The climate scandal nobody talks about
We straight up don't understand one of the biggest factors in climate change
Granted, it doesn’t look like a giant scandal. This figure in the Intergovernmental Panel on Climate Change’s latest Assessment Report looks like typical impenetrable IPCC gobbledygook.
But behind the technocratic façade lies an outrage. Once you get what’s happening in this chart, you’ll never think about Climate Change the same way again.
The chart summarizes what scientists know about what’s driven changes in the atmosphere’s energy balance since 1750. In the jargon, this is known as “radiative forcing.”
Each of the items in the chart is making the atmosphere more or less energetic — warmer or cooler, to you and me. The bars in red point to things tending to make the world warmer, the bars in blue correspond to influences tending to make the world cooler.
The biggest factor is, quite rightly, up on the top row: carbon dioxide — CO2.
This is the one we all obsess about, and yes it really is the biggest factor. The CO2 we’ve emitted since 1750 has probably trapped 2.16 watts of energy for every square meter in the atmosphere. That’s a lot.
There is, inevitably, some uncertainty about the exact impact any of these components is having on the atmosphere’s energy balance, so the IPCC quite rightly includes error bars around each estimate. These solid bars “represent best estimates, and very likely (5–95%) ranges are given by error bars.” The narrower the bars, the more confident scientists are that their estimate is right. For CO2, scientists are highly confident that the right answer is somewhere between 1.9 and 2.41 watts per square meter.
As you can see, there is some uncertainty around each of these estimates. Most of them look reasonably tight — CO2, methane, ozone, changes in land use each could be causing a bit more radiative forcing than the mean estimate, or a bit less, but probably not vastly more or less. Which is why those error bars are reasonably narrow…until you get to the aerosols.
All of a sudden, we’re in crazytown.
The aerosol error bars are huge!
Things are bad for aerosols in general, but when it comes to the way aerosols interact with clouds our ignorance becomes truly astonishing. The IPCC error bars extend all the way from -1.45 watts per square meter, which would mean aerosols interacting with clouds counteract three-quarters of the warming effects of CO2, down to just -0.25 W/m2, which would mean they’re counteracting barely a tenth of it.
Which one is it?
We. Do. Not. Know.
This is totally crazy, people!
Turns out the question of how exactly tiny particles suspended in the air interact with clouds is one of the great unknowns in climate science.
Researchers know that, in some circumstances, some kinds of aerosols can make clouds more reflective, which makes them better at cooling what’s underneath them. In other circumstances, aerosols do the opposite. Beyond that, there’s a thick fog of uncertainty — which figures, as aerosols are a key reason fog forms.
This has massive consequences for climate policy. Obviously. A world where aerosols are masking three quarters of the warming effect of CO2 is a vastly different world from one where they’re masking just a tenth. You’d think figuring out which of those world’s we live in should be a matter of scientific urgency. You’d imagine billions upon research billions would be flowing into an urgent scientific push to find answers to this enormously consequential question.
Alas, no.
Aerosol-Cloud Interaction —ACI, as researchers call it— is sort of a niche pursuit in atmospheric science, a slightly quirky subfield vastly overshadowed by the giant academic scientific machine working to narrow the slender little error bars up towards the top of that chart a little bit more. Sure, some scientists work on it, some papers do get published, the field isn’t entirely non-existent. But it’s an afterthought. As far as plenty of people are concerned, ACI is the place promising atmospheric science careers go to die.
It’s a testament to how acute Carbon Tunnel Vision has become in our public sphere that ACI gets as little attention as it does, even though the IPCC knows full well it’s by far the biggest source of uncertainty in its radiative forcing calculations. In a different, saner world, nailing down the details of how clouds interact with aerosols would be the sexiest subfield in climate science, the place the brightest kids are drawn to, because it’s the place where the highest impact discoveries are still to be made.
If, like me, you have a sneaking suspicion the climate crisis is ultimately going to end up requiring some kind of climate repair program, ACI has the additional draw that anything you learn about ACI out in nature is inevitably of interest to any future Marine Cloud Brightening program.
That’s an aside, though.
Even if you took MCB entirely off the table, those damn error bars in AR6’s Figure 7.6 are an ongoing scandal. We stumble around in acknowledged ignorance about one of the main factors in anthropogenic climate change, and just whistle past as though this wasn’t a big deal. It is.
Nice clickbait.
Two comments:
1. Climate scientists do write about this in papers. Reducing uncertainty of past observations is an important area of climate research, but when the past is unknown (or has large error bars) because no one was able to measure it, it's unknown (or continues to have large error bars). But still, they try.
Here's one example:
Prospects for narrowing bounds on Earth’s equilibrium climate sensitivity, Bjorn Stevens, Steven C. Sherwood, Sandrine Bony & Mark J. Webb, Earth's Future (2016)
2. There are lots of areas of climate with major uncertainty but rule #2 of climate scientists *in media communications* is not to mention major uncertainty. Rule #1 *in media communications* is not to mention good news.
The process that allocates funds for research is far from rational, but a "scandal", I don't think so.
I have known or known of quite a number of scientists specializing in atmospheric chemistry, which takes them to aerosols. The one I know best has won major awards for that work; it has not been a path to obscurity.
What is notable, for that scientist among others, is that their research over time produces results that are taken as strengthening or reducing the case for climate alarm. They have reported that their treatment by that crowd changes incredibly based on what their latest result is thought to imply.
The reality is that no one result in that field can be definitive and, as you say, you would need to pour buckets of money into it to make progress more quickly. Which raises questions about the motivations of the climate alarmists.