Climate Primer #36: Positive Feedback – 1. Albedo

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 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.

Because out-of-control climate change (or a runaway greenhouse effect) could easily be fueled, among other things, by positive feedback, I thought about titling this post: Positive Feedback Loops (Relative to Climate Crisis, They’re Negative). What is positive feedback? In brief, in a positive feedback loop, a signal/change in a system occurs that drives its own further amplification. A good example from human life can be found in birth, in the process of which the release of oxytocin stimulates contractions, which trigger the release of more oxytocin, which triggers yet more intense contractions, in an intensifying positive feedback loop, ideally until a healthy baby is born to a healthy birthing person, at which point, contractions cease. (Positive feedback loops tend to be escalatory – at least up until a point – whereas negative feedback loops tend to be range-constrained; in both stable climates and healthy biological systems, negative feedback loops, which maintain balance/homeostasis, tend to predominate. A classic, simple example of a negative feedback loop, in a rich country context, is the functioning of a thermostat: If the target temperature is 78 degrees Fahrenheit, then the thermostat can be imagined to turn on the air conditioning whenever the temperature rises to 79 degrees, and turn off the air conditioning whenever the temperature drops to 77, thereby maintaining the air temperature in the range between 77 and 79 degrees Fahrenheit, or roughly at 78.)

Relative to climate crisis, positive feedback loops occur when anthropogenic changes disrupt Earthly conditions which – at least for the ~10,000 years of the Holocene, and until historically recently – had remained relatively stable, in such a fashion as to drive still further like disruption. Today’s post will highlight changes in average global albedo as a positive feedback loop which is driving further planetary warming. As this primer from NASA puts it: “Ice is white and very reflective, in contrast to the ocean surface, which is dark and absorbs heat faster. As the atmosphere warms and sea ice melts, the darker ocean absorbs more heat, causes more ice to melt, and makes the Earth warmer overall. The ice-albedo feedback is a very strong positive feedback.”

It’s not hard to imagine that the melting of glaciers and ice caps is contributing to the same “strong positive feedback” effect, although in some instances – for example, the destruction of California’s forest, and the likely ecological regime shift to follow – climate crisis may lead to changes on Earth’s surface that increase albedo (in that trees tend to have green leaves for much of the year, whereas, if the forests are all destroyed by fire, disease, and encroachment – which, at least in much of California, strikes me, grimly, as a near certainty at this point – the new scrub or desert land may very well be more tan than green, and thus more reflective, though I wouldn’t count that as any net great win for climate stability). Similarly, the science, at least so far as I understand it, still seems to be out on what effect heating (and other climatic shifts) will have on cloud cover; increases in cloud cover increase albedo, thus significant heating-driven increases in cloud cover could, in turn, dampen heating (and hence would constitute a negative, rather than a positive feedback). So far as ice is concerned though – a lot of which is currently melting – the effect is unequivocally to reduce albedo, which is positive, in a negative way.

Note: I’ve failed, in spite of my mother’s request, to inject terribly much optimism into these posts as yet; I do think that an honest encounter with and unsparing foundation in the facts is prerequisite for charting any viable path forward, and only hope that as the harsh realities of global circumstances become ever more readily apparent, that people of conscience will summon the courage to confront sad realities – for example, that settler-colonial California, as we have known it, is over and never coming back – as part of a grieving process that might yet open up to a life-affirming future on Earth. My intention is, in time, to address various climate “solutions” and solutions (if it is even fair to talk about the latter), but, in the meantime, for readers feeling a bit starved for sources of hope, there’s always Project Drawdown.

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