OH radicals are born if NOx is hit by UV radiation in sunlight. (And water vapour in the air reduces this OH-birthing process, see posts above.) OH Radicals only have a very short lifetime of less than a few seconds because they bomb anything to bits that comes their way, or rather, they react with anything in their neighborhood. If a #methane molecule is bombed by OH radicals, the result is water vapour and CO2.
NOx is born in cow and pig shit, in artificial fertilizer, and also in high-heat combustion processes like lightening strikes, forest fires, and cars, trucks, planes, and ships.
NOx and the chemicals born when NOx is hit by UV sunlight (eg ozone), are harmful to living beings. So anthropogenic NOx gets reduced technologically after national and regional #CleanAir regulations. And by the international shipping organisation IMO, see eg https://www.ukpandi.com/news-and-resources/articles/2022/imo-tier-iii-nitrogen-oxide-nox-emission-compliance/ It also describes some techy ways for reducing NOx emissions during fuel combustion.
IIUC, #diesel engines burn fuel at higher heat than Otto motors. This makes diesel motors more efficient, leading to less CO2 emissions per km – but to more #NOx. Which must then be scrubbed from the exhaust.
We all recall the two (!) diesel scandals 2004 and 2015 where European car industry was found to cheat deliberately wrt NOx from diesel. (Cheating isn't the right word when you consider that people get sick and die from NOx' ozone pollution. Hence the regulations. And people with the car industry know this – so their cheating is really murder according to German law and recent verdicts [on other cases but with similar circumstances relevant to the legal definition of #murder].
The fact that German state attorneys chose to only prosecute the fraud speaks volumes wrt how car-centred their minds work. IMO, those managers and engineers should spend their lives in a prison cell. #Dieselgate #CleanDiesel Together with the software manufacturers at #Bosch, and the Rex Tillersons of this world. #ExxonKnew
Murderous cheating wrt Otto motors is also known https://de.wikipedia.org/wiki/Abgasskandal#Manipulation_bei_Fahrzeugen_mit_Ottomotoren
Here it is a software for reducing #CO2 emissions on the testing stand. )
Anyway. Where was I?
Ah, yes, the NOx-creation process and how these give birth to OH radicals in UV sunlight: OH radicals are born when UV sunlight hits NOx molecules. After only a few seconds, the suicidal radical bombs a suitable molecule like methane. But new radicals are born all day long. Because NOx is replenished constantly, in lightening strikes, forest fires, burning fossil fuels in
, and:
Together with the new finding that more moisture in the air due to global warming reduces UV sunlight, and hence reduces the births of OH radicals, which in turn increases CH4 lifetime https://www.science.org/doi/10.1126/science.adn0415 #Prather et al 2024
I have been also wondering for a few years now whether NOx regulations and technological scrubbing (where it does occur, harr harr), and also a serious electrification in transport, industry and homes already have, and will have later on, a sufficiently large effect on increasing CH4 lifetime.
And I am wondering again whether a reduced NOx abundance during the warm=wet and less fire-prone, stronger forested #Miocene caused CH4 to linger for longer because fewer OH radicals were born.
Adding the new finding to this theory, that more water vapour decreases OH concentration, makes my theory even more pertinent:
With high temperatures during the miocene at surprisingly low CO2 values, methane could explain parts of the discrepancy. But we don't have proxies for methane concentration.
Kind of important because today's climate sensitivity for doubling CO2 = 3°C, is in part fed by findings in #paleoclimate such as the Miocene.
The Miocene had a different land mass layout, different ocean currents, and also different biomes, hydrological cycle and whatnot.
So it's not a good analog for our experiment today as I often point out, eg in this thread https://climatejustice.social/@anlomedad/112767092856263574
It's also mentioned in passing in Gavin Schmidt's new blog post about the paper that had prompted my thread above, with its spurious claim of climate sensitivity. https://www.realclimate.org/index.php/archives/2024/08/oh-my-oh-miocene/#ITEM-25598-4
So these system setting differences explain part of the temperature/CO2 discrepancy.
But not all.
#anloCH4 #anloOH
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