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

August 31, 2015 • Public Comments 

By [Patrick J. Michaels](https://www.cato.org/people/patrick-michaels) and [Paul C. “Chip” Knappenberger](https://www.cato.org/people/chip-knappenberger) 

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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)

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

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##### About the Authors 

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##### [Patrick J. Michaels](/people/patrick-michaels)

Former Director, Center for the Study of Science 

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##### [Paul C. “Chip” Knappenberger](/people/chip-knappenberger)

Former Assistant Director, Center for the Study of Science 

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](https://twitter.com/PCKnappenberger) 

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