Like CO2 (carbon dioxide), H2O (water vapor) is a strongly heteropolar molecule — having one end with a positive electrical charge, and another end with a negative electrical charge — and absorbs outgoing Infrared Radiation (IR) from Earth’s surface, thus capturing heat in the atmosphere. Homopolar molecules like N2 (nitrogen) and O2 (oxygen) are transparent to IR. Inelastic molecular collisions redistribute that heat (as kinetic energy) to other atmospheric molecules (N2, O2, mainly) and atoms (Ar, He, trace components).
Most of Earth’s surface heat eventually diffuses into the oceans. Heat flows along the heat gradient in the negative direction from warmer air to colder water. The heat capacity (storage ability) of the oceans is IMMENSE (this is where ‘global warming’ ends up), and their heat content takes centuries to diffuse into a stable stratified distribution, rearranged by thermo-haline currents (a solar forcing effect) and by geometry (oceans as a spherical shell with warm equator and cold poles, so ocean heat diffuses poleward).
The fundamental problem of global warming is the ‘excess’ capture of outgoing IR (infrared radiation), reducing the rejection of Earth heat (originally delivered by incoming LIGHT radiation) into space: causing an imbalance between incoming energy (in the form of light to which atmospheric molecules are almost completely transparent) and outgoing energy (IR, to which heteropolar molecules, like CO2, H2O, CH4, NOx, are all quite opaque — absorbing).
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The process of capturing atmospheric CO2 with rocks on the ground is one of rock weathering. CO2 in the air that brushes against the surface of carbonate and silicate rocks has a finite (and very low) probability of undergoing a chemical reaction with the rock surface, fixing the airborne CO2 onto a solid substrate. This is the longest term natural process of capturing CO2 from the atmosphere (10s to 100s of millennia).
A shorter term process is capture by the surface waters of the oceans, and that aqueous CO2 then combining with water molecules and already existing carbonate ions (CO3-2) in the water to form carbonic acid (H2CO3), which is weakly bound and both acidifies the oceans and scarfs up free floating carbonate ions to both starve mollusks, corals and foraminifera of the easiest chemical species from which to grow their shells (CO3-2), and even dissolving such shells of existing organisms (most being part of the masses of plankton, the base of the oceanic food chain).
The surface (not too deep) load of absorbed acidifying CO2 is then slowly cycled to the ocean floor by the ~1,000 year vertical currents, and at the bottom it dissolves the chalk deposited as the calcium carbonate (CaCO3) remnants of dead sea life, basically bone, shell and foraminifera casing ‘fossils’ — an ocean acidifying effect. So ocean capture of CO2 happens all the time, but the intake rate can saturate as the ocean becomes more acidified; eventually this intake process could shut off, coral reefs being a long lost memory by then.
Loss of “excess” ocean CO2 requires a low CO2 concentration atmosphere that can accept the gaseous release (is not saturated with CO2) of ocean CO2 that slowly diffuses out on mainly kilo-year timescales. A technically accurate description of ‘the carbonate system in seawater’ is given at https://sundoc.bibliothek.uni-halle.de/diss-online/04/04H141/t5.pdf. My more formal article than the discussion here, ‘Global Warming and Ocean Acidification Accelerate,’ is at https://manuelgarciajr.com/2020/07/18/global-warming-and-ocean-acidification-accelerate/.
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Manuel Garcia Jr., CounterPunch, 13 September 2021. Full article.
