(Returning after a short break from posting)
There have recently been a few studies showing that permafrost is melting and that large amounts of CO2 and methane (CH4) are being released. Reports of melting of arctic sea floor clathrates (methane) are also on the web. Jim Hansen has described this potential climate feedback as the ‘Methane Gun’. Fossil fuel emissions are the trigger.
An article was published in Nature on the 1st December setting out what 41 scientists think will happen to our permafrost. These people study various aspects of permafrost. They were asked to put a figure on emissions of CO2 and CH4 for four warming scenarios through the next 300 years. The main points from the article include…
“The lowest warming scenario projects 1.5 C arctic warming (above the 1985-2004 average) by 2040 ramping up to 2 C by 2100; the highest warming scenario considers 2.5 C by 2040 and 7.5 C by 2100. In all cases the temperature would remain steady from 2100 to 2300 so that we could assess opinions about the time lag in the response of permafrost carbon to temperature.
…the highest warming scenario will degrade 9-15% of the top 3m of permafrost by 2040, increasing to 47-61% by 2100 and 67-79% by 2300 (95% confidence intervals). The estimated carbon release from this degradation is 30 to 63 billion tonnes by 2040, reaching 232 to 380 billion tonnes by 2100 and 549 to 865 billion tonnes by 2300. These values, expressed in CO2 equivalents, combine the effect of carbon released as both CO2 and CH4 (methane).
Our estimate for the amount of carbon released by 2100 is 1.7 – 5.2 times larger than those reported in several recent modelling studies, all of which used a similar warming scenario. This reflects in part our percieved importance of abrupt thaw processes as well as our heightened awareness of deep carbon pools.
Across all of the warming scenarios, we project that most of the released carbon will be in the form of CO2 with only about 2.7% in the form of CH4. However, because CH4 has a higher global warming potential almost half of the effect of future permafrost zone carbon emissions on climate forcing is likely to be from CH4. That is roughly consistant with the tens of billions of tonnes of CH4 thought to have come from oxygen-limited environments in northern eco-systems after the end of the last glacial period.
All this points towards significant carbon releases from permafrost zone soils over policy-relevant timescales. It also highlights important lags whereby permafrost degradation and carbon emissions are expected to continue for decades or centuries after global temperatures stabilize at new higher levels.
…once the soil thaws, emissions are likely to continue for decades, or even centuries.
…our survey outlines the additional risk to society caused by thawing of the frozen north and underscores the urgent need to reduce atmospheric emissions from fossil fuel use and deforestation.”
A very worrying report on all accounts. Especially when one realises that the lowest scenario of 1.5 C of arctic warming is virtually certain to be much too low. Recent arctic temperatures have been well beyond this figure already.