BONN, GERMANY—Agreeing that public perception of how they were handling the climate crisis had never been more important, world leaders signed a major new accord Tuesday in which they pledged to cut carbon emissions to the extent that they could realistically back out of a few years from now. “This agreement sets ambitious goals for reducing our carbon footprint, but not so ambitious that we can’t come up with a plausible-seeming excuse when we inevitably fail to meet its benchmarks,” read a joint statement issued through the U.N. Framework Convention on Climate Change, in which top officials from the United States, China, Germany, Canada, Russia, and France signaled their support for easily reversible measures to combat global warming. “The time for dramatic pronouncements that can be quickly walked back is now. We have vowed to transition away from fossil fuels and set a deadline far enough in the future that hopefully everyone will forget about it. But if necessary, we are fully committed to rationalizing our inaction in terms the United Nations finds palatable.” At press time, a new report issued by the U.N. had found that half of the parties had already succeeded in reneging on the agreement signed earlier that morning.