Why the Permian-Triassic Extinction is Pertinent to Human Warming

[GliderGuider]

A Deadly Climb From Glaciation to Hothouse — Why the Permian-Triassic Extinction is Pertinent to Human Warming

The PETM has been a period of very intense study for leading climatologists such as James Hansen who has warned of the potential for a mini-runaway warming event of this kind should humans continue along a business as usual path of fossil fuel burning through the 21rst Century. In particular interest in the PETM corollary scenario is both the amazing velocity of the initial human warming, with CO2 and greenhouse gas releases occurring at rates that are orders of magnitude faster than during previous warming events. So rapid and powerful rate of forcing puts at risk of greater release a number of very large global carbon deposits including the massive CO2 and carbon stocks stored in the world’s melting permafrost as well as the even larger stores of carbon locked in methane hydrates scattered across the world’s oceans. Hansen and other scientists have noted a potential for a 4-7 degree Celsius or greater warming by 2100 (at between 700 and 1000 ppm CO2) through a combination of human greenhouse gas emissions and Earth systems carbon emissions. Overall warming by 2300 from Earth Systems feedbacks, even if human emissions were to stop by 2100, is likely to be twice this level.

But this scientific scenario is based, in part, on knowledge gleaned by studying past geological periods such as the Eemian, Pliocene, and the PETM hyperthermal (other information is derived from the still-developing climate models of terrestrial, ocean, and Earth systems). And, in looking at each of these paleoclimate periods, we find that a single key factor is missing: they all occurred during periods in which Earth was either ice-free, or in which Earth was settling into its current period of glaciation. In the case of human-caused warming, the exact opposite process is ongoing. As during the great Permian Extinction event of around 250 million years ago, the Earth is rising out of a period of glaciation and into a potential human-caused hot-house.

During the Permian, anoxic ocean states were thought to be far, far more intense. Paleontological research conducted by Peter Ward found a massive series of three extinction events ranging over the course of about 165,000 years in which death began at the bottom of the Permian ocean and climbed toward the atmosphere.

A stratified, anoxic ocean developed which started increasing mortality among deep water life forms first. As anoxia rose through the deep and mid levels of the ocean, death advanced up the water column as green and purple algae found sunlit regions and proliferated, adding hydrogen sulfide gas as a killing mechanism to ocean acidification and low ocean oxygen levels. Eventually, the hydrogen sulfide reached the surface waters at which point it began bubbling into the atmosphere. The anoxic ocean had fully transitioned to a primordial Canfield Ocean.

This is an unfortunately thorough look at the situation. Can we avoid this outcome, or has it already been triggered? Is it unfolding around us now - so slowly that we can still dismiss the possibility of danger? The inexorable white thread of the tsunami-wave looks so innocuous out there on the horizon. Let's just keep gathering these pretty shells on our suddenly water-free beach, there will still be enough time to run later...

[chervilant]

1. Did you know that photosynthesis

Last edited Tue Aug 13, 2013, 05:48 AM - Edit history (1)

stops at 104°F?

[GliderGuider]

2. Yes. Yes I did.

Those nasty plants are going to get what's coming to them...

[cprise]

3. I think he may be missing something

Maybe I'm wrong, but it seems the significance of having a hothouse event emerge quickly from within a long glacial period is not only the impact of freshwater from ice melt, but also the possibility that a great deal more methane has been stored in the Earth's crust.

[GliderGuider]

4. Most people are missing the methane angle.

Perhaps not for much longer, though...

http://envisionation.co.uk/index.php/blogs/72-co2-let-me-introduce-you-to-my-little-friend-ch4-methane

Check out the interview with Dr. Natalia Shakhova halfway down that page.

Here's how I think the chain of events will play out:

Early climate change (now) => loss of Arctic sea ice (now) => destabilized permafrost (now) => abrupt methane release (5 to 20 years) => positive feedback with the warming climate => increased Arctic amplification => reduced thermal gradient between the equator and the pole => Rossby wave slowing and disruptions => extreme weather changes => reduced agricultural output in the Northern Hemisphere.

In 20 years the cycle could be complete, as far as we're concerned.

[cprise]

5. I think the 20-40 yr estimate will turn out wrong

It will still be a blink of an eye compared with geologic time scales, but even at the accelerated rate of warming such a large pulse is probably more than a hundred years away.

[GliderGuider]

6. We'll see, won't we? I'd love to be wrong.

But Dr. Shakhova sounds distinctly pessimistic and alarmed in that interview, and I don't think it's all just Russian gloominess.