Question: Will we meet the goal of holding the rise of mean global temperature to below 2°C?

Answer: Yes and no, simultaneously.

Welcome to Schrödinger’s climate, a paradox in which commentary on climate change policy assumes we will meet the 2°C goal, for that is the motivation behind aggressive emission controls and other mitigation measures, but at the same time assumes we will not meet the 2°C goal, for that is the motivation behind aggressive measures to adapt to the impacts of climate change.

Austrian physicist Erwin Schrödinger famously described a paradox that follows from quantum physics theory, which posits that particles in a quantum system exist in multiple states at the same time, assuming a final position only when observed from the external world. In his scenario, a cat is placed in a sealed box with a quantum particle and, through a contraption that reacts to the state of the particle, will either live or die depending on the state of the particle. Under quantum theory, Schrödinger argued, the cat would be simultaneously alive and dead until the lid of the box was unsealed and lifted off, at which point the observer would see the cat as either alive or dead.

It is important for climate change mitigation policy to have a goal. Whether expressed as parts per million of atmospheric carbon dioxide or average global temperature rise, the goal is used by mitigation policy commenters to rally support for emission controls. The goals used to be 350ppm and 1.5°C. Those are history now. The Paris accord moved the upper limit to 2°C. “We will hold the rise to below 2.0°C!”

At the same time, climate change adaptation policy commenters use scenarios built around different temperature rises to motivate action. While it is not as if no adaptation will be necessary in a 1.5°C or 2.0°C scenario, things start looking really messy above 2.0°C. If we are honest, 2.0°C may be a best-case scenario, so adaptation policy needs to get rolling. “We will not hold the rise to below 2.0°C!”

The Schrödinger’s climate paradox arises from the necessity of pursuing both mitigation policy and adaptation policy at the same time. There was a time when talk of adaptation was frowned upon, lest it lead to complacency on mitigation policy. Even modest sea level rise, however, threatens island nations and developing nations with large coastal populations, pushing adaptation into the international climate policy discourse. As it became clearer and clearer that climate change will have a wide range of nasty effects in many parts of the world—developed and developing—the need for adaptation policy became increasingly apparent. The urgency of mitigation policy depends on meeting the 2°C goal. The urgency of adaptation policy becomes more salient above the 2°C goal. To engage in the broad climate policy discourse these days—to advocate action across the board—one must enter the box of Schrödinger’s climate. 

Yet this leads to awkward conversations between those focused on mitigation and those focused on adaptation. “We need to prepare for massive human migration,” says the adaptationist. “Oh my,” says the mitigationist, “But we’re going to hold it to below 2.0°C, right?”  “Uh, sure,” says the adaptationist, “But we really need to prepare for bad stuff happening.” “Um, right,” says the mitigationist, then changes the topic. Tension between mitigationists and adaptationists remains in the air inside the Schrödinger climate box.

We do not have the luxury of lifting the lid off the box to observe whether the future is above or below 2°C. We are a world in dire and present need of aggressive mitigation and adaptation policies. Adaptation cannot be portrayed as a contingent policy for mitigation failure. Acting as if adaptation policy need only prepare us for the worst if we don’t meet the 2°C goal means we won’t be prepared for the worst. We need to shape mitigation policy around the idea that we will attain 2°C, and we need to shape adaptation policy around the idea that we will not. Ironically, this means climate policy must behave as if 2°C is both alive and dead.  This conundrum should no longer be cause for uncomfortable conversations.  “Embrace the paradox of Schrödinger’s climate!”