Climate Impact of Decreasing Atmospheric Sulphate Aerosols and the Risk of a Termination Shock
Today I presented our first findings during the Annual Aerosol Science Conference of @AerosolSociety
@DrJamesEHansen @SkyECHO_Yann #COP26
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Significant reduction in atmospheric sulphate aerosols contributes to albedo reduction, acceleration in Earth’s Heating Rate and could cause an aerosol termination shock.
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Global warming to date is caused by greenhouse gases, but sulfur emissions cool ~-0.5°C, hiding part of warming.
Global shipping was responsible for a large part of anthropogenic emissions of sulfur over oceans.
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Most Earth Heat Gain from increased greenhouse gas concentrations warms oceans, which cover 71% of Earth surface and absorb ~89% of heat gain.
Sulfur emissions from shipping reduced with ~80% from 2020 from regulation of the International Maritime Organization (IMO2020).
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Emission regulation of IMO decreased sulfur emissions over seas and oceans over Emissions Control Areas, with ~90% from 2015 and globally with ~80% from 2020.
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Models show large uncertainties in the effect of the ~80% reduction in global shipping. The low end would't be measurable and the high end could result in rapid regional and global warming.
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Differences in forcing estimates are caused by uncertainties in aerosol load, atmospheric lifetime, relative emission of direct SO4, DMS, emission distribution and seasonal variability.
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The past two decades saw an albedo decrease and an increase in planetary heat uptake, coinciding with a decrease in anthropogenic sulfur emissions.
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This trend could accelerate further with more sulfur emission reductions.
An aerosol termination shock whereby rapid anthropogenic aerosol emission reductions cause rapid global warming, can not be excluded.
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Reflection of Earth (Albedo) is decreasing. Sulfur emission reduction could be a leading cause.
With less solar radiation reflected back to space, warming is accelerating.
Ship sulfur emission reduction contributes to rapid albedo decrease over the N Pacific and Atlantic Oceans.
Compliance to low sulfur fuel regulations for shipping looks very strong, based on inspections of compliance, low sulfur fuel sales and scrubber installations.
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There already is an observed increase in the rate of Earth net heat uptake.
More solar radiation is absorbed from a decrease in cloud cover and surface albedo (mainly from melting of ice).
A warmer Earth radiates more heat, while more water vapor and other GHGs absorb IR.
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A well documented change in emissions and cloud changes happened over Europe since the 1980s
Large scale reduction in SO2 emissions coincided with a cloud cover reduction of ~5% and an increase of annual sunshine of ~75 h/yr.
Global & European temp increase accelerated.
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Rapid reduction of SOx emissions from global shipping could prove an unintentional abrupt cessation of SRM.
If the higher range ERF effects of IMO2020 are a reality, this could be quantified a termination shock, even more so when combined with other SOx reduction effects.
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There is a strong upward trend in the increase of Absorbed Solar Radiation globally and even more pronounced over the N Pacific Ocean and N Atlantic Ocean, both areas of high shipping density, where sulfur emissions were reduced the last decade and more from 2020.
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The North Pacific is a region of 37.1 million km² and if the trend of increase heat uptake continues, this could have significant consequences for the regional and global energy balance and climate.
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The North Pacific Ocean absorbs about 80'000 GW more solar heat since 2020 than before 2010, which is before any significant sulfur regulations for shipping came into effect.
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On the other side of the Arctic Ocean is the North Atlantic Ocean. This region of 22.2 km² now absorbs about 50'000 GW of solar heat more than in the period before ship regulations.
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Total absorbed solar heat increase in these two regions is ~130'000 GW. Compare this to the average total human energy use of about 19'000 GW.
This is a lot of additional heat available to warm seawater, melt ice, heat the atmosphere, increase rainfall, storm intensity etc.
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With the limited time since the IMO 2020 regulation has come into effect, the long term effect of this significant reduction in sulfur emissions is still uncertain.
Natural variability (ENSO, volcanoes, forest fires, dust storms) can temporarily change the radiation balance.
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Human aerosol emissions and reduction thereof will keep impacting the climate.
Further global reduction in sulfur emissions is expected from health and environmental policies, cleaner fuel use and installation of desulfurization systems, mainly at coal fired power plants.
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*22.2 million km² that is of course..
This an updated and improved version of the graph.
These desulfurization systems are enormous.
These images show the decommissioning of a flue gas washer at an old coal fired powerplant in The Netherlands.
People living in and around this area might want to know that the amount of Absorbed Solar Radiation in this area increased to +4.3 W/m² in 2023 since 2000-2009!
This is more than the greenhouse gas forcing from all greenhouse gases we've added to the atmosphere since 1750!
