Response: Climate of Complete Certainty

An April 29 op-ed piece by newly-hired New York Times writer Bret Stephens, a neoconservative formerly of The Wall Street Journal, has caught the attention of many. Mr. Stephens pretends to accept the claim of climate scientists that the planet is warming and that humans are causing it, but that he is above the fray and holds a healthy skepticism concerning the certainty of scientists as to exact direction we are heading. Here we have the simple tactic used by climate change deniers: obfuscation—let’s use some fancy language and a few strategically-placed statistics to cast some more doubt, delaying our action even further down the road. (Four more years?)

Perhaps the most troubling sentence in the article is this one: “Anyone who has read the 2014 report of the Intergovernmental Panel on Climate Change knows that, while the modest (0.85 degrees Celsius, or about 1.5 degrees Fahrenheit) warming of the earth since 1880 is indisputable, as is the human influence on that warming, much else that passes as accepted fact is really a matter of probabilities.” Modest? We continue to pump out greenhouse gases every second of every day, Mr. Stephens, and we are essentially adding to this “modest” temperature increase every day. We are already more than halfway to the globally-accepted target of no more than warming of 1.5 degrees Celsius, to stave off the worst possible effects, and we are not doing nearly enough to meet that target.

One more thing: This is not about probabilities, but about basic physics. It is about energy imbalance and energy budgets. NASA’s description of the basic physics is informative:

Carbon dioxide forces the Earth’s energy budget out of balance by absorbing thermal infrared energy (heat) radiated by the surface. The absorption of outgoing thermal infrared by carbon dioxide means that Earth still absorbs about 70 percent of the incoming solar energy, but an equivalent amount of heat is no longer leaving. The exact amount of the energy imbalance is very hard to measure, but it appears to be a little over 0.8 watts per square meter. The imbalance is inferred from a combination of measurements, including satellite and ocean-based observations of sea level rise and warming.

When a forcing like increasing greenhouse gas concentrations bumps the energy budget out of balance, it doesn’t change the global average surface temperature instantaneously. It may take years or even decades for the full impact of a forcing to be felt. This lag between when an imbalance occurs and when the impact on surface temperature becomes fully apparent is mostly because of the immense heat capacity of the global ocean. The heat capacity of the oceans gives the climate a thermal inertia that can make surface warming or cooling more gradual, but it can’t stop a change from occurring.

The changes we have seen in the climate so far are only part of the full response we can expect from the current energy imbalance, caused only by the greenhouse gases we have released so far. Global average surface temperature has risen between 0.6 and 0.9 degrees Celsius in the past century, and it will likely rise at least 0.6 degrees in response to the existing energy imbalance. As long as greenhouse gas concentrations continue to rise, the amount of absorbed solar energy will continue to exceed the amount of thermal infrared energy that can escape to space. The energy imbalance will continue to grow, and surface temperatures will continue to rise.

Have even one climate change denier explain to us how our understanding of this basic process is all wrong—and use decades of peer-reviewed science to back up his claim—and then we’ll stop marching in the streets and go back to our day jobs satisfied that everything will be just fine for future generations, after all.

The conversation has shifted, Mr. Stephens, from “Is climate change really happening?” to “Ok, what do we do about it now?”. We can certainly have intelligent discussions about what policies we should enact to ween ourselves from fossil fuels (and ween we must), but we can’t waste more time questioning the proven science. No climate scientist claims to know to the hundredth of a degree how much we will warm and when, and no climate scientist states exactly where the worst effects will occur, but no real climate scientist will tell us to sit back and wait for it to all play out so that we can obtain this precision. It’s called the Precautionary Principle (“When human activities may lead to morally unacceptable harm that is scientifically plausible but uncertain, actions shall be taken to avoid or diminish that harm.”), and the beings of this planet—and future ones—deserve precaution. We have enough data and enough science to act now, even as the science continues.