By any measure, our carbon budget is small and our time is short. According to the Intergovernmental Panel on Climate Change’s report on the physical science of climate change, we can “spend” only 400 more gigatons of greenhouse gas emissions into the atmosphere. That’s the number that gives us a fighting chance (50 percent, according to the IPCC) to limit global warming to 1.5 degrees Celsius over pre-industrial levels, the red line between a habitable Earth and a scenario for disaster. At the world’s current rate of emissions, we will exhaust our entire carbon budget before 2030. Hence the urgent need for drastic emissions cuts.
Setting the budget even lower gives us a better chance of averting runaway climate disaster. If we emit less than 300 gigatons by 2050, the probability of keeping our planet inhabitable rises to 83 percent.
Under the plan put forward by Speed & Scale, we can stay within our carbon budget by slashing global emissions by half by 2030 and reaching net zero—where we’re no longer adding carbon to the atmosphere—by 2050. At that point, we can continue to stay within our budget by keeping annual emissions to 3 gigatons in the power sector, 3 more gigatons in industry, 2 gigatons in transportation, and 2 gigatons in agriculture. That adds up to the total of 10 gigatons of stubborn carbon earmarked for carbon removal by either nature or engineered solutions.