Seite - 24 - in options, Band winter 2016/2017

asia 24 options + winter 2016/2017 www.iiasa.ac.at regional focus A tale of two cities: Beijing  before and after 2000 Around the year 2000 Beijing’s urban and industrial sprawl tipped the city’s carbon sequestration balance from positive to negative. This tale of two cities—pre‑ and post‑2000 Beijing—is illustrated in work by IIASA researcher Brian Fath, along with Ursula Scharler, Linlin Xia, and Yan  Zhang. Between 1992 and 2008 a fifth of cultivated and more than a quarter of forested land in the Beijing basin was built upon. This  carbon‑sink land lost out to the demands of industry, transport, and housing. The result is that now only 2.4% of the city’s carbon emissions are being offset within its boundaries. “The expansion of transportation led to the expansion of the urban area,” says Linlin Xia referring to rapid development between 1995 and 2000. “This unbalanced the carbon metabolism because of limitations on land available for development.” The discovery that green areas need protection and that carbon emissions require control came “late” say the researchers. However, they point to the possibility of recovery with Beijing now protecting key ecological zones. “It’s a hard and long‑term task,” says Xia, adding that it’s much better to have a good plan for sustainable city development. The paper, says Fath, “provides an objective basis for adjusting Beijing’s land use to improve its carbon metabolism and reduce greenhouse gas emissions.” KS Further info Xia  L, Fath  BD, Scharler  UM, Zhang  Y  (2016). Spatial variation in  the  ecological relationships among the components of Beijing’s carbon metabolic system. Science of the Total Environment 544:103–113 [pure.iiasa.ac.at/11711]. Brian Fath fath@iiasa.ac.at Beijing’s bad air boom is partly homemade Images of Beijing cloaked in choking pollution, its citizens breathing through masks, are now iconic. On the city’s red alert days this extreme pollution confines people to their homes and brings industry to a halt. While Beijing authorities are shutting down coal‑fired power stations and cleaning up industry, work  by IIASA researchers Jun Liu and Zbigniew Klimont shows  that  dramatic improvements in air quality could also be achieved in the living rooms and kitchens of the city’s residents. “Coal is the primary fuel for heating in winter while biomass and coal are the primary fuels for cooking,” says  Liu. She points out that many of the heating and cooking devices have no end‑of‑pipe emission controls. As a result, these household emissions remain largely unrecognized as a source of ambient air pollution. At the same time reduction in pollution from power stations means the residential sector’s share of total emissions is increasing. What will help Beijing’s citizens breathe freely? More efficient stoves in the short‑term say the researchers, but cleaner fuel and eliminating solid fuel should be the long‑term goal. Another powerful incentive to clean up Beijing’s air is climate change mitigation. “Clean‑burning stoves improve air quality but do not reduce greenhouse gas emissions by  much,” says  Liu. To hit both targets—clean air and climate mitigation—the researchers recommend investment in renewable energies such as solar and biogas. KS Further info Liu  J, Mauzerall  DL, Chen  Q, Zhang  Q, et  al.  (2016). Air  pollutant emissions from Chinese households: A major and underappreciated ambient pollution source. PNAS  113(28):7756–7761 [pure.iiasa.ac.at/13421]. Jun Liu liujun@iiasa.ac.at § Zbigniew  Klimont klimont@iiasa.ac.at