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

几千年来，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。科学家们已经广泛研究了这些活动如何改变地球化学循环（例如，水和碳），以及它们如何影响地表水，从而影响大气的辐射平衡。植被排放的生物碳氢化合物（异戊二烯，C5H8，是最大的排放量），其化学寿命为几天或更短，可导致臭氧的产生，这是一种地表空气污染物，也是对流层上部的温室气体。我们知道，从现场测量，不同的植被排放这些活性碳氢化合物在不同的速度，使改变植被的空间格局将改变预算的生物源碳氢化合物与地表臭氧的严重影响。我们知道热带生态系统排放了全球异戊二烯预算的70%。对人类活动将如何改变地球自然土地覆盖的良好理解是未来几十年气候预测的基础。本提案的主要科学目标是减少与人类活动有关的土地使用变化预测的不确定性，以及生物碳氢化合物排放和地表臭氧的规模和分布随之发生的变化。预测人类活动及其在土地使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贡献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，考虑了整个范围的社会经济现象，但这种复杂性有效地限制了探索替代的社会经济未来，因为计算的限制。我们的建议是开发一个更简单的模型，只有几个描述参数，捕捉到许多更复杂的模型的广泛规模的功能。这样的模型可以更全面地探索（和不确定性分析）替代未来。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。生物燃料生产是当前土地使用变化的社会经济驱动因素的一个很好的例子。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，越来越多地被用作汽车柴油和发电站的一种成分。棕榈油是最重要的生物燃料，主要在东南亚种植。棕榈油的生产和相关的热带森林砍伐率因需求而迅速增加，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，生物燃料生产的增加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使用模型中考虑。我们将使用基于现场测量的库存来估计生物源碳氢化合物的排放量，以便对土地使用进行预测，我们将获得生物源碳氢化合物排放量的相关分布。为了量化这些排放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。运行这样一个模型是计算密集型的一个大的合奏生物烃排放清单，所以我们将我们的计算限制在最小，最大和最有可能的全球生物烃排放。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的影响的不确定性。

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.