HI mate - sorry I didn't reply to this.

So, from what I've read recently in the literature there have been some fairly key concessions by climate scientists. For instance. their modelling generally assumes rapid population growth. We can see this is not continuing, and maybe wasn't actually occurring when a lot of this modelling was done sort of 30-15 years ago. Another is that costs for renewable energy have drastically dropped, against assumption. Several countries have also decoupled their emissions targets and levels with their GDP. So there's no sort of central predictability measure which was assumed. Overall, that means that the high ECS models are marginally outstripping lower tails we're seeing in the real-world data without some calibration and compensating errors assumed - worst case scenarios tend to now be rejected by the scientists:

"While the IPCC community has opted against estimating likelihoods associated with future emission scenarios, it does indicate that the worst-case scenarios for future climate change (specifically the scenario leading to 8.5 W/m2 radiative forcing in 2100, RCP8.5, SSP5-8.5) have become implausible 8"

While this needs to be tempered - the paper is survey questions about the likelihood of certain outcomes under the current assumptions - we can see that those may need to be adjusted as the introduction aptly notes.

There is the added spanner of human adaptation, which is much more swift than most models take into account so things like technological cooling adoption will adjust downward in real-world terms. Upsides like the increase in edible biomass globally are ignored, greening we see in some arid areas of the world and that with higher CO2, plants are more efficient with their water on average:

"This increased C02 is not just driving climate change, but also fast-tracking photosynthesis in plants. By allowing them to use scarce water more efficiently, the CO2-rich air fertilizes vegetation growth in even some of the driest places"

(the use of a zero instead of "O" there is in the article, not me).

All this seems to suggest that there was just a bit of over-caution. Not suggesting anything untoward of any kind whatsoever here. I don't make any kind of real conclusion. I stay looking at all sides, but "act as if" regardless.

Hi Amadeus, no worries, thank you for the reply.

I generally agree with you concerning the factors that might go into the amount of greenhouse gasses we will be emitting. We won't be seeing a linear growth of population and probably also not of the economy, like we have had for say the past century.

In my original reply I was thinking about the climate sensitivity to changes in greenhouse gasses in the atmosphere. This might have been underestimated in the models. Basically, as I understand it, there are two camps in climate science. Those that think the sensitivity is a lot larger and warming has been masked by other pollution in the atmosphere, like sulfur emissions. And then there are those that thought the models have been correct by and large. But even the latter seem to think now that something is missing because anomalies in 2023 or 2024 that don't quite fit the models. Gavin Schmidt is one of those mainstream climate scientists that has been voicing that concern if you want a source to check.

And then there's tipping points and positive feedbacks which still seem like a bit of an unknown.

The greening effect is real, but it's unclear to me how this will combine with other factors like droughts and generally more extreme weather. Also apparently faster leaf growth because of increased CO2 seems to also have to effect of reducing the amount of nutritious substances in plants, which would mean we have to eat more of them to get the same amount.

But yes, I certainly can agree with the sentiment to stay open to all kind of information and arguments... it is a complicated issue.

For sure - and I want to be damn clear I am not denying that it's happening, that its anthropocentric, or that we should be doing things about it. Just for anyone would might take it that way... :) Thanks a lot for the exchange!

All this seems to suggest that there was just a bit of over-caution — AmadeusD

But the biggest changes in the climate wouldn't be felt for a few more centuries. There's still a gigantic amount of coal to burn. What we do with our coal reserves is the biggest factor in determining the extent of the change according to David Archer. This is why it's disturbing that the Chinese are building one coal burning power plant per week.

But it's not like we can reach 500 years into the future and remind humans not to burn that coal. The coal will always be there as an easy power source. This is one reason people have started looking to how to adapt. It's a particularly challenging thing to adapt to because there's no plateau in it. There's a big spike in temperatures that will last for a couple of thousand years. Then it will drop off again, coming back close to where we are now. It will be a wild ride.