Some people, especially in Canada at this time of year, may not want to hear this, but we’ll miss Jack Frost when he’s gone. An international group of scientists and diplomats concerned with one of the planet’s least-noticed ‘spheres,’ the cryosphere of frozen places, released a cautionary survey of the science that paints a grim picture of a defrosted world: baked-in coastal retreat, and the threat of a big belch of greenhouse gasses that could overwhelm de-carbonizing of the human economy.
The cryosphere is warming much faster than the global average with effects on everything from seasonal snow cover and frost extent to polar ice sheets, mountain glaciers, and permafrost zones. “Thresholds and Closing Windows: Risks of Irreversible Climate Change,” a project of the International Cryosphere Climate Initiative (ICCI), focuses on five distinct threats as these melt.
One is the escalation of sea-level rise and coastal encroachment on some of the world’s most populous cities. One meter of rise is already “committed” the cryo-scientists say. Ten more meters (33 ft.) of rise, they warn, is “close to imminent irreversibility” as ice sheets in West Antarctica and Greenland slip into the sea at what for glaciers is breakneck speed.
Although mountain glaciers might recover in some future era when temperatures are returned to lower values, most are doomed for now. “The almost immediate consequences,” the ICCI says “would include the loss of reliable water resources for millions of people.”
As ominously, they expect the “irreversible” loss of “anywhere between 30% and 70% of the permafrost in its top few metres of soil by 2100,” depending on where the planet’s temperature peaks between 1.5°C and 4.5°C. “Any loss of permafrost would increase atmospheric emissions of carbon dioxide and methane,” the group observes, “fuelling further warming. And this loss will be irreversible.”
For some parts of what is now the cryosphere, the next few years could trigger an “unstoppable transition to a climate system most scientists believe has not existed for 35-50 million years.”
“We are worried by the disconnect between cryosphere dynamics and the policy response,” said Pam Pearson, ICCI’s founder and director. “Unless governments move quickly and effectively towards larger, earlier commitments to keep peak temperatures in the cryosphere as low as possible, the windows to prevent some of these changes may close during the 2020-2030 commitment period. And some of these thresholds . . . cannot be reversed at all.”