zlacker

>>Brajes+(OP)
Is there a site showing our socioeconomical possibilities and coutries' carbon-heavy investments that are in the pipeline?

I hear 1.5 C, 2 C all the time, but not much is happening [1] so I am looking for a best estimate to what should I expect in 2030, 2040 and 2050; not that 1.5 is "technicaly possible" cause it's practically impossible.

[1] https://www.nationalobserver.com/2018/12/12/analysis/co2-vs-...

>>badten+Si
In 1990, the U.S. Navy predicted that the Earth would warm as much as 4 degrees Celsius by 2040 https://documents.theblackvault.com/documents/weather/climat...

>>nebrie+lk
And that was a reasonable prediction at that time. Since than climate models have improved significantly, computing power has increased by several orders of magnitude, and policies and technology has changed—both as a response to the climate crises, and as technology and infrastructure improves around the world.

Today’s models predict 1.5°-2.0° C by 2040, and 4° C by 2100 if no additional climate mitigations (not even promised or pledged) are implemented. The 4° C scenario is generally regarded as unrealistic so most climate models have another prediction which accounts for some additional climate mitigation which most countries have promised and pledged and put the increase at 2°-3° in 2100.

>>runarb+Kq
> The 4° C scenario is generally regarded as unrealistic

Why? It sounds like you might mean that, by about +2 °C (~double today's avg warming) we start to notice the impacts a little too acutely and take more action, am I reading that right?

>>lucb1e+IJ
4° C is an extrapolation from current trends. Straight up extrapolations are seldom good predictions. There are usually some feedbacks and feed forwards in a complex systems. It is not unreasonable to assume that governments will follow through with at least some of their promises and pledges, especially as the effects of the climate disaster becomes more apparent. And doubly so as new industries pop up around climate solutions with enough money to influence governments over what the dying fossil fuel industry.

That said, I'm under no disillusion that 2° C warming is not a horror scenario and that if governments actually cared about human lives they would limit warming to 1.5° I know they don't and the won't

>>runarb+oU
Ah, unrealistic because it's a plain extrapolation without accounting for any behavior change or indeed feedback effects. That makes sense, thanks!

> It is not unreasonable to assume that governments will follow through with at least some of their promises and pledges

FWIW, it actually looks like we're on a path to 2.5-2.9 °C of warming with current policies, and nearly another 1°C reduction with current pledges which are indeed much less likely to fully materialise. Via https://en.wikipedia.org/wiki/Climate_change#/media/File:Gre... which appears to use 2021 data. The "no climate policies" scenario is shown as having the lower error margin actually above +4°C

>>lucb1e+0V
> FWIW, it actually looks like we're on a path to 2.5-2.9 °C of warming with current policies.

This is true, I actually used 2° C as a shorthand for 2° C - 3° C. I shouldn’t have done that. I actually believe we are more likely to be closer to 3° C at the end of this century than 2° C.