The real fight over climate change

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The basic facts about climate change have been clear for many decades: Burning fossil fuels produces carbon dioxide, which alters the chemical composition of the atmosphere and causes it to trap ever greater amounts of heat from the sun. Those facts are set in stone.

It's a shame then that, partly because of ugly disinformation campaigns run by fossil fuel companies, we've spent the past 30 years debating indisputable facts. We could have saved a lot of time if we had instead butted heads about the things that are still genuinely uncertain.

Consider, for example, the use of computer-generated scenarios to understand our climate future. While mathematical simulation of reality is never perfect—whether you're predicting the planet's changing temperature or what song will become your favorite—it is a powerful tool to answer a difficult question: What's likely to happen next?

For many years, climate modelers relied on the most aggressive of several scenarios to do much of their research. With China pushing the world's emissions push higher and higher, this scenario, known as "RCP 8.5" (don't ask), looked like a pretty good match for what was actually happening. The world, it seemed, was pressing its collective foot to the accelerator of our fossil-fuel energy system. This high-end scenario was thus spoken of as "business as usual."

Then something happened—something good. As the global climate-science and energy-transformation conversations each grew in scale, the two discovered they weren't always dealing with the same givens. The energy modelers took one look at RCP 8.5 and how heavily climate scientists relied on it and started clearing their throats—initially on Twitter, and eventually in some of the field's most prominent journals for research and commentary.

Zeke Hausfather, director of climate and energy at the Breakthrough Institute, argued in Nature in January that the energy system is changing faster than we anticipated, such as through rapid cost declines in renewables. So the projected emissions scenarios under RCP 8.5 should no longer be called "business as usual." It would be better to adopt the more recently developed SSP scenarios (again, don't ask), which provide more nuance than the RCP scenarios, which have been use for more than a decade.

Partly in response to Hausfather, Christopher Schwalm and his colleagues from the Massachusetts-based Woods Hole Research Center on Monday published a full-throated defense of the use of RCP 8.5 in research in the journal Proceedings of the National Academy of Sciences. They argue that, while the use of "business as usual" is debatable, this scenario has tracked actual emissions over the past 15 years much better than other less aggressive scenarios. While the RCP scenarios all start out following more or less the same track, they diverge drastically as they reach the year 2100. Even if the extremely high emissions seen in RCP 8.5's projections in later decades don't come to pass, Schwalm and his colleagues argue, it's reasonable to expect the scenario to be useful at least until 2050. (Hausfather has tweeted a response.)

The reason this fight matters goes to the heart of what divides these two research communities, each of whose work is absolutely critical to understanding and charting a way out of the climate crisis. Think of it this way: If you're facing a situation as pervasive and intimidating as climate change, there's at minimum two things you'd want to know. You want to know, as best you can, what's likely to happen. But you also want to know, as best you can, what is the worst thing that can happen. Prepare for the worst and hope for the best, as they say.

So if you're looking for a good climate fight to have, it's not about whether the world is warming (it is), whether we're causing it (we are), or whether we have the technology and know-how to beat it (we do). If you really want to feel like you're "in it," the cutting edge fight is about how to help these two communities reconcile the tools they have to understand where we're headed—and just how bad it could get.

Written with Eric Roston. Akshat Rathi writes the Net Zero newsletter on the intersection of climate science and emission-free tech. You can email him with feedback.