Good morning, John.

One of the biggest debates in climate change is whether we should be talking about direct air capture of carbon dioxide. Just taking carbon dioxide out of ambient air seems like a good idea.

My perspective's a little weird on this. I think that you and I should not be talking about this. At the moment, removing a pound of carbon dioxide from the atmosphere is way more expensive than just figuring out how to not emit another pound of carbon dioxide. It's much easier to not emit it than it is to capture it. Here is my absolute favorite climate graph. It shows so many things all at once, but you have to understand it, which is tricky.

On the left is the amount of CO2 that is abated, that is either not emitted or removed. It starts at five gigatons, which is the amount of CO2 emitted by the US per year. And here's a question. Can you guess when it is projected that number will hit its peak? Trick question. It peaked in 2007 at six gigatons. So, like, that's nice. No matter how many times I hear it, this number still surprises me. 2007, six gigatons is a full gigaton, more than five gigatons. Obviously, though, we still got a lot of work to do. We want the colored part of this graph to get down not just to zero, but to below zero, because the CO2 we have already emitted does not just disappear, it's still there. We need to get rid of that stuff now. The x-axis of a graph is often time, but like, scrub that out of your head, because in this case, the x-axis on the bottom is money. It's the dollar cost of a ton of carbon dioxide abated, either removed or not emitted. That number is like, how big of a climate premium are we willing to pay? At the current moment, though-- and this is kind of amazing.

The Mac curve, and it's called the Mac curve, by the way, shows that at a climate premium of $0. So just doing what does not cost anything extra, that would take us all the way down to 3.75 gigatons per year. The only reason we haven't done that yet is because it takes time and work to build the infrastructure. And you can see over on the right hand side what exactly that infrastructure would be to replace those carbon emissions. At a $50 per ton premium, we get down to below half of our original CO2 emissions peak. But something weird happens at 100. A lot of things level off at that point. You can't squeeze much more abatement out of solar or wind or evs at that point, a bunch of other weirder stuff starts to make sense, like synthesizing zero carbon fuels or hydrogen infrastructure. And then eventually, all the way beyond the $200 per ton of CO2 mark, it starts to make sense to capture CO2 from the air. That's a lot of money per ton of CO2. Like, a carbon tax of $250 per ton of CO2 would break a lot of things. I think people would freak out. But for $0, there's a lot of good we can do right now. And for $50, there's a lot of good we can do right now. So let's focus on those things, right?

I recently visited a test facility for a technology that captures carbon dioxide from the air passively. It's called a mechanical tree, and it's like a tree in that it takes in carbon dioxide, but unlike a tree in that it's made of metal and plastic, and it takes in way more CO2 than a tree. But also, it does not turn that CO2 into anything else. Like a tree turns it into tree. It's really quite cool. Basically, the thing extends upward, and then all those interior plates are exposed to the air. And depending on the amount of wind and heat and moisture in the air, the material inside binds to CO2 at various rates, and then it's lowered back down into the container, where the CO2 is basically sucked off of the plates and then pumped out. Then if this were actually a commercial plant, you'd need to do something with that carbon dioxide. Use energy to turn it into a fuel or pump it underground or make it like a solid or something so it doesn't get released back into the atmosphere.

This is one of dozens of designs for different ways to capture CO2 from the air. And all of them are entirely economically infeasible. This technology is at the baby stages right now. We can do an amazing amount of good with zero climate premium and another huge amount of good with just $50 per ton of premium. But that Mac curve that I showed you only shows things as they are today. Right now, the broader public focus on direct air capture of carbon dioxide would mostly be a distraction.

A lot of people say we don't have to worry about burning fossil fuels because we'll just capture it with direct air capture. But that's silly, because it's way more expensive to do that than to just not release the carbon in the first place. So my perspective is that you and I shouldn't be thinking much about direct air capture of CO2, because it's not what needs to be implemented right now. Now, there are like physics reasons why direct air capture is hard and expensive. The concentration in the air is low, CO2 molecules are very stable and nonpolar, so it's hard to get them to stick to stuff. But there are also reasons to think that costs will come down.

If you imagine in your brain the Mac curve extending out on a third axis this one time, you can imagine that the costs of all of these things will come down and everything will move over to the left as time progresses. But regardless of the cost going down, only so much good can be done with more solar and wind and electric vehicles. So eventually the cost of direct air capture is going to come down and there won't be many other ways to get the existing carbon dioxide out of the atmosphere. And suddenly it's going to become important. It's just going to be a while before it becomes important. That's why these people are working on it at the research phase. That's why the US government and private companies are working with universities to try and figure out the details of this stuff now. Sometimes I feel like if I'm personally not focusing on something, then it's not getting done. But that's not how the world works.

There are people everywhere working to solve problems, sometimes in ways that are right in front of our faces that we don't really need to pay attention to. But it's nice to pay attention to it sometimes nonetheless. Thanks very much to the amazing guy from the center for Negative Carbon Emissions at Arizona State University who responded to my text message extremely quickly and showed me around the facility.

Just very cool to get to do that. John, I'll see you on Tuesday.