Reconciling Volcanic Forcing and Climate Records throughout the Last Millennium (Vol-Clim)

火山喷发是气候变率和气候变化的重要驱动因素，但气候模式模拟结果与大震级火山喷发引起的温度变化幅度数据并不一致。voll - clim项目将通过使用英国开发的最先进的地球系统模型（UKESM1）得出新的和改进的火山强迫估计来解决这一差异，这将使我们能够量化并更好地了解自1250年以来大型爆炸性火山爆发如何影响气候系统。该模式明确解释了火山爆发期间化学、动力和气溶胶微物理过程的相互作用，所有这些过程都会影响气候响应的大小。然而，这些过程在以前对1250年以来火山爆发引起的气候变化和自然气候变率的评估中没有考虑到。详细地说，自公元1250年以来，根据极地冰芯中的火山沉积物，已经发现了至少60次火山爆发。大规模喷发将二氧化硫排放到平流层，在那里被氧化形成硫酸蒸汽，硫酸蒸汽成核并凝结形成硫酸盐气溶胶颗粒。这些气溶胶粒子散射并吸收来自太阳的能量，从而使地球表面降温。就地表冷却的幅度而言，树木年轮（和其他数据）似乎显示出半球温度对火山爆发的响应（最高1摄氏度）比目前气候模型模拟的要小。这种不匹配意味着目前我们还不能完全理解包括云在内的气候系统在火山爆发后是如何反应的。我们也不完全了解树木的生长和随后的年轮是如何作为火山喷发引起的降温的结果作出反应的。总的来说，这些不确定性影响了我们使用气候模式来模拟过去、现在和未来气候变化的能力。目前的气候模式对火山效应的实现很简单，忽略了火山爆发后许多关键的化学和物理过程。利用UKESM1，我们将能够以前所未有的复杂程度模拟火山气溶胶颗粒的演变，这有可能大大提高预测气候影响的保真度，并使模式模拟和火山爆发后的气候变化观测记录相一致。我们在UKESM1上的模拟将涵盖1250 CE至今的时期，这将使我们能够描述和评估不同频率和强度的火山喷发对全球和半球表面温度、气候变率以及表面海洋温度的影响，这些影响从年到百年的尺度。voll - clim是一个雄心勃勃的项目，与国际倡议和NERC的主要目标密切相关。量化火山喷发对过去一千年气候变率的贡献是理解当前和未来十年尺度气候变率的关键；这与NERC的主要目标“了解和预测地球是如何运行的”是一致的。voll - clim还将帮助社会为未来火山爆发的影响做好准备。voll - clim还与国际活动密切相关，如新的过去全球变化（PAGES）工作组“火山对气候和社会的影响（VICS）”以及PMIP（古气候模拟比对项目）和CMIP（耦合模式比对项目）社区。我们将生成一个火山气溶胶强迫时间序列（公元1250年至今），用于那些不考虑平流层中化学和物理气溶胶过程的模式。这些成果与cmip6认可的活动相关，如VolMIP（火山强迫气候响应模式比对项目）和RFMIP（辐射强迫模式比对项目），以及IPCC。

Volcanic eruptions are an important driver of climate variability and climate change, yet climate model simulations do not agree with data on the magnitude of temperature changes caused by large-magnitude volcanic eruptions. The Vol-Clim project will resolve this discrepancy by deriving new and improved estimates of volcanic forcing using a state-of-the-art Earth System Model developed in the UK (UKESM1), which will allow us to quantify and better understand how large explosive volcanic eruptions affected the climate system since 1250 CE. The model explicitly accounts for the interaction of chemical, dynamical and aerosol microphysical processes during volcanic eruptions, all of which affect the magnitude of the climate response. However, these processes have not been taken into account in previous assessments of climate change and natural climate variability caused by volcanic eruptions since 1250 CE. In detail, at least 60 volcanic eruptions have been detected based on volcanic deposits in polar ice-cores since 1250 CE. Large-magnitude eruptions emit sulphur dioxide high into the stratosphere where it is oxidized to form sulphuric acid vapour, which nucleates and condenses to form sulphate aerosol particles. These aerosol particles scatter and absorb energy from the Sun thereby cooling the Earth's surface. In terms of the magnitude of this surface cooling, tree-rings (and other data) appear to show a smaller hemispheric temperature response (of up to 1 degree Celsius) to volcanic eruptions than simulated by current climate models. This mismatch means that at present we do not fully understand how the climate system including clouds responds after volcanic eruptions. We also do not fully understand how tree growth and subsequently tree-rings respond as a consequence of the cooling induced by a volcanic eruption. Overall, these uncertainties affect our ability to use climate models to simulate past, present and future changes of climate. Current climate models have simple implementations of volcanic effects, ignoring many key chemical and physical processes relevant after volcanic eruptions. Using UKESM1 we will be able to simulate the evolution of volcanic aerosol particles with unprecedented sophistication, which has the potential to greatly improve the fidelity of predicted climatic effects and reconcile model-simulated and observational records of climate change after volcanic eruptions. Our simulations in UKESM1 will cover the period 1250 CE to present, which will enable us to characterize and evaluate annual to centennial-scale effects on global and hemispheric surface temperatures, climate variability and impacts on surface ocean temperatures for eruptions of different frequencies and intensities. Vol-Clim is an ambitious project that aligns closely with international initiatives and NERC's main goals. Quantifying the contribution of volcanic eruptions to climate variability over the past millennium is key to understanding present day and future decadal-scale climate variability; this is in line with NERC's main goal 'to understand and predict how the planet works'. Vol-Clim will also help prepare society for the effects of future eruptions. Vol-Clim is also strongly aligned to international activities such as the new Past Global Changes (PAGES) working group "Volcanic Impacts on Climate and Society (VICS)" and the PMIP (Paleoclimate Modelling Intercomparison Project) and CMIP (Coupled Model Inter-comparison Project) communities. We will generate a volcanic aerosol forcing time-series (1250 CE to present) for use in those models that do not account for the chemical and physical aerosol processes in the stratosphere. These deliverables are relevant for CMIP6-endorsed activities such as VolMIP (Model Inter-comparison Project on the Climatic Response to Volcanic Forcing) and RFMIP (Radiative Forcing Model Inter-comparison Project), and also the IPCC.