TerraFIRMA: Future Impacts Risks and Mitigation Actions

TerraFIRMA旨在提高我们对全球气候变化相关风险和影响的认识。它还将评估旨在限制未来气候变化幅度的一些主要缓解方案。为此，它将开发并应用耦合地球系统的先进模型，即大气层、海洋、陆地、海冰和陆地冰的计算机数学模型，包括有关的物理、化学和生物过程及过程相互作用。这些模型在过去运行，以评估其模拟地球系统关键现象的准确性，包括变量的任何趋势，如表面空气温度。在TerraFIRMA中，我们将设计未来的温室气体排放量，使全球变暖超过一些关键的国际政策目标，例如比工业化前的值高2摄氏度，上升到3摄氏度，然后在稍后的某个日期冷却回2摄氏度的水平。这种冷却假设广泛部署从大气中去除二氧化碳的技术。使用这些所谓的过冲情景，我们将调查地球系统三个特征快速变化的风险;可能影响全球海平面上升的南极冰盖，海洋生态系统，以及渔业和热带森林，如亚马逊。我们的目标是确定随着气候变暖，这些现象发生快速变化的风险，以及如果在一定程度的变暖之后引发这种快速变化，如果气候冷却到低于给定目标，这种变化是否是可逆的。利用同样的实验，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）水资源和水的可用性，（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。对于前四个影响，我们集中在三个主要的地理区域：（a）撒哈拉以南非洲，（B）南亚季风区，包括陆地和邻近的海洋，（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，以研究两种广泛讨论的限制（缓解）未来气候变化的方案的有效性。第一个行动是迅速减少被称为短期气候因子（NTCF）的非二氧化碳气体的排放。与在大气中存在数百年的二氧化碳不同，NTCF（如甲烷，臭氧，一氧化二氮和气溶胶）的大气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甲烷等气体减排的功效，看看它们是否有助于减少近期气候变化，并与对变暖有长期影响的二氧化碳减排一起应用。第二个行动是广泛植树造林，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）。我们将设计一组模型实验，以评估广泛植树造林对大气二氧化碳的影响（树木在生长时会从大气中去除二氧化碳），同时考虑植树造林对树木所在地气候的直接影响。我们的目标是很好地了解我们可以预期多少冷却，以及这种广泛植树造林的时间尺度。我们设计的缓解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