Ting Wei^a, Shili Yang^a, John C. Moore^a,b,c, Peijun Shi^a, Xuefeng Cui^a, Qingyun Duan^a, Bing Xu^a,d, Yongjiu Dai^a, Wenping Yuan^a, Xin Wei^a, Zhipeng Yang^a, Tijian Wen^a, Fei Teng^e, Yun Gao^f, Jieming Chou^a, Xiaodong Yan^a, Zhigang Wei^a, Yan Guo^a, Yundi Jiang^g, Xuejie Gao^g, Kaicun Wang^a, Xiaogu Zheng^a, Fumin Ren^g, Shihua Lv^h, Yongqiang Yuⁱ, Bin Liu^e, Yong Luo^j, Weijing Li^k, Duoying Ji^a, Jinming Feng^a, Qizhong Wu^a, Huaqiong Cheng^a, Jiankun He^e, Congbin Fuⁱ, Duzheng Yeⁱ, Guanhua Xu^a, Wenjie Dong^a

^a State Key Laboratory of Earth Surface Processes and Resource Ecology, College of Global Change and Earth System Science, Beijing Normal University, Beijing 100875/Zhuhai 519087, China;

^b Arctic Centre, University of Lapland, PL122, 96100 Rovaniemi, Finland;

^c Department of Earth Sciences, Uppsala University, Villavägen 16, Uppsala SE-75236, Sweden;

^d Department of Environmental Science and Engineering, Tsinghua University, Beijing 100084, China;

^e Energy, Environment, and Economy (3E) Research Institute, Tsinghua University, Beijing 100084, China;

^f Climate Change Division, Department of Science and Technology, China Meteorological Administration, Beijing 100081, China;

^g National Climate Center, China Meteorological Administration, Beijing 100081, China;

^h Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China;

ⁱ Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China;

^j Center for Earth System Science, Tsinghua University, Beijing 100084, China;

^k Laboratory for Climate Studies, China Meteorological Administration, Beijing 100081, China.

Abstract: At the United Nations Framework Convention on Climate Change Conference in Cancun, in November 2010, the Heads of State reached an agreement on the aim of limiting the global temperature rise to 2 °C relative to preindustrial levels. They recognized that long-term future warming is primarily constrained by cumulative anthropogenic greenhouse gas emissions, that deep cuts in global emissions are required, and that action based on equity must be taken to meet this objective. However, negotiations on emission reduction among countries are increasingly fraught with difficulty, partly because of arguments about the responsibility for the ongoing temperature rise. Simulations with two earth-system models (NCAR/CESM and BNU-ESM) demonstrate that developed countries had contributed about 60–80%, developing countries about 20–40%, to the global temperature rise, upper ocean warming, and sea-ice reduction by 2005. Enacting pledges made at Cancun with continuation to 2100 leads to a reduction in global temperature rise relative to business as usual with a 1/3–2/3 (CESM 33–67%, BNU-ESM 35–65%) contribution from developed and developing countries, respectively. To prevent a temperature rise by 2 °C or more in 2100, it is necessary to fill the gap with more ambitious mitigation efforts.

Keywords: climate modeling; Coupled Model Intercomparison Project phase 5; Cancun pledge; climate ethics; geoengineering.