What counts as carbon removal?

Direct-air carbon capture a la stripe.com/climate.

The spirit of this prediction is for assessing how critical it is to reduce emissions. If carbon capture is expected to get cost-effective enough then reducing emissions now is less critical. Presumably. So anything that permanently un-emits carbon counts. Anything that just prevents emission in the first place, including things like smokestack scrubbing that capture carbon before it's actually emitted, do not count.

By when?

"Eventually." See the next section. But this will resolve on January 1, 2050 at the latest based on scientific consensus.

What does "pivotal" mean?

That carbon removal will end up being responsible for an impactful decrease in atmospheric CO2 concentration -- enough to yield half a degree Celsius less warming than we'd otherwise see.

The idea is to predict whether carbon capture will get cheap enough to do at a big enough scale to matter and be worthwhile.

The atmospheric CO2 decrease doesn't have to have happened by 2050.

Updates

1. Early on, after discussion in the comments, we changed the criterion to be about atmospheric CO2 concentrations rather than temperature.

2. This was originally meant to resolve in a few years based on scientific consensus but then Manifold added loans. Now betting in very long-term markets is perfectly incentive-compatible so we'll wait till we're certain about this to resolve it (latest 2050).

3. Originally there was some ambiguity about whether the full CO2 decrease had to be achieved by 2050. The answer is no, we just need scientific consensus that we're on track for removing that much CO2.