Phase 2 MDHD Fuel Efficiency Standards for Medium, Heavy Duty Engines and Vehicles: Draft Environmental Impact

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We applaud the NHTSA for doing what most other federal agencies are not wont to do—that is, make a direct determination of the impact that this proposed regulation will have on the course of future climate change. As a result of your analysis, you conclude (pg. S-24):

The magnitude of the changes in climate effects that would be produced by the most stringent action alternative (Alternative 5) is roughly 1.2 ppm less CO2, a few thousandths of a degree difference in temperature increase, a small percentage change in the rate of precipitation increase, and about 1 millimeter (0.03 inch) of sea-level rise.

Further, you go on to explain (page 5-75, footnote 37) that:

[T]he projected reductions in global climate effects for each of the alternatives are too small to incorporate into a regional/local‐scale analysis, which would likely introduce uncertainties at the same magnitude or more than the projected change itself (i.e., the projected change would be within the noise of the model)