The Threat of Global Warming causing Near-Term Human Extinction



The Potential For Huge Abrupt Temperature Rise

The image below, from an earlier post, shows that temperatures typically moved up and down by roughly 10°C (ten degrees Celsius, or eighteen degrees Fahrenheit, i.e. 18°F) between a glacial and interglacial phase of the ice ages, suggesting that a 100 ppm rise of carbon dioxide and 300 ppb rise of methane go hand in hand with a 10°C temperature rise. In other words, it looks like high levels of greenhouse gases in the atmosphere have already locked us in for a future temperature rise of 10°C



How fast could temperatures rise? 

How fast could such a rise eventuate? There a number of reasons why - despite the high levels of greenhouse gases in the atmosphere - a huge temperature rise has until now unfolded only slowly, including: 
  • Carbon dioxide emissions reach their greatest warming impact ten years after release. In other words, the full wrath of the carbon dioxide emitted over the past decade is yet to come.
  • A rapid temperature rise is held off by the temporary masking effect of aerosols emitted when burning fuel (especially sulfur dioxide from coal-fired power plants). Once this masking effect falls away, a huge sudden rise in temperature can be expected.
  • A rapid temperature rise is further held off by the fact that some feedbacks can take time to kick in. There is a huge (but decreasing) capacity of oceans, ice sheets and glaciers to act as a buffer for heat. Demise of the ice and snow cover in the Arctic and methane releases from the seabed of the Arctic Ocean can take time to eventuate and much sunlight is still reflected back into space by the snow and ice cover in the Arctic. However, even though their impact may now look only minimal, one or more feedbacks can cause a dramatic non-linear rise, speeding up the way one or more feedbacks kick in, not only in terms of progression of a non-linear rise, but also due to interaction between feedbacks.
    created by Sam Carana, part of AGU 2011 poster
    As an example of a non-linear temperature rise, Arctic sea ice demise is causing more heat to be absorbed in the Arctic, resulting in further decline of the snow and ice cover, in turn causing more sunlight to be absorbed (rather than reflected back into space as before). This self-reinforcing feedback loop accelerates warming in the Arctic.

    Much carbon is stored in large and vulnerable pools (see image below) that have until now been kept stable by low temperatures. A rapid temperature rise would hit vulnerable carbon pools hard, making them release huge amounts of greenhouse gases, further contributing to the acceleration of the temperature rise.


    The scenario of a rapid 10°C temperature rise thus becomes a distinct possibility when considering the size and vulnerability of some of the terrestrial and marine carbon pools and the combined warming impact of:
    • Carbon dioxide emitted over the past decade reaching their peak impact soon
    • Falling away of the masking effect that aerosols currently exercise over global warming; and
    • Feedbacks causing even higher levels of greenhouse gases (carbon dioxide, methane, water vapor, ozone, etc.), resulting in less heat being radiated from Earth, while increasingly less sunlight is getting reflected back into space (albedo decline).

      The Potential For Huge Methane Releases

      The methane feedback deserves some further attention. Note that the above Unesco image gives an estimate of 10x10³ or 10,000 Gt C for ocean methane hydrates, but that several studies give even higher estimates, as illustrated by the image below, from Pinero et al.

      The amount of carbon stored in hydrates globally was in 1992 estimated to be 10,000 Gt (USGS), while a later source gives a figure of 63,400 Gt C for the Klauda & Sandler (2005) estimate of marine hydrates.

      Natalia Shakhova et al. in 2010 estimated the accumulated potential for the East Siberian Arctic Shelf (ESAS) region alone (image on the right) as follows:
      • organic carbon in permafrost of about 500 Gt
      • about 1000 Gt in hydrate deposits
      • about 700 Gt in free gas beneath the gas hydrate stability zone.

      Methane hydrates are present at many locations. Further warming of the Gulf Stream is causing methane eruptions off the North American coast. Methane eruptions from marine sediments have also been reported off the coast of New Zealand and in many further locations.

