CURB CO2: Carbon Uptake Revisited - Biases Corrected using Ocean Observations

当我们通过工业活动向大气中排放二氧化碳（CO2）时，只有大约一半的二氧化碳留在大气中，其余的二氧化碳通过光合作用被陆地上的植物吸收，并被海洋吸收。这些人为的二氧化碳“汇”从本质上拯救了我们，使我们避免了全球变暖的大部分，否则我们将会经历全球变暖。新的证据表明，我们对大气中二氧化碳含量如何变化以及将如何继续变化的估计可能过高，这意味着我们可能比以前认为的更有希望防止大气中二氧化碳浓度上升得过高。虽然我们可以估计出我们目前排放了多少二氧化碳，可以测量大气中二氧化碳的浓度，从而计算出这些碳汇的强度（即它们从大气中吸收了多少二氧化碳），但如果我们要确定我们作为一个社会可以排放多少二氧化碳而不超过大气中危险的二氧化碳浓度，我们必须计算出这个数字在未来将如何变化。这个项目的目的是通过纠正我们在用于预测的模型中发现的偏差，让我们更好地了解大气中二氧化碳含量的未来变化是什么。我们利用日益全面的地球系统模式（气候模式，也包含碳循环等附加过程的表征）来预测陆地和海洋二氧化碳汇在未来可能发生的变化。虽然这些模型是我们模拟未来气候变化的最佳工具，但它们还远远不够完美。我们已经证明，在二氧化碳吸收最密集的北大西洋，这些模型低估了二氧化碳吸收增加的速度，并发现了模型的错误之处。该项目将把这项工作从北大西洋扩展到整个海洋，并通过纠正导致模型低估这一变化的偏差，产生新的和改进的未来海洋二氧化碳吸收估计。一旦我们对海洋碳汇强度的未来变化有了更好的估计，我们就会考虑陆地二氧化碳汇对这种变化的反应，并产生一组新的情景，描述如果我们不超过与全球变暖相关的大气二氧化碳浓度，那么随着时间的推移，人类活动可以排放多少二氧化碳，这与工业化前的温度升高1.5到2摄氏度有关。该项目的总体目标是为英国和国际政府提供尽可能公正的信息，从中他们可以计划如何最好地努力实现2015年12月巴黎气候大会设定的全球变暖目标（“巴黎协定”）。

When we emit carbon dioxide (CO2) to the atmosphere through industrial activity, only around half of that CO2 remains in the atmosphere, with the remainder being taken up approximately equally through photosynthesis by plants on land and being absorbed by the oceans. These anthropogenic CO2 'sinks' are essentially saving us from a large part of the global warming that we would otherwise be experiencing. New evidence suggests that our estimates of how this fraction of CO2 that stays in the atmosphere is changing, and will continue to change, may be too high, meaning that there may be more hope that we can prevent atmospheric CO2 concentrations rising too high than was previously thought.Whilst we can estimate how much CO2 we are presently emitting, and can measure the concentration of CO2 in the atmosphere, and therefore work out how strong these sinks are (i.e. how much CO2 they are taking out of the atmosphere), we must calculate how this number will change in the future if we are to determine how much CO2 we can emit as a society without exceeding dangerous CO2 concentrations in the atmosphere. This project aims to give us a better understanding of what this future change in the fraction of CO2 staying in the atmosphere is, by correcting a bias we have identified in the models we use to make these projections.We make projections of how the land and ocean CO2 sinks may change in the future using increasingly comprehensive Earth System Models (which are climate modes which also contain a representation of additional processes such as the carbon cycle). While these models are the best possible tools we have to simulate future climate change, they are still far from perfect. We have shown that in the North Atlantic, which is the most intense ocean CO2 sink, these models underestimate how quickly the CO2 absorption is increasing, and have identified what the models are doing wrong. This project will extend this work from the North Atlantic to the full ocean, and by correcting for the biases that cause the models to under-predict this change, produce new and improved future estimates of ocean CO2 absorption.One we have our improved estimates of future changes in the strength of the ocean carbon sink, we will account for how the land CO2 sink responds to this, and produce a set of new scenarios describing how much CO2 can be emitted through human activity through time if we are not to exceed the atmospheric CO2 concentrations linked to global warming of 1.5 to 2 degrees C above preindustrial temperatures.The overarching aim of this project is to provide UK and international governments with the best possible impartial information from which they can plan how best to work towards the global warming targets (the 'Paris Agreement') set at the Paris Climate Conference in December 2015.