Carbon emissions: It’s an ill wind…

The original saying emerged in Shakespeare’s Henry IV Part 2 (Act 5, Scene 3) during a jocular exchange when Ancient Pistol brings news from Court to Sir John Falstaff and other old codgers at dinner in Gloucestershire. Falstaff: ‘What wind blew you hither, Pistol?’ Pistol: ‘Not the ill wind which blows no man to good’. In the present context it seems anthropogenic CO2 emissions have staved off the otherwise inevitable launch of another glacial epoch. Climate-change deniers will no doubt pounce on this in the manner of a leopard seizing a tasty young monkey.

Auyuittuq National Park: Penny Ice Cap

Penny Ice Cap on Baffin Island ( credit: Wikipedia)

Climatologists at the Institute for Climate Impact Research in Potsdam, Germany, Potsdam University and the Santa Fe Institute in New Mexico, USA set out to develop a means for predicting the onset of ice ages (Ganopolski, A. et al. 2016. Critical insolation-CO2 relation for diagnosing past and future glacial inception. Nature, v. 529, p. 200-203) Many researchers have concluded from the oxygen isotope data in marine sediments, which tracks changes in the volume of glacial ice on land, that the end of previous interglacial periods by inception of prolonged climatic cooling may be attributed to reduction of solar heating in summer at high northern latitudes. This conclusion stems from Milankovic’s predictions from the Earth’s astronomically controlled orbital parameters and fits most of previous interglacial to glacial transitions. But summer insolation at 65°N is now more or less at one of these minima, with no signs of drastic global cooling; rather the opposite, as part of 7 thousand years of constant global sea level during the Holocene interglacial.

The latest supercomputer model of the Earth System (CLIMBER-2) has successfully ‘predicted’ the last eight ice ages from astronomical and other data derived from a variety of climate proxies. It also forecasts the next to have already begun, if atmospheric CO2 concentration was 240 parts per million; the level during earlier interglacials most similar to that in which we live. But the pre-industrial level was 280 ppm and the model suggests that would have put off the return of huge ice caps in the Northern Hemisphere for another 50 thousand years – partly because the present insolation minimum is not deep enough to launch a new ice age with that CO2 concentration – making the Holocene likely to be by far the longest interglacial since ice-age cycles began about 2.5 Ma ago. Based on current, industrially contaminated CO2 levels and a rapid curtailment of carbon emissions the model suggests no return to full glacial conditions within the next 100 ka and possibly longer; a consequence of the sluggishness of natural processes that draw-down CO2 from the atmosphere.

English: Ice age Earth at glacial maximum. Bas...

Simulation of the Earth at a glacial maximum. (Photo credit: Wikipedia)

So, does this indicate that unwittingly the Industrial Revolution and subsequent growth in the use of fossil fuels tipped the balance away from global cooling that would eventually have made vast tracts of both hemispheres uninhabitable? At first sight, that’s the way it looks. But the atmospheric carbon content of the 17th century would have resulted in much the same long drawn out Holocene interglacial; an unprecedented skipping of an ice age in the period covering most of the history of human evolution. This raises a question first posed by Bill Ruddiman in 2003: did human agriculture and associated CO2 emission begin the destabilisation of the Earth system shortly after Holocene warming and human ingenuity made farming and herding possible since about 10 thousand years ago?

But, consider this, the CLIMBER-2 Earth System model is said to be one of ‘intermediate complexity’ which is shorthand for one that relies on the ages-old scientific method of reductionism or basing each modelled scenario on modifying one parameter at a time. Moreover, for many parameters of the Earth’s climate system – clouds, dust, the cooling effect of increased winter precipitation as snow, and much else – scientists are pretty much in the dark (Crucifix, M. 2016. Earth’s narrow escape from a big freeze. Nature, v. 529, p. 162-163). Indeed it is still not certain whether CO2 levels have a naturally active or passive role in glacial-interglacial cycles, or something more complex than the simple cause-effect paradigm that still dominates much of science.

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2 responses to “Carbon emissions: It’s an ill wind…

  1. Brian Roy Rosen

    It wasn’t so long ago (1960s-1970s) that some glaciologists were warning us of ‘ice surges’ and the possibility of the next ice age arriving very suddenly. Also I recall (not necessarily accurately) that the oxygen temperature curve at the time were being extrapolated to infer that the next temperature downturn would begin ~1000 y from now, i.e. according to the Milankovic cycle. With all the preoccupations with global warming since then, it seems that all this has been quietly consigned to science history.

    • Hi Brian

      Yep, I too am fed-up with modellers of all kinds, most of all those with a bent for climate. It’s not so easy to model D-O events, and lets face it the Younger Dryas is not something anyone would have cared to have witnessed without a decent jacket, because they are not astronomically modulated. Modelling ignores complexity, almost by definition, and with so many parameters involved in climate chaotic behaviour is the only feature that can be predicted with any certainty, but sadly we have no clue what form that might take. Had all the rain that fell in Cumbria last month been in the form of snow there would be a long-lived ice cap on Scafell!

      Regards

      Steve

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