A letter in Nature says climate change is going to cause economic damage, and meeting the UN’s emissions targets would reduce that damage. Here’s the abstract, and the article itself is open access.

 International climate change agreements typically specify global warming thresholds as policy targets1, but the relative economic benefits of achieving these temperature targets remain poorly understood2,3. Uncertainties include the spatial pattern of temperature change, how global and regional economic output will respond to these changes in temperature, and the willingness of societies to trade present for future consumption. Here we combine historical evidence4 with national-level climate5 and socioeconomic6 projections to quantify the economic damages associated with the United Nations (UN) targets of 1.5 °C and 2 °C global warming, and those associated with current UN national-level mitigation commitments (which together approach 3 °C warming7). We find that by the end of this century, there is a more than 75% chance that limiting warming to 1.5 °C would reduce economic damages relative to 2 °C, and a more than 60% chance that the accumulated global benefits will exceed US$20 trillion under a 3% discount rate (2010 US dollars). We also estimate that 71% of countries—representing 90% of the global population—have a more than 75% chance of experiencing reduced economic damages at 1.5 °C, with poorer countries benefiting most. Our results could understate the benefits of limiting warming to 1.5 °C if unprecedented extreme outcomes, such as large-scale sea level rise8, occur for warming of 2 °C but not for warming of 1.5 °C. Inclusion of other unquantified sources of uncertainty, such as uncertainty in secular growth rates beyond that contained in existing socioeconomic scenarios, could also result in less precise impact estimates. We find considerably greater reductions in global economic output beyond 2 °C. Relative to a world that did not warm beyond 2000–2010 levels, we project 15%–25% reductions in per capita output by 2100 for the 2.5–3 °C of global warming implied by current national commitments7, and reductions of more than 30% for 4 °C warming. Our results therefore suggest that achieving the 1.5 °C target is likely to reduce aggregate damages and lessen global inequality, and that failing to meet the 2 °C target is likely to increase economic damages substantially.

My head gets just a little twisted around thinking of reduced damages. This means the economy, and presumably our grandchildren’s quality of life, will be worse than it could have been if we started making an effort and investment now. But this doesn’t tell us if they will be absolutely better or worse off in a “future baseline” scenario compared to now, just that they will be worse off relative to that future baseline if we don’t take action than if we do. I think the various (very eye catching) graphs in this paper probably contain the answers to these questions, but I didn’t get it after an admittedly short few minutes staring at them, and I admit I didn’t read every word in the paper.

The other thing here is that we are taking a given climate scenario (1.5 or 3 degrees C warming for example), and talking about the benefits of those two future scenarios against each other. What I don’t see is the cost to the current generation if we choose to make this sacrifice, or even if it is a sacrifice at all. What investment would we have to make to achieve 1.5 vs. 3 degrees, and are there alternative investments we could make that could have a bigger payoff. I am not arguing against climate action, I am just questioning how this paper is communicating about costs and benefits in the present and in the future.