Global Warming Has Accelerated
Are the United Nations and the Public Well-Informed?
[No!]
Notes from the presentation of this groundbreaking new paper by James Hansen (@DrJamesEHansen) et al. (2025), with leading climate scientists:
🧵
1/
@DrJamesEHansen Global warming has accelerated, which can't be explained by natural variability
@DrJamesEHansen The anthropogenic forcings are greenhouse gases and aerosols.
Aerosols are likely understimated by the IPCC
@DrJamesEHansen Faustian bargain of greenhouse gases and air pollution
@DrJamesEHansen Sulphur air pollution has been reduced over the past decades, especially from shipping:
@DrJamesEHansen Earth's reflectivity (albedo) has decreased:
@DrJamesEHansen The region with most shipping emissions shows the strongest increase in Absorbed Solar Radiation:
@DrJamesEHansen The new study estimates that the reduction in shipping emissions contributes an enormous global climate forcing of +0.5 W/m² (much more over the Northern Hemisphere).
@DrJamesEHansen Even though El Niño has faded, we shouldn't expect temps to decrease much this year (as we saw by January 2025 reaching a new monthly record).
If the heat stays in the Southern Hemisphere (through AMOC shutdown) we could experience multiple meters of global sea level rise.
@DrJamesEHansen This is very worrying:
Ice melt will accelerate now.
Warm water enters below ice sheets, melting them from below
Models underestimate deep water warming, which is why we need better observations to improve models
"The 2C target is dead"
The CO2 emissions from fossil fuel use is still increasing, because people need energy.
Energy infrastructure doesn't change overnight.
Only Sweden has largely decreased CO2 emissions, mainly through the use of nuclear power:
We need a price on Carbon!
We need global cooperation
Young people have more power than they think.
We need a political party that doesn't take money from special interest:
Jefrey Sachs introduces Pushker Kharecha:
Half a percent-point decrease in albedo (over 35 times larger than world energy use!)
Effect of shipping emissions is over 10 times humanity's energy use
The main shipping regions (North Atlantic and Pacific) show the main effect, as ocean air is relatively pristine with little other regional emissions (both natural and anthropogenic)
Climate sensitivity is underestimated when the effects of aerosols are underestimated.
Including a strong shipping aerosol forcing explains the increased rate of warming.
Sachs asks: where do we stand if we'd have a neutral ENSO (El Niño & La Niña).
Answer: Shipping emission changes add about 0.2C, which means temperatures won't decrease much from this point.
This means we've breached 1.5C for all intents and purposes.
Sachs Sussane Bauer from @NASAGISS
"We shouldn't talk about aerosols so much any more, because they are rapidly going away and greenhouse gases are taking over!"
The aerosol cloud effect decreases 30 years after the direct effect of aerosols! 🤯
Also note the decrease of aerosols from China, while India still increases aerosols
Clouds react to aerosols more over regions with less pollution
Sachs introduces Anton Keskinen from Operaatio Arktis
We need the precautionary approach!
The West-Antarctic Ice Sheet collapse could cause multiple meters of sea level rise.
This has happened before during the Last Interglacial (Eemian), when Sea Surface Temperatures were lower than they are today.
We need RESEARCH on Purposeful Global Cooling
1. Acceptability of impacts in the pipeline?
2. Risk vs risk assessment!
3. Effects on mitigation [never use Sunlight Reflection Methods (SRM) as an excuse for not reducing greenhouse gas emissions!]
Jeffrey Sachs underscores that James Hansen been more right about the science than anyone else in the world!
'You warned us about what was coming'
@DrJamesEHansen James Hansen: The AMOC transports 1 PW of heat to the Northern Hemisphere.
That's equal to the effect to doubling the amount of CO2 over the Northern Hemisphere (4 W/m² over 255 Millions square kilometres)!!!
Hansen:
The IPCC shows that nuclear power is the most effective technology for reducing greenhouse gas emissions, this was largely ignored.
You can't rely on the IPCC report with regard to AMOC slowdown, as it underestimates reality.
All agree:
We need greenhouse gas emission reductions as fast as possible
We need to sop electing politicians that ignore reality and peddle to special interests
Susanne Bauer:
The lack of the [aerosol] masking effect underscores the importance of reducing greenhouse gases.
Don't forget about methane!
Hansen:
You can't reverse AMOC shutdown!
On politics:
The power needs to be with the people, not with those with money to buy politicians
Thank you again for taking this serious and for your tireless effort to get to the bottom of what the data shows, @DrJamesEHansen
If anyone spreads doubt about the main findings, please ask them to give an alternative explanation for the enormous increase in Absorbed Solar Radiation and Sea Surface warming over the Northern Hemisphere's mid-latitudes!
They most likely can't.
Global Warming Has Accelerated
@DrJamesEHansen et al.
Find here a recording of the paper launch presentation, with contributing scientists:
youtube.com/live/d6wOjk2OC…
Find a link to the new paper here:
We will discuss all this in detail next Sunday on Climate Chat.
Please join us
Share this Scrolly Tale with your friends.
A Scrolly Tale is a new way to read Twitter threads with a more visually immersive experience.
Discover more beautiful Scrolly Tales like this.