this post was submitted on 03 Dec 2023
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Discussion of climate, how it is changing, activism around that, the politics, and the energy systems change we need in order to stabilize things.

As a starting point, the burning of fossil fuels, and to a lesser extent deforestation and release of methane are responsible for the warming in recent decades: Graph of temperature as observed with significant warming, and simulated without added greenhouse gases and other anthropogentic changes, which shows no significant warming

How much each change to the atmosphere has warmed the world: IPCC AR6 Figure 2 - Thee bar charts: first chart: how much each gas has warmed the world. About 1C of total warming. Second chart: about 1.5C of total warming from well-mixed greenhouse gases, offset by 0.4C of cooling from aerosols and negligible influence from changes to solar output, volcanoes, and internal variability. Third chart: about 1.25C of warming from CO2, 0.5C from methane, and a bunch more in small quantities from other gases. About 0.5C of cooling with large error bars from SO2.

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Open secret at climate talks: The top temperature goal [1.5°C] is mostly gone (www.politico.com)
submitted 1 year ago by silence7@slrpnk.net to c/climate@slrpnk.net
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I'll note that it's still worth fighting for every 1/10 of a degree, and that we had a goal of 2°C before trying to aim for 1.5°C.

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[–] benjhm@sopuli.xyz 13 points 1 year ago

Indeed it has always been worth fighting for every 0.1ºC, and round numbers of degrees were always arbitrary political targets. Remember also that as well as the peak temperature,

  • The rate of warming also matters - especially for ecosystems to migrate and agriculture to adapt
  • The integral of warming also matters - especially for ice melt and sea-level rise
  • Other issues matter - models paths strictly below 1.5C mostly achieve this with BECCS, competing for land with biodiversity and food production.

Many scientists have long concluded privately that the world will at least temporarily miss that target.

Yes, that's true, if you define it strictly. I've left the default in my model (which doesn't include BECCS) at 1.75ºC for years now. Earlier, the default was 2ºC, and it/I was the first to analyse that probabilistically (2003), indeed maybe this helped in pushing the shift to 2ºC from x50ppm concentration targets we had before that. Don't get me wrong - I was wearing those "1.5 to stay alive" badges in COPs 15 years ago, before it was common policy, and contributed to the 1.5C conference leading to the IPCC report. However I observed that China never agreed to this - it was very hard to get them to agree <2ºC, and nor did India - despite being urged to do so by all its smaller neighbours. Without those two on board we had little hope. Staying well below 2ºC is different - they all agreed to that, and their actions are plausibly approaching consistency with that (that doesn't apply, of course to the arabian-gulf petro-states, nor to russia). However 2ºC probably won't save the Greenland and West-Antarctic ice, without which bye-bye to Shanghai, Tianjin, Mumbai, Kolkata, etc.. So I guess we'll all keep trying, but increasing numbers will have to relocate - I consider (pending how this COP goes) whether to shift to analyse such migration, rather than continue with detail on mitigation policy.