One scorching summer doesn't confirm that climate change is real any more than a white Christmas proves it's a hoax. What matters is the trend—a decades-long march toward hotter and wilder weather. But with more than 26,000 heat records broken in the last 12 months and pervasive drought turning nearly half of all U.S. counties into federal disaster areas, many data-driven climate skeptics are reassessing the issue.

Respected Republican leaders like Govs. John Kasich of Ohio and Chris Christie of New Jersey have spoken out about the reality of climate change. Rupert Murdoch's recent tweet—"Climate change very slow but real. So far all cures worse than disease."—may reflect an emerging conservative view. Even Exxon Mobil CEO Rex Tillerson, during public comments in June, conceded the reality of climate change while offering assurances that "there will be an engineering solution" and "we'll adapt."

If both sides can now begin to agree on some basic propositions, maybe we can restart the discussion. Here are two:

The first will be uncomfortable for skeptics, but it is unfortunately true: Dramatic alterations to the climate are here and likely to get worse—with profound damage to the economy—unless sustained action is taken. As the Economist recently editorialized about the melting Arctic: "It is a stunning illustration of global warming, the cause of the melt. It also contains grave warnings of its dangers. The world would be mad to ignore them."