With China and the U.S. coming to an agreement in 2014 on
limiting their respective greenhouse-gas emissions, the Peru talks suddenly
gained new momentum toward a deal on a global scale. To be sure, even the
U.S.-China agreement would not kick in for years, if not decades, and a global
agreement would not even take effect until 2020 at the earliest. This drawback
may pale in comparison to one of nature’s own contributions to greenhouse-gas
emissions, and nature itself cannot agree to voluntarily restrict its own
output. Accordingly, we should not assume that a global agreement will save the
day, rendering the planet still inhabitable for humans in the next century.
The full essay is at "Beyond the Reach of Any Greenhouse-Gas Agreement."