Are feedbacks here already?

By June 28, 2019Environment, Science

Almost a year ago, a scientific paper appeared in the Proceedings of the US National Academy of Sciences detailing the feedback cycles which it suggested were likely to kick in at about a 2 degrees C increase over the pre-industrial level (we are now at 1 degree C above this level). I wrote about it in September 2018 and noted these feedbacks included: thawing of the permafrost; weakening of land and ocean carbon sinks; increased bacterial respiration in the ocean; and Amazon and boreal forest dieback. The authors of the paper suspected that these would add another half a degree on top of that 2 degrees C by the year 2100, but that these could lead in turn to a cascade of feedbacks after that time1.

Early this month I reported on a concerning increase in the concentration of methane in the atmosphere. It had been increasing about 1 part per billion per annum, but this has now jumped to 10 parts per billion per annum. It is even worse at mid-altitudes in the atmosphere with an increase of 35 parts per billion from 2017 to 2018. It was suspected that this increase was caused by a combination of thawing of permafrost and the release of methane from hydrates on the sea floor2. However, there was little evidence to actually sheet it home to these specifically.

Now, a recent paper dealing with time series observations (between 2003 and 2016) at several permafrost sites in the Canadian High Arctic has been published in the journal Geophysical Research Letters. These sites are of very cold permafrost which normally has a mean annual ground temperature of -10 degrees C or lower. When these areas thaw, they cause the ground surface to subside, and the data obtained indicate this is happening much more rapidly than expected, and is producing small thaw (thermokarst) ponds. This is because the Arctic is rapidly warming, and between 1990 and 2016, it has increased up to 4 degrees C, considerably more than the global average increase of 1 degree C3,4. The Intergovernmental Panel on Climate Change (IPCC) tends to be conservative in its assessments, and its ‘moderate’ climate change modelling predicted that thawing of permafrost on this scale would likely not happen until later this century, probably around 2090. The fact that it is happening 70 years earlier than those moderate models suggest is alarming. This is so because it allows microbes to start converting what trapped organic material there was in the permafrost into carbon dioxide5. This is feedback starting now, and it will probably be impossible to stop.

As if the threat from methane2 and carbon dioxide5 wasn’t bad enough, now we have another greenhouse gas to worry about. Back in 2010, the US Environmental Protection Agency expected the amount of Nitrous Oxide (N2O) to be released from thawing permafrost to be negligible. However, a recent paper published in the journal Atmospheric Chemistry and Physics demonstrates that Nitrous Oxide emissions from permafrost are about 12 times higher than previously assumed7,8. Since Nitrous Oxide traps heat some 300 times more efficiently than Carbon Dioxide, this could mean that the Arctic and thereby the global climate are in more danger than we thought.

As I have said above and elsewhere6, the IPCC reports, by their very nature as consensus documents, tend to be conservative in their predictions. This may also be true of the paper on feedback cycles likely beginning when global mean temperature reaches 2 degrees C above preindustrial levels1. These feedbacks seem to have already started and that means that human civilisation is in grave danger.




  • Mark Dougall says:

    Thank you for another thought provoking piece, even if I don’t like the thoughts provoked. We are like a mob of Frankensteins staring uncomprehendingly into the ravening face of the monster we have created as it starts to destroy us and all we love. We have already hugely damaged our ecological systems and changed our planet’s future as a life sustaining world. As this article suggests the changes could well be permanent

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