Thread by @hausfath

If emissions had peaked back in 2000 we would be skiing down a bunny slope toward 1.5C. Today we face a double black diamond, and in a few years it will be a cliff.

We are almost certainly going to overshoot 1.5C and need large-scale permanent carbon removal to get back down.

Scenarios commonly used to limit warming to 1.5C include a lot of late century negative emissions – sucking a quarter to a half of current emissions out of the atmosphere each year by 2100 – in order to make near-term reductions more plausible:

https://twitter.com/hausfath/status/1424891447652716548

There is, of course, no guarantee that negative emissions of that scale will pan out, but any chance of ultimately limiting warming to 1.5C likely requires both speeding up emissions reductions significantly and building a robust carbon removal industry later in the century.

Thankfully, the pathways to 2C with limited net-negative emissions are a lot less daunting, but every year global emissions continue to rise or stay flat it too becomes much more difficult to achieve:

It is worth mentioning that reducing global emissions 20 years ago would have been much harder than today. China was still industrializing rapidly through expanded coal use, clean energy was expensive, and political will was lacking.

Its much easier to mitigate today, but at the same time the emissions that have accumulated in the atmosphere over the past 20 years make it much more difficult to meet our ambitious climate mitigation targets.

Finally, its worth emphasizing that climate change is fundamentally a matter of degrees rather than thresholds. It not like 1.4C is fine but at 1.6C there be dragons; similarly, things do not suddenly spiral out of control at 2.1C. Its important to mitigate as much as we can.

Thanks to @robbie_andrew for creating these no-net-negative emissions pathways; it got a lot of attention when we first featured them at @CarbonBrief back in 2017, and recently has really blown up (e.g. with this new @climate visualization): bloomberg.com/graphics/2021-…