Radiative forcing from the 2020 shipping fuel regulation is large but hard to detect

A global reduction in sulfur pollution from shipping that has inadvertently contributed to recent warming of the Earth by unmasking greenhouse gas warming is providing insights into the challenge of evaluating one of two major proposed solar geoengineering approaches, marine cloud brightening.
Radiative forcing from the 2020 shipping fuel regulation is large but hard to detect
Like

Share this post

Choose a social network to share with, or copy the URL to share elsewhere

This is a representation of how your post may appear on social media. The actual post will vary between social networks

In 2020, the International Maritime Organization imposed a sharp reduction in the level of sulfur in ship fuel to reduce emissions of sulfate aerosols and sulfur dioxide — pollutants associated with premature deaths from asthma, lung cancer, cardiovascular and pulmonary diseases, to improve air quality in coastal and large port communities. By decreasing sulfur pollution, the cleaner fuels also reduced the reflectivity of low-level marine clouds that aerosol particles in the exhaust had previously brightened – reducing the cooling effect of clouds. 

Soon, observers noticed a decrease in “ship tracks,” those distinct, bright white, linear clouds that form in the trail of large ships, allowing more sunlight to heat the ocean surface. But quantifying the warming effect of increased sunshine on the ocean surface using conventional climate models has proven challenging because they simply can’t represent clouds well enough. We devise an innovative Machine Learning approach to capture and reproduce the complex physical and chemical processes that control cloud formation and unmask the true climate impact that these ship-induced, sunlight-reflecting clouds once had. 

To estimate the cooling effect that these ship tracks used to have, an ensemble of neural networks was trained with multiple years of global cloud observations from satellites and model reanalysis of the meteorological fields collected before 2020 over three major shipping corridors in the Pacific and Atlantic oceans where ship tracks are the most prevalent. The neural networks were then tasked with simulating counterfactual cloud fields, representing the “observation record” beyond 2020 as if the IMO2020 regulation had never taken place (as a “business as usual” scenario). Differencing the counterfactual fields from the true 2020-2022 observational record of cloud radiative effect reveals a warming effect of 0.074 ±0.005 W m-2 as a result of this event. Furthermore, by comparing this event against the natural variability in clouds, using statistical significance tests, we concluded that changes in cloud radiative effect whether intentional or due to climate change will be difficult to detect above natural variability, a finding that has direct implications for evaluating the potential of marine cloud brightening.

These results raise concerns that future reductions in aerosol emissions, despite the important health benefits, will exacerbate global warming due to reduced aerosol radiative forcing (a net cooling effect). Our findings imply a strong, regionally-dependent masking effect of natural variability on the detectability of proposed deliberate modification to the cloud radiative effect. Such effort, if attempted, will need to be substantial in order to overcome the low detectability.

Please sign in or register for FREE

If you are a registered user on Research Communities by Springer Nature, please sign in

Follow the Topic

Earth Sciences
Physical Sciences > Earth and Environmental Sciences > Earth Sciences
Artificial Intelligence
Mathematics and Computing > Computer Science > Artificial Intelligence
Geoengineering
Technology and Engineering > Civil Engineering > Geoengineering
Climate Sciences
Physical Sciences > Earth and Environmental Sciences > Earth Sciences > Climate Sciences
Climate Change
Physical Sciences > Earth and Environmental Sciences > Earth Sciences > Climate Sciences > Climate Change
Environmental Policy
Humanities and Social Sciences > Society > Sociology > Environmental Social Sciences > Environmental Policy

Related Collections

With collections, you can get published faster and increase your visibility.

Complexity and dynamics in ecological systems

This cross-journal Collection between Communications Physics, Communications Earth & Environment, and Scientific Reports aims at showcasing the methodological advances in treating the complexity of ecological systems, as well as the application of already established methods to generate new insight in the dynamics and response of ecological networks.

Publishing Model: Open Access

Deadline: May 31, 2025

Human health and the environment

In this Collection, we present articles that explore emerging threats to health and wellbeing posed by the environment, health benefits the environment can provide, and policies that can help improve air, water and soil quality, limit pollution and mitigate against extreme events.

Publishing Model: Hybrid

Deadline: Mar 31, 2025