[arctangos]

The authors don't include some extremely nasty feedback loops the appear to currently be happening. For example, methane release from permafrost melt.

As a result, the simulation appears to be misleadingly optimistic.

- This tool is based on climate interactive's previous one, C-Road.

- in the C-Road simulation when you click on parameters -> assumptions to add parameters about methane release through permafrost melting and human activities. By default, it's set to zero, but even their maximum values don't seem as impactful as I would expect.

- in EN-Road simulation (this one) the methane release parameters are removed! So, no possibility to add any positive feedback loops. It feels like the relation between CO2 and temperature is a simple linear equation, or close to it.

[koheripbal]

While negative feedback loops are big in the media, they are not well understood and difficult to model.

Also, other feedback mechanisms seem to get little attention. Are we only looking to model the feedback mechanisms that reinforce a narrative of cataclysm?

Don't other feedback mechanisms exist that lessen CO2 concentrations, or temperature dissipation?

[breakyerself]

No. They aren't "only looking at feedback mechanisms that reinforce cataclysm." Modelers include every feedback that they can quantify well enough to include and the ones they don't understand well enough are studied carefully to be able to work out what the uncertainties are.

Scientists 50 years ago predicted that we would be at around 1C (1.8F) of warming by 2020 with a 40% over preindustrial co2 level. That's exactly what we have now. They predicted almost perfectly today's climate decades before it came to pass. That may not seem like a big deal until you understand that global temperatures haven't been this high in 130,000 years.

It isn't being recognized properly yet in the media, but the stunning accuracy of predictions by climate modelers is one of the greatest achievements in the history Earth sciences.

[mistermann]

This sounds like you're saying that 50 years ago there was a single climate model, upon which significant consensus among scientists had been reached, that predicted a 1C temperature rise. I've read quite a few articles and discussions on this topic but have never heard this before.

Am I misunderstanding you? If not, do you have a link that discusses this?

[atotic]

"Evaluating the performance of past climate model projections"

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019...

"We found that climate models – even those published back in the 1970s – did remarkably well, with 14 out of the 17 projections statistically indistinguishable from what actually occurred."

[mistermann]

Yes, I read that report and participated in the subsequent discussion [0] where I raised a number of concerns with the study, but wasn't able to find anyone who would seriously and objectively address them.

Frustrated by the unwillingness of anyone to engage in rigorous discussion in that thread, I also contacted the authors to see if they were willing to address some of the concerns. Unfortunately, I did not hear back.

I must confess, this strange combination of group declaration that "the science is in", combined with complete refusal to discuss "the science", leaves me feeling a bit suspicious about the degree to which anyone has actually read the science, or is thinking critically on this matter.

If you could address some of the concerns I raised in [0], I would be delighted.

[0] https://news.ycombinator.com/item?id=21708936

[mturmon]

> I raised a number of concerns with the study, but wasn't able to find anyone who would seriously and objectively address them.

This is an inaccurate summary of that thread, in which you raised a simple accusation that the article cherry-picked the models, were swatted down with a citation from the article referenced in the OP, and then retreated into a maze of long, twisty replies that failed to raise any other specific points.

Your comments in this thread have had the same flavor. Consider brevity and specificity.

[phaemon]

Perhaps the Sawyer paper from 1973? https://www.carbonbrief.org/analysis-how-well-have-climate-m...

[mistermann]

Surely there was one model that happened to come up with the right prediction, I would assume there were multiple. But my questions is whether there was one model with consensus support (which seems to be the claim), which would be necessary to rule out survivorship bias.

[phaemon]

> Surely there was one model that happened to come up with the right prediction

What does that mean? This "model" is someone sitting down and, using what we know of physics, calculating how something will warm up when you add some extra energy (in this case, the earth). You surely don't think that physics works by people randomly guessing answers and then one of them "happened" to be correct?

You don't, do you?!

[jellicle]

If they did exist, we would take their effects as baseline assumptions and just ratchet down our opinion about the crisis, if that makes sense. To the extent there are buffers, we just assume their effects, and we'll be unpleasantly surprised when the buffers run out.

Examples: in the 70s we had a great deal of particulate smog, which effectively reduced some of the radiation hitting the Earth and camouflaged the effects of global warming. But instead of saying "hey, global warming must be a big problem since we're noticing X amount of warming EVEN WITH PARTICULATE SMOG", it just let us ignore global warming for longer.

Example: the deep oceans have been an effective heat sink and some amount of the global heat has gone into them. Again, instead of saying "global warming must be a big problem since we're noticing X amount of land warming EVEN THOUGH THERE'S A GIANT HEAT SINK", it just let us ignore global warming for longer.

So, to the extent that there are any buffers, we'll just build them into our baseline of "how bad the problem is", and therefore ALL of our surprises and feedback effects will be seen to be negative.

[CalRobert]

"While negative feedback loops are big in the media"

You mean positive, right? As in self-reinforcing? Negative would mean the opposite, and there are a few of them (greater plant growth etc.) but they seem to be more than cancelled out by the positive (bad) feedback loops.