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. Image
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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*22.2 million km² that is of course..

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