We need better information on the impact of climate change

livemint.com:

It isn’t hard to understand that global warming is already changing how we live. In India’s capital, New Delhi, this summer has been so hot—above 40° Celsius even at night—that people are gasping, tap water is scalding and the walls of their homes emit heat like radiators. The Saudi Arabian authorities said that 1,300 pilgrims have already died on this year’s Hajj.

Players at the European soccer championships are collapsing due to exhaustion. And yet economists—clearly able to keep cool heads when everybody else is losing theirs—are in the middle of a fresh debate about the real costs of climate change. A new working paper from two academics at Harvard and Northwestern, published by the National Bureau of Economic Research, argues that the macroeconomic damage from climate change might be as much as six times higher than previously estimated.

Their model predicts that a single degree increase “in global mean temperatures leads to a gradual decline in world GDP that peaks at 12% after six years and does not fully mean-revert even 10 years after the shock." They point out that this makes unilateral climate action worth it for countries like the US; that argument must surely also hold countries that are poorer but far more exposed to climate change, such as India. The paper has set off a storm of furious criticism, and not just from economists. The climate scientist John Kennedy argues that its methodology may be flawed.

He isn’t sure, for example, that we can easily extrapolate from the historical record of 0.3-degree shocks to global temperature to the larger, one-degree changes associated with climate change. It’s clear that global warming is already having a malign effect on human health and livelihoods. We just need