Estimating our Commitment to Global Warming

Transitioning from a fossil fuel-based economy to one based on renewable energy is impeded by widespread existing energy infrastructure: not only primary energy infrastructure such as coal<!–[if supportFields]> XE “coal” <![endif]–><!–[if supportFields]><![endif]–>-fired power plants, but also transportation infrastructure such as motor vehicles or airplanes and residential infrastructure such as natural gas-burning furnaces or stoves. Unless this infrastructure is prematurely decommissioned or widely retrofitted with expensive carbon capture and storage<!–[if supportFields]> XE “carbon capture and storage (CCS)” <![endif]–><!–[if supportFields]><![endif]–> technology, this “infrastructural inertia” represents committed CO2 emissions as we move into the future. Davis et al. (2010) calculated the cumulative future emissions of existing energy infrastructure and found that if we completely discontinued the production of net CO2-emitting infrastructure, existing infrastructure alone would contribute 496 gigatonnes of CO2 to the atmosphere between 2010 and 2060, increasing mean global temperatures by 1.3 °C. Noting the difference between this quantity and estimated future warming, the authors conclude that the sources of most emissions are yet to be built. However, they believe that extraordinary efforts are required to prevent the continued expansion of CO2-emitting infrastructure. —Lucinda Block

Davis, S. J., Caldeira, K., Matthews, D., 2010. Future CO2 emissions and climate change from existing energy infrastructure. Science 329, 1330–1333.

          Steven J. Davis and Ken Caldeira of the Carnegie Institution of Washington along with Damon Matthews of Concordia University in Montreal used datasets of worldwide CO2 emissions from directly emitting infrastructure such as power plants and motor vehicles as well as estimates of emissions produced by industry, households, businesses, and other forms of transport to predict cumulative global CO2 emissions through 2060. Historical data provided them with lifetimes and annual emissions of infrastructure. The authors estimated emissions from non-energy sources such as land use change or agriculture<!–[if supportFields]> XE “agriculture” <![endif]–><!–[if supportFields]><![endif]–> using the International Panel on Climate Change’s (IPCC<!–[if supportFields]> XE “Intergovernmental Panel on Climate Change (IPCC)” <![endif]–><!–[if supportFields]><![endif]–>) Special Report on Emissions Scenarios A2 scenario<!–[if supportFields]> XE “IPCC A2 scenario” <![endif]–><!–[if supportFields]><![endif]–>. They used an intermediate-complexity coupled climate-carbon model, the University of Victoria Earth System Climate Model, in order to calculate changes in atmospheric CO2 and temperature based on emissions.
          Davis et al. calculated a cumulative 496 gigatonnes (1 Gt=1012 kg) of global CO2 emissions between 2010 and 2060, with 282 and 701 Gt CO2 being the lower and upper bound estimates. Accounting for non-energy CO2 emissions, the total atmospheric CO2 in this scenario stabilizes below 430 parts per million (ppm), with an increase of global temperatures of 1.3 °C (1.1–1.4 °C above pre-industrial levels or 0.3–0.7 °C above current temperatures). The authors calculate emissions through 2060 (as opposed to through 2100, as with many other climate predictions) because by 2060 all energy-related sources of CO2 emissions are predicted to be no longer functional. Whereas they calculate a mean cumulative emissions of 496 Gt CO2 from existing energy infrastructure, scenarios considering the continued expansion of fossil fuel-based infrastructure through 2100 predict cumulative global emissions of 2986 to 7402 Gt CO2. In those scenarios, global temperatures increase by 2.4–4.6 °C above pre-industrial levels and atmospheric CO2 stabilizes above 600 ppm. Internationally, a rise in temperature of 2 °C and an atmospheric CO2 level of 450 ppm are considered to be the benchmark past which geophysical, biological and socioeconomic systems are especially vulnerable. Thus, the authors note, as existing energy infrastructure does not surpass the benchmark, the infrastructure that represents the most threatening CO2 emissions has yet to be built.
          Existing energy infrastructure is concentrated in highly developed countries such as Western Europe<!–[if supportFields]> XE “Europe” <![endif]–><!–[if supportFields]><![endif]–>, the United States, and Japan and populous countries experiencing rapid development, particularly China<!–[if supportFields]> XE “China” <![endif]–><!–[if supportFields]><![endif]–>. China accounts for the greatest energy inertia, where almost one quarter of worldwide electrical generating capacity has been commissioned as coal<!–[if supportFields]> XE “coal” <![endif]–><!–[if supportFields]><![endif]–> plants since 2000. The young age of its existing infrastructure compared to that of the U.S., Japan, or Western Europe also contributes to China’s large emissions commitment, approximately 37% of the global total. However, emissions commitment per capita in China is comparable to Japan and Western Europe and far less than that of the U.S. (136 tons CO2 per person versus 241). Davis et al. emphasize the importance of historic emissions in already developed countries and consumption in those countries as a driving force of Chinese emissions. They also note that committed emissions per unit of GDP is much higher in developing countries than already developed ones, showing that infrastructural inertia of emissions is greatest where industrialization is occurring but incomplete.
           Davis et al. conclude that although their estimates of cumulative committed global emissions of CO2 do not push us past the threshold of 450 ppm CO2 and 2 °C of warming, avoiding great quantities of CO2 emissions from not yet built infrastructure will require a tremendous political effort and shift, partially because of the supporting infrastructure for CO2 emitting devices such as highways or factories that produce internal combustion engines. Though their findings do not have groundbreaking implications for climate change studies, the study provides a useful benchmark of what future emissions are inevitable without high-cost retrofitting or halting of industry and what future emissions can more easily be reduced. 

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