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Comment by sfn42 | Hacker News Reader

> that was considered to be an unlikely extreme scenario

By the same people who just realized we're missing 1.5C as we're blazing past it at mach 12, still accelerating not slowing down? You really believe those guys?

You have to understand that there are several camps of climate science. The mainstream ones like IPCC and UN etc are heavily politicized, they can't publish anything that isn't sugarcoated beyond recognition. At least I assume that's why they're so obviously wrong.

Here's a judgement I think is more realistic

> There is a strong probability that the ambition gap will lead to a temperature rise of 2 to 5 degrees Centigrade compared to pre-industrial temperatures by 2100, the realisation gap to a further rise of several degrees Centigrade.[1,2,VI] There is a danger that the mean temperature will already have risen by 3 degrees Centigrade by 2050.

https://www.dpg-physik.de/veroeffentlichungen/publikationen/...

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Yes, I do. IPCC's reports are sensible. They're not unreliable just because they don't support the "doom and burning land" narratives.

By the way, there is no "just realized we're missing 1.5C". That projection was always the very low end of possibilities - the "assume rapid, radical climate action on global level" scenario.

Yes, that's a dumb thing to assume. We've never been on track for it. But the "assume extremely high emissions and no green transition ever, 5C+ by 2100" scenario on the other end is about as unlikely to materialize. Those are the boundaries of the expectation range - not median expectations.

I'm pessimistic. We're still producing more CO2 each year than the last, and several feedback loops are kicking in that accelerate the warming further such as permafrost thawing, arctic and antarctic sea ice disappearing, glaciers are melting, the amazon is being demolished, etc. I don't know how much of this is included in the projections.

I hope the optimists are right, it just doesn't look like it to me at all. It looks to me like we're speeding along right into the worst predictions and beyond. We're building lots of green energy production but it seems to just come in on top of existing and new fossil production not replace it.

It does seem like the CO2 output is plateauing which is good, but we really need it to start declining drastically very soon and I don't really see that happening with the current political climate. Also remember CO2 is far from the only greenhouse gas - methane, nitrous oxide and fluorinated gas emissions all seem to be rising rapidly still.

As a rule: feedback loops are overrated.

They are, in fact, included in the projections - we'd be on track to ~2C by 2100 instead of ~3C by 2100 if they weren't. They just aren't that big.

There is no "Make Earth Into Venus Feedback Loop Of Doom" that a lot of people seem to imagine when they hear "feedback loop". There is, however, a dozen of things that add about +5% each.

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