Paul, I've been trying for 3 days to address your varied points. In general.... It's important to hold and recall several different scales in mind, simultaneously, but also not to confuse them. Speaking about the stability over billions of years can't be compared with the stability of a few hundred thousand years--plus different systems contributed to stability and change during each of those scales you compared. Very different
relative stabilities existed before each of the revolutions of life, oxygen, complex life, terrestrial life, soils, biodiversity, and even stable ice caps developed; so comparisons are problematic.
So please lets not get caught up in determining the correct position for all the deck chairs on the Titanic. "Chaotic attractors" develop, and relative stability ensues; I think we can all agree on that basic physical principle.
But over the past few days, I wanted to mention:
not a level slope but a steady slope downwards before the methane clathrate release that warmed the earth 11 millenia ago.
if you will note there was a level slope around 180 millenia ago when avg temps were -8 degrees below.
*Level slope means stable climate, so stable climate is fairly rare--especially in warmer phases.
if it were not for that release the earth would still be in an ice age.
*Insolation at 65 N latitude, which varies due to Milankovitch cycle, is what causes the regular pattern of glaciations and retreats. Clathrates are more unstable at warmer temperatures, and stablilized by colder temperatures. Why would clathrates be released at the maximum of a glacial advance?
that release is what stabilized the climate and methane is one of the most potent global warmers.
*Methane oxidizes into CO2 fairly quickly, within a decade or so at most....
*Do you think the clathrates operate this way to terminate every glacial cycle?
5MyrIce
the warming brought more abundant oxygen breathing life.
the added co2 that oxygen breathing life released has helped the plant life to thrive.
*What!? If by "oxygen breathing life" you mean big animals, and not bacteria/fungus, then I think you'll find they contribute less than a percentage of so of difference. I'd like to be proved wrong, if you'll do the research; but seriously I think the availability of nutrients and water have more to do with abundance than does temperature.
the abundant plant life has the ability to store co2 as you noted and as the plant life dies and rots more methane is released to keep the planet warm.
*Methane or CO2 comes from all the oxidized (rotted) plant material; right. But a small percentage of that abundant plant life gets incorporated into the soil--eaten by the soil--so that the carbon content of the soil can rise up to 10% in the richer soils. Temperate soils used to have carbon richness approaching 10% globally, but over half of that has now been lost--increasingly over the past several hundred years. That is not counting actual soil erosion which simply transfers the carbon richness into the waterways and oceans to act as fertilizer for algae and diatoms.
Sure the Amazon forest produces a quarter of the world's oxygen, but the forest immediately reuses that oxygen. The nutrients washed out to sea, from the cycles of rot and oxidation in that forest, are what fertilize the growth of algae--that supply half of the world's oxygen--so we can enjoy oxygen on a global scale.
I think the earth understands the need for climate stability more than we do.
and although we work against the earths efforts, the earth along with the plant and animal life has achieved the current level of balance with a little help from us but our changes are just a blip as you say that only seems to us to have greatly changed the climate.
*I think, as a part of "the earths efforts," we are doing just what we are supposed to do. We are figuring out how managing soils can act as a global thermostat. Since CO2 levels affect actual heat balance over decades and centuries, whereas orbital variations mostly affect distribution of heat, managing CO2 levels can over-ride any multi-millennial scale Milankovitch influences.
A change in solar forcing of about a quarter Watt loss, over several hundred years, changed conditions from MWP to LIA. CO2 is several times that amount of forcing, but hasn't yet operated for a century or more. We haven't experienced climate change "greatly" yet, but only the beginnings of changes to weather patterns--that will cumulatively add up to climate shift eventually. If enough shift accumulates, then the climate could change into a different mode of operation--a new chaotic attractor. [if you search this neat concept "chaotic attractor," be sure to click on "images"]
the Antarctic ice is advancing early again this year by 5 days. it has been advancing early for several years.
*Perhaps someplace has to get colder, as heat invades and overwhelms the usual routes of escape. We could be headed into a bi-polar climate mode, with a warm N.Pole partially ringed by continental ice, and a cold E. Antarctic accompanied by a temperate W. Antarctic. It is about heat transport (especially latent heat such as snow), rather than any temperature or local weather pattern here or there.
maybe the correct place would be a place that would deposit some of the global warming soot onto the Antarctic to maintain our current level slope.
Africa , Australia , maybe even the Antarctic itself.
*Put the soot in the soil, and keep the coal in the hole; and not either on the pole.
I know it sounds manipulative but look at the chart, we were not capable of doing that type of thing before, we are now.
[altered]We could do what the earth and plant life cannot; to help to maintain the level slope.[/alter
*We've been increasingly geoengineering the planetary systems for fun and profit, so why not do it to create value and enduring sustenance. Unless we do, we will need to learn how to enjoy and profit from a tropical world with temperate poles, and a greatly reduced biodiversity--not a paradise.
Paul, what you describe as "seems to us to have greatly changed the climate," are observations of the first effects derived from many simple robust chaotic systems being pushed to their limits. Nothing has yet broken, but the limits will be exceeded eventually--as "locked in" heating continues to wear away the resilience of complexity emerging from our many simple systems.
In other words, we already have enough extra heating--which will continue heating and causing changes--worked into the planet's systems, so that Milankovitch cooling has been completely overwhelmed. We are in danger of overshooting in the warming direction, so we don't need to work on ways to melt the poles; but rather ways to maintain the poles. Too many of our other critical systems depend upon the polar differentials.
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