The Debate over the United Nations’ Energy Emissions Projections

https://eos.org/articles/the-debate-over-the-united-nations-energy-emissions-projections

Source:  By Kate Wheeling, Eos/AGU. 

Excerpt: A new study finds the economic factor driving the divergence between emissions trajectories in climate assessments and reality. ...There is no question that climate change is reshaping Planet Earth and that things are getting ugly as global warming progresses. The debate now centers on just how bad things will get. But there are still major uncertainties when it comes to modeling future climate. Chief among them: How much more carbon dioxide will humans emit, and how sensitive is the climate system to all those emissions anyway?...To account for those uncertainties, the United Nations Intergovernmental Panel on Climate Change (IPCC) created several baseline scenarios, known as Representative Concentration Pathways (RCPs), to describe just how much warming might result from a range of carbon emissions. ...The most extreme model, RCP 8.5—sometimes called the business-as-usual scenario—describes rampant burning of fossil fuels, a global average temperature increase of nearly 5°C, and mean sea levels roughly a meter higher than they are today. But climate and energy experts disagree over how likely it is that this high-emissions scenario will come to pass. A recent study published in Environmental Research Letters found that the emissions trajectories in climate assessments from the IPCC overshot actual energy emissions over the past 15 years. ...Economic growth and emissions have grown more or less in tandem since the Industrial Revolution began, and the high-emissions scenarios rely on continued economic growth. But many economists are now questioning whether the high growth rate of the past century can continue throughout the present one. “What if it’s just inevitable that growth is going to slow almost to a halt in this century in developed countries for a bunch of reasons that have very little to do with the environment?” Aging populations, debt, plateauing rates of educational attainment, urbanization, and women entering the workforce have all been shown to slow economic growth and could continue to do so in the coming years. ...not many people on the environmental side of climate discussions were paying attention to this economic debate, despite its clear implications for global warming models. ...For one thing, RCP 8.5 predicts that coal use will increase sixfold by the end of the century, although current data suggest that global coal use peaked in 2014….