My impression is a lot of the high-emissions scenarios being used lets you demonstrate that there is an impact easily, even if the actual date of that impact looks to be somewhat later than under the most likely emissions scenarios.
And yes, the economic models are particularly awful; DICE has a bunch of assumptions in it about economic impact not affecting sectors which operate indoors and about damage being in the form of a fraction of GDP for that sector. eg: if agriculture is 3% of the economy by value, and it goes to zero, the overall impact is a 3% cut to economic output, even though no food means no economy.
My impression is a lot of the high-emissions scenarios being used lets you demonstrate that there is an impact easily, even if the actual date of that impact looks to be somewhat later than under the most likely emissions scenarios.
And yes, the economic models are particularly awful; DICE has a bunch of assumptions in it about economic impact not affecting sectors which operate indoors and about damage being in the form of a fraction of GDP for that sector. eg: if agriculture is 3% of the economy by value, and it goes to zero, the overall impact is a 3% cut to economic output, even though no food means no economy.