PLEA Network

9 April 2018, Carbon Brief, Analysis: How much ‘carbon budget’ is left to limit global warming to 1.5C? In 2015, by signing up to the Paris Agreement on climate change, nearly every country pledged to keep global temperatures “well below” 2C above pre-industrial levels and to “pursue efforts to limit the temperature increase even further to 1.5C”. Limiting warming to 1.5C requires strictly limiting the total amount of carbon emissions between now and the end of the century. However, there is more than one way to calculate this allowable amount of additional emissions, known as the “carbon budget”. While calculations based on Earth System Models (ESMs, see below) used in the last Intergovernmental Panel on Climate Change (IPCC) report suggest that we have only a few years left at our current rate of emissions before we blow the 1.5C carbon budget, some recent studies have suggested that the remaining carbon budget is much larger. In this article, Carbon Brief assesses nine new carbon budget estimates released by different groups over the past two years. Most show larger allowable emissions than were featured in the last IPCC report. A number of studies suggest that carbon budgets estimates based on ESMs may be on the low side as a result of limitations with how some models represent the carbon cycle. However, there is still a wide range of variation in these new carbon budgets, arising from differences in approaches, timeframes, estimates of warming to-date and other factors. Recent studies suggest the remaining carbon budget to limit warming to “well below” 1.5C might have already been exceeded by emissions to-date, or might be as large as 15 more years of emissions at our current rate. Read more here