Peter Ward’s important classic, Under a Green Sky, presents us with some
important questions: how close are we to the time when emanations of H2S to
(“brimstone”) or radiation induced by a new ozone hole (“fire”) start
growing to the point where all higher mammals on earth, including humans,
would be killed? Ward’s book (and the paper by Kump which he
cites) proves that these problems have caused mass extinctions many times in
the past, but he doesn’t unravel the mechanisms of HOW this happens well
enough to give us any kind of decent early warning. He argues that a new
kind of crossdisciplinary cooperation would be needed, between people who
study the long history of earth and people who study the relevant types of
ocean currents — “thermohaline currents” (THC), in order to understand just
how bad the problem is for us today. He does suggest that we are in fact on
a road to a new mass extinction, sooner than we think.
I have done a lot of google scholar search and such, to see whether anyone
on earth has made the right connections to analyze this situation. Failing
that — I have groped to try to make the connections myself. Just yesterday,
I had a chance to study a paper by Iris Grossman, of the Carnegie Mellon
climate change group, which explains the relevant THC more clearly than any
other paper I have found as yet. The picture is complicated, but here are..
MY CRUDE INITIAL IMPRESSIONS OF THE BOTTOM LINE
1. There is a very tight coupling between the warming northern Gulf Stream
(“GS”) currents and the deep currents (“NDWA”?) which protect us from a
Green Sky event.
2. For the moment, the melting of ice on Greenland reduces the saltiness
(salinity) of water in the North Atlantic, which weakens the warming current
(adding some cold and snow and such to places like England, France and New
England) and the NDWA. However, the AMOUNT of weakness of these currents is
proportional to the RATE of melting of the Greenland ice; if it keeps
melting at the same rate, the cold storms would not get worse, and the ocean
will not become more stagnant than it is today. It may even be that this
problem peaked at around 1970, when there was a “Great Saline Anomaly” (low
salinity and a weakening for a few years of the warming GS).
3. Midterm, the situation seems even less threatening. The NDWA seems to
depend on the salinity of the cold North Atlantic and North Pacific water
more than anything else. For now, melting of Greenland ice is a major
factor, but when that is totally gone (just as the Arctic ice is on path to
disappear), this effect goes away. Then we fall back to the long-term
drivers of salinity: rain and evaporation. Thanks to melting, we know to
expect less rain in places like the Himalayas (due to the “albedo effect”);
warming and low albedo should also increase evaporation. That all should
4. HOWEVER: this nice NDWA of ours is new. In most of earth’s history, we
did not have it at all. In most of earth’s history, agricultural runoff like
what we had today, combined with stagnant flows in the deep ocean, would be
enough to cause a “green sky” effect — and many times did, killing
everyone. What was different about the THC back then?
The obvious answer: the THC now is very sensitive to effects of salinity
when water is in the very special and unique regime between 0 degrees C and
4 degrees C. (Notice how little the salinity and temperature at the equator
seems to change this story!) Back then, the poles were warmer. Bottom line:
there probably exists a “tipping point” when temperatures at the North Pole
would get high enough to turn off the NDWA, both in north Atlantic and north
Pacific, quite enough to get us all killed.
BOTTOM LINE: It looks as if the Green Sky problem is current reducing;
however, when things get warm enough in the water in the North Pole area,
that will reverse. We do not yet know the critical temperature which kills
us all, but on the whole, the bottom line feels a lot like Ward’s position,
even though the logic behind it is quite different.
Needless to say, this cries out for scientific analysis, and quantitative
analysis, far beyond anything I have done here.
It doesn’t help us that the South Pole is in a different regime.
I find myself thinking back to the old movies, AI and Wall-E.
Thoughts about robots and archaea. But the bottom line here really cries out
for more direct follow-ups.
Best of luck… we all need it…