Glacier in retreat – will denialists follow?
With my thanks to Climate Denial Crock of the Week, I present this Spot the Difference competition using photos of the Columbia Glacier in Alaska taken in 1938 (USGS), 1986 and 2011 (NASA).
As a Google search of images of the Columbia Glacier will reveal, it had been static for decades prior to the 1980s, since when it has retreated 12 miles. In the 2011 photo, the terminus of the glacier (or rather glaciers – since the West and Main branches no longer meet) can be found by looking for the point where the stripes in the glacier are replaced by the mish-mash of floating ice and underwater morraine (thin red line added by me – see Climate Denial Crock of the Week for a better look at the orginals). The extent of this particular retreat would be much clearer if the 2011 photo had been taken in July too. However, even so, the evidence is clear: After decades (if not centuries and/or millennia of stability), the glacier has retreated 12 miles in less than 30 years.
This pattern is repeated all over the world; and the only place where glaciers may not currently be retreating like this is the Himalayas; which are the highest mountains on Earth (albeit nearest the equator). However, as predicted, the polar regions of the planet are warming fastest; therefore the retreat is more noticeable at higher latitudes. Despite all this, glaciers in the Himalayas have retreated over the last 90 years, so any current hiatus in retreat there (i.e. probably caused by a combination of atmospheric pollution, oceanic circulation effects and low sun spot activity) is not good grounds for global complacency and/or optimism. Glaciers that have retreated 12 miles are not suddenly going to grow back in any timescale relevant to human lifetimes. On the contrary, all the evidence suggests that wherever they are retreating, the rate of retreat is accelerating due to subglacial lubrication by meltwater, etc. (i.e. one of many insidious positive feedback mechanism we can do little or nothing to stop). This is the Anthropocene Era writ large on the canvas of our planet.
Global Glacier Changes: facts and figures from The World Glacier Monitoring Service.