We have been told wrong that CO2 re-radiates heat directly into the atmosphere?
No, I think that's correct. Increased CO2 in the atmosphere causes radiant energy from the earth's surface to be captured as heat in the atmosphere, thus creating an imbalance between energy in, vs. energy out. The imbalance eventually causes the entire planet to get warmer, until energy balance can be restored. But the process of warming creates feedback effects.
I think that the energy imbalance caused by CO2 changes, could be compared directly with the effect of insolation changes caused by Milankovitch cycles. Maybe that could be an indirect way to predict the climate's sensitivity to CO2, by comparing to its sensitivity to Milankovitch-caused perturbations.
Does the melting of ice represent a virtual acidification of salty ocean water? If so, I wonder how many corals were killed or extincted by the ice sheets melting into the Holocene? Of course, the ocean water back at the start of all that must have been really salty by comparison.
Salt (
sodium chloride) doesn't do much to effect the acidity of ocean water, since it's neither an acid or a base. That is, it doesn't contribute either H+ or OH- ions to the solution.
But, I'm sure that the "limit cycle" pH change events discussed above, must have resulted in massive die-offs of corals, and some extinctions. The miracle is that some corals (and other species) survived the mass extinction events.
From the paleolithic record, it's believed that Earth has been through at least five mass extinction events over the past 500 million years. In his book "
Under A Green Sky", Peter Ward argues that our current experiment in fossil fuel consumption could easily trigger another such event, often referred to as "the sixth mass extinction". Ward argues that all past mass extinction events have been characterized by high CO2, high temperatures and ocean toxicity. Quote:
IT IS HERE PROPOSED THAT EACH OF the greenhouse extinctions had a similar cause, and here we can summarize the sequential steps.
First, the world warms over short intervals of time because of a sudden increase of carbon dioxide and methane, caused initially by the formation of vast volcanic provinces called flood basalts. The warmer world affects the ocean circulation systems and disrupts the position of the conveyer currents. Bottom waters begin to have warm, low-oxygen water dumped into them. Warming continues, and the decrease of equator-to-pole temperature differences reduces ocean winds and surface currents to a near standstill. Mixing of oxygenated surface waters with the deeper, and volumetrically increasing, low-oxygen bottom waters decreases, causing ever-shallower water to change from oxygenated to anoxic. Finally, the bottom water is at depths where light can penetrate, and the combination of low oxygen and light allows green sulfur bacteria to expand in numbers and fill the low-oxygen shallows. They live amid other bacteria that produce toxic amounts of hydrogen sulfide, and the flux of this gas into the atmosphere is as much as 2,000 times what it is today. The gas rises into the high atmosphere, where it breaks down the ozone layer, and the subsequent increase in ultraviolet radiation from the sun kills much of the photosynthetic green plant phytoplankton. On its way up into the sky, the hydrogen sulfide also kills some plant and animal life, and the combination of high heat and hydrogen sulfide creates a mass extinction on land. These are the greenhouse extinctions.
The sequence of events outlined above can be considered a combined hypothesis for the cause of greenhouse extinctions and can be named the conveyer disruption hypothesis. There was obviously variability in each extinction, but if the extinctions are examined in a fashion similar to how taxonomists classify living organisms as a species, it seems quite clear that the mass extinctions considered here as greenhouse extinctions are a different beast than the K-T, our now sole known impact extinction.
What would Earth be like in the midst of such an event? Let us crank up a hypothetical time machine and visit one. We have a lot of choices of where to go, back in time: the mass extinctions ending the Cambrian, some 490 million years ago; the late Ordovician mass extinction, some 450 million years ago; several late Devonian mass extinctions, around 360 million years ago; the Permian mass extinction(s), ranging from 253 million to about 247 million years ago; the Triassic mass extinctions, ranging from 205 million to 199 million years ago; the Toarcian mass extinction, some 190 million years ago; the Jurassic–Cretaceous mass extinction, some 144 million years ago; Cenomanian–Turonian mass extinction, some 93 million years ago; and the Paleocene thermal event, some 55 million years ago. All are united by cause, increased carbon dioxide in the atmosphere, leading to change in ocean currents, and eventual anoxia. Just because we get to see some dinosaurs, let’s go back to near the end of the Triassic period, to the site in Nevada that begins this book:
No wind in the 120-degree morning heat, and no trees for shade. There is some vegetation, but it is low, stunted, parched. Of other life, there seems little. A scorpion, a spider, winged flies, and among the roots of the desert vegetation we see the burrows of some sort of small animals—the first mammals, perhaps. The largest creatures anywhere in the landscape are slim, bipedal dinosaurs, of a man’s height at most, but they are almost vanishingly rare, and scrawny, obviously starving. The land is a desert in its heat and aridity, but a duneless desert, for there is no wind to build the iconic structures of our Saharas and Kalaharis. The land is hot barrenness.
