Tian Hanqin, Chen Guangsheng, Lu Chaoqun, Xu Xiaofeng, Hayes Daniel J, Ren Wei, Pan Shufen, Huntzinger Deborah N, Wofsy Steven C
International Center for Climate and Global Change Research and School of Forestry and Wildlife Sciences, Auburn University, Auburn, AL 36849 USA.
Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA.
Clim Change. 2015;129(3-4):413-426. doi: 10.1007/s10584-014-1072-9. Epub 2014 Mar 14.
The terrestrial ecosystems of North America have been identified as a sink of atmospheric CO though there is no consensus on the magnitude. However, the emissions of non-CO greenhouse gases (CH and NO) may offset or even overturn the climate cooling effect induced by the CO sink. Using a coupled biogeochemical model, in this study, we have estimated the combined global warming potentials (GWP) of CO, CH and NO fluxes in North American terrestrial ecosystems and quantified the relative contributions of environmental factors to the GWP changes during 1979-2010. The uncertainty range for contemporary global warming potential has been quantified by synthesizing the existing estimates from inventory, forward modeling, and inverse modeling approaches. Our "best estimate" of net GWP for CO, CH and NO fluxes was -0.50 ± 0.27 Pg CO eq/year (1 Pg = 10 g) in North American terrestrial ecosystems during 2001-2010. The emissions of CH and NO from terrestrial ecosystems had offset about two thirds (73 %±14 %) of the land CO sink in the North American continent, showing large differences across the three countries, with offset ratios of 57 % ± 8 % in US, 83 % ± 17 % in Canada and 329 % ± 119 % in Mexico. Climate change and elevated tropospheric ozone concentration have contributed the most to GWP increase, while elevated atmospheric CO concentration have contributed the most to GWP reduction. Extreme drought events over certain periods could result in a positive GWP. By integrating the existing estimates, we have found a wide range of uncertainty for the combined GWP. From both climate change science and policy perspectives, it is necessary to integrate ground and satellite observations with models for a more accurate accounting of these three greenhouse gases in North America.
北美陆地生态系统已被确定为大气中二氧化碳的汇，尽管在其规模上尚未达成共识。然而，非二氧化碳温室气体（甲烷和氧化亚氮）的排放可能抵消甚至颠覆由二氧化碳汇所产生的气候冷却效应。在本研究中，我们使用一个耦合生物地球化学模型，估算了北美陆地生态系统中二氧化碳、甲烷和氧化亚氮通量的综合全球变暖潜能值（GWP），并量化了1979 - 2010年期间环境因素对GWP变化的相对贡献。通过综合清单、正向建模和反向建模方法的现有估计值，对当代全球变暖潜能值的不确定性范围进行了量化。2001 - 2010年期间，北美陆地生态系统中二氧化碳、甲烷和氧化亚氮通量的净GWP的“最佳估计值”为-0.50±0.27Pg二氧化碳当量/年（1Pg = 10¹⁵克）。陆地生态系统中甲烷和氧化亚氮的排放抵消了北美大陆约三分之二（73%±14%）的陆地二氧化碳汇，三国之间差异很大，美国的抵消率为57%±8%，加拿大为83%±17%，墨西哥为329%±119%。气候变化和对流层臭氧浓度升高对GWP增加的贡献最大，而大气二氧化碳浓度升高对GWP降低的贡献最大。特定时期的极端干旱事件可能导致正的GWP。通过综合现有估计值，我们发现综合GWP存在很大的不确定性范围。从气候变化科学和政策角度来看，有必要将地面和卫星观测与模型相结合，以便更准确地核算北美这三种温室气体。
