Seeing an old climate outlook going around (https://mastodon.energy/@MatthiasSchmelzer@mastodon.world/110657312337452580) so just noting that the IEA's 2021 Stated Policies Scenarios has global temperatures increasing by a bit more than 2.5°C by 2100, not 4°. https://www.iea.org/reports/world-energy-outlook-2021/scenario-trajectories-and-temperature-outcomes
@chrisnelder The “stated policy” scenario doesn’t reach net zero. It will therefore keep warming after 2100. That year is purely conventional in that context. Within uncertainties, +4°C can eventually be reached. The graph you referred to has a geological time scale, so it’s impossible to read from it which century that temperature would be reached. So not contradictory.
@ljbo Thanks for the clarification on that. I would have to look at what the "stated policy" scenario assumed circa 2018 (probably earlier actually?) but I don't think that's the outlook now. However it was defined then, most experts I speak to see 2.0° - 2.4° within reach under current targets, and under 3° for current policies, and never reaching 4° (this century or later). Which was my point. These projections are changing relatively quickly & the worse-case ones becoming improbable.
@chrisnelder Yes, when I got aware of global warming in the early 00’s, business as usual was basically RCP 8.5, and over +4°C *by 2100* We are way better now for sure.
@chrisnelder On top of that, the knowledge that there is no warming inertia, I.e. that temperatures stabilise very quickly after reaching net zero, that was not mainstream back then. Big reason for optimism. If we seriously work on decarbonation of course.