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 for an individual to grasp, but so far, this sub-series has covered: global heating, Arctic amplification, heat waves, droughts and floods, and disruption of oceanic and atmospheric patterns. 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.
In the spirit of economy (of words, not money), today’s post centers the cryosphere in its totality. The cryosphere, put simply, is the part of the Earth that is covered by frozen water (either in the form of ice, snow, or permafrost/frozen ground) at any given moment. Already, in the above-linked post on Arctic amplification, mention has been made of the dramatic loss of sea ice in recent decades, but glaciers, ice caps, the two extant ice sheets (of Greenland and Antarctica), and snowfall are all now in sharp decline. Obviously, the most sensational threat posed by loss of these cryospheric features of the now bygone Holocene is that of sea level rise: Were the Greenland Ice Sheet to melt entirely, global mean sea level (GSML) would rise ~6 meters or 20 feet; were the Antarctic Ice Sheet to melt entirely, GSML would rise ~60 meters or 200 feet. So if they were both to melt, that would amount to 220 feet of sea level rise (for people in the US who are accustomed to thinking in our non-standard standard units). That’s unlikely to happen anytime soon, though multiple feet by the end of this century looks like almost a certainty at this point, and with Indonesia moving its capital out of Jakarta, sunny-day flooding in Miami now the norm, and a surprising number of the world’s key cities (their positions very often a function of colonial trade networks and the garrisoning of the globe by the major imperialist powers over the last ~500 years) starkly menaced by rising tides, it’s understandable that increases in GSML are a special area of focus and concern; however, just as threatening for human populations and societies is the risk that the disappearance of glaciers and the shift in precipitation from snow to rain will radically alter hydrology with devastating impacts on agriculture and communities that depend on snow- and ice-fed river flows.
I’m putting today’s AR5 excerpt at the bottom (because it’s a doozy) in case people want to simply ignore it without missing anything below, but for readers especially interested in issues related to snow and ice, I can happily/sadly recommend The End of Ice from the courageous war-turned-climate reporter, Dahr Jamail.
As for the IPCC, here’s some of what AR5 had to say about unfolding and imminent changes to/driven by Earth’s cryosphere: