January 2021

As the climate crisis intensifies, many people are looking to better understand it and even help solve it (a reason for optimism in 2021). Yet ramping up, even to the point of basic orientation, can be surprisingly hard.

There's no shortage of information. Excellent books, articles and podcasts exist on various pieces of the puzzle — solar, plant-based food, electrification, the grid, nuclear, and so on. But how do these pieces fit together to solve the problem? How important are each of these solutions relative to one another?

This goal of this piece is to provide a mental model for what the world needs to do to solve climate change. I've intentionally excluded a lot of detail in an attempt to help make clear the forest from the trees. While far from perfect, my hope is that this piece might serve as useful orientation to those trying to get up to speed quickly on this critically important topic.

The goal

To avoid the most catastrophic effects of climate change, we should aim to limit global average temperature increase to 1.5°C above pre-industrial levels, which corresponds to reducing global annual emissions from about 50 gigatons of carbon dioxide equivalents (Gt CO2e) as of 2019, to net zero by 2050. We need to get about halfway there by 2030.

Source: stripe.com/climate

Source: stripe.com/climate

There are two main levers to achieve that goal

There are two main levers we can pull to get to net zero by 2050.

  1. Reduce emissions. Emit less CO2e into the air in the first place.
  2. Remove carbon. Remove CO2 out of the air.

The figure below charts the path to net zero by 2050 and the respective roles of each lever in achieving that goal.

https://s3-us-west-2.amazonaws.com/secure.notion-static.com/da8e399b-cabf-4627-b446-24963bf1a185/Untitled.png

Why can't we get all the way there with emissions reductions (Lever 1)? There are two big reasons.

  1. Some emissions will be very hard to decarbonize, such as making jet fuel used to fly zero emissions planes. Realistically, we won’t reduce 100% of emissions. So in order to achieve net 0 by 2050, we’ll need to actively remove any CO2e we’re emitting so that, cumulatively, they cancel out to zero (per the diagram above).
  2. The concentration of CO2 in the air is already too high. Even if we reduced emissions to 0 today, we'll still need to take carbon out.

How much we need to pull any one lever depends, in part, on how well we pull the other. For example if we only reduce emissions to 25 Gt per year by 2050, we'll need to do much more carbon removal than this chart suggests. Still, it’s helpful to have a rough rule of thumb of the magnitude that we’ll likely need to do of each lever. Roughly, we need to decrease emissions from 50 Gt per year to 10 Gt per year by 2050. We need to increase carbon removal from ~0 Gt to ~10 Gt per year.