Warming in a global cool period
By Peter N. Spotts| Staff Writer for The Christian Science Monitor/ September 25, 2008 edition
Graph above added by Anthony – not part of original article
With all the focus on human-triggered global warming, it may be hard to imagine that the world is riding a 50-million-year-long cooling trend.
But it is, and blame the trend on a continental-scale collision, say geophysicists Dennis Kent of Rutgers University and Giovanni Muttoni of the University of Milan in Italy.
Researchers say there is strong evidence that increases in atmospheric CO2 contributed to a warm spell 50 million years ago dubbed the Early Eocene climate optimum – the warmest period in 65 million years. But over the following 15 million years, deep sea temperatures fell by about 10.8 degrees F., reflecting a significant cooling at the surface. This cooling ultimately allowed the cycle of ice ages to emerge.
Drs. Kent and Muttoni have mined paleomagnetic and other data and suggest that atmospheric CO2 dropped because India collided with Eurasia, shutting down a productive, natural CO2 factory.
Some 120 million years ago, the subcontinent that is now India was migrating north from Antarctica. As it moved, it shoved the ocean crust that was ahead of it under an existing crustal plate. As long as this zone off the Eurasian coast was under water, bottom muck enriched by carbon from the biologically-rich ocean plunged under the plate. It got recycled as lava in volcanoes along a geological feature dubbed the Kohistan Arc, as well as in a vast lava-oozing formation called the Deccan Traps. The eruptions released the carbon as CO2, which helped warm the climate. But once India collided with Eurasia 50 million years ago, India rode over the top of the zone and shut off the process. This, plus changes in ocean circulation as continents rearranged themselves, contributed to the long chill, the researchers suggest.
The results appear in the current issue of the Proceedings of the National Academy of Sciences.
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Well then… maybe all that SO2 created acid rain that killed a major portion of the vegetation. As we know, acid rain leeched soil takes a long time to regenerate and get plants growing again. Drive around Sudbury, Ontario and you will see what it looks like.
The reduced vegetation will have the concentration of CO2 in the atmosphere rise. But then you have to admit that the absorption spectrum of CO2 gets saturated at relatively low level. On the other hand, less vegetation also means less water evaporation which could also turn to global cooling.
They can’t reconstruct the last century or the MWP but 50 million years can be? Oh my, such vanity.
Interesting observation, considering the earth is only 6012 years old according to venerated Archbishop James Ussher.
Another explanation of the early Cenozoic warming goes like this: following the KT-boundary event, a tremendous amount of methane was released in the putrefication of the biomass. Within the cooling caused by the atmospheric debris, the methane settled on the ocean surface to sink and become methanehydrates. As things got back to “normal,” the oceans warmed such that methane hydrates in the shallower area were released causing a higher than normal concentration of atmospheric methane and creating a super greenhouse effect.
The onset of the Indian subcontinent colliding with Asia began around 50 mya causing the draining of the Tethys Sea (which, by the way, created condition that led to whales).
The Tasman seaway deepened around the Middle and Late Eocene boundary (37.2 mya) allowing the first major flow from the Indian to Pacific Oceans. Just prior to that by about a million years, the onset of the Antarctic bottom water regime appears. The combination of those two led to a Late Eocene cooling. The Drake Passage is breached in the Late Oligocene creating a circum-Antarctic flow . . . and global cooling. Without going into much detail, other events that changed global climate dramatically include the Isthmus of Gibralter closing in the Late Miocene and the Isthmus of Panama closing in the early Late Pliocene.
In 2005, I took Bila Haq’s sea level frequency data (with permission) and calibrated it to the Gradstein GTS (time scale) with Polar Ocean Equivalent temperature differences and notations on major geologic events. The geologic events correlate well with the sea level flux. It doesn’t appear to me that CO2 drove any of the changes. The methane story (as published in Nature a couple of years ago) is interesting.
Great Posting – Very Interesting – and as always great comments to go around
Yup. What I’ve been saying for years. We live in the coldest era of Earth’s history. It has almost always been warmer than now. Warmer is the normative condition. Better for Life as we know it.
Warmer is Better — Fight the Ice
G Alston- Actually there have been a number of studies, summarized in a paper by Segalstad, with measurements from the 1950’s thru the 1970’s, that pin it down to 5-7 years as the residence time for CO2 in the atmosphere. The much larger numbers come from IPCC authors who claim that CO2 cycles many times from atmosphere to surface before being sequestered. Of course, if you adopt this approach to the calculation, then the resident time of water vapor is also years or decades, since it cycles many times prior to being sequestered at either pole or in a glacier.
The 5-7 year number is based on measurements. Anything longer is based on models.
Given the reality of anthropogenic global warming, and in light of the political effectiveness of exxonogenic climate skepticism, maybe it would be more accurate to say that the Earth *was* on a 50-million year cooling trend.
paminator — Yes I’m vaguely aware of the studies, and the upshot is that the cycling prior to sequestration is completely unknown, hence the answers always being all over the map. (Does this take 1 cycle? 23? Anyone? Bueller?) I would guess that GCM’s have a supposition of what this longevity is as a basis for calculations. Change it and the predictions change. This in turn suggests that GCM’s get their closest predictions (and in hindcasts at that!) by dialing longevity up. I can’t think of any other reason the IPCC and their supporters (minions?) keep claiming that CO2 atmospheric residency is up to 200 years.
