ranges predicted by scientists range from several centuries to up a few thousand years.

And yes, scientists are uncertain when they predict the impacts of our warming climate and our oceans becoming more acidic.  However, this uncertainty cuts both ways.  When scientists make predictions about the effects of global warming on climate, sea level rises and ecosystem disruptions, they tend to use conservative assumptions in their models and will usually throw out the more extreme modeled results.   Similarly, the scientists ignore any feedback mechanisms that can either accelerate the warming or, with glaciers, the melting processes unless those mechanisms are already known to be occurring and are understood enough to be well modeled.  In the case of the IPCC, even then these feedback are often ignored.  Therefore, there is a strong possibility that the uncertainty is not that the scientists are over-exaggerating the danger but that they are grossly underestimating it – simply because their models cannot extrapolate into climatic regions for which we have no modern, prior data.  Furthermore, the study of the Earth’s climate well before man tends to support the idea that our current models are underestimating impacts.  This is why some of the most outspoken climate scientists, such as Dr. James Hansen, are those who have devoted most of the scholarly research in the study of climate tens of thousands to hundreds of millions in the past.

Therefore, my message to those who like to cite the uncertainty in the science of climate change, I would like to remind them that this uncertainty cuts both ways.  Yes, the scientists could very well be over-estimating the impacts but there is also the very real possibility that they could be instead severely underestimating the situation.  Considering the lag time in the response of our climate to whatever actions we take and the essentially irreversible nature of these changes within in the lifetime of our grandchildren and their children, can we afford to take the chance of assuming the uncertainty is that scientists have over-estimated the dangers?

Thomas H. Pritchett
Department of Chemical & Physical Sciences
Cedar Crest College