Update of Greenland Ice Sheet Mass Loss: Exponential?

26 December 2012

James Hansen and Makiko Sato




In this paper, Hansen and Sato point out that the IPCC rise in sea level projections need updating.  As I understand it, the models used in the past did not take into consideration the possible – Hansen and Sato suggest that it is probable- non-linear increase in ice sheet loss due to human contributions to the rising global temperature due the greenhouse effect.  Sea level rises will most probably be far greater than the 1 meter mentioned by the IPCC.  Sadly, it will be too late to do anything about it when enough data is collected to convince reluctant sceptics.  I suggest that powers that refuse to change the status quo understand this and will at that time just shrug their shoulders and say, in effect, “Too late to do anything now, so let’s just keep on keeping on the way we have been and enjoy what we have while we have it.”  Of course, only the 1%ers will be enjoying their lives whilst the rest of us waste away in cold and hunger.  You don’t think this can happen?

Of course, what has not been mentioned is the question:  How will Gaia maintain stable, life enabling global temperature without glaciers and ice sheets?  The Gaia Theory plainly points out that the earth should be a lot warmer due to the expanding heat from an expanding sun over the last 5 billion years. We need to work hard to understand how Gaia operates and cooperate rather than destroy her enabling structures and global health measures.


“A crucial question is how rapidly the Greenland (or Antarctic) ice sheet can disintegrate in response to global warming. Earth’s history makes it clear that burning all fossil fuels would cause eventual sea level rise of tens of meters, thus practically wiping out thousands of cities located on global coast lines. However, there seems to be little political or public interest in what happens next century and beyond, so reports of the IPCC (Intergovernmental Panel on Climate Change) focus on sea level change by 2100, i.e., during the next 87 years.”


“…future sea level rise of greatest concern is that from the Greenland and Antarctic ice sheets, which has the potential to reach many meters. Hansen (2005) argues that, if business-as-usual increase of greenhouse gases continue throughout this century, the climate forcing will be so large that non-linear ice sheet disintegration should be expected and multi-meter sea level rise not only possible but likely.”


“Perceived authority2 in the case of ice sheets stems from ice sheet models used to simulate paleoclimate sea level change. However, paleoclimate ice sheet changes were initiated by weak climate forcings changing slowly over thousands of years, not by a forcing as large or rapid as human-made forcing this century.”


“The increasing Greenland mass loss in Fig. 1 can be fit just as well by exponentially increasing annual mass loss, a behavior that Hansen (2005, 2007) argues could occur because of multiple amplifying feedbacks as an ice sheet begins to disintegrate. A 10-year doubling time would lead to 1 meter sea level rise by 2067 and 5 meters by 2090. The dates are 2045 and 2057 for 5-year doubling time and 2055 and 2071 for a 7-year doubling time.”