To summarize, climate crisis is the defining issue of the century. Buildup of anthropogenic greenhouse gases (GHGs) in Earth’s atmosphere is driving global heating, while a convergence of global crises threatens to rupture key planetary boundaries. Although the human activities which drive these converging crises (for simplicity: the climate crisis) are diverse and complex, the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) breaks down the sources of anthropogenic GHG emissions into five high-level sectors. Similarly, the impacts of climate crisis – in their variety and complexity – are almost impossible to grasp, but this (linked) representative selection gives a sense of the enormity of the current global impasse. In the absence of dramatic global climate action this decade, climate crisis will likely spiral out of control, rupturing key planetary boundaries and endangering the future of organized human life on Earth.
A previous post on climate feedback loops addressed albedo. Today’s brief post will focus on methane emissions. As previous posts have covered, methane is a powerful greenhouse gas (with warming potential an order of magnitude or two greater than carbon dioxide’s over the first ten to hundred years after its release, after which it eventually breaks down into still more carbon dioxide) that is emitted by a number of anthropogenic processes (especially animal/ruminant agriculture, natural gas extraction/distribution, and rice farming) as well as by any number of non-anthropogenic processes on Earth (such as those that occur in healthy wetlands). With respect to positive feedback loops, however, the most worrying methane emissions are those triggered by anthropogenic warming; in particular, thawing of Arctic permafrost is likely to release very large quantities of methane, which, in turn, is likely to drive further warming, which, in turn, is likely to trigger further thawing and further methane release…
Such is the nature of these positive feedback loops, and while the state of the science on the balance of emissions from thawing permafrost continues to evolve as we live through scenarios unprecedented in human history, nonetheless, it seems highly likely that the net methane emissions from thawing permafrost (as from some warming freshwater bodies) will be positive, and so threaten to fuel the type of runaway warming it is the work of this century to avert.
For a different sort of knock-on effect to climate crisis, I recommend you read this InsideClimate News piece entitled “Battered, Flooded and Submerged: Many Superfund Sites are Dangerously Threatened by Climate Change.”