By Chelsea Harvey, The Washington Post.

As people around the world gather to celebrate Earth Day, world leaders have convened New York this morning to sign a landmark agreementaimed at slashing greenhouse gas emissions and keeping global climate change in check. And as discussions intensify around the agreement’s likelihood of success, a growing number of experts are arguing that carbon pricing — a controversial economic method intended to cut down on emissions — may be the key.

On Thursday, a group of world leaders came forward with an ambitious new vision statement calling for the world to double the extent of global emissions covered under carbon pricing schemes by the year 2020 — and quadruple it within the next decade.