blindboy

In the field of climate science James Hansen is pre-eminent. After early work in the late sixties and early seventies on the runaway greenhouse effect on Venus he turned his attention to Earth's climate and published the first global temperature analysis in 1981. By 1988 he was reporting to the US Senate that the warming trend his work had measured was almost certainly caused by the accumulation of greenhouse gases in the atmosphere.

The failure of governments around the world to heed that warning may well emerge as the greatest tragedy in human history. But it was not oversight or legitimate doubt that caused the failure rather it was through the determined efforts of the fossil fuel industry. By funding any scientist willing to push their agenda, through a variety of phony institutes with credible sounding titles, they created the impression of scientific doubt where there was none.

By selectively funding only those politicians who would oppose any effort to reduce emissions, they maintained the huge subsidies to their industry that limited the competitiveness of alternative energy sources. The process continues even now when the world in which we live is changing at a rate almost beyond our comprehension. We have in effect, allowed the wealthiest people on the planet to radically change its climate so that they could accumulate yet more wealth.

There has been no doubt now for several decades about the big picture, that the atmosphere will warm, climate patterns will change, ice cover will be reduced and sea levels will rise. The details of how those changes will unfold though, remain unclear. We cannot be sure of timescales or of the end results. We cannot at this stage even be sure that emissions will be reduced in the immediate future.

Given these uncertainties the great fear has always been that some unknown process would radically disturb the climate over a short time scale. Hansen's latest paper suggests just such a process and presents strong, though not conclusive, evidence for it. If the lingering doubt concerned an issue with less risk of catastrophic change we could afford to gather further evidence at our leisure. In our present situation it is a red flag. The risks he identifies, added to the risks of which we are already aware, create an irrefutable argument for a serious, concerted effort to reduce emissions now.

His argument is based on the behaviour of freshwater from melting ice which, being less dense, floats above the sea water forming an insulating layer. The sea water then remains warmer than it would otherwise be, while the surface temperature of the freshwater layer is lower than it would otherwise be. In both Greenland and Antarctica the leading edges of the ice shelves extend below sea level into the zone of warmer sea water. This creates a classic positive feedback loop so that the rate of melting increases exponentially.

The most obvious consequence of this would be that sea levels might rise much more rapidly than current IPCC estimates. This is of great concern but so is the second predicted consequence: superstorms. The strength of any storm depends on the temperature difference driving its formation. The greater the temperature difference, the stronger the storm. Cooler Arctic and Antarctic water combined with the warmer tropical water caused by existing climate change potentially create the conditions for storms orders of magnitude stronger than those we currently experience.

A prediction of this kind would be disturbing enough even if it was based only on climate models but when there is also significant geological evidence of such storms occurring during past periods of warming it creates such unprecedented concern about the future that Hansen raises the possibility of all our coastal cities becoming dysfunctional. Cities might, at great cost, build defences against sea level rise, or migrate slowly landward if that rise is slow but nothing can sustain them against the combination of sea level rise and storms capable of driving 40m of run up.

To consider the fate of surfing in such a scenario is an almost obscene waste of effort. You can probably work out the impacts yourself. The original paper is here. //blindboy

Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 ◦C global warming could be dangerous