Thanks for this reference Andrew and Renaud! I've added it to our draft climate cooling paper (ref 21): https://www.nature.com/articles/s41586-022-05122-0 Best, Ron Baiman
On Fri, Oct 7, 2022 at 6:27 AM Renaud de RICHTER <[email protected]> wrote: > phys.org /news/2022-10-analysis-shipping-emissions-reveals-air.html > <https://phys.org/news/2022-10-analysis-shipping-emissions-reveals-air.html> > New > analysis of shipping emissions reveals that air pollution has a larger > effect on climate than previously thought > ------------------------------ > > October 6, 2022 > > by University of Oxford <http://www.ox.ac.uk/> > > A group of researchers based at Oxford University's Climate Processes > Group has used novel methods of analyzing satellite data to more accurately > quantify the effect of human aerosol emissions on climate change. The > results are published today in the journal *Nature*. > > Human aerosol emissions have a cooling effect > <https://phys.org/tags/cooling+effect/> on the planet, because they can > make clouds brighter by providing extra condensation nuclei on which cloud > droplets <https://phys.org/tags/cloud+droplets/> form. Brighter clouds > reflect more of the sunlight that strikes them, deflecting it from the > earth's surface. However, it is currently unclear how large this cooling > effect is, particularly if the cloud brightness change cannot be seen in > satellite > images <https://phys.org/tags/satellite+images/>. This could be when the > emissions are diffuse, such as from a city's traffic, or when there are > winds that disperse them. The cooling effect offsets some of the warming > effect of greenhouse gasses, and provides the largest uncertainty in human > perturbations to the climate system. > > To investigate this, the research team analyzed data on ship emissions as > a model system for quantifying the climatic effect of human aerosol > emissions in general. Sometimes, when a ship passes underneath a cloud, its > aerosol emissions brighten the cloud in a long line, similar to a contrail. > These so-called ship tracks have been studied previously, however the vast > majority of ships leave no visible tracks. This was the first study to > provide a quantitative measure of the impact of invisible ship tracks on > cloud properties, and thus their cooling effect. > > Key findings: > > - Invisible shipping tracks had a clear impact on the properties of > clouds they polluted. > - Surprisingly, the specific effects were different to those of > visible shipping tracks. > - Invisible ship tracks showed a smaller increase (roughly 50% less) > in the number of droplets in the clouds, but the amount of water increased > more, compared to the effect of visible tracks. This implies that for a > given increase in droplets, the increase in water is larger than thought, > equating to a greater cooling effect. > - The same may be true for aerosol emissions more generally—clouds may > react more strongly to air pollution than previously thought, getting > brighter and having a stronger cooling effect. > > Ship emissions often occur in remote ocean environments, and so provide > unique opportunities to study the effects of aerosols in isolation of other > human-induced factors that affect the climate. This new study, led by DPhil > student Peter Manshausen, used a global database of ship routes containing > the locations of almost all ships at a given time: more than two million > ship paths over six years. > > Combining these with historical weather observations, the researchers then > simulated where all these ships' emissions were carried by the wind and > entered the cloud. Studying these locations in satellite data > <https://phys.org/tags/satellite+data/> allowed them to measure the > number of droplets and the amount of water in the polluted and unpolluted > clouds. Importantly, this method does not depend on the ship emissions > being visible in satellite images. > > According to the research team, the findings indicate that human health > policies to reduce air pollution must be carefully considered when > forecasting future climate change <https://phys.org/tags/climate+change/> > scenarios. In a recent study > <https://www.pnas.org/doi/10.1073/pnas.2206885119>, the Climate Processes > Group also found that ship tracks reduced by around 25% almost immediately > after the International Maritime Organization introduced strict new fuel > regulations in 2020 to reduce air pollution caused by global shipping. This > analysis used a machine learning approach to automatically measure more > than one million visible ship tracks from satellite images over a 20 year > period. > > Professor Philip Stier (who leads the Climate Processes Group in the > Department of Physics, Oxford University), a co-author for the study, said, > "These techniques show the value of combining novel data science approaches > with the huge amount of earth observational data > <https://phys.org/tags/observational+data/> now available. They will > allow us to transform the analysis of climate processes in earth > observations from case studies <https://phys.org/tags/case+studies/> to > global monitoring, providing entirely new observational constraints on our > understanding of the climate system and future climate models." > > The study, "Invisible ship tracks show large cloud sensitivity to > aerosol," has been published in *Nature*. > ------------------------------ > *More information:* Peter Manshausen et al, Invisible ship tracks show > large cloud sensitivity to aerosol, *Nature* (2022). DOI: > 10.1038/s41586-022-05122-0 <https://dx.doi.org/10.1038/s41586-022-05122-0> > *Journal information:* Nature <https://phys.org/journals/nature/> > <http://www.nature.com/nature/index.html> > <http://www.nature.com/nature/index.html> > > Le jeu. 6 oct. 2022 à 16:45, Andrew Lockley <[email protected]> a > écrit : > >> >> https://www.nature.com/articles/s41586-022-05122-0 >> >> >> Published: 05 October 2022 >> Invisible ship tracks show large cloud sensitivity to aerosol >> Peter Manshausen, Duncan Watson-Parris, …Philip Stier Show authors >> Nature volume 610, pages101–106 (2022)Cite this article >> >> Metricsdetails >> >> Abstract >> Cloud reflectivity is sensitive to atmospheric aerosol concentrations >> because aerosols provide the condensation nuclei on which water condenses1. >> Increased aerosol concentrations due to human activity affect droplet >> number concentration, liquid water and cloud fraction2, but these changes >> are subject to large uncertainties3. Ship tracks, long lines of polluted >> clouds that are visible in satellite images, are one of the main tools for >> quantifying aerosol–cloud interactions4. However, only a small fraction of >> the clouds polluted by shipping show ship tracks5,6. Here we show that even >> when no ship tracks are visible in satellite images, aerosol emissions >> change cloud properties substantially. We develop a new method to quantify >> the effect of shipping on all clouds, showing a cloud droplet number >> increase and a more positive liquid water response when there are no >> visible tracks. We directly detect shipping-induced cloud property changes >> in the trade cumulus regions of the Atlantic, which are known to display >> almost no visible tracks. Our results indicate that previous studies of >> ship tracks were suffering from selection biases by focusing only on >> visible tracks from satellite imagery. The strong liquid water path >> response we find translates to a larger aerosol cooling effect on the >> climate, potentially masking a higher climate sensitivity than observed >> temperature trends would otherwise suggest >> >> -- >> You received this message because you are subscribed to the Google Groups >> "geoengineering" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/geoengineering/CAJ3C-061oB98M9ON7GadUKH26PSmgVMuSQ54eyjJxhRPiEAMKA%40mail.gmail.com >> <https://groups.google.com/d/msgid/geoengineering/CAJ3C-061oB98M9ON7GadUKH26PSmgVMuSQ54eyjJxhRPiEAMKA%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> > -- > You received this message because you are subscribed to the Google Groups > "geoengineering" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/geoengineering/CAHodn98sW-wn%3DoxLX5Ee9okPTXWEqQ3HtgTJ_d1Fqk7Fpr1%3DHw%40mail.gmail.com > <https://groups.google.com/d/msgid/geoengineering/CAHodn98sW-wn%3DoxLX5Ee9okPTXWEqQ3HtgTJ_d1Fqk7Fpr1%3DHw%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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