Abstract Land use affects the global climate through greenhouse gas and aerosol emissions, as well as through changes in biophysical properties of the surface. Anthropogenic land use change over time has caused substantial climate forcing related to albedo, i.e. the share of solar radiation reflected back off the ground. There is growing concern that albedo change may offset climate benefits provided by afforestation, bioenergy or other emission reduction measures that affect land cover. Conversely, land could be managed actively to increase albedo as a strategy to combat global warming. Albedo change can be directly linked to radiative forcing, which allows its climate impact to be compared with that of greenhouse gases in Life Cycle Assessment (LCA). However, the most common LCA methods are static and linear and thus fail to account for the spatial and temporal dependence of albedo change and its strength as a climate forcer. This study sought to develop analytical methods that better estimate radiative forcing from albedo change by accounting for spatial and temporal variations in albedo, solar irradiance and transmission through the atmosphere. Simplifications concerning the temporal resolution and aggregation procedures of input data were evaluated. The results highlight the importance of spatial and temporal variations in determining the climate impact of albedo change in LCA. Irradiance and atmospheric transmittance depend on season, latitude and climate zone, and they co-vary with instantaneous albedo. Ignoring these dependencies led to case-specific errors in radiative forcing. Extreme errors doubled the climate cooling of albedo change or resulted in warming rather than cooling in two Swedish cases considered. Further research is needed to understand how different land use strategies affect the climate due to albedo, and how this compares to the effect of greenhouse gases. Given that albedo change and greenhouse gases act on different time scales, LCAs can provide better information in relation to climate targets if the timing of flows is considered in life cycle inventory analysis and impact assessment.

中文翻译：

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生命周期评估中地表反照率变化的气候影响：地点和时间依赖性的影响

摘要 土地利用通过温室气体和气溶胶排放以及地表生物物理特性的变化影响全球气候。随着时间的推移，人为土地利用的变化导致了与反照率相关的大量气候强迫，即从地面反射回来的太阳辐射的份额。人们越来越担心反照率变化可能会抵消植树造林、生物能源或其他影响土地覆盖的减排措施提供的气候效益。相反，可以积极管理土地以增加反照率，作为应对全球变暖的策略。反照率变化可以与辐射强迫直接相关，这使得可以在生命周期评估 (LCA) 中将其气候影响与温室气体的影响进行比较。然而，最常见的 LCA 方法是静态和线性的，因此无法解释反照率变化的空间和时间依赖性及其作为气候因素的强度。本研究旨在开发分析方法，通过考虑反照率、太阳辐照度和大气传输的空间和时间变化，更好地估计反照率变化的辐射强迫。对输入数据的时间分辨率和聚合程序的简化进行了评估。结果强调了空间和时间变化在确定 LCA 反照率变化对气候影响方面的重要性。辐照度和大气透射率取决于季节、纬度和气候带，它们与瞬时反照率共同变化。忽略这些依赖性会导致辐射强迫中的特定案例错误。在考虑的两个瑞典案例中，极端错误使反照率变化的气候变冷加倍或导致变暖而不是变冷。需要进一步研究以了解不同的土地利用策略如何因反照率而影响气候，以及与温室气体的影响相比如何。鉴于反照率变化和温室气体在不同的时间尺度上起作用，如果在生命周期清单分析和影响评估中考虑流量的时间安排，LCA 可以提供与气候目标相关的更好信息。