Have We Already Passed Earth's Warming Limits?
(updated April 24, 2008)
For some time it has been clear to me that the changes we're seeing in the arctic, especially, prove beyond a reasonable doubt that we have long since passed critical major tipping points in the Earth's climate system. Perhaps the most important surprise from the science of recent years has been that the Earth's climate is fundamentally unstable, and that we have, for many millennia, been perched on a ledge, where just a relatively small push toward the warmer was sufficient to begin to flip the planet into a greatly warmed, stable state, the likes of which haven't been seen for many millions of years.
The reasons are basically: 1) That a thin coat of mirror-like white snow and ice coats the top of the globe and it can flip relatively easily to a dark state in the sunny arctic summer, and 2) The massive buildup of carbon stored as permafrost in the arctic has been dependent on keeping the global average temperature about one degree Fahrenheit lower than today's global average to remain frozen.
Climate scientists have been guessing, for many years, how far we can raise the atmospheric CO2 concentration (not counting CO2 equivalents contributed by methane, nitrous oxide and the many artificial, man-made greenhouse gasses) without triggering extremely serious changes to the global system. They've talked about the CO2 leveling off at 550 ppm if we worked hard to curb our uses of fossil carbon fuels, and the importance of somehow leveling off at 450 ppm if at all possible.
Now, for the first time, America's leading climate researcher has apparently postulated in an upcoming article that if we don't level out at a level well below the current level of 385 ppm CO2 only, by winding up before long at a level of either (it's unclear which from the article) 350 ppm CO2 equivalent (meaning CO2 plus all the other gasses combined) or 350 ppm CO2 only, that we will not avoid dangerous (translation = catastrophic) changes.
(See "New Focus on Coal's Part in Warming" by Juliet Eilperin, Sunday, April 6, 2008 (requires login for free viewing)
These changes will include major changes in sea level, major changes in the weather we need for agriculture, major changes in the weather conditions necessary for continued water supplies, major loss of wildlife habitats, generally worse weather, etc. If the article in Science postulates that we need to stabilize at 350 ppm of CO2 equivalent, this means that the CO2 concentration itself would need to level off perhaps in the range of 250 to 270 ppm. I have been guessing 250 ppm or lower, especially because we are now in a position to need to reverse the rapidly accelerating group of major positive warming feedbacks.
Recently, Dr. James Hansen, director of NASA's Goddard Institute for Space Studies, submitted an article to the journal Science, in which he explains that the recent evidence which has been rolling in, all points to far more rapid changes than anyone had been predicting and that merely levelling off at some higher level than today's rapidly climbing level of CO2 is far from adequate after all.
Given that the permafrost has been in an accelerating melting process for about 15 years already, and that the floating arctic sea ice has too, for over a decade now, I think it's quite obvious that the planet is already rolling over that cliff, heading toward some new, stable state. The scary thing about this is that the changes we are seeing are, in effect, being caused by pollution levels dating back to the 1980s, because the oceans are a giant buffer against changes caused both by warming and by CO2 buildup. Before the planet can fully warm in response to a change in the greenhouse, the ocean surface layer must also warm up and it takes 35 to 50 years for that process to become mostly complete, for any given change in the greenhouse (the climate forcing). Further, the oceans have sucked up nearly half the CO2 that we've put into the sky to date (though the relative rate of absorbtion is falling), causing the ocean to become, in effect, more carbonated (like one very big soda) and less alkaline, and threatening to end most life in the oceans long before the end of this century due to the inability of animals to precipitate calcium carbonate shells in the decreasingly alkaline water.
I believe that it's already obvious that we will need to push actual CO2 concentration below pre-industrial levels (250 or lower), as quickly as we can, in order for the CO2 equivalent to remain near pre-industrial levels, if we are to stop the continued, rapid flip in the global climate system in which the arctic is no longer white in the summer and in which the vast stores of surface carbon in the permafrost, peat bogs, tropical forests, etc., become part of the sky and kill the oceans with falling pH.
Considering that we are very rapidly heading in exactly the opposite direction with regard to greenhouse emissions, this means, among other things, that we need to hope that Dr. Klaus Lackner's scheme for removing CO2 from the sky for as little as $30 per ton can be made to work.
http://www.npr.org/templates/story/story.php?storyId=10621219
It would appear, that only by combining a very rapid transition away from nearly all uses of fossil carbon with a massive program to capture CO2 which is already in the atmosphere, can we have any reasonable prospect for retaining our planet's miraculously good weather and have hope of seeing our civilization continue, reasonably intact, for much longer.
Here is a timely NYT article on the current outlook:
http://www.nytimes.com/2008/04/06/weekinreview/06revkin.html?_r=1&oref=slogin
And here is a one-year old article on progress toward Dr. Lackner's invention coming true:
http://www.earthinstitute.columbia.edu/news/2007/story04-24-07.php
What's the alternative to sustainability?