A team of climate scientists reports that humankind is headed down the worst-case scenario, despite the progress made against our emissions.
Last Monday, August 3, Christopher Schwalm, Spencer Glendon, and Philip Duffy of the Woods Hole Research Center published their findings in the Proceedings of the National Academy of Sciences. The basis of their study is the total cumulative carbon dioxide (CO₂), which is reportedly in line with the RCP 8.5 estimates.
Representative Concentration Pathway (RCP)
Back in 2014, the Intergovernmental Panel on Climate Change (IPCC) submitted a recommendation of possible outcomes based on the global trend with respect to climate change. The special body under the United Nations has devised the Representative Concentration Pathway (RCP) system. An article details the different scenarios containing greenhouse emission conditions, with specific designs to adapt to any projected changes in the world's mean surface temperature and ocean levels.
There are four main RCP scenarios--2.6, 4.5, 6.0, and 8.5--tagged after the values for "radiative forcing." Also known as climate forcing, radiative forcing is the difference between the sunlight absorbed, and the sunlight reflected into space. The RCP values are taken since 2005 and are projected well until 2100. Each of the RCP scenarios has varying assumptions regarding population, economy, emissions, and fossil fuel use.
The high emission scenario, RCP 8.5, is referred to as a "business as usual" scenario. Several previous studies on climate change have focused on the possibilities of the worst-case scenario happening.
For fifteen years now, Schwalm's team identified that the greenhouse gas emission levels are close to the RCP 8.5 projections. "It is a very good characterization of where we are going to be if current trends are simply extrapolated out forward in time ... And it tracks historical emissions within 1 percent," Schwalm said.
RCP 8.5 - A Conservative Estimate?
By combing through historical greenhouse emission records, energy emission forecast data from the International Energy Agency, and climate change policy commitments by countries around the world, the researchers have created a possible projection where humanity might be by 2030 and then by 2050--and it is somewhere RCP 4.5 and 8.5.
Furthermore, the researchers noted that the RCP fails to include some environmental factors in determining its scenarios. Complex natural feedback loops like permafrost thaw, soil carbon dynamics, presence of pests, and forest fire frequency and severity actually worsen the projections outlined in the study, pushing the actual score closer to an RCP 8.5 scenario.
However, not all studies regarding climate change concur with the latest findings from Schwalm's team. Back in January, a study led by Zeke Hausfather, director of climate and energy at the Breakthrough Institute, advocated that "more realistic baselines make for better policy."
Hausfather argued that RCP 8.5 had been used by some experts, policymakers, and the media as something else entirely: as a likely 'business as usual' outcome. The worst-case scenario has been blown out of proportion as the most probable. Furthermore, RCP 8.5 apparently underestimates emissions from changing land use and, on the other hand, overestimates energy emissions.