New climate change report from Giving What We Can

I haven't read the articles yet, though I did study climate change as part of my undergraduate and externally, so I'll have a crack at answering your technical question (Q3).

The point of mitigation is to reduce greenhouse gas emissions (including carbon dioxide and methane) or to capture and store them (number of ways to do this, underground gas to liquid storage, growing trees etc.). CO2 actually has a much shorter residence time in the atmosphere, but it does then get stored in the ocean for up to centuries. Methane is also a big problem, because it has a larger impact on warming (around 20 times greater), but has a shorter residence time (around 8 years in the atmosphere). For this reason, some people propose that mitigation, at least in the short term, should focus on reducing methane gas, as it has a larger short term effect, and if we hypothetically cut methane to zero (not going to happen as there are still natural sources, but for arguments sake), we would see the impact of methane disappear quite quickly, compared to cutting carbon.

To answer the rest of your question, the fact that carbon is transferred from the atmosphere to the oceans, soil and organic matter over time means that there is some particular amount of greenhouse gas (GHG) that can be put in the atmosphere without warming, as the Earth as a whole can absorb it (assuming no man-made carbon capture). This point is called the equilibrium state. We have well and truly exceeded the equilibrium point through man-made emissions, which is why the planet is warming. If we could reduce emissions to the equilibrium emission rate and below that, the planet would, eventually, start to cool. Even if we expect we will only get below equilibrium in 100 years, any reduction in emissions now will mean the atmosphere will have warmed less by the time we get there.

Hi Sam,

Thanks! Glad you liked it. It's currently just a preview and not actually published yet, so that's why some links and functionality may not work (and the post on the model I used is still yet to go up).

In regards to Q1 - I would like to, yeah. When it comes to the probabilities of different levels of warming though, it's super uncertain. The ~1% chance of 10 degrees of warming is only under one of several possible probability distributions and we really just don't have any clue which of those distributions is accurate. And in addition to the uncertainty there, we know very little about just how bad those high levels of warming would be for us as there's minimal research on it, so giving expected values would be a major challenge - one which I'm not sure I'm up to, but which definitely warrants some more research in future. There's also the values and risk profiles of different donors to think of too - many want direct measurable benefits rather than minor reductions in existential risk somewhere in the future - so even if we got a decent estimate of the expected impact of emission reduction including tail risks, it'd have to be given separately.

Q2 - Largely the same issue as above - seriously difficult to estimate. But as far as mentioning them, that's certainly something that can be added in before we publish. Cheers for that!

Q3 - Yeah, so reducing present emissions just temporarily won't really help much (unless it gives us longer to adapt). But when I'm talking about emissions reduction, I mean permanently preventing that quantity of emissions from ever being emitted (e.g. through deforestation). Reducing (or preventing) emissions in this way should not only delay the point at which we reach a given temperature but also reduce the eventual peak temperature. And Michael's spot on with his reply too (we haven't looked at methane emissions specifically here but it does seem like it might be possible to reduce methane emissions at roughly $5/tCO2eq through ACE's recommended animal charities - highly uncertain though).

Q4 - I've also just finished an evaluation of the most promising lobbying organisation we've found. It should be up sometime soon. We think it might be a slightly better option for donors with a greater appetite for risk, but for others it still seems like Cool Earth is the better option.

Q5 - The US. That seems pretty certain, as they're not only a massive emitter (2nd worldwide) but it's pretty widely accepted that a lot of action elsewhere won't happen if the US doesn't get the ball rolling. This'll get mentioned in that other evaluation though.

Q6 - I'm not sure. It probably wouldn't be a bad use of most people's time, and the advocacy charity we've been looking at does use a lot of volunteers. Then again, they're currently getting hundreds of thousands of volunteer-hours each year already so it might be more effective to volunteer elsewhere or in a different cause area. I really don't know though.