President Obama and President Xi Jinping last week at a news conference in Beijing. (Feng Li/Getty Images)

While environmentalists, Democrats and other supporters of last week’s U.S.-China climate deal rushed to outdo themselves with hyperbolic congratulations (“game-changer”, “historical”, “this century’s most significant agreement”), the other side can’t dump enough cold water: “terrible”, “changes nothing”, a “waste of time.” And in a way, the skeptics are absolutely right. This deal will definitely not solve the climate problem.

But the rest of their criticism makes no sense.

The first complaint about the deal is that it’s nothing new. On the U.S. side, this criticism requires a misreading of current U.S. policy. John Kemp, writing for Reuters, claims that the contours of U.S. emissions-cutting target are “essentially the same as those proposed in the Clean Power Plan published by the Environmental Protection Agency in June.” But the Clean Power Plan, as its name suggests, only targets carbon dioxide from power plants, which are less than a third of U.S. greenhouse gas emissions. The new commitment, in contrast, covers the entire U.S. economy.

Is the deal just “business as usual” for China, as many critics have claimed? Forecasters broadly agree that, given current policies, Chinese emissions are unlikely to peak before the 2030 target announced last week. Some analysts have, however, produced forecasts that assume new policies, surprising technological gains or stark Chinese economic weakness, and some of those do foresee Chinese emissions peaking by 2030. (No mainstream projections anticipate China getting 20 percent of its energy from zero-carbon sources by 2030 – the other goal announced last week.) It is these projections that skeptics are using as their baseline when they claim that the deal is nothing new. But you can’t dismiss novel policies as nothing new simply because some people predicted that they would be imposed.

Another criticism holds that the agreement won’t bind anyone to anything. It has no legal force and no penalties for non-compliance. It isn’t codified in a formal document and isn’t backed up by specific policy promises. That’s all true – but it doesn’t mean that the deal won’t influence future emissions. International agreements, even if informal, can exert important influence in domestic action. At the 2009 Copenhagen climate talks, the United States made a non-binding promise to cuts its emissions to 17 percent below 2005 levels by 2020. The U.S. government anticipated doing that through a cap-and-trade bill that was then in Congress.

Less than half a year later, cap-and-trade blew up. Yet the administration has continued to focus on the 17 percent goal, which has shaped policymaking at the White House and in interagency negotiations over efforts as diverse as power plant rules and refrigerant standards. The new promises might do something similar in China and the United States: They won’t guarantee a good outcome, but for policymakers who want to drive down emissions, they’re one more political tool with which to accomplish their goals.

The final criticism is that the deal isn’t ambitious enough to keep the world from warming more than two degrees, the threshold around which international climate diplomacy is currently organized. This is a true statement but is far too demanding as a standard for diplomatic agreements. The United States and China alone can’t put the world on a two-degree path – they are the two biggest emitters in the world but together account for less than half of global emissions. Nor can any deal with a meaningful time horizon point confidently to climate safety: the amount that Earth will warm will depend on emissions over the next 100  years, yet promises regarding emissions cuts even 50 years hence lack credibility.

It is also wrong to fix narrowly on the two-degree benchmark. It is a laudable goal, and one that is technically achievable, but by most honest reckonings, is politically implausible. And the difference between other amounts of warming – say between two degrees and three and four – could be dramatic. An agreement that cuts emissions is worthwhile even if it doesn’t deliver the two degree goal.

To be sure, none of this makes the deal the “gamechanger” that some people have heralded, or means that it will “save the world” as others have claimed. Critics and enthusiasts of climate diplomacy alike focus too much on super-high standards when assessing climate agreements. Supporters have wrongly obsessed with achieving a comprehensive global climate treaty, and their opponents have gloated when attempts to negotiate such an agreement have inevitably failed. (A corollary: Those who welcomed the U.S.-China announcement primarily as a sign that a big global treaty might be possible next year are missing its main point.) Just as Cold War arms control never eliminated the risk of nuclear war, even as it substantially reduced nuclear dangers, so climate diplomacy can help the world by reducing the risks of global warming, even as it never rids the planet of them. That’s the right standard by which to judge the big U.S.-China climate announcement – and, by that measure, the deal is a genuine success.