The Cryosphere

The International Polar Year of 2007-08 did much to update human knowledge of climate impacts in these regions, with the participation of thousands of scientists across many disciplines (see www.ipy.org).  Today in 2020, with new research coming every day, it has become clear that the cryosphere is not merely the canary in the coal mine, or an early indicator of climate change.  Instead, it has become a prime driver of changes throughout the globe.  Today, virtually all scientists agree that even a 2°C sustained global mean temperature is too high – we can see in Earth’s past a planet with 15-20m higher sea levels at that temperature.  The science indeed says that even 1.5°C is too costly over time.  Instead, 1.5°C should be seen as a “guardrail”: a level which we should not exceed or exceed only briefly, working to come down below 1°C as soon as possible.  These are simple geo-physical realities, not hyperbole: driven entirely by the melting point of water.  For greater detail, see the Cryosphere1.5° Report, written and reviewed by over 30 leading IPCC and other cryosphere scientists, released at COP-25 in Madrid; and Thresholds and Closing Windows, released in conjunction with the 2015 Paris Agreement.