Projections of mid-century summer air-quality for North America: effects of changes in climate and precursor emissions
Projections of mid-century summer air-quality for North America: effects of changes in climate and precursor emissions
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DOI：
10.5194/acp-12-5367-2012
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发表时间：
2012-01-01
影响因子：
6.3
通讯作者：
Plummer, D. A.
中科院分区：
文献类型：
--
作者：
Kelly, J.;Makar, P. A.;Plummer, D. A.
使用由区域气候模式驱动的区域空气质量模式对北美目前和未来的空气质量进行了十年模拟，而区域气候模式又由环流模式驱动。模拟了三个独立的夏季情景：一个代表1997 - 2006年的情景，以及两个代表2041 - 2050年的SRES A2气候情景。第一个未来气候情景利用2002年的人为前体排放，第二个未来气候情景利用IPCC代表性浓度途径6 （RCP 6）情景得出的排放比例因子，根据现有的2020年预估估算2050年的排放量。使用北美监测站的臭氧和PM2.5的十年平均值来评估该模式当前的化学气候学。研究发现，该模式对臭氧的预测结果与实际天气预报模式的预测结果相似。PM2.5的预测有较大的负偏差，可能是由于缺少雨水蒸发，以及在这里使用的气候模型版本中，地表温度场的次区域负偏差。两个未来气候模拟和当前气候模拟之间的差异被用来预测在未来变暖的气候中可能出现的空气质量变化，如果人为前体排放保持在当前水平不变，而不是采用rcp6排放控制。在模拟中比较了浓度、人类健康和生态系统损害的指标。在未来气候和当前人为排放的情况下，空气质量会比当前情况更差——也就是说，在所有其他因素相似的情况下，仅气候变化的影响将导致空气质量恶化。这些影响在空间上是不均匀的，变化的幅度和标志随区域而变化。2050年未来气候和rcp6排放情景导致空气质量改善，主要污染物浓度下降，与空气污染相关的急性人类死亡率下降，生态系统中的硫和臭氧沉积减少。研究发现，rcp6减排的积极结果比气候变化本身的负面结果要大得多。然而，与目前的氨排放水平相比，RCP 6情景预计会增加氨排放，从而导致氮沉积增加。这项研究的结果提出了这样一种可能性，即同时减少温室气体和空气污染前体可能进一步降低空气污染水平，同时还能立即减少空气污染对人类和生态系统健康的影响。因此，建议采用进一步的方案来调查这种可能性。
Ten year simulations of North American current and future air-quality were carried out using a regional air-quality model driven by a regional climate model, in turn driven by a general circulation model. Three separate summer scenarios were performed: a scenario representing the years 1997 to 2006, and two SRES A2 climate scenarios for the years 2041 to 2050. The first future climate scenario makes use of 2002 anthropogenic precursor emissions, and the second applied emissions scaling factors derived from the IPCC Representative Concentration Pathway 6 (RCP 6) scenario to estimate emissions for 2050 from existing 2020 projections. Ten-year averages of ozone and PM2.5 at North American monitoring network stations were used to evaluate the model's current chemical climatology. The model was found to have a similar performance for ozone as when driven by an operational weather forecast model. The PM2.5 predictions had larger negative biases, likely resulting from the absence of rainwater evaporation, and from sub-regional negative biases in the surface temperature fields, in the version of the climate model used here.The differences between the two future climate simulations and the current climate simulation were used to predict the changes to air-quality that might be expected in a future warmer climate, if anthropogenic precursor emissions remain constant at their current levels, versus if the RCP 6 emissions controls were adopted. Metrics of concentration, human health, and ecosystem damage were compared for the simulations. The scenario with future climate and current anthropogenic emissions resulted in worse air-quality than for current conditions - that is, the effect of climate-change alone, all other factors being similar, would be a worsening of air-quality. These effects are spatially inhomogeneous, with the magnitude and sign of the changes varying with region. The scenario with future climate and RCP 6 emissions for 2050 resulted in an improved air-quality, with decreases in key pollutant concentrations, in acute human mortality associated with air-pollution, and in sulphur and ozone deposition to the ecosystem. The positive outcomes of the RCP 6 emissions reductions were found to be of greater magnitude than the negative outcomes of climate change alone. The RCP 6 scenario however resulted in an increase in the deposition of nitrogen, as a result of increased ammonia emissions expected in that scenario, compared to current ammonia emissions levels.The results of the study raise the possibility that simultaneous reductions of greenhouse gases and air pollution precursors may further reduce air pollution levels, with the added benefits of an immediate reduction in the impacts of air pollution on human and ecosystem health. Further scenarios to investigate this possibility are therefore recommended.