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Re: Under a Green Sky

Very interesting basic idea about anoxia and hydrogen sulfide...

The gist of it is that there is a natural 60
million-year cycle of climate that moves between warm and cool periods.

Can you explain that in some more detail? (I should have access to Proc. R. Soc. B tomorrow, though.) We don't have anywhere near the same climate as 60 million years ago -- is the fact that the landbridge between South America and Antarctica has ripped apart in the meantime the only difference?

Right now, the current state of the climate follows suit as it warms
from its recent glacial state.

Ouch!!! This is nonsense. The _end of_ the last ice age is over, and has been over for 11,000 years.

It's interesting how over the past couple of years, the climate modeling community has become less skeptical about just how bad conditions were, for example, 250 mya, even though the evidence is clearly laid out in the rocks.

It isn't _so_ clear. Reconstructing the CO2 content of the atmosphere is quite difficult to get right to less than an order of magnitude beyond the Cenozoic.

Climate models have become sophisticated
enough to reproduce past climate systems with enough fidelity to
re-create conditions like those seen preserved in the rocks... even for
those conditions that defy belief as in severe greenhouse worlds which
cooked the planet 4 times over the past 520 million years.


P-Tr boundary, Cenomanian-Turonian boundary, Pal-Eocene boundary, and?

Of course, how can you trust models of past and future climate if the
models of current climate can't get it right? Well, here's the thing...
models of current climate DO get it reasonably right. They are not as
far out to lunch as the media would lead you to believe.


What media? The US ones?

Picture this: "Shorelines encrusted with rotting organic matter. From shore to horizon â as far as the eye can see there is an unending purple color, a vast flat oily purple. We are under a pale green sky, and it has the smell of death and poison."

Nah. Hydrogen sulfide is dangerous when you don't smell it anymore. (Unlike hydrogen cyanide, which is just as poisonous, but which you only smell when it's almost too late.)

But asteroids do not explain the other mass extinctions.

Published evidence for impacts doesn't explain the others, that's right so far.

Records show that environmental change began to accelerate when atmospheric CO2 hit 1,000 parts per million. Today's levels are one-third of that and rising.

They are not going to reach 1000 ppm unless we manage to trigger a methane burp (and then we'd have immediate trouble from the methane anyway).

Looking at the ancient evidence, Ward notes that ice caps began to
shrink. "Melting all the ice caps causes a 75-meter increase in sea
level. [That] will remove every coastal city on our planet."

Not going to happen. But if things continue, Greenland will be ice-free in a few hundred years. That means "only" 7 m of sea level increase. Half that, and Bangladesh is practically gone. Even just 1 m would make half of the country disappear in the dry season and the rest during the monsoon. How will we evacuate 150 million people (present estimate)?

(Besides, when Greenland melts, West Antarctica does the same... last time Greenland was ice-free (the exceptional interglacial 400,000 years ago) the sea level was 22 m above today's.)

"It will happen if we do not somehow control CO2 rise in the
atmosphere."


Every time the tropical-sea temperatures were about 7 degrees warmer
than they are now and stayed that way for enough years, there was a
die-off.


Degrees what? Fahrenheit? How much is 7 ÂF?

But extinctions were likely happening anyway as temperatures were increasing, Mayhew said. Massive volcanic activity, which releases large amounts of carbon dioxide, has also been blamed for the dinosaur extinction.

<wince> <wail>