Paleoclimate Implications for Human-Made Climate Change

Below you will find several points from James E. Hansen and Makiko Sato’s paper released last week titled Paleoclimate Implications for Human-Made Climate Change.

The planet is on track to reach +6 degrees C to +7 degrees C from preindustrial levels according to the MIT integrated model (the most complete we have yet still omits Arctic climate feedbacks). A 7C temperature rise means the planet is then committed to 12C. This will add up to the Venus effect that Hansen has warned us about. Yet only Hansen with the exception of perhaps 4 other scientists publicly state we are past DAI (dangerous atmospheric  interference.  To date – aside from these 4 scientists – no one supports Hansen’s planetary emergency call.

From the paper:

  • The fate of humanity and nature may depend upon early recognition and understanding of human-made effects on Earth’s climate (Hansen, 2009). (p 1)
  • However, the need for a CO2 target below the current CO2 amount, and the rapid emissions reduction that such a target implies, has not been recognized and acted on by the international political community. Thus there is an urgency to extract and clarify the implications of paleoclimate data for human-made climate change. (p 9)
  • Atmospheric CO2 amount in the Pliocene is poorly known, but a typical assumption, based on a variety of imprecise proxies, is 380 ppm (Raymo et al., 1996). (p 13)
  • We conclude that Pliocene temperatures probably were no more than 1-2°C warmer on global average than peak Holocene temperature. And regardless of the precise temperatures in the Pliocene, the extreme polar warmth and diminished ice sheets are consistent with the picture we painted above. Earth today, with global temperature having returned to at least the Holocene maximum, is poised to experience strong amplifying polar feedbacks in response to even modest additional global mean warming. (p 7)
  • If human-made global warming reaches Pliocene levels this century, as expected under BAU scenarios, these greater volumes of ice will surely begin to contribute to sea level change. Indeed, satellite gravity and radar interferometry data reveal that the Totten Glacier of East Antarctica, which fronts a large ice mass grounded below sea level, is already beginning to lose mass (Rignot et al., 2008). (p 16)
  • Ice cores suggest that the Eemian and Holsteinian interglacials were warmer than the Holocene by 2°C or more. In contrast, ocean cores suggest that these earlier interglacials were warmer than the Holocene by at most one degree, perhaps by only tenths of a degree Celsius.
  • We conclude that the ocean core data are correct in indicating that global temperature was only slightly higher in the Eemian and Holsteinian interglacial periods than in the Holocene, at most by about 1°C, but probably by only several tenths of a degree Celsius. (p 18)
  • Augmentation of peak Holocene temperature by even 1°C would be sufficient to trigger powerful amplifying polar feedbacks, leading to a planet at least as warm as in the Eemian and Holsteinian periods, making ice sheet disintegration and large sea level rise inevitable. (p 19)
  • We suggest that a nonlinear process spurred by an increasing forcing and amplifying feedbacks is better characterized by the doubling time for the rate of mass disintegration, rather than a linear rate of mass change. If the doubling time is as short as a decade, multi-meter sea level rise could occur this century. Observations of mass loss from Greenland and Antarctica are too brief for significant conclusions, but they are not inconsistent with a doubling time of a decade or less. The picture will become clearer as the measurement record lengthens. (p 20)
  • BAU scenarios result in global warming of the order of 3-6°C. It is this scenario for which we assert that multi-meter sea level rise on the century time scale are not only possible, but almost dead certain. Such a huge rapidly increasing climate forcing dwarfs anything in the paleoclimate record. Antarctic ice shelves would disappear and the lower reaches of the Antarctic ice sheets would experience summer melt comparable to that on Greenland today. (p 20)
  • We have presented evidence in this paper that prior interglacial periods were less than 1°C warmer than the Holocene maximum. If we are correct in that conclusion, the EU2C scenario implies a sea level rise of many meters. It is difficult to predict a time scale for the sea level rise, but it would be dangerous and foolish to take such a global warming scenario as a goal. ( p 20)


Warning bells that continue to be dismissed. Could we all agree that we need to take a harsh honest look at our strategies – as they have not changed (Even after Cancun – when it was made very clear that the people, the planet and all life has been abandoned by those in power).  How much time do we have left before nature overwhelms – once this happens everything is out of our hands. Since NGOs/organizations have worked on this for decades (1992 let’s say) emissions are up over 40% – so we can safely say – all strategies to slow down/eradicate emissions to date have failed beyond measure.  To continue using the same strategies must be considered a type of denialism. What did Einstein say? … the definition of insanity – doing the same thing, over and over again, but expecting different results. It would be worthwhile to make this a main topic of discussion for 2011. Does anyone agree?  Does anyone have radical ideas to share?



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  3. Stephen Klaber

    When you refer to those in power having abandoned the planet, you forget that if they were to try to implement your proposals, they would be immediately out of power. More important than the greenhouse gases is the water problem. We must divert our attention to it. If we fix our lakes and streams so that they do their job of cooling and watering the land, they will do the rest for us. H2O is more important than CO2.

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