Study: our Paris carbon budget may be 40% smaller than thought | Dana Nuccitelli

How we define “pre-industrial” is important

In the Paris climate treaty, nearly every world country agreed to try and limit global warming to no more than 2°C above pre-industrial temperatures, and preferably closer to 1.5°C. But a new study published in Nature Climate Change notes that the agreement didn’t define when “pre-industrial” begins.

Our instrumental measurements of the Earth’s average surface temperature begin in the late-1800s, but the Industrial Revolution began in the mid-1700s. There’s also a theory that human agriculture has been influencing the global climate for thousands of years, but the mass burning of fossil fuels kicked the human influence into high gear.

Either the Paris targets have to be revised, or alternatively, we decide that the existing targets really were meant to describe only the warming since the late 19th century.

1) Above about 2°C we start to get into the realm where there’s a significant risk of major climate impacts, like widespread coral bleaching, declining food production, significant sea level rise, and up to 30% of global species at risk of extinction.

2) From a practical political standpoint, meeting the 2°C carbon budget is about the best we can do. Even that will require aggressive global action, with countries ratcheting down their carbon pollution targets.