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Ben See Profile picture
@ClimateBen
Nov 26, 2021 • 10 tweets • 4 min read • Read on X
'The last time global surface temperature was sustained at or above 2.5°C was over 3 million years ago' in the Pliocene, with CO2 levels like today.

We could reach 2.5°C by 2100 if emissions 'stay close to today's levels over a few more decades'.

May that even risk 3°C-4°C?

1/
Scientists tell me not to expect 4C by the 2060s (see 2009 article), but they appear to be clear 3.5C-4C by 2081-2100 is entirely plausible.

If emissions don't drop by the 2040s, could we face up to unthinkable 3.5C-4C,not just horrific 2.5C?

2/
theguardian.com/environment/20…
The best estimates (and very likely ranges) for 2081-2100 in the two scenarios that I believe are widely considered to correspond to our current situation are 2.7C (2.1-3.5C) and 3.6C (2.8-4.6C).

Could another 15-25 years of emissions around today's levels mean 3-4C by 2090?

3/ Image
1.5C-2.5C is already catastrophic enough to leave 100,000s or millions of species struggling, including humans in my opinion.

I ask whether and under what conditions 3-4C by 2090 would be plausible in light if this conversation from yesterday:



4/
'We have already observed impacts of climate change on agriculture. We have assessed the amount of climate change we can adapt to. There’s a lot we can’t adapt to even at 2C. At 4C the impacts are very high and we cannot adapt to them'

2C by 2038-2052?

5/theconversation.com/ipcc-expert-wr…
This excellent IPCC AR6 WG1 thread by @valmasdel is extremely helpful. Clear, concise, fascinating, and terrifying.

6/
How many people have grasped this?

⬇️



7/
Have media and education systems made the ideas in this thread clear to us all? I think not.

8/
There's every reason to think we can't avoid 2.3-2.8C.

Can this be delayed for many centuries or beyond (which may help species to adapt) or will it hit by 2050-2150 which would be too fast for species to cope?

Most scientists expect 2.3-2.8C by 2100.

9/cbc.ca/news/science/c…
We could still hit 4C-5C. What survives that? See here:



10/

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More from @ClimateBen

Ben See Profile picture
Sep 18
12-40% of species extinct is considered catastrophic. So many amphibian species (~50%), plant & bird species (~40-50%), insect & mammal species (~30-40%), and reptile & fish species (~25%) are currently seen as being at risk. 48% of species are in decline. How will humans cope?
1. under a pessimistic global warming scenario (~4°C increase), climate change alone might only cause the extinction of ~20–30% of extant species in the next ~50–100 years [41,42]. Taken together, these losses would be catastrophic, but very far from 75%.'
sciencedirect.com/science/articl…
2. 'Current projections of future extinction seem more consistent with ~12–40% species loss, which would be catastrophic but far from the 75% criterion used to argue for a 6th mass extinction.'

Some experts fear >50% at 3-4°C even with moderate emissions.
sciencedirect.com/science/articl…
Read 4 tweets
Ben See Profile picture
Sep 10
Earth's species will suffer 2-2.6°C and rising even in capitalism's most ambitious decarbonization scenario. Scientists anticipate unsurvivable 3-7°C, with geologic periods like the Miocene climatic optimum (MCO) seen as good analogues for our current 21st century climate hell.🧵 The multimethod, multitaxon pCO2 reconstruction presented here indicates that pCO2 was moderately elevated at ~450–550 ppm during the MCO. These results are somewhat higher than most previously published pCO2 records, which generally report pCO2 < 450 ppm (see Foster et al., 2017), but still considerably lower pCO2 than climate modeling requires to reproduce MCO temperatures (Goldner et al., 2014). This indicates that climate sensitivity must have been elevated during the MCO, leading to highly elevated temperatures at moderately elevated pCO2. With 415 ppm measured for the first time in sp...
1/The race is now on to improve our knowledge of the Earth system in order to understand whether.. moderate levels of pCO2 may.. cause a devastating..increase of up to 7°C in the (near?) future, and if so, take action to prevent it. agupubs.onlinelibrary.wiley.com/doi/10.1029/20… x.com/ClimateBen/sta…
2. The temperature regime reconstructed for most of the Miocene, ∼5°C–8°C above modern, is equivalent to projected future warming in about a century under unmitigated carbon emissions scenarios.. an important warm-climate analog..
agupubs.onlinelibrary.wiley.com/doi/full/10.10…
x.com/ClimateBen/sta…
Read 7 tweets
Ben See Profile picture
Aug 27
COLLAPSE/EXTINCTION: scientists fear global warming of 3.5°C, which wipes out 33-70% of species (IPCC AR4 2007, IPCC AR6 2022), will likely hit by the 2060s give or take a decade or two 🧵
1. IPCC scenario SSP3-7.0 shows 3.5°C by 2080 or from 2062 (not the worst-case scenario). Even a moderate emissions scenario can lead to 3.5°C this century (new research shows 2060s-80s possible).


Species extinct IPCC:
3.5C 40-70% 2007
3C 29%, 4C 39% 2022esd.copernicus.org/articles/12/25…
2. A new pre-print from highly respected climate scientists implies 3.5°C by 2065-77 at current rates of warming. The authors warn this rate could increase or decrease perhaps suggesting 3.5°C by around 2055-2087 rather like IPCC high emissions scenarios.
researchsquare.com/article/rs-607…
Read 5 tweets
Ben See Profile picture
Aug 25
BREAKING: scientists say Earth's major systems are undergoing abrupt changes — and soon we'll all feel them 🧵
1. 'prepare for a future of abrupt change.. choices made now will determine whether we face a future of worsening impacts and irreversible change or one of managed resilience to the changes already locked in.' phys.org/news/2025-08-s…
2. Society must now brace for catastrophic impacts.

Thread:
Read 7 tweets
Ben See Profile picture
Aug 9
Destruction of habitats and wildlife has intensified and accelerated to an almost unimaginable degree during the capitalist era. Scientists say the 40-50% of plant species now facing extinction will be obliterated in a handful of decades. It didn't have to be like this. Rethink. Plants are going extinct up to 350 times faster than the historical norm
1. Capitalism: a 'meteorite'

'previous mass extinctions.. took 10,000s, 100,000s, even millions of years to happen. this is happening so fast, now in just two, three decades..'
google.com/amp/s/www.cbsn…

Recovery: "we most likely won’t be there to see it"..
discovermagazine.com/earth-is-on-th…
2. Current estimates of plant extinctions are, without a doubt, gross underestimates. Extinctions will surpass background rates by 1000s of times over the next 80 years. universityofcalifornia.edu/news/plants-ar…
Read 8 tweets
Ben See Profile picture
Aug 7
BREAKING: as tropical forests show increasingly clear signs they are entering a collapse phase scientists warn irreversible mass extinction conditions are on the horizon 🧵
1. rapid warming & collapse

".. warming could continue to accelerate.. even if we reach zero human emissions. We will have fundamentally changed the carbon cycle in a way that can take geological timescales to recover, which has happened in Earth’s past.”scitechdaily.com/mass-extinctio…
2. “There will be a point in the not too distant future when we suddenly see and feel this mass extinction all around us very clearly”

“A key point of extinction crises is that life has always recovered.. However..we most likely won’t be there to see it."
Read 5 tweets

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