The Telegraph reports today that carbon emissions look set to delay (and probably avert) the next ice age which is just the sort of new year message we all need. A considerable bonus will be that it will also mean that Unesco will not need to set up an Ice Age Education programme, and perhaps it'll even be safe to fly again – though I doubt it.
Anyway, as it's just the Telegraph citing one paper in the journal Nature Geoscience (with no citations), I though I'd best follow it up.
Here's what's on the journal's web:
No glacial inception is projected to occur at the current atmospheric CO2 concentrations of 390 ppmv (ref. 1). Indeed, model experiments suggest that in the current orbital configuration – which is characterized by a weak minimum in summer insolation – glacial inception would require CO2 concentrations below preindustrial levels of 280 ppmv (refs 2, 3, 4). However, the precise CO2 threshold (refs 4, 5, 6) as well as the timing of the hypothetical next glaciation (ref 7 ) remain unclear. Past interglacials can be used to draw analogies with the present, provided their duration is known. Here we propose that the minimum age of a glacial inception is constrained by the onset of bipolar-seesaw climate variability, which requires ice-sheets large enough to produce iceberg discharges that disrupt the ocean circulation. We identify the bipolar seesaw in ice-core and North Atlantic marine records by the appearance of a distinct phasing of interhemispheric climate and hydrographic changes and ice-rafted debris. The glacial inception during Marine Isotope sub-Stage 19c, a close analogue for the present interglacial, occurred near the summer insolation minimum, suggesting that the interglacial was not prolonged by subdued radiative forcing (ref 7). Assuming that ice growth mainly responds to insolation and CO2 forcing, this analogy suggests that the end of the current interglacial would occur within the next 1500 years, if atmospheric CO2 concentrations did not exceed 240±5 ppmv.
This is a bit more nuanced than the Telegraph managed (though it did ok, I'd say). Question is: do I pay the $18 to read the rest ...
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