I loved the “Temperature of Science” piece. I can only imagine the patience with which you all are making the data public as well as doing your regular job of making the data! So sorry about the police escort here in Houston, but better safe than sorry. I nearly came to blows in the street when debating climate change and future use of fossil fuels with downtown coworkers.
How we all wish it were as easy to get started on an alternative path as it would have been even twenty years ago...begun forty years back, cakewalk might seem an operative term. Unfortunately the natural positive climate feedbacks have been kicking in all the while we have waited for our better angels. You know the drill - Less ice cover, more melting tundra, eventually the recovery of normal solar output, reduction of aerosols aloft due to cleaner technology in China or various economic disasters, saturation of carbon sinks, increased natural burnings of forests (including cities) and coal seams, potential explosions of a few methane hydrate deposits: the list could go on. The effect is a diminishing return on human climate protection effort of any kind, or conversely a multiplier of human climate protection effort that will be required over time, even as formidable adaptive expenses mount.
It would be interesting if Dr. Hansen et. al. could hazard a projection of about when natural feedbacks can be expected to marginalize human efforts to mitigate climate change. I don’t know if “marginalize” means the point when actual emissions equalize between all anthropogenic and all natural (feedback) sources, or the crossing of a tipping point that locks in massive natural increases in GHG, or even when the trajectory of likely total anthropogenic and natural emissions makes crossing a tipping point unavoidable. I remember reading somewhere that natural releases of CO2e recently amounted to 2 billion tonnes per year, which would have been close to 5% of the total anthropogenic GHG emissions in 2005.
Many of us have taken literally the idea that only a decadal window remained open to achieve serious reversal of the trajectory of anthropogenic GHG emissions. Recall Michael Jackson's mention in rehearsal captured for the motion picture "This Is It" of the fact "we have four years left," if I remember the dialog during his beautiful “Save the World” song properly. Yet the picture of an immediate abrupt turnaround into a drastic linear reduction of GHG emissions painted at both Kyoto and Copenhagen seems on its face patently impossible.
Figure 1 Proposed GHG Reductions (secondary sources available in original spreadsheet, and please forgive the obvious amateurishness of my work)
A fairly straight line logarithmic projection of the global trend in GHG emissions established 1995-2005 which I think may be reasonable based on expected human population growth puts us around 60 billion tonnes anthropogenic GHG emissions per year by mid-century, half again higher (negative 50% on the above graphic) than in 1990 if we allow ourselves to burn that much fossil fuel. How will natural (positive feedback) emissions compare during this period? Doubtless they will increase. But when will natural emissions then outweigh whatever humans can or will do going forward? That point surely is coming. It seems to me, if identifiable, to form the natural endpoint of human mitigation efforts, and marks a full move into utter survival mode for civilization and many millions of human beings.
Perhaps better than any U-N temperature rise by any date certain, certainly better than any Chinese energy intensity measure, the day that natural feedback GHG emissions probabilistically trump human emissions could serve as a meaningful endpoint against which to measure mitigation and adaptation alternatives and options, especially such human processes as urban planning and reconstruction, refugee resettlement and assimilation rates, typical warfare blooms and technology adoption rates. Call it a “futility point” or an “end of game” or a “new age begins here”, it is this invisible windmill against which we tilt! Is there any way to know approximately when that point may be reached in the real world?
Thanks so much for all you guys do!!!!
Paul M. Suckow,
Senior Planner
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