James Hansen, 12/26/12, Update of Greenland Ice Sheet Mass Loss (PDF)
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...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....Our simulations (Hansen and Sato, 2012) suggest that a strong negative feedback kicks in when sea level rise reaches meter-scale, as the ice-melt has a large cooling and freshening effect on the regional ocean. Such a slowdown in the rate of sea level rise would be little consolation to humanity, however, as the high latitude cooling would increase latitudinal temperature gradients, thus driving powerful cyclonic storms (Hansen, 2009),Storms of My Grandchildren: The Truth About the Coming Climate Catastrophe and Our Last Chance to Save Humanity, by James Hansen
When the history of the climate crisis is written, Hansen will be seen as the scientist with the most powerful and consistent voice calling for intelligent action to preserve our planet's environment.
— Al Gore, Time Magazine
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He claims high latitude cooling due to ice melt will increase the latitudinal gradient. Consider though how great seasonal ice melt already is - massive! That sinusoidal chart we're all familiar with shows Artic ice extent ranging from 14 to 5 (mill sq km?). Any additional melt from emissions will hit both the seasonal maximum and minimum. So it's hard to see what Hansen is getting at, the increasing additional melt due to global warming is insignificant against seasonal variations.
But, his argument about the latitudal gradient does seem to have merit, that the temperature difference can (they do!) drive cyclonic turbulence. And even Skeptical Science admits that an enhanced greenhouse effect will warm the poles more than the middle - so the latitudinal temperature gradient is expected to decrease!
http://www.skepticalscience.com/The-human-fingerprint-in-the-seasons.html
The difference in trend between summer and winter, between land and ocean warming, between the equator and the poles - these all hold vital clues into what has caused climate change since the instrumental record began in the 1800s.
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Solar warming should result in the tropics warming faster than the poles. What we observe instead is the poles warming around 3 times faster than the equator. All these pieces of evidence paint a consistent picture - greenhouse gases, not the sun, are driving global warming.
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