A group of prominent scientists, policymakers, and corporate leaders released a statement Wednesday warning that if the world doesn’t set greenhouse gas emissions on a downward path by 2020, it could become impossible to contain climate change within safe limits.
The group, led by Christiana Figueres, who oversaw the United Nations negotiations that produced the Paris climate agreement, base their case on simple math. The world, they calculate, probably has a maximum of 600 billion remaining tons of carbon dioxide that can be emitted if we want a good chance of holding the rise in planetary temperatures within the Paris limit of 1.5 to 2 degrees Celsius (2.7 to 3.6 degrees Fahrenheit).
With 41 billion tons emitted every year from energy consumption and other sources, such as deforestation, there are only about 15 years before that budget is exhausted.
Emissions can’t suddenly go to zero after 15 years — the world economy would grind to a halt if they did. Therefore, they must be put on a downward path almost immediately.