In What we learned about climate in 2017 – and why it’s terrifying, David Spratt sums up what climate science told us last year. Global 2017 temperature averaged 1.2°C above pre-industrial.
It’s misleading to discuss climate change ice impacts using the year 2100, because that hides the most important changes - new irreversible impacts and new steady state situations. For example, the consensus is that the irreversible melting of Greenland is locked in at 1.6°C rise. While Greenland won’t completely melt out by 2100, it’s later impact on sea level will be 6 meters (20 feet).
New research papers from 2017 say that interglacial equilibrium climate sensitivity (relevant to us) is around 4.88°C. When major positive climate feedbacks, not including the carbon cycle are taken into account, equilibrium climate sensitivity becomes 4.5-4.7°C, but counting carbon feedbacks could add another 1°C to warming by 2100.
Over all, research from 2017 tells us that Paris Accord pledges would not produce 3°C warming, but 4°C and above.
“…human-induced climate change is an existential risk to human civilisation, yet much climate research understates climate risks and provides conservative projections.”
“… climate models simply omit emissions from the warming permafrost, but we know that is the wrong answer because that tacitly assumes that these emissions are zero and we know that’s not right…”
“If climate policymaking is to be soundly based, a re-framing of scientific research within an existential risk-management framework is now urgently required.” [bold mine in quotes]
As World Bank President Jim Yong Kim said, “There is no certainty that adaptation to a 4°C world is possible.”
Past warming of 4°C remade Earth from an ice age to a warm interglacial. Heating of the same magnitude surely will remake our planet just as drastically.