THE EUROPEAN UNION’S parliamentary elections, which ended Sunday, were expected to herald the rise of the populist right across a continent roiled by Brexit and other nationalist movements. True to expectations, blocs that included British and French right-wing ideologues, such as Britain’s Nigel Farage, gained seats. But so did a bloc of liberals more aligned with the traditional European mainstream — and, most surprisingly, so did the Greens, who will be the fourth-largest faction in the European Parliament, and in a better position than they ever have been to influence policy continentwide.

The Greens’ success can represent a positive turning point in European politics, if the new political energy to confront climate change is channeled into effective reforms rather than the overhyped preoccupations that sometimes animate European environmental activism.

Europe sorely needs smart reform. The continent’s cap-and-trade program, the E.U. Emissions Trading System (ETS), was supposed to be the world’s marquee climate policy, showing that putting an economically efficient price on greenhouse-gas emissions could transition a huge, diverse economy to clean energy steadily and without wasting resources on government-sponsored boondoggles. Instead, European officials designed a weak system. That spurred demand for more aggressive action in European capitals, which has translated into inadvisable national-level initiatives. The most spectacular example is Germany’s Energiewende, an expensive, intrusive program of renewable-energy subsidies, paired with a rejection of carbon-free nuclear power. That has failed to curb German coal-burning to the degree that smarter policy would have.

It is good, then, that the platform of Europe’s newly empowered Greens includes reforming the ETS, which should be a top priority of the next Parliament. If European officials get their carbon-pricing mechanism working adequately, it would enable the Greens to reasonably demand more ambitious emissions targets for the continent; they seek a 60 percent cut from 1990 levels by 2030. In a world bereft of U.S. leadership on such a crucial issue, the E.U. should also fill the gap as best it can. The Greens suggest more closely tying European diplomacy to climate matters, which could keep pressure on world governments to honor their climate commitments — and on the laggard Trump administration to develop a more productive response than denial of the problem.

Where the Greens could go wrong is in emphasizing counterproductive responses to real — or perceived — environmental threats. The European left’s obsession with genetically modified crops puts hysteria above scientific fact. Its skepticism of nuclear power ignores the fact that the proven, emissions-free technology would likely play a substantial role in any sensible transition off coal, oil and gas.

As the incoming European Parliament’s factions sort themselves out in the coming days, the Greens should prioritize demands that would do the most good for the climate — and de-emphasize the ones that would help least to protect the planet.

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