TerraFIRMA: Future Impacts Risks and Mitigation Actions

TerraFIRMA旨在提高我们对与全球气候变化相关的风险和影响的理解。它还将评估一些旨在限制未来气候变化幅度的主要缓解办法。为此，它将开发并应用耦合地球系统的先进模型，即大气、海洋、陆地、海冰和陆冰的计算机数学模型，包括相关的物理、化学和生物过程以及过程相互作用。这些模型是在过去运行的，以评估它们在模拟关键地球系统现象方面的准确性，包括任何变量的趋势，如表面空气温度。然后使用一系列假定的未来温室气体排放，如二氧化碳、甲烷和一氧化二氮，以及气溶胶和对未来土地利用的估计，来运行这些模型。在TerraFIRMA中，我们将设计未来的排放量，使全球变暖超过一些关键的国际政策目标，例如比工业化前的温度高2摄氏度，上升到3摄氏度，然后在稍后的某个日期回落到2摄氏度的水平。这种降温需要从大气中去除二氧化碳的技术得到广泛应用。利用这些所谓的超调情景，我们将调查地球系统三个特征快速变化的风险；南极冰盖可能影响全球海平面上升、海洋生态系统、渔业和热带森林，如亚马逊。我们的目标是确定随着气候变暖，这些现象快速变化的风险，以及如果在一定程度的变暖之后触发这种快速变化，如果气候冷却到给定目标以下，这种变化是否可逆。使用相同的实验，我们还将评估全球变暖超过关键目标对以下现象的影响，这些现象都影响人类活动和福祉；(i)水资源和水资源供应，（ii）空气污染，（iii）野火，（iv）海洋生态系统和渔业，以及(v)全球海平面上升。对于前四种影响，我们主要关注三个主要地理区域：(a)撒哈拉以南非洲，(b)南亚季风区，覆盖陆地和邻近海洋，以及(c)东北大西洋和英国。除了分析超调情景外，我们还将设计一组模型实验，以调查两种广泛讨论的限制（缓解）未来气候变化的方案的有效性。第一项行动是迅速减少非二氧化碳气体的排放，这种气体被称为短期气候影响因子（nctfs）。二氧化碳在大气中的寿命为数百年，而nccs（如甲烷、臭氧、一氧化二氮和气溶胶）在大气中的寿命从几天到十年不等。因此，这些气体的大量减排可以相当迅速地（即在短期内）影响气候变暖的程度。我们将设计实验来评估减少甲烷等气体排放的效果，看看它们是否有助于减少近期的气候变化，并将其应用于对变暖有长期影响的二氧化碳减排之外。第二项行动是广泛种植树木（造林），可能与直接碳捕获相结合，即所谓的生物能源与碳捕获储存（BECCS）。我们将设计一套模型实验来评估广泛造林对大气二氧化碳的影响（树木在生长时从大气中去除二氧化碳），同时也考虑造林对树木所在地区的当地气候的直接影响。我们的目标是很好地了解我们可以预期多少降温，以及在什么时间尺度上进行如此广泛的植树造林。我们设计的减缓实验以及结果将与参与制定英国气候政策的英国政府部门进行讨论

TerraFIRMA aims to increase our understanding of the risks and impacts associated with global climate change. It also will assess a number of leading mitigation options aimed at limiting the magnitude of future climate change. It will do this by developing and then applying advanced models of the coupled Earth system, meaning computer-mathematical models for the atmosphere, ocean, land, sea ice and land ice, encompassing relevant physical, chemical and biological processes and process interactions. These models are run for the past, to evaluate their accuracy in simulating key Earth system phenomena, including any trends in variables, such as in surface air temperature. The models are then run into the future using a range of assumed future emissions of greenhouse gases, such as carbon dioxide, methane, and nitrous oxide, as well as aerosols and estimates of future land use.In TerraFIRMA we will design future emissions that see global warming exceed some of the key international policy targets, such as 2 degreeC warmer than pre-industrial values, rising to 3C, before then cooling back down to the 2C level at some later date. This cooling assumes widespread deployment of technologies that remove carbon dioxide from the atmosphere. Using these, so-called overshoot scenarios, we will investigate the risk for rapid changes in three features of the Earth system; Antarctic ice sheets that may impact global sea-level rise, marine ecosystems, and fisheries and tropical forests, such as the Amazon. We aim to determine the risk for rapid change in these phenomena as the climate warms and whether such rapid changes if triggered after a certain amount of warming, are reversible if the climate is cooled back below a given target. Using the same experiments we will also assess the impact of global warming exceeding key targets on the following phenomena that all impact human activities and well-being; (i) water resources and water availability, (ii) air pollution, (iii) wildfires, (iv) marine ecosystems and fisheries and (v) global sea-level rise. For the first four of these impacts, we concentrate on three primary geographical areas: (a) sub-Saharan Africa, (b) the South Asian monsoon region, covering both land and adjacent oceans, and (c) the North-East Atlantic and the UK. In addition to analyzing the overshoot scenarios, we will also design a set of model experiments to investigate the efficacy of two widely discussed options for limiting (mitigating) future climate change. The first action is to rapidly reduce the emission of non-CO2 gases known as Near Term Climate Forcers (NTCFs). Unlike carbon dioxide, which has a lifetime of hundreds of years in the atmosphere, NTCFs (such as methane, ozone, nitrous oxide, and aerosols) have atmospheric lifetimes ranging from days to a decade. Hence, large emission reductions in these gases can impact the amount of climate warming quite rapidly (i.e. in the near term). We will design experiments to assess the efficacy of emission reductions in gases such as methane to see whether they can help reduce near-term climate change and be applied in addition to carbon dioxide emission reductions that have a longer-term impact on warming. The second action is the widespread planting of trees (afforestation), potentially combined with direct Carbon capture, so-called Bio-Energy with Carbon Capture Storage (BECCS). We will design a set of model experiments to assess the impact widespread afforestation has on atmospheric carbon dioxide (trees remove carbon dioxide from the atmosphere when they grow), while also considering the direct impact of afforestation on the local climate where the trees are located. We aim to get a good idea of how much cooling we can expect, and on what timescale from such widespread afforestation. The mitigation experiments we design, as well as the results, will be discussed with UK government departments involved in setting UK climate policy