on non-linearity: wot happens in ‘albedo flip’?

albedo flips as melting ice goes dark

These days we see lots of problems with the IPCC's consensus view of ice melt, and it's NASA scientists who are bringing the heat. Literally.

Course, their sat shots show us key features of the melting process, so we shouldn't be surprised (hi W!) if James Hansen and colleagues are the first to flag the 'fly' in the consensus ointment: the prospect of 'albedo flip' (via enviro graffiti).

Say wot? Turns out, the IPCC took a (by now outdated) assessment of warming on the polar ice caps and compounded its error by extrapolating the melt process in a linear fashion, says Hansen.

Hansen's familiarity with the feedback loops in climate change leads him to worry about a particular kind of non-linear event called the "albedo flip."

That's when the sunlight reflected by white ice is suddenly absorbed as ice melts to become the dark surface of open water, says Hansen.

Looking back over recorded climate history, Hansen notices that our planet often gets whipsawed between climate states. So, conditions can change dramatically...and fast.

Says Hansen:

"The 'albedo flip' property of water substance provides a powerful trigger mechanism. A climate forcing that "flips" the albedo of a sufficient portion of an ice sheet can spark a cataclysm."

The problem with the IPCC report, says Hansen, is not just that its assessment of the rate of ice melt is way too low. The potentially fatal miscalculation, says Hansen, is in failing to note how close we already are to this 'trigger point'.

Hansen's specific concern is that "the IPCC foresees little or no contribution to twenty-first century sea-level rise from Greenland and Antarctica. However, the IPCC analyses and projections do not well account for the nonlinear physics of wet ice sheet disintegration, ice streams and eroding ice shelves."

Hansen's recent paper called Climate change and trace gases notes that:

"With global warming of only 2–3 °C and CO2 of perhaps 350–450 ppm it was a dramatically different planet, without Arctic sea ice in the warm seasons and with a sea level 25 ± 10 m higher."

"The nonlinearity of the ice sheet problem makes it impossible to accurately predict the sea level change on a specific date", says Hansen.

As a physicist, Hansen finds it ?almost inconceivable that (business-as-usual) BAU climate change would not yield a sea level change of the order of meters on the century timescale. The threat of a large sea level change is a principal element in our argument that the global community must aim to keep additional global warming less than 1 °C above the 2000 temperature, and even 1 °C may be too great. In turn, this implies a CO2 limit of about 450 ppm, or less. Such scenarios are dramatically different than BAU, requiring almost immediate changes to get on a fundamentally different energy and greenhouse gas emissions path. "

Wot's the clue? We gotta find a way to keep emissions below 450ppm.

So, how would Hansen do it? In a recent Grist interview, Hansen lists three ways:

  1. Dramatically reduce emissions immediately
  2. Conserve remaining oil and gas
  3. Pull CO2 out of the air

The best way to achieve emissions reductions, says Hansen, is to stop all new coal power plants until we get the carbon sequestration thang figured out.

On conserving the oil we've got, Hansen says "we're going to have to find energy sources that don't produce CO2. In order to give us time to do that, we need to use oil and gas, which are precious fuels, as if they were precious."

The best way to pull CO2 out of the air? That's wot Hansen's not so clear about.

Either way, Hansen says we have about 10 years to put into effect the draconian measures needed to curb CO2 emissions quickly enough to avert a dangerous rise in global temperature.

Otherwise, the extra heat could trigger the rapid melting of polar ice sheets, made far worse by the "albedo flip"

Published by Ken on July 2nd, 2007 tagged Climate Change, Systems Thinking

Comments are closed.