All a bit surreal, because it really isn’t a physical threshold - just a diplomatic one, lower than 2ºC (too high to save some islands, deltas, food, ecosystems), and higher than 1ºC (already passed when they wanted a lower target). There was originally some paleoclimatic justification for 2ºC, but not with any precision, these round numbers depend on our definition of degrees as 1% of the range from freezing to boiling water.
Sure the physical climate system includes many tipping points, but their thresholds vary by region and sector and we don’t know them with precision. So when you try to integrate risk across projected impacts (result of which depends strongly on value judgements) you get a curve, on which nobody has shown that 1.5 marks a special nonlinearity.
Diplomatic thresholds do matter for our social system, but we should acknowledge these for what they are.
Otherwise it tempts the reaction - ok we failed, world’s going to end, let’s go have another [conference of the] party.
All a bit surreal, because it really isn’t a physical threshold - just a diplomatic one, lower than 2ºC (too high to save some islands, deltas, food, ecosystems), and higher than 1ºC (already passed when they wanted a lower target). There was originally some paleoclimatic justification for 2ºC, but not with any precision, these round numbers depend on our definition of degrees as 1% of the range from freezing to boiling water.
Sure the physical climate system includes many tipping points, but their thresholds vary by region and sector and we don’t know them with precision. So when you try to integrate risk across projected impacts (result of which depends strongly on value judgements) you get a curve, on which nobody has shown that 1.5 marks a special nonlinearity.
Diplomatic thresholds do matter for our social system, but we should acknowledge these for what they are.
Otherwise it tempts the reaction - ok we failed, world’s going to end, let’s go have another [conference of the] party.