Yet as sepulchral as the land is, it is the sea itself that is most frightening. Waves slowly lap on the quiet shore, slow-motion waves with the consistency of gelatin. Most of the shoreline is encrusted with rotting organic matter, silk-like swaths of bacterial slick now putrefying under the blazing sun, while in the nearby shallows mounds of similar mats can be seen growing up toward the sea’s surface; they are stromatolites. When animals finally appeared, the stromatolites largely disappeared, eaten out of existence by the new, multiplying, and mobile herbivores. But now these bacterial mats are back, outgrowing the few animal mouths that might still graze on them.
Finally, we look out on the surface of the great sea itself, and as far as the eye can see there is a mirrored flatness, an ocean without whitecaps. Yet that is not the biggest surprise. From shore to the horizon, there is but an unending purple color—a vast, flat, oily purple, not looking at all like water, not looking like anything of our world. No fish break its surface, no birds or any other kind of flying creatures dip down looking for food. The purple color comes from vast concentrations of floating bacteria, for the oceans of Earth have all become covered with a hundred-foot-thick veneer of purple and green bacterial soup.
At last there is motion on the sea, yet it is not life, but anti-life. Not far from the fetid shore, a large bubble of gas belches from the viscous, oil slick–like surface, and then several more of varying sizes bubble up and noisily pop. The gas emanating from the bubbles is not air, or even methane, the gas that bubbles up from the bottom of swamps—it is hydrogen sulfide, produced by green sulfur bacteria growing amid their purple cousins. There is one final surprise. We look upward, to the sky. High, vastly high overhead there are thin clouds, clouds existing at an altitude far in excess of the highest clouds found on our Earth. They exist in a place that changes the very color of the sky itself: We are under a pale green sky, and it has the smell of death and poison. We have gone to the Nevada of 200 million years ago only to arrive under the transparent atmospheric glass of a greenhouse extinction event, and it is poison, heat, and mass extinction that are found in this greenhouse.
Ward, Peter D.. Under a Green Sky (pp. 137-140). HarperCollins e-books. Kindle Edition.
Now, let me be clear that I don't want to cause a panic here. For all we know, Richard Lindzen could be correct that the climate sensitivity to CO2 could be overestimated by most scientists. Our crystal ball is still pretty cloudy. Maybe there's nothing to worry about.
Or maybe (as Gary says) if this does happen, it might take a thousand years or more for the worst to unfold.
What is Mr. Milankovitch up to next? Is he going further down or back up?
The Wikipedia paragraph dedicated to this topic, looks like the result of an edit war that left no one satisfied. There are four scientific papers cited, making various and apparently conflicting claims. The references are:
https://en.wikipedia.org/wiki/Milankovitch_cycles#Present_and_future_conditions
- J Imbrie; J Z Imbrie (1980). "Modeling the Climatic Response to Orbital Variations". Science. 207 (4434): 943–953. Bibcode:1980Sci...207..943I. doi:10.1126/science.207.4434.943. PMID 17830447.
- ^ "NOAA Paleoclimatology Program – Orbital Variations and Milankovitch Theory".
- ^ Berger A, Loutre MF (2002). "Climate: An exceptionally long interglacial ahead?". Science. 297 (5585): 1287–8. doi:10.1126/science.1076120. PMID 12193773.
- ^ A. Ganopolski, R. Winkelmann & H. J. Schellnhuber (2016). "Critical insolation–CO2 relation for diagnosing past and future glacial inception". Nature. 529 (7585): 200–203. Bibcode:2016Natur.529..200G. doi:10.1038/nature16494. PMID 26762457.
