How to shift the Overton Window in favor of climate repair

Bring discussion of aerosols into the mainstream and a broader conversation will develop

[Our effort on behalf of Irish Tenant-rights] will make people believe that there is something in it. Many who before regarded legislation on the subject as chimerical, will now fancy that it is only dangerous, or perhaps not more than difficult. And so in time it will come to be looked on as among the things possible, then among the things probable;—and so at last it will be ranged in the list of those few measures which the country requires as being absolutely needed. That is the way in which public opinion is made.

-Mr. Monk in Phineas Finn, by Anthony Trollope

Joseph Overton is usually given credit for noting how the range of politically imaginable choices changes over time, even if Anthony Trollope knew all about it back in the 1860s. Overton did manage to get his name immortally attached to what we now know as well, the Overton Window —the constantly shifting range of policy ideas judged worthy of serious consideration at any one time.

Of course, as of 2024, climate repair remains well outside the Overton Window. We know this is the case because stratospheric brightening and marine cloud brightening aren’t so much rejected as ignored: treated as somewhere between radical and unthinkable.

Our task for the next decade or two is to gradually shift the Overton Window so that, by the end, climate repair will be ranged in the list of those few measures which the world requires as being absolutely needed.

These kinds of shifts happen all the time, but they’re gradual. When I was a kid in the 1980s the notion that same sex marriage would become normal all around the world within my lifetime would’ve sounded fantastical.

The legalization of cannabis, of sports gambling and of physician-assisted dying, the bans on spanking and on indoor smoking, all were somewhere between unthinkable and radical a generation ago. Then the Overton Window shifted in their favor.

The paradigmatic example remains same sex marriage: a beyond-the-fringe position in the 80s that isn’t even controversial anymore. What can we learn from that experience?

It’s easy to forget that a generation ago, gay rights activists didn’t talk about same sex marriage. Not at first. They moved the Overton Window step by step, chipping away at the problem from its edges. They began campaigning for AIDS research funding, for the right to visit their partners in hospital, for employment and housing non-discrimination.

That was shrewd. Activists realized that while straight society as a whole might not be prepared to afford them full civil rights all at once, there were at least some issues where their cause was so obviously just they could begin to chip away at the old prejudices. They figured that once people had accepted in principle that gay people had rights, it would be awkward to limit those rights to some spheres and not others. It was shrewd, it was smart, and it worked incredibly well.

I spend a lot of time thinking what the analogous move would be on behalf of climate repair. I think the answer has to do with aerosols. Mainstreaming a discussion of aerosol effects in the climate space seems to me relatively easy: aerosols really are a huge deal for the climate, and a vast scientific question mark. We should be talking about them, because the biggest uncertainties in climate research tend to cluster around aerosols.

We don’t know how much global warming is being offset by airborne particles right now. And when I say we don’t know I mean we really don’t know. The error bars around the IPCC’s estimates of the impact of aerosols and aerosol-cloud interactions on global warming are simply enormous. All they can say is that Aerosols are offsetting somewhere between 10% and 75% of the warming effects of carbon dioxide: an insanely wide range.

Getting clearer on how much aerosols are doing to cool the planet now should be a scientific priority quite independently of climate repair. A world where aerosols and ACIs are offsetting three quarters of the warming effect of CO₂ is a vastly different world than one where they’re offsetting a tenth. The policy implications are absolutely huge. In terms of understanding where we are and where we’re going, narrowing the error bars around the radiative forcing effects of aerosols ought is urgent.

To my mind, aerosols are also just super interesting in their own right. Because they tend to linger near(ish) the place where they’re emitted, they can have strange localized effects — impacting the climate locally in ways that aren’t always obvious. I’ve written about this in the context of the mega-drought the Sahel experienced in the 1960s-1990s, and of the hurricane lull of that same era. But there are any number of other interesting stories to be told about anthropogenic aerosols and everything from precipitation in China and South East Asia and glacier melting, the health of the Indian and African monsoons, and probably three dozen others topics I don’t know about yet.

Climate journalists do sometimes write about aerosol effects, a bit, but there’s always this sense that they’re taking a vacation from their real job: writing about greenhouse gas reductions, about decarbonization, renewables and the usual shibboleths of the mainstream climate movement.

My sense is that to challenge the taboo on climate repair, one of the most useful things we can do is just to start talking more about aerosols: raising their profile, establishing in the public imagination just the idea that little things floating in the air can act as heat shields and letting people know this is an active area of scientific inquiry.

Discussing aerosol effects could end up playing for climate repair the role that employment non-discrimination played in the fight of same sex marriage. It’s just a much less threatening topic, and one where even our opponents will find it hard to impose silence.

Our ignorance of aerosol effects is a major source of uncertainty across climate models. Serious climate scientists all know this. Nobody seriously doubts the need to vastly improve parameterization of aerosol effects to make models more accurate. This is the weakest bit of the taboo, and the one where we ought to spend most of our time first.

As we understand aerosol radiation interactions and aerosol cloud interactions better, as we discuss these things more openly in the climate space, there’s every chance that the conversation will gradually turn towards the other thing. Just like it became awkward to argue that gay people had a right to visit their partners in hospital, the right not to be discriminated against in housing, but not the right to marry, it’s going to become very awkward to say that yes we know aerosols cool the climate, yes we know they can do so safely, but no we can’t even talk about doing it deliberately.