Adding sulfur to jet fuel might be another method to consider but it would definitely not, as you note, be a "reversion to the status quo ante" and therefore would take much more time and development to implement.
On Tue, Jun 27, 2023 at 5:30 PM Ron Baiman <[email protected]> wrote: > Thank you Lester! My understanding is that tropospheric aerosols > generally fall out pretty quickly, especially when it rains, so that if > emitted far from land not much would still be in the atmosphere even taking > into account windflow (though I defer to others who know more about this > than I do!). Regarding the crews on the ships, if this has been a > significant occupational health problem, perhaps there are other specific > measures that can be taken with regard to smokestacks, or masks when near > the source etc.? The question it seems to me (as is often the case in these > risk- risk comparisons) is what are the harms of returning to a "partial > status quo ante" versus significant additional global warming (per my > initial post modelers are working on getting better estimates of how much > as we speak)? Of course if the status quo ante posed a significant health > risk to the crews on the ships, this would have to be addressed as well. > Best, > Ron > > On Tue, Jun 27, 2023 at 5:06 PM Lester Wyborny <[email protected]> wrote: > >> Since ships emit their pollutants, such as sulphate particles, in the >> lower atmosphere, it would create a greater breathing problem for people >> who would be exposed to the high sulfate and other particulate matter >> emissions from these ships. Although you are suggesting that these >> particles would be emitted over the open ocean, they would still be >> transported to land areas via atmospheric weather patterns where it would >> create breathing and other associated health issues. This is why the ships >> were forced to reduce their sulfur levels. >> >> A better idea would be to dose jet fuel with sulfur-containing chemicals >> when the jets are operating at high altitudes to emit the sulfate particles >> in the upper atmosphere which is less likely to expose the human population >> and also remain there for longer periods. The concern with this idea is >> that changes in the fuels used by passenger airlines creates a concern >> about the potential impact on their safe operation, and agreeing to such a >> change would take many years to test out and implement. It has been a >> while since I reviewed the data on this, but the jet fuel typically >> contains ~700 ppm sulfur. Conversely ship bunker fuel, before the >> standards forced these vessels to use lower sulfur fuel, contained ~3%, or >> ~30,000 ppm sulfur, so a lot more sulfur/sulfate emissions. >> >> On Tue, Jun 27, 2023 at 1:07 PM Ron Baiman <[email protected]> wrote: >> >>> Dear Colleagues, >>> >>> A bunch of us (in forums and communications within the groups in the >>> lists above) have been discussing a potential immediate practical step >>> (that earlier has been raised by others) that may provide at least a >>> modicum of cooling especially over the oceans: *a relaxation of the >>> "bunker fuel" sulfur content regulations that just came into effect in 2020 >>> (https://www.theguardian.com/environment/2020/jan/01/shipping-fuel-regulation-to-cut-sulphur-levels-comes-into-force >>> <https://www.theguardian.com/environment/2020/jan/01/shipping-fuel-regulation-to-cut-sulphur-levels-comes-into-force> >>> ) for inter-port "high seas" shipping. *The idea is that cargo ships >>> and tankers would be able to use the old dirty sulfur laden fuel in the >>> open ocean but switch to the cleaner fuel when they are near ports or human >>> habitation. Apparently many ships have multiple fuel tanks so that they may >>> be able to switch fuels in transit. >>> >>> *To be clear, we would stress that we fully support getting off of >>> fossil fuels, but if fossil fuels are going to be used anyway it makes no >>> sense not to at least benefit from fossil fuel burning maritime sulfur >>> aerosol generation that is known to have a significant cooling effect *(how >>> much is currently being re-estimated using the "termination shock" signal >>> from the 2020 abrupt change in sulfur emissions due to the regulation). >>> *Looking >>> forward this also points the way to including effective (and hopefully less >>> harmful to human health) tropospheric aerosol generators in future non GHG >>> emitting replacements for the bunker fuel* (see the HPAC direct climate >>> cooling petition for some possible options: >>> https://drive.google.com/file/d/1yHe2Fe6fU11odfcH-4GwdYDNTCk7uB-J/view?usp=sharing >>> ). >>> >>> Any thoughts or data on this that might be helpful in working up (or >>> not) this proposal would be appreciated. >>> >>> For example, the last sentence in this excerpt from a quote in this >>> Guardian piece ( >>> https://www.theguardian.com/environment/2023/jun/19/marine-heatwave-uk-irish-coasts-threat-oysters-fish-high-temperatures) >>> shared in recent ocean heat spike thread: >>> https://www.theguardian.com/environment/2023/jun/19/marine-heatwave-uk-irish-coasts-threat-oysters-fish-high-temperature >>> suggests that this may be a factor causing the recent unprededented spike >>> in ocean heating: >>> >>> "Piers Forster, a professor of climate physics at the University of >>> Leeds, said: “Both Met Office and NOAA analyses of sea-surface >>> temperature show temperatures are at their highest ever level – and the >>> average sea-surface temperature breached 21C for the first time in April. >>> These high temperatures are mainly driven by unprecedented high rates of >>> human-induced warming. Cleaning up sulphur from marine shipping fuels is >>> probably adding to the greenhouse gas driven warming..."" >>> >>> Best, >>> Ron >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "Healthy Climate Alliance" 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/healthy-climate-alliance/CAPhUB9B0%2BSovib9pcGn1_a4_3abjXs0DfWkec7VM%2BhFQJEuvBw%40mail.gmail.com >>> <https://groups.google.com/d/msgid/healthy-climate-alliance/CAPhUB9B0%2BSovib9pcGn1_a4_3abjXs0DfWkec7VM%2BhFQJEuvBw%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]. 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