Mitigating the Climate Crisis: An Overview

Late last year, we announced the USV Climate Fund. At the time, we wrote that “[m]itigation is working on the causes of the climate crisis through either emissions reduction or drawdown of existing greenhouse gases from the atmosphere.” In today’s post, we want to provide some background on the scale of the problem, as well as a framework for thinking about different approaches.

Let’s first start with the observation that the accumulation of carbon dioxide and methane in the atmosphere is turning the world into a gigantic greenhouse. Sunlight can enter, but heat radiation (in the form of infrared light) is increasingly absorbed and then partially sent back down. In that regard, the gasses act exactly like the windows on a car, which is why cars can get very hot on the inside, even on an otherwise only moderately warm day.

Here are the two charts that show just how rapidly the concentration of two crucial greenhouse gases has been rising in the atmosphere during the Industrial Age.

First up carbon dioxide (CO2)

And second an eerily similar chart for methane (CH4)

In each case, a roughly ten thousand-year period of stability (coinciding largely with the Agrarian Age) is followed by a nearly vertical increase during the Industrial Age.

These charts look bad, even if all you know is that they are charting something that’s causing a problem. Once you understand the magnitude of the problem, though, the charts look downright scary. Just how much extra heat are these greenhouse gases trapping in the Earth’s atmosphere and oceans that during the agrarian age was able to escape into space? The answer is a shocking four Hiroshima-sized nuclear bombs worth of heat every second. Yup. That’s not a typo. Every second of every minute of every hour of every day. That’s a lot of heat. We are not feeling it all that much yet because so far more than 90% of all that heat has warmed the oceans.

Now finally for some good news. The rapid build-up of these gases in the atmosphere is reversible. We know how to do it in principle. What we need is to take the initiative, which will require a combination of government regulation and entrepreneurial activity. To figure out what needs to be done, it helps to understand that the atmosphere is a bus stop and the concentration of gases within it is like a queue forming at this bus stop. Why? Because gases both arrive and depart from the atmosphere in large volumes. At a bus stop if passengers arrive faster than they depart, then the queue builds and builds and builds (that’s the atmospheric concentration line going up and up and up). To reduce the queue we can work on both sides of the problem: have fewer passengers arrive (work from home, ride a bike, etc.) and more passengers depart (more frequent buses, taxi pickup at the bus stop, etc.). The same goes for the atmosphere. We can work on both emitting less and on making existing gases depart the atmosphere faster.

Here are two charts that show the total atmospheric equation. The grey arrows show how much is arriving in the atmosphere and the green arrows show how much is leaving it annually.

Carbon dioxide (annual gigatons of C, multiply by 3.67 for CO2), based on the numbers for the carbon cycle

And methane based on the much smaller methane cycle (numbers are in annual gigatons of CH4)

In both cases the red arrow indicates the net arrival rate in the atmosphere. We need to basically reverse those arrows.

Let’s tackle methane first because here the story is relatively straightforward. Why? First, the amounts involved are tiny compared to carbon dioxide (smaller by three orders of magnitude). Second, we have big levers available that allow us to address the problem on the emissions side only. 

Here are the sources for global methane emissions (Why global? Because it is one atmosphere — it doesn’t matter where something is emitted, it all goes to the same bus stop.)

We can see that about half (51%) of the emissions are from just two sources: oil & gas and the odd “enteric fermentation” — which is basically cows burping out methane. So here is a simple bit of math 51% of 62% of 0.58 = 0.18 gigatons. If we were able to cut those two sources by a quarter each, we would be emitting 0.25 * 0.18 = 0.045 gigatons less than at the moment and the red arrow would be reversed!

Now to be clear, that’s not at all an easy task. But it shows that much as the methane build up is scary, the math on reversing it doesn’t seem entirely daunting. In future posts we will drill into specific ways to have less methane from cows (involving both fewer cows and less methane per cow) and ways to have less methane spillage from oil & gas.

Now let’s turn our attention to carbon dioxide. Here the math looks rather different. As it turns out for the huge up arrow only a measly 4% is caused by human activity. That’s a “good news bad news” insight. First the bad news: if we wanted to work on emissions reduction only (the approach suggested above for methane), then to reverse the arrow, we would have to basically eliminate all human carbon dioxide emissions! Contrast that with eliminating only a quarter of two types of methane emissions.

To see further how basically impossible that is any time soon, consider where those emissions come from. Here is again a global chart:

Pretty much all of these are activities that we are doing more of every year. And each of these blocks hides a myriad of different activities all around the world. Here, for example, is what it looks like to double click on the transportation sector:

As an aside, we can see that passenger flights account for only 81% of 11.6% of 14% = 1.3% of all human-made carbon dioxide emissions. Now it is important to point out that these are caused by a small fraction of humanity, but even if we were to eliminate them entirely (for instance by stopping to fly), it unfortunately wouldn’t make a big dent. Of course we should still work on reducing emission from aviation. A big tax on jet fuel or outright bans are potential incentives for accomplishing that — we just shouldn’t get our hopes up that this will make a big difference overall.

In future posts, we will dig into many of the sources of carbon dioxide emissions in great detail, such as how to electrify passenger road transportation and also options for road freight beyond electric, such as carbon capture from trucks. Another very promising place of course is the production of electricity and heat, about which we will be writing as well.

But let’s be clear: reversing the arrow for carbon dioxide cannot happen quickly, if at all, by focusing exclusively on emissions. Now the good news part: We can also look at the green down arrow and figure out how to grow that, in what is known as carbon removal or drawdown. To understand what that might entail here are some rough numbers: about 40% of the carbon dioxide coming down goes into the oceans and about 60% into biomass (above and below ground). So, if we can make those sinks a bit bigger we could make a big difference.

Just how big? Well to completely reverse the current net increase we would have to grow the sinks by about about 5% if we didn’t cut any emissions. Now that may not sound like much but it will still require Herculean efforts.

Take planting trees as an example. Every tree that grows draws carbon from the atmosphere. But if that tree burns in a forest fire all that carbon goes right back up and even if the tree just dies and decomposes then the same is true (only a small fraction of the carbon of a rotting tree stays behind on the ground — mostly the roots that were in the soil and a bit of what was above). So not only do we need to plant a lot of trees, but we also need to protect the ones we have to take the ones that have fallen down and stabilize their carbon.

All of these are doable things. Many of them offer incredible opportunities for startups and we will be writing about those in detail in the coming months. But it is also true that in order to unleash the full potential of human capabilities on the climate crisis we need government mobilization on a scale similar to the world wars. We will be writing more about that as well.

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