The fight over fuel economy rules is getting messy

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Legal wrangling among the federal government, the state of California, and four automakers who—oddly—are asking for more stringent regulations got even more knotty this month, when the Department of Justice reportedly launched an antitrust probe into companies that struck a deal with California climate regulators.

Now some members of Congress are urging an independent investigation of the investigation, amid suspicions that the probe is an attempt to punish the automakers—and California—for parting ways with federal policy on fuel economy.

The “what’ is confusing; the “why,” less so. If the average global temperature rises by 4°C by the end of the century, as it may be on track to do, scientists say a whole bunch of bad things would likely happen: higher sea levels, more extreme weather. In the US, transportation is responsible for 29% of greenhouse gas emissions, and nearly 60% of those come from light-duty vehicles like passenger cars.