Digressing here, but the ozone hole over the antarctic was always going to take time to recover because of the approximately 50 year residence time of the CFCs in the upper atmosphere. Cold temperatures can actually speed up depletion because of certain ice crystal formations that give a boost in the CFC+sunlight+O3 reaction rate. Note that it doesn't mean that 50 years are needed to get rid of all CFCs in the atmosphere, it is just a measure of the amount of time it is expected to take for half of the gas that is already there to be removed. That doesn't account for the amount of time it has taken for CFC usage to drop in the first place, and the fact that there are still CFC pollution occurring (albeit far less than in the 80's).

Ben Root

https://ozone.unep.org/nasa-provides-first-direct-evidence-ozone-hole-recovery
https://csl.noaa.gov/assessments/ozone/1998/faq11.html


On Tue, Nov 24, 2020 at 2:07 PM Charles R Harris <charlesr.harris@gmail.com> wrote:


On Tue, Nov 24, 2020 at 11:54 AM Benjamin Root <ben.v.root@gmail.com> wrote:

Given that AWS and Azure have both made commitments to have their data centers be carbon neutral, and given that electricity and heat production make up ~25% of GHG pollution, I find these sorts of power-usage-analysis-for-the-sake-of-the-environment to be a bit disingenuous. Especially since GHG pollution from power generation is forecasted to shrink as more power is generated by alternative means. I am fine with improving python performance, but let's not fool ourselves into thinking that it is going to have any meaningful impact on the environment.

Ben Root

Bingo. I lived through the Freon ozone panic that lasted for 20 years even after the key reaction rate was remeasured and found to be 75-100 times slower than that used in the research that started the panic. The models never recovered, but the panic persisted until it magically disappeared in 1994. There are still ozone holes over the Antarctic, last time I looked they were explained as due to an influx of cold air.

If you want to deal with GHG, push nuclear power.

<snip>

Chuck 
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