Daily carbon dioxide crosses 430 ppm

That line jumped out to me as well. It's simplistic extrapolation of data without any physical basis. We're at 430ppm now. 500ppm by 2032 would be a climate disaster. 1200ppm would be a mass extinction. But hey, good news, we'll probably only need to deal with a disaster.

Getting to 1200ppm would mean burning thousands of gigatons of carbon in the next 7 years. We currently burn 12 GtC annual - we'd need to increase our fossil fuel consumption by 30x starting today. I'm not sure we even have the petroleum and coal reserves or infrastructure to do that, even if we wanted to. Unless there's some yet-unknown natural feedback loop waiting to release massive amounts of carbon, 1200ppm by 2032 isn't possible.

That's an extrapolation based on some worst-case scenarios. From their blog post:

- falling sea ice volume causing hydrates to destabilize, resulting in methane eruptions

- falling albedo as a result of reduction in sea ice extent

- falling albedo as a result of a reduction in lower clouds

- El Niño developing in the course of 2025

- sunspots reaching a maximum in the current cycle (predicted to occur July 2025)

- reductions in sulfur aerosols combined with an increase in black carbon and brown carbon

- less ocean heat reaching deeper parts of the ocean as a result of changes in ocean currents

That would indeed be extremely bad. It's not "barely breathable": OSHA lets you have up to 5,000 ppm for extended periods at work. But it is going to cause massive interruptions to weather patterns and agriculture, and would make for heat waves causing millions of deaths.

On a risk-cost basis, it's not likely, but likely enough with high enough costs that significant efforts should be made to avoid it.