Earth's Cryosphere Still Within Safe Operating Space?

The frozen parts of Earth – its ice sheets, glaciers, sea ice, snow cover and permafrost – play a vital role in regulating the planet's climate, water supply, and carbon cycles, among other ecosystem services. But the essential functions of the cryosphere are no longer in a safe operating space (SOS), pushed beyond their bounds to an extent that will create long-term challenges for the planet's population, according to a new analysis by Bo Su and colleagues. As part of the planetary boundaries approach, SOS defines the environmental limits for an Earth system that remains stable and resilient and where humans and ecosystems can thrive. Su et al.'s analysis of key control variables including land ice volume, sea ice area, snow cover area, and permafrost temperature concludes there is an "accelerating and partly irreversible loss of cryospheric integrity. The control variables have deteriorated beyond or committed to deteriorating past the Holocene levels that define the cryosphere SOS, they note. "Maintaining and restoring Earth System resilience now requires urgent global action to halt and reverse greenhouse gas and black carbon emissions, and to reduce the effects of local human disturbances such as infrastructure expansion in cryospheric regions," they write.