Naik Vaishali, Wuebbles Donald J, Delucia Evan H, Foley Jonathan A
Department of Atmospheric Sciences, University of Illinois, 105 S. Gregory Avenue, Urbana, Illinois 61801, USA.
Environ Manage. 2003 Sep;32(3):373-81. doi: 10.1007/s00267-003-2993-7.
Various geoengineering schemes have been proposed to counteract anthropogenically induced climate change. In a previous study, it was suggested that a 1.8% reduction in solar radiation incident on the Earth's surface could noticeably reduce regional and seasonal climate change from increased atmospheric carbon dioxide (CO2). However, the response of the terrestrial biosphere to reduced solar radiation in a CO2-rich climate was not investigated. In this study, we hypothesized that a reduction in incident solar radiation in a Doubled CO2 atmosphere will diminish the net primary productivity (NPP) of terrestrial ecosystems, potentially accelerating the accumulation of CO2 in the atmosphere. We used a dynamic global ecosystem model, the Integrated Biosphere Simulator (IBIS), to investigate this hypothesis in an unperturbed climatology. While this simplified modeling framework effectively separated the influence of CO2 and sunlight on the terrestrial biosphere, it did not consider the complex feedbacks within the Earth's climate system. Our analysis indicated that compared to a Doubled CO2 scenario, reduction in incident solar radiation by 1.8% in a double CO2 world will have negligible impact on the NPP of terrestrial ecosystems. There were, however, spatial variations in the response of NPP-engineered solar radiation. While productivity decreased by less than 2% in the tropical and boreal forests as hypothesized, it increased by a similar percentage in the temperate deciduous forests and grasslands. This increase in productivity was attributed to an approximately 1% reduction in evapotranspiration in the Geoengineered scenario relative to the Doubled CO2 scenario. Our initial hypothesis was rejected because of unanticipated effects of engineered solar radiation on the hydrologic cycle. However, any geoengineering approaches that reduce incident solar radiation need to be thoroughly analyzed in view of the implications on ecosystem productivity and the hydrologic cycle.
人们已经提出了各种地球工程方案来应对人为引起的气候变化。在之前的一项研究中，有人提出，将入射到地球表面的太阳辐射减少1.8%，可以显著减少因大气二氧化碳（CO₂）增加而导致的区域和季节气候变化。然而，在富含CO₂的气候条件下，陆地生物圈对太阳辐射减少的响应并未得到研究。在本研究中，我们假设在CO₂浓度翻倍的大气中，入射太阳辐射的减少将降低陆地生态系统的净初级生产力（NPP），这可能会加速大气中CO₂的积累。我们使用了一个动态全球生态系统模型——综合生物圈模拟器（IBIS），在未受干扰的气候条件下研究这一假设。虽然这个简化的建模框架有效地分离了CO₂和阳光对陆地生物圈的影响，但它没有考虑地球气候系统内部的复杂反馈。我们的分析表明，与CO₂浓度翻倍的情景相比，在CO₂浓度翻倍的世界中将入射太阳辐射减少1.8%，对陆地生态系统的NPP影响可忽略不计。然而，NPP对工程太阳辐射的响应存在空间差异。正如假设的那样，热带和北方森林的生产力下降不到2%，而温带落叶林和草原的生产力则增加了类似的百分比。生产力的这种增加归因于地球工程情景下相对于CO₂浓度翻倍情景，蒸散量减少了约1%。由于工程太阳辐射对水文循环产生了意外影响，我们最初的假设被否定了。然而，鉴于对生态系统生产力和水文循环的影响，任何减少入射太阳辐射的地球工程方法都需要进行全面分析。
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