Yet this claim is extremely misleading, as I’ll demonstrate in this post. The projection of a 10-percent hit to GDP is an extremely unlikely (less than a 5-percent chance) event even if we assume we are in the most pessimistic of emission scenarios, while the scenario itself rests upon an assumption that progress on renewables and other technologies occurs much more slowly over the next century than it has already occurred historically. This means that anybody citing the NCA projections isn’t allowed to also tout imminent breakthroughs in wind and solar, because such optimism renders the NCA projections invalid.
Even more astonishing, the NCA gives projections of the “cost of inaction” on climate change, but does not give any estimate of the costs of action on climate change. (It’s a bit like a mechanic warning that you need a new part to avoid engine failure down the road, but refusing to tell you how much the part will cost.) Yet if we follow the citations to other work (such as from the United Nations) that the NCA cites, we see that even using the NCA’s own diagram, it is not clear that aggressive steps to fight climate change would be worth the cost.