      Methane hydrates in marine sediments aren't the only type of hydrates that should be considered. Methane also appears to be erupting from hydrates on land in Siberia, on Antarctica, on the Qinghai-Tibetan Plateau and on Greenland. The hydrates are kept stable by the pressure of large volumes of snow and ice, but wild weather swings could cause cracks and the resulting pressure changes could destabilize such hydrates. Methane is also present in large quantities in lakes, such as at the bottom of Lake Baikal.

      Furthermore, methane contained in hydrates isn't the only type of methane that is contained in marine sediments. Marine sediments also contain methane in the form of free gas and carbon that could be transformed by microbes into methane.

      Methane and carbon contained in marine sediments typically have an organic origin. Additionally, there is mantel methane, which has a geological origin and can rise through the sediment in the form of free gas or can form hydrates in marine sediments.

      The sheer size of the above carbon pools makes that there is a huge danger that methane levels in the atmosphere will grow rapidly, due to releases from methane hydrates and from terrestrial permafrost. What adds to the danger of such methane releases is that levels of greenhouse gasses in the atmosphere currently are very high and rising rapidly.

      Danger can be specified on three dimensions, i.e. probability (the possibility of something eventuating), severity (the damage that could result from the event) and timescale. The risk of a 10°C temperature rise is incalculably high. On the severity dimension, the impact of such a temperature rise is beyond catastrophic, i.e. we're talking about extinction of species at massive scale, including humans. On the probability dimension, this outcome appears to be inevitable if no comprehensive and effective action is taken.


      Above danger assessment also uses a third dimension, i.e. timescale. A 10°C temperature rise could eventuate within one decade and this also makes the danger imminent, adding further weight to the need to start taking comprehensive and effective action, as described in the Climate Plan.

      The Threat

      With little or no action taken on global warming, it appears that the Antropocene will lead to extinction of the very human beings after which the era is named, with the Anthropocene only running from 1950 to at most 2050, a mere 100 years and much too short to constitute an era. In that case a better name would be the Sixth Extiction Event, as also illustrated by the image below.

      This could trigger huge abrupt methane eruptions leading to mass destruction and extinction.
      Potential warming by more than 10°C or 18°F by 2026 (from: Climate Plan Summary, see also: the extinction page)
      In conclusion, it's high time that homo sapiens starts acting as genuinely wise modern human beings and commit to comprehensive and effective action as discussed at the Climate Plan.

      Continue reading at . . Will humans be extinct by 2026?
      and Warning of mass extinction of species, including humans, within one decade


      Links

       Will the Anthropocene last for only 100 years?
      http://arctic-news.blogspot.com/2014/05/will-the-anthropocene-last-for-only-100-years.html

       How much time is there left to act?
      http://arctic-news.blogspot.com/p/how-much-time-is-there-left-to-act.html

       The Mechanism leading to Collapse of Civilization and Runaway Global Warming
      http://arctic-news.blogspot.com/p/the-mechanism.html

       Climate Plan
      http://arctic-news.blogspot.com/p/climateplan.html

      • Extinction
      http://arctic-news.blogspot.com/p/extinction.html

      • Feedbacks
      http://arctic-news.blogspot.com/p/feedbacks.html

      • Potential for methane release (2011 post)
      http://arctic-news.blogspot.com/p/potential-for-methane-release.html

      • Warning of mass extinction of species, including humans, within one decadeWarning of mass extinction of species, including humans, within one decade

      1 comment:

      1. The Climate Plan calls for comprehensive action through multiple lines of action implemented across the world and in parallel, through effective policies such as local feebates. The Climate Plan calls for a global commitment to act, combined with implementation that is preferably local. In other words, while the Climate Plan calls for a global commitment to take comprehensive and effective action to reduce the danger of catastrophic climate change, and while it recommends specific policies and approaches how best to achieve this, it invites local communities to decide what each works best for them, provided they do indeed make the progress necessary to reach agreed targets. This makes that the Climate Plan optimizes flexibility for local communities and optimizes local job and investment opportunities.

        Click for more on multiple lines of action, on recommended policies, and on the advantages of feebates.

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