In March, U.S. President Barack Obama and Canadian Prime Minister Justin Trudeau pledged to cut net greenhouse gas (GHG) emissions 80 percent by 2050, a historic agreement. This “deep decarbonization” of the global economy will require much more than basic measures in efficiency and renewable energy. It demands profound changes in how we interact with the entire global carbon cycle, from sky to sea to soil. Our modern effort at deep decarbonization can learn much from the planet’s original endeavor in this field, and from that episode’s central players. The lessons learned offer a vision and the tools to reverse much of the past century’s misdeeds.