Probabilistic estimation of changes in BVOC emissions due to projected land-use change: atmospheric and policy implications

数千年来，人类已经改变了地球的自然陆地表面，例如农业、森林砍伐、生物质燃烧。科学家们广泛地研究了这些活动如何改变生物地球化学循环（例如水和碳），以及它们如何影响地表反照率，从而影响大气的辐射平衡。植被释放出许多生物源碳氢化合物（异戊二烯，C5H8，排放量最大），其化学寿命为几天或更短，可导致臭氧的产生，臭氧是对流层上层的一种地面空气污染物和温室气体。我们从实地测量中得知，不同的植被以不同的速率释放这些活性碳氢化合物，因此改变植被的空间格局将改变生物源碳氢化合物的预算，对地表臭氧产生严重影响。我们知道热带生态系统排放的异戊二烯占全球总量的70%。对人类活动将如何改变地球自然土地覆盖的充分了解，是未来几十年气候预测的基础。这项建议的主要科学目标是减少与人类活动有关的土地利用变化预测的不确定性以及随后生物源性碳氢化合物排放和地表臭氧的大小和分布的变化。预测人类活动及其在土地利用变化中的作用是困难的，涉及许多不同的社会经济问题。然而，它是地球系统的一个组成部分，如果我们要改进气候预测，我们必须考虑到这一人为因素。到目前为止，人类对土地利用变化的影响一直被认为独立于气候系统的其他部分。过去的工作主要集中在开发复杂的模型，这些模型考虑了整个社会经济现象的范围，但由于计算的限制，这种复杂性有效地限制了对替代社会经济未来的探索。我们的建议是开发一个更简单的模型，只有几个描述参数，可以捕获更复杂模型的许多大尺度特征。这样的模型可以更全面地探索（和不确定性分析）可选择的期货。这种概率方法使我们能够确定统计上最有可能的未来。在我们的工作中，我们将使用开发的模型来探索未来40年最有可能由人类引起的土地利用变化。当前社会经济驱动土地利用变化的一个很好的例子是生物燃料生产。生物燃料可以说是燃烧传统化石燃料的一种更清洁的替代品，并且越来越多地被用作汽车柴油燃料和发电站的成分。棕榈油是最重要的生物燃料，主要种植在东南亚。棕榈油的生产和与之相关的热带森林砍伐率正在因应需求而迅速增加，这表明热带土地覆盖发生了重大变化。在许多情况下，棕榈油的碳氢化合物排放量大于本地作物，因此增加的生物燃料生产有效地增加了全球生物源碳氢化合物预算，对地表空气污染产生了（尚未量化的）影响。未来的生物燃料生产将在土地利用模式中考虑。我们将使用基于现场测量的清单来估计生物源碳氢化合物的排放量，以便对土地利用进行预测，我们将有一个生物源碳氢化合物排放的相关分布。为了量化这些排放物对地表空气污染的影响，我们将使用最先进的大气化学和运输计算机模型。运行这样一个模型对于大量的生物源碳氢化合物排放清单来说是计算密集型的，因此我们将把计算限制在最小、最大和最可能的全球生物源碳氢化合物排放上。我们的计算将大大减少人类因素对土地利用变化和地表空气污染影响的不确定性。

Humans have altered Earth's natural land surface for thousands of years, e.g., agriculture, deforestation, biomass burning. Scientists have studied extensively how these activities alter the biogeochemical cycles (e.g., water and carbon), and how they affect surface albedo and consequently the radiative balance of the atmosphere. Vegetation emit a number of biogenic hydrocarbons (isoprene, C5H8, represents the largest emission) with chemical lifetime of days or less that can lead to the production of ozone, a surface air pollutant and a greenhouse gas in the upper troposphere. We know from in situ measurements that different vegetation emit these reactive hydrocarbons at different rates so that altering the spatial patterns of vegetation will alter budgets of biogenic hydrocarbons with serious implications for surface ozone. We know that tropical ecosystems emit ~70% of the global isoprene budget. A good understanding of how human activity will alter Earth's natural land cover underpins climate projections of the next few decades. The main scientific objective of this proposal is to reduce uncertainty in land-use change projections related to human activity and subsequent changes in the magnitude and distribution of biogenic hydrocarbon emissions and surface ozone. Projecting human activity and its role in land-use change is difficult, involving many different socio-economic issues. However, it is an integral part of the Earth system and if we are to improve climate projections we must consider this human element. Up until now, the human contribution to land-use change has been considered independent of the rest of the climate system. Past work has focused primarily on developing complex models that consider a whole range of socio-economic phenomena but this complexity effectively limits the exploration of alternative socio-economic futures because of computational constraints. What we propose is to develop a simpler model, with only a few describing parameters, that captures many of the broad scale features of the more complex models. Such a model enables a more comprehensive exploration (and uncertainty analysis) of alternative futures. This probabilistic approach allows us to determine the most statistically likely future. In our work we will use the developed model to explore the most likely human-induced land-use change over the next 40 years. An excellent example of a current socio-economic driver of land-use change is biofuel production. Biofuels represent an arguably cleaner alternative to burning traditional fossil fuels and is increasingly being used as an ingredient in car diesel fuel and in power stations. Palm oil is the most prominent biofuel, which is grown largely in Southeast Asia. Production of palm oil, and associated rates of tropical deforestation, is increasing rapidly in response to demand, representing significant changes in tropical land-cover. In many cases hydrocarbon emissions from palm oil are larger than the indigenous crops so that increased biofuel production effectively increases the global biogenic hydrocarbon budget with (yet unquantified) implications for surface air pollution. Future biofuel production will be considered in the land-use model. We will estimate emissions of biogenic hydrocarbons using inventories based in situ measurements so that for projection of land-use we will have an associated distribution of biogenic hydrocarbon emissions. To quantify the impact of these emissions on surface air pollution we will use a start-of-the art computer model of atmospheric chemistry and transport. Running such a model is computationally intensive for a large ensemble of biogenic hydrocarbon emission inventories so we will limit our calculation to the minimum, maximum and most likely global biogenic hydrocarbon emissions. Our calculations will significantly reduce uncertainty on the human element on land-use change and implications for surface air pollution.