G Alston says:
The different answers that you see represent not so much uncertainty but rather the fact that the concept of a lifetime for CO2 in the atmosphere is ill-defined because when a slug of CO2 released into the atmosphere, the concentration decays in a very non-exponential fashion. Thus, it is not characterized by a single lifetime. Roughly speaking, about half of it disappears almost right away, another quarter of it stays around for hundreds of years, and the final quarter stays around essentially “forever” from the point of view of human timescales (e.g., tens to hundreds of thousands of years). See the discussion here: http://www.realclimate.org/index.php/archives/2005/03/how-long-will-global-warming-last/
I’m also skeptical of the CO2 atmospheric residence time given as hundreds of years. If it’s so, and temps have “suddenly” jumped in the last 30 years, then the longevity of 200 years is pretty much bunk. CO2-caused warming would have been slower and longer if the climate were responding to every single tiny increase since the Industrial Revolution.
So that means CO2 and SO2 from high-alititude eruptions stay in the atmosphere about the same amount of time.
Anthony,
Have you previously posted this article by Dr. Roy Spencer: http://globalwarming-arclein.blogspot.com/2008/02/roy-spenser-on-co2-anthropogenic.html
Atmospheric CO2 Increases: Could the Ocean, Rather Than Mankind, Be the Reason? by Roy W. Spencer,1/25/2008?
The article predates my monitoring of Watts Up With That?
Meanwhile — a full 20 F below average in DC today. Avg high in DC in Sept 81, currently 61F
Dan Lee says:
Your whole argument rests on a number of misconceptions that I will try to clear up:
(1) No serious scientist that I know of is claiming that there is a Venus-like instability and the climate is going to “spiral out-of-control into a life-baking oven” once CO2 levels hit 400ppm. The positive feedbacks just magnify the warming due to CO2 alone…They are not strong enough to lead to an instability. (On Venus they could because it is closer to the sun and hence receives more W/m^2 of solar energy.)
(2) The concept of “tipping points” is used rather confusingly in a variety of contexts. There are the possibility of some true tipping points, like a sudden shift or shutdown of ocean currents…and there is evidence that this has happened in the past. Some people, like Hansen, have also used the concept of tipping points more loosely to talk about a point beyond which, given the positive feedbacks due to melting arctic ice and so forth, we will be committed to enough temperature rise to cause, say, several meters of sea level rise (with considerable controversy remaining over how fast that rise could occur).
(3) Noone serious is claiming that the temperature reached will be a temperature that have never been experienced before in the geological history of the earth. However, what is being said is that they are temperatures that have not been experienced in quite some time (probably in the entire history of our species) and that the change will be very rapid relative to past temperature changes and will thus cause problems for both human civilization (a healthy fraction of which lives pretty close to sea level) and ecosystems (which are already being severely stressed by pollution, overfishing, habitat fragmentation, etc.)
(4) The lessons that scientists have learned from studying paleoclimate data is, contrary to what you seem to believe, that their current estimates of the climate sensitivity are likely correct…or, if anything, too low to account for what has happened in the past. See, for example, this paper: http://www.sciencemag.org/cgi/content/summary/sci;306/5697/821
How long does CO2 stay in the atmosphere?
At current concentrations, the atmosphere has about 2*10^12 tonnes of CO2. Assuming a total contribution (nature and man) of 200*10^9 tonnes, that gives an average lifetime of 10 years.
Paminator:
The question of interest is not how long it takes a given CO2 molecule to cycle through. Rather it is how long it takes the atmospheric concentration to be restored to within a certain percentage of its initial value after a slug of CO2 (that has been sequestered from the atmosphere, e.g., in the form of fossil fuels) has been released into it. Hence, your statements about residence times, even if correct, are irrelevant to the discussion.
Sudbury? We cut down our trees long ago for open crib burning (which turned our rocks black and killed lichen) and to help rebuild Chicago after the fires. The lack of trees allowed soil erosion making the soil erode downhill off the rock. Most plants don’t grow very well on the exposed rock.
Northern Ontario lakes between here and North Bay are indeed acidic and thus not as conducive to life as they should be. Many lakes have been limed and many people lime their yards, but that won’t stop plants that tolerate the acid from growing like birch and blueberries. It is the erosion that did us in. You can see it using google maps to search for gps coordinates 46.48 -81.0 Zoom out a bit and you can see the brown oval.
John M Reynolds
“If CO2 is such a great warmer it should be something that could be duplicated in a lab.”
Indeed. Heh.
Retired Engineer (13:27:28) :
How long does CO2 stay in the atmosphere?
After nuclear weapons were created, it was rather simple to trace how long CO2 stayed in the atmosphere. The result was 7 years on average.
At 385ppm, the Earth is still short of CO2 that plants need to use in photosynthesis. Even the CO2 deficite-tollerant plants that we have today would stop growing and die if atmospheric CO2 dropped to around 180ppm or lower.
If CO2 levels drop, plants will become less hardy. Our pitifull little species is totally dependent on plantlife which depends on CO2. I don’t know what they teach in biology these days, but the CO2-hating greens should be more descriptively called the browns, lower CO2 will lead to plant die-off, not a green revolution.
The trend appears to portend a Mars-like future more than a Venus-like future.
Folks, global warming has just become SERIOUS!
I could not care less about shrinking ice sheets, but THIS…
http://www.dailymail.co.uk/tvshowbiz/article-1061809/Is-Jennifer-Lopezs-famously-rounded-derri-actually-SHRINKING.html
WE MUST TAKE ACTION NOW!
jmrSundbury get your history and chemistry straight. The vegetation holocaust in Sudbury was cause by The Inco Mine. The plume and devastation can be seen from space. http://www.sprol.com/?p=64
RE: Pieter F (12:16:49) :
It would be interesting to get Doug Erwin’s take on what you wrote. I interfaced with him a bit early in his career, and found him to be a very forward thinking individual. I would definitely not discount what you have have outlined.