Historical emissions from the world’s largest producers of oil, gas, coal, and cement could continue to contribute to global warming for centuries, even in a future scenario of low emissions. The conclusion results from an analysis that projected the evolution of the climate up to the year 2500.
American researchers analyzed the effects of accumulated emissions from 178 of the world’s largest producers of fossil fuels and cement and modeled different scenarios for the coming centuries. The results suggest that the weight of historical emissions on future warming could become particularly significant as new emissions are reduced.
At first glance, this result may seem counterintuitive. However, in a scenario in which humanity ceases to add large quantities of greenhouse gases to the atmosphere, the warming associated with past pollution represents an ever larger share of the total warming that remains.
In a scenario of high emissions, future emissions continue to add large quantities of greenhouse gases to the atmosphere. In that context, the relative contribution of historical emissions to total warming is smaller, although global warming is, overall, higher.
The study thus sought to evaluate not only the evolution of emissions in the near and medium term, but also the persistence of their effects over several centuries. The projections extend through 2500 and show that accumulated emissions in the past can continue to influence the climate system long after they have been released.
The researchers emphasize that the relevance of historical emissions increases precisely as the pace of new emissions slows. In other words, in a future of low emissions, the share of warming attributable to accumulated pollution from the past becomes relatively more important.
The results highlight the long persistence of the effects of greenhouse gas emissions and add a temporal dimension to discussions about the transition to a low-emission economy.
The study analyzes the climate contribution of historical emissions and does not, in itself, determine specific legal or financial responsibilities of the companies analyzed.
