The largest source of uncertainty in global climate models isn’t clouds or ocean circulation but humans. And one of the largest sources of human uncertainty at present is China, whose spectacular rise has left the world awestruck and fearful of greenhouse gas emissions yet to come. Now a group of researchers from Lawrence Berkeley National Laboratory in California suggests that there are limits to Chinese growth.
The idea is quite simple: Even in a nation of 1.4 billion people, demand for air conditioners, roads and skyscrapers must level off at some point. When that happens energy consumption is likely to slow as well, and with it greenhouse gas emissions. The researchers, led by Mark Levine, refer to this as “saturation” in the report.
The end result, translated into greenhouse gas emissions, is illustrated in the graph above. Plotted against projections from the Chinese government’s Energy Research Institute, the Berkeley Lab’s projections show emissions peaking between 2025 and 2035 and then beginning to decline. This is true even in the baseline “Continued Improvement Scenario” (dark blue), indicating that the current rapid growth in emissions is likely to level off and ultimately bend below an optimistic energy-efficient scenario. In the “Accelerated Improvement Schedule” (red), China takes more aggressive action to boost energy efficiency and emissions peak around 2025.
The analysis suggests that the Chinese government’s goal of reducing carbon intensity (a measure of carbon emissions to economic output) by at least 40 percent by 2020 is possible. But neither of the main scenarios assumes carbon capture and sequestration (included for perspective in a third scenario, light blue) nor major new shifts in climate policy. Even in the aggressive scenario, emissions are well above an International Energy Agency scenario for limiting atmospheric carbon dioxide concentrations to 450 parts per million, an oft-stated goal on the international scene. The researchers do, however, assume a significant deployment of nuclear energy and electric vehicles. Coal’s share of the overall energy drops from 74% in 2005 to between 30 and 47 percent in 2050.
The notion that exponential growth cannot continue indefinitely isn’t exactly surprising. China is already bumping up against limits to the production and transport of coal – its primary domestic resource – and will increasingly need to rely on imports from abroad to meet rising energy demand. This is one reason why the country is pursuing energy efficiency and advanced coal technologies. And as with oil, some feel there may be broader constraints on coal in the coming decades as well.
But the Berkeley Lab’s report hastens the time-line regarding China’s energy and economic transformation. This is good news, given the lack of progress in the international climate talks. But as climate modellers know all too well, it’s awfully difficult to reduce the uncertainty in human systems.