Under a Green Sky: Global Warming,
the Mass Extinctions of the Past, and
What They Can Tell Us About Our
Future by Peter D. Ward
Best Analysis Of Co2 So Far But Raises Important Questions
More than 200 million years ago, a cataclysmic event known as the
Permian extinction destroyed more than 90% of all species and nearly
97% of all living things. Its origins have long been a puzzle for
paleontologists, and during the 1990s and the early part of this century a
great battle was fought between those who thought that death had come
from above and those who thought something more complicated was at
work.
Paleontologist Peter D. Ward, fresh from helping prove that an asteroid
had killed the dinosaurs, turned to the Permian problem, and he has come
to a stunning conclusion. In his investigations of the fates of several groups

of mollusks during those extinctions and others, he discovered that the
near-total devastation at the end of the Permian was caused by rising
levels of carbon dioxide leading to climate change. But its not the heat (nor
the humidity) thats directly responsible for the extinctions, and the story of
the discovery of what is responsible makes for an fascinating, globe-
spanning adventure.
Personal Review: Under a Green Sky: Global Warming, the
Mass Extinctions of the Past, and What They Can Tell Us About
Our Future by Peter D. Ward
This book is THE most important thing for anyone to read before forming
an opinion on how important it really is to reduce CO2 emissions. It is also
the most complete big picture review I have seen to date (though others
have gone into more depth on the issue of sea level effects).
(NONE OF THE VIEWS HERE REFLECT THE VIEWS OF ANY OF THE
ORGANIZATIONS I AM CONNECTED TO. I hope to learn more from them
later.)
The book tries really hard to be folksy and appealing to the layman. That
gets to be a bit annoying in the first few pages, but after awhile it is useful,
as it gives you a concrete feeling for the empirical data which underlies his
analysis. He has many pages of solid scientific citations in the back, which
he explains in commonsense terms.
What's important for the policy-maker: he claims that if CO2 gets to 1000
ppm in the atmosphere (which will probably happen if we do not take more
competent and effective action very soon), we will probably set off an
inexorable chain of events which leads to H2S poisoning of the
atmosphere and high radiation, which within a certain number of centuries
would be enough to kill off all humans and all mammals as
soft as us.
What's important for the scientist: he provides a unique and credible
depth of analysis in explaining the major mass extinctions which have
happened in the past, with a special focus on the biggest ones -- for which
the empirical data he has collected himself are important evidence.
He gets deeper into the chain of logic than anything else I have seen.
He also shows links to the global climate models. It's an essential starting
point for real understanding of what's going on.
But there are major holes in the analysis, even so.
For example -- at one point he seems to say that 1000 ppm CO2 in the
atmosphere leads to melting of the icecaps, which then changes the
oceanic "conveyer belts" so that there is very little oxygen in the deep
ocean, which then causes a huge production of H2S in the deep ocean,
which gets to the atmosphere, poisoning us all and destroying the
stratospheric ozone layer as well. But he also shows that CO2 has been
WELL over 1000 ppm for very large chunks of earth's history without this
happening, and he suggests that the poles were ice-free for a large part of
that times as well.

In a more detailed discussion, he says that all of this was crucial -- but it
also required upwelling of deep ocean water (to get the H2S into the
atmosphere)and a "volcanic trigger" as well, to get to extinction. So why is
a volcanic trigger needed? Just what new does it do? Are we home free
today if we don't get that trigger (which is unlikely)? He doesn't say. Lots of
folks in this field are interested in the role of volcanoes. Could volcanoes
BY THEMSELVES explain the mass extinctions? I didn't see so much
discussion of that here.
At a later part of the book, he compares CO2 levels with mass
extinctions, across time. That's a very impressive graph. The peaks and
the extinctions line up very well. We shouldn't ignore something like that.
He then argues that the RATE OF INCREASE OF CO2 is the number
which really drives extinctions, not the actual level, a story which seems to
fit his graph. If it is the RATE of CO2 increase which matters, then we are
indeed at great risk today. But the problem is that his story about ice caps
and conveyer belts seems to depend on the LEVEL of CO2; he doesn't
explain WHY the rate of increase of CO2 should be the driving variable,
instead of the level.
He does offer one possible clue as to why the rate should be important.
In the oceans, he says that a SLOW but LARGE increase in dissolved
CO2 is largely buffered by very slow chemical processes, so that the
acidity of the ocean does not change much. But a RAPID increase
is not buffered, and leads to large regions of acidity. This leads to some
important questions: is it the ppm of CO2 dissolved in the ocean that we
should be worried about, rather than the CO2 in the air? Could
it be that the ACIDITY kills the benevolent purple bacteria he talks about
(the ones which eat the H2S before it gets to the atmosphere), or that it
stimulates the growth of archaea which produce H2S and methane?
If so, we may be in trouble just as serious as he claims, but we may need
to use totally different metrics (and new types of sensor systems) in order
to know just how far away we really are from possible disaster.
And the detailed dynamics remain unproven.
Also... the role of green bacteria, and the importance of purple bacteria
versus upwelling, are rather unclear in this discussion. There is a lot we
would need to nail down, to know how far off (and in what direction) is the
nearest point of no return we need to avoid.
In practical terms... it is sometimes said that the "damage payment" for
CO2 emission based only on sea level effects would not be enough to
justify really draconian caps on CO2 emission under present technology.
The issues raised in this book are a crucial starting point to evaluating
whether more than such a moderate "damage payment" or carbon tax is
really called for.
In summary, this is an essential starting point which we need to follow
up on... but we don't yet know what it really adds up to.
And perhaps I need to look at the volcano story more closely.
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