+4.3 W/m² for over 10% of the Earth's surface!
If people understood what this means, it would be front page news everywhere.
We all know this won't be covered anywhere.
These +4.3 W/m² over 54,340,000,000,000 m² added 7.4 ZJ of additional heat in the 12 months of 2023!:
The world absorbed a lot more sunlight, as less was reflected.
While greenhouse gases kept most of the additional heat in.
Add El Niño and all temperature records shattered!
More 👇🧵
Let's start with the sun. It's a bit brighter, as it is starting to reach the peak of its 11-year cycle.
But that doesn't explain why our planet absorbed an additional 2.3 Watts per square meter over its 510 trillion m² surface, compared to the first decade of satellite data:
As global temperatures increased, the amount of Outgoing Longwave Radiation (OLR) increased.
But not as much as the Absorbed Solar Radiation (ASR) increased, leading to an increased rate of global heat uptake: Earth's Energy Imblance.
The North Atlantic Ocean reached 365 days of continuous record high temperatures!
Thank you to the journalists who have accurately reported on this!
E.g:
Scientists warn Earth warming faster than expected — due to reduction in ship pollution cbc.ca/news/science/m…
After the publication of our @DrJamesEHansen et al. Pipeline paper, the person smearing our research and question my qualifications, coauthored a paper agreeing with the @NASA CERES data we presented.
Unfortunately, global warming is indeed accelerating:
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I did some basic energy and water calculations on the scary AMOC study (1) that's making headlines, so you don't have to.
It's quite simple, so please don't let the orders of magnitude scare you off.
This is a Big F*cking Deal (BFD)!
First, what are we talking about here?
What is the Atlantic Meridional Overturning Circulation?
It's a shitload of water transporting a shit ton of heat energy North, through the Atlantic Ocean!
The study starts with an AMOC strength of about 15 sverdrups, or 15,000,000 cubic meters of ocean water per second.
This transports about 1 PW (1 petawatt = 1*10^15 watt) of heat North from the Southern Hemisphere and the tropics.
That's about 32 ZJ (32 zettajoules = 32*10^21 joules) of heat per year.
When the AMOC tips, most of this ocean heat transport stops.
The obvious question people are asking is "could this happen any time soon and how?"
The study (as have others, for example @DrJamesEHansen et al. (2016) (2), which is not referenced for some reason) shows that a lot of fresh water input from rainfall and Greenland ice melt could shut this thing down this century.
The more fresh water is added, the slower the AMOC becomes.
The tipping in the model happens at about 0.5 sverdrups (0.5 Sv, 500,000 m³ per second) of fresh water input.
There is a lot of fresh water waiting to add those 0.5 Sv, if only there was enough heat available to melt the ice sheet of Greenland.
0.5 Sv is 1.6*10^13 m³ of water per year.
Greenland holds 2.85*10^15 m³ of ice, which could provide about 170 years of 0.5 sverdrups of fresh water (after which global sea levels would be over 7 meters higher).
To melt 0.5 sverdrups worth of ice for a year takes 5.3 ZJ of heat.
Since 1970, our greenhouse gases have caused about 450 ZJ of additional heat to accumulate in the Earth system. ~90% of that warmed the oceans.
Aerosols, notably from coal plants and ships burning sulfur rich fuels, have reduced that heat accumulation.
Now that we are reducing aerosols, more heat is accumulating.
The larger North Atlantic Ocean region shows a spike in how much sunlight is being absorbed over recent years, while higher temperatures cause more heat radiation to space.
The net effect is a spike of over 2.4 W/m² above the 2000-2009 average. This spike added 4 ZJ of heat over 12-months:
The record high global energy imbalance is now (2023) about 1.8 W/m², which adds 29 ZJ of heat to the Earth system over a year.
To make a long story short, the heat is there to melt enough Greenland ice to shut the AMOC down.
And we don't need all that heat to be directed to the melting of ice, as more precipitation also contributes.
And of course, we are only making the climate forcing and Earth's Energy Imbalance worse by rapidly increasing greenhouse gas concentrations while decreasing aerosols.
Sorry I couldn't make this more hopeful.
But numbers don't lie.
(1): Physics-based early warning signal shows that AMOC is on tipping course
René M. van Westen et al. (2024)
(2): Ice melt, sea level rise and superstorms: Evidence from paleoclimate data, climate modeling, and modern observations that 2°C global warming is dangerous
@DrJamesEHansen , @MakikoSato6 et al. (2016) science.org/doi/10.1126/sc… acp.copernicus.org/articles/16/37…
Also see this thread, and this great article by @bberwyn: