C-FORCE: Carbon-Cycle Feedbacks from Response to Carbon Emissions

人为全球变暖的主要驱动力是大气中温室气体二氧化碳的增加。由于燃烧化石燃料、砍伐森林和制造水泥，二氧化碳的排放量正在增加，只有约45%留在大气中。其余的储存在地球表面或附近的其他储存库中，包括海洋、树木、土壤、永久冻土和甲烷冰，以及沉积物和岩石。碳通过光合作用、腐烂、风化、埋藏和海洋环流等过程在大气和这些储层之间自然流动。总的来说，这些储层之间的碳交换被称为碳循环。未来气候变化最大的不确定性之一是碳循环将如何回应（或“反馈”）我们变暖的地球。例如，如果全球变暖超过某个阈值，储存在海底的永久冻土和甲烷冰可能会迅速融化，从而向大气中增加更多的温室气体，加速变暖。很难预测像这样的“临界点”行为是否会在全球碳循环中发生。c - force将测量在过去一段由碳基温室气体排放到大气中导致的全球变暖期间，全球碳循环从头到尾是如何响应的。古新世-始新世极热期（PETM）是近6500万年来最大的自然气候变化事件，也是与现代全球变暖和碳温室气体排放速率最接近的自然比较物。在始新世新世，几千年来全球变暖4-5摄氏度的部分原因是由一次异常大规模的火山活动产生的碳排放造成的，随后气候在10多万年的时间里逐渐恢复到原来的状态。c - force将使用一个新的全球碳循环模型来比较火山活动提供的碳与始新世新世新世的总碳收支。这两种预算之间的差异可归因于碳循环反馈。我们将通过测量产生岩浆的过程，对整个始新世纪火山活动向大气提供碳的速率做出新的高分辨率估计。我们将通过生成新的高分辨率海洋酸化记录，计算导致气候变化的大气碳排放总量。我们的碳循环模型将使进行这两套测量的科学家能够有效地结合起来，首次解决净全球碳循环反馈问题。此外，由于地球上的碳储层在同位素组成上有所不同，我们可以确定哪些储层最有可能在始新世纪（PETM）的过程中充当碳源或碳汇。因此，C-FORCE将确定全球碳循环在整个始新世纪是如何演变的，并显示是否发生了临界点行为。了解地球的碳库如何对全球变暖做出反应，对于预测未来很长一段时间的大气二氧化碳浓度和气候变化至关重要。最终，提高对碳循环的了解将影响到未来将全球变暖限制在1.5或2摄氏度的碳预算，因此对于制定缓解目标和政府政策是必要的。除了提供研究产品之外，C-FORCE还挑战了目前对碳循环的理解，我们认为我们的角色是在这个领域赋予力量。公众对气候变化的讨论混杂着不满和焦虑，因此C-FORCE将采取与传统公众参与不同的方向，与社区组织者和地方政府合作，培训、指导和共同发展我们与年轻人的公众参与。

The dominant driver of anthropogenic global warming is the increasing amount of the greenhouse gas carbon dioxide in the atmosphere. This is increasing because it is being emitted by the burning of fossil fuel, deforestation and cement making, with only ~45% staying in the atmosphere. The rest is stored in other reservoirs at or near Earth's surface including the ocean, trees, soils, permafrost and methane ice, as well as sediments and rock. Carbon flows naturally between the atmosphere and these reservoirs by processes like photosynthesis, decay, weathering, burial and ocean circulation. Collectively, the exchange of carbon between these reservoirs is termed the carbon cycle. One of the biggest uncertainties about future climate change is how the carbon cycle will respond to (or 'feed back' on) our warming planet. It is possible, for example, that if global warming exceeds a threshold, permafrost and methane ice stored at the seafloor will melt rapidly, adding further greenhouse gases to the atmosphere and accelerating the warming. It is very difficult to predict whether 'tipping point' behaviour like this will occur in the global carbon cycle.C-FORCE will measure how the global carbon cycle responded from start to finish during a past period of global warming that was driven by emissions of carbon-based greenhouse gases to the atmosphere. The Paleocene-Eocene Thermal Maximum (PETM) is the largest natural climate change event of the last 65 million years, and the closest natural comparator to the modern rates of global warming and carbon greenhouse gas emissions. During the PETM, initial global warming of 4-5 degrees Celsius over a few thousand years was partially driven by carbon emissions from an unusually massive episode of volcanism, and the climate then gradually recovered to its pre-existing state over more than 100 thousand years.C-FORCE will use a novel model of the global carbon cycle to compare the carbon supplied by volcanism with the total PETM carbon budget; the difference between these two budgets can be attributed to carbon cycle feedbacks. We will make new high-resolution estimates of the rate at which volcanism supplied carbon to the atmosphere throughout the PETM by measuring the processes that generated the magma. We will calculate the total budget of carbon emissions to the atmosphere that caused the climate change by generating new high-resolution records of ocean acidification. Our carbon cycle modelling will allow the scientists who make these two sets of measurements to interface effectively to solve the net global carbon cycle feedback problem for the first time. Furthermore, because Earth's carbon reservoirs differ in isotopic composition, we can fingerprint which reservoirs most likely acted as carbon sources or sinks over the course of the PETM. Thus C-FORCE will determine how the global carbon cycle evolved throughout the PETM, and show whether or not tipping point behaviour occurred. Understanding how Earth's carbon reservoirs respond to global warming is crucial for predicting atmospheric carbon dioxide concentrations and climate change long into the future. Ultimately, an improved understanding of the carbon cycle affects future carbon budgets to limit global warming to 1.5 or 2 degrees Celcius and is therefore necessary for shaping mitigation targets and government policy.Beyond delivering a research product, C-FORCE challenges current understanding of the carbon cycle and we see our role as an empowering force in this space. The public discourse on climate change is a mixture of disaffection and anxiety, so C-FORCE will take a different direction to traditional public engagement, by partnering with community organisers and local government to train, mentor and co-develop our public engagement with young people.