Quantifying immediate radiative forcing by black carbon and organic matter with the Specific Forcing Pulse
Quantifying immediate radiative forcing by black carbon and organic matter with the Specific Forcing Pulse
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DOI：
10.5194/acp-11-1505-2011
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发表时间：
2011-01-01
影响因子：
6.3
通讯作者：
Koch, D. M.
中科院分区：
文献类型：
--
作者：
Bond, T. C.;Zarzycki, C.;Koch, D. M.
短寿命气候强迫因子的气候效应不同于长寿命温室气体的气候效应，因为它们在排放后迅速发生，而且取决于排放区域。依赖全球平均数或长期整合的措施无法反映这些影响的独特时空性质。在这里，我们提出了一个简单的措施，具体的强迫脉冲（SFP），量化这些污染物的气候变暖或冷却，我们定义为“立即”主要发生在排放后的第一年内。SFP是指在地球-大气系统中，某一化学物质在一个接收区域中增加或减少的能量，与源区域中的排放量成正比。我们将SFP的应用限制在在大气中停留时间少于一年的物种上。政策讨论中使用的参数，如总强迫或全球变暖潜能值，很容易从SFP中得出。然而，SFP传达纯粹的物理信息，而不会招致政策的影响，选择一个时间范围的全球变暖potential. Use一个模型（社区大气模型，或CAM），我们计算SFP值的黑碳（BC）和有机物（OM）排放的23个源区域组合。大气层和冰冻圈影响的全球SFP按接收纬度划分。由于排放时间的原因，露天燃烧排放的可吸收性系数通常大于与能源有关的排放（矿物燃料和生物燃料）。不同区域与能源有关的排放量，全球可再生能源可再生能源对BC的影响约为45%。如果没有补偿效应，这种变化会更大。当排放气溶胶具有较大的冰冻圈强迫时，由于深层对流较少和大气寿命较短，其大气强迫往往较低，单一模式的结果不足以捕捉不确定性。我们开发了一个最好的估计和不确定性SFP结合强迫结果从12个额外的模式。我们概述了一个框架，结合大量的简单的模型与数量较少的增强模型，具有更大的复杂性。黑碳内部混合和区域变异的调整进行了讨论。具有更多深对流的发射区具有更大的模式多样性。我们对全球平均SFP的最佳估计是黑碳的直接大气强迫为+1.03 +/- 0.52 GJ g（-1），黑碳的直接和冰冻圈强迫为+1.15 +/- 0.53 GJ g（-1），有机物为-0.064（-0.02，-0.13）GJ g（-1）。这些值取决于发射的区域和时间。对于任何区域，对大气层顶直接强迫产生中性效应所需的最低OM：BC质量比为15：1。任何较低的比率都会导致正的直接强迫。然而，重要的过程，特别是倾向于冷却的云变化，没有包括在这里。全球平均SFP的能源相关排放可以转换为100年的GWP约740 +/- 370 BC没有雪强迫，和830 +/- 440与雪强迫。100-OM的年GWP为-46（-18，-92）。假设总排放率为7.4和45 Tg yr（-1），黑质和有机质对大气辐射影响的最佳估计值（无雪强迫）分别为+0.47 +/- 0.26 W m（-2）和-0.17（-0.07，-0.35）W m（-2）。假设人为排放率为6.3和32.6 Tg yr（-1），BC和OM的人为强迫分别为+0.40 +/- 0.18 W m（-2）和-0.13（-0.05，-0.25）W m（-2）。黑碳强迫仅比政府间气候变化专门委员会（IPCC）给出的值高出18%，尽管这里给出的值包括由于内部混合而增强的吸收。
Climatic effects of short-lived climate forcers (SLCFs) differ from those of long-lived greenhouse gases, because they occur rapidly after emission and because they depend upon the region of emission. The distinctive temporal and spatial nature of these impacts is not captured by measures that rely on global averages or long time integrations. Here, we propose a simple measure, the Specific Forcing Pulse (SFP), to quantify climate warming or cooling by these pollutants, where we define "immediate" as occurring primarily within the first year after emission. SFP is the amount of energy added to or removed from a receptor region in the Earth-atmosphere system by a chemical species, per mass of emission in a source region. We limit the application of SFP to species that remain in the atmosphere for less than one year. Metrics used in policy discussions, such as total forcing or global warming potential, are easily derived from SFP. However, SFP conveys purely physical information without incurring the policy implications of choosing a time horizon for the global warming potential.Using one model (Community Atmosphere Model, or CAM), we calculate values of SFP for black carbon (BC) and organic matter (OM) emitted from 23 source-region combinations. Global SFP for both atmosphere and cryosphere impacts is divided among receptor latitudes. SFP is usually greater for open-burning emissions than for energy-related (fossil-fuel and biofuel) emissions because of the timing of emission. Global SFP for BC varies by about 45% for energy-related emissions from different regions. This variation would be larger except for compensating effects. When emitted aerosol has larger cryosphere forcing, it often has lower atmosphere forcing because of less deep convection and a shorter atmospheric lifetime.A single model result is insufficient to capture uncertainty. We develop a best estimate and uncertainties for SFP by combining forcing results from 12 additional models. We outline a framework for combining a large number of simple models with a smaller number of enhanced models that have greater complexity. Adjustments for black carbon internal mixing and for regional variability are discussed. Emitting regions with more deep convection have greater model diversity. Our best estimate of global-mean SFP is +1.03 +/- 0.52 GJ g(-1) for direct atmosphere forcing of black carbon, +1.15 +/- 0.53 GJ g(-1) for black carbon including direct and cryosphere forcing, and -0.064 (-0.02, -0.13) GJ g(-1) for organic matter. These values depend on the region and timing of emission. The lowest OM: BC mass ratio required to produce a neutral effect on top-of-atmosphere direct forcing is 15: 1 for any region. Any lower ratio results in positive direct forcing. However, important processes, particularly cloud changes that tend toward cooling, have not been included here.Global-average SFP for energy-related emissions can be converted to a 100-year GWP of about 740 +/- 370 for BC without snow forcing, and 830 +/- 440 with snow forcing. 100-year GWP for OM is -46 (-18, -92). Best estimates of atmospheric radiative impact (without snow forcing) by black and organic matter are +0.47 +/- 0.26 W m(-2) and -0.17 (-0.07, -0.35) W m(-2) for BC and OM, respectively, assuming total emission rates of 7.4 and 45 Tg yr(-1). Anthropogenic forcing is +0.40 +/- 0.18 W m(-2) and -0.13 (-0.05, -0.25) W m(-2) for BC and OM, respectively, assuming anthropogenic emission rates of 6.3 and 32.6 Tg yr(-1). Black carbon forcing is only 18% higher than that given by the Intergovernmental Panel on Climate Change (IPCC), although the value presented here includes enhanced absorption due to internal mixing.