RUNAWAY CLIMATE CHANGE
IPCC AR5 records that the risk from Arctic carbon feedback emissions is huge FAQ 6.2: Could Rapid Release of Methane and Carbon Dioxide from Thawing Permafrost or Ocean Warming Substantially Increase Warming?
from Arctic methane emissions by Ivar S. A. Isaksen et al found new evidence that indicates a large risk of Arctic feedback runaway.
The magnitude and feedbacks of future methane release from the Arctic region are
unknown. Despite limited documentation of potential future releases associated with
thawing permafrost and degassing methane hydrates, the large potential for future methane
releases calls for improved understanding of the interaction of a changing climate with
processes in the Arctic and chemical feedbacks in the atmosphere. Here we apply a “state
of the art” atmospheric chemistry transport model to show that large emissions of CH4
would likely have an unexpectedly large impact on the chemical composition of the
atmosphere and on radiative forcing (RF). The indirect contribution to RF of additional
methane emission is particularly important. It is shown that if global methane emissions
were to increase by factors of 2.5 and 5.2 above current emissions, the indirect
contributions to RF would be about 250% and 400%, respectively, of the RF that can be
attributed to directly emitted methane alone. Assuming several hypothetical scenarios of
CH4 release associated with permafrost thaw, shallow marine hydrate degassing, and
submarine landslides, we find a strong positive feedback on RF through atmospheric
chemistry. In particular, the impact of CH4 is enhanced through increase of its lifetime,
and of atmospheric abundances of ozone, stratospheric water vapor, and CO2 as a
result of atmospheric chemical processes.
There is a possibility that the Arctic temperature increases could be followed by extensive the permafrost thawing with enhanced methane emission from thermokarst lakes with later release of methane from gas hydrates that would eventually be affected by warming temperatures. Considering the large non-linear atmospheric And chemistry feedbacks discussed here future methane emissions from permafrost deposits could be a larger concern for climate warming than previously thought
In a 2010 review POSSIBLE ROLE OF WETLANDS, PERMAFROST, AND METHANE HYDRATES IN THE METHANE CYCLE UNDER FUTURE CLIMATE CHANGE the risk of catastrophic runaway climate change was spelled out.
We have made an assessment of the available scientific literature on methane feedbacks related to natural sources of methane are plans permafrost and ocean sediments.
In summary the complex and non-linear processes governing the sources and atmospheric chemistry of methane causes feedback loop between the climate the terrestrial vegetation, as the source of the BVOCs (biogenic volatile organic compound), the oxidation capacity of the atmosphere and the atmospheric methane burden.
The feedback loop can be described in simple terms as follows rising methane emissions from wetlands thawing permafrost and destabilising marine hydrates increase atmospheric methane concentrations; this increase in methane concentration amplified by the effect of methane on its own chemical lifetime results in an even greater radiative forcing of climate and terrestrial ecosystems.
The ecosystems given our current understanding respond to a warmer and more humid conditions by an increase in the BVOCs which further augments the lifetime of methane.
Finally, the resulting additional radiative forcing (from fast responding wetland methane) could lead to more or faster thawing of permafrost, further destabilization of marine hydrates, and potentially even larger wetland CH4 emissions.