Ben See Profile picture
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

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
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
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
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
Jul 23
icymi: our coastal cities will be smashed by multi-metre sea level rise within decades Peak global mean temperature, atmospheric CO2, maximum global mean sea level (GMSL), and source(s) of meltwater.  Light blue shading indicates uncertainty of GMSL maximum. Red pie charts over Greenland and Antarctica denote fraction (not location) of ice retreat.
The Greenland ice sheet is now losing around 9 billion litres of ice an hour [Geological Survey of Denmark &Greenland]

With the ice sheet at “a tipping point of irreversible melting”, scientists currently expect an unavoidable sea level rise of 1-2 metres.weforum.org/stories/2025/0…
4 to 10 m sea level rise committed in the coming 2000 years, with the majoroty of that in the coming decades/centuries it would appear.
science.org/doi/10.1126/sc…

x.com/climate_ice/st…
Read 4 tweets
Jul 21
BREAKING: horrific worst-case scenarios firmly back on the table as scientists confirm large-scale Earth systems such as forests, ice sheets, and ocean currents may already be collapsing 🧵
'large-scale Earth systems may be experiencing gradual collapses that are easy to miss, with profound implications

"we may already be crossing tipping points without realizing"

Slow changes can be deceptive

some systems may slide into collapse silently'
phys.org/news/2025-07-e…
Read 5 tweets

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