Schrödinger’s cat and climate choices

I stepped away from my computer the other day and came back to find my cat Bembé staring at the screen. Bembé has always expressed a cat-like indifference to my climate science work.

Why would projections of global temperatures grab his attention? Perhaps it is that cats have a special appreciation for choices. They exist in a constant state of betweenness: simultaneously affectionate and indifferent, curious and cautious.

Physicist Erwin Schrödinger’s famous thought experiment demonstrating the philosophical challenges of quantum mechanics illustrates the nature of betweenness. And, of course, it involves a cat. Schrödinger imagined a cat in a box with a deadly poison that may or may not kill the cat before the box is opened. His conclusion is that while the cat is in the box, the cat exists in a state of being partially alive and partially dead — until the box is opened, and the cat’s state is revealed. The act of checking on the cat determines its final state. Cats are comfortable with ambiguity, it is a part of cat life. They know that the ambiguity will be resolved once someone bothers to check on them.

With Schrödinger in mind, I’m confident that what drew Bembé to my screen was the duality in the graph. The graph simultaneously shows the projection of global mean temperature under our current fossil-fuel economy and the trajectory if we rapidly shift from fossil fuel.

These future outcomes are not quite as discrete as the ones Schrödinger presented, although the stakes are nearly as high. So far this year, at least 538 people in the U. S. have died in weather-related disasters that have cost the nation $104 billion. All of this happened in one year under 1.1 degrees Celsius of global warming. The high CO2-high warming scenario on my graph rises to 4 degrees Celsius. Under this scenario, disasters and other climate impacts would consume 4 percent of U.S. GDP, a serious drain on the economy. Heat-related deaths would increase by a factor of 10. 

Under the lower scenario which limits warming to 1.5 degrees Celsius, deaths and disasters increase, but are only slightly higher than what we are currently experiencing. All of these numbers get magnified in the developing world, where the impacts are more intense and where the resources to deal with them are scarce. 

Next week, the nations of the world will get together in Glasgow for the UN climate conference COP26, with a goal to build a framework for reducing global carbon emissions enough to keep warming below 2 degrees Celsius, and ideally closer to 1.5 degrees.

It is easy to think of this as another international meeting with people arguing over esoteric pieces of international policy like “nationally determined commitments” for voluntary emissions reduction and development banks. Instead, think of COP26 as us taking a peek inside a box, a box that contains not just cats, but all of us. Our world exists simultaneously on two climate paths. The decisions that come out of Glasgow will tell us whether we are likely to stay on the expensive, deadly, high-CO2 path — or whether there is a chance that we are on the path that is safer for people and cats.

I left my computer and came back to find my cat Bembé staring at it. He’s never shown much interest in my work, but I’m glad he’s finally starting to take climate projections seriously. #COP26 #IPCC #ClimateMatters pic.twitter.com/399vCNNyCM

— Andrew Pershing (@Sci_Officer) October 28, 2021

One thing that Bembé’s quantum cat brain can’t quite process is that there are more than two climate futures. Unlike Schrödinger’s experiment, opening the box in Glasgow won’t be the final word. There will be future climate summits that will keep slogging away on international agreements. Individual countries, states, cities, as well as companies and people will continue to make decisions about their carbon use. Each of these UN climate meetings offers another peek in the box that updates which of the simultaneous paths are still available to us. Unlike Schrödinger’s cat, we get to decide how alive we want to be.

Andrew Pershing is the director of Climate Science at Climate Central. He is an expert on how climate trends and events impact ecosystems and people and recently led the Oceans and Marine Resources chapter of the fourth U.S. National Climate Assessment. Follow him on Twitter: @Sci_Officer