Developing a Coarse-Grained Model to Investigate Long-Term Climate Behaviour

该项目着眼于长期气候行为，旨在深入了解过去和未来的环境变化。这与EPSRC的LWEC研究领域有关，因为我将调查轨道和地质现象对环境的影响，以及人类对环境的影响。地球的气候在不断变化，有些变化需要数百万年，有些变化只需十年。目前的气候紧急情况主要是由二氧化碳排放量的显著增加引起的，这引起了人们对未来气候的日益关注。全球气候模型（GCM）利用大型数据集以100年的时间尺度预测地球的状态。gcm是大型复杂模式，试图模拟海洋、大气、冰冻圈、生物圈和人类圈的相互作用行为。目前的大多数gcm都经过高度调整，可以在十年的时间尺度上进行准确预测。对于地势平坦、海拔较低的荷兰等脆弱地区来说，这对应对海平面上升等气候事件很重要。也有更大规模的变化发生，大约10万年，最显著的是规律的冰期旋回或“冰期”。这些变化可能与中短期气候变化有关，但尚未被理解，这使它们成为未来研究的重要目标。米兰科维奇周期描述了地球运动的周期性变化，包括以41000年为周期的地轴倾斜，以及以10万年为周期的轨道偏心率。在过去的一百万年里，地球的平均温度和冰盖的表面面积以可靠的10万年为周期波动。虽然人们一致认为地球轨道的偏心驱动了这种气候变化，但它并不是完全负责任的。在过去的100万年里，这些气候周期约为4.1万年，似乎与地轴倾斜有关。解释这种从一个周期到另一个周期的转变，被称为“10万年问题”，因为气候科学家还没有理解它。此外，数据表明地球的平均温度对米兰科维奇周期没有线性响应，这表明地球具有与米兰科维奇周期相互作用的非线性反馈机制。这个博士学位将探索和发展整个地球系统的基本模型，重点关注已知的过去行为，地球的冰川周期和未来1000年时间尺度上可能的气候变化。20世纪50年代开发的Budyko能量平衡模型提供了一种简单的方法来估计在1000至100万年的时间尺度上大气CO2浓度和米兰诺维奇循环对全球温度的影响等参数的影响。最近，Widiasih对Budyko模型进行了调整，将极地冰盖纳入其中，使其成为研究冰川循环b[3]的候选模型。然而，所得到的模型并不能再现已知的冰期旋回的过去历史，因为偏心率旋回的直接影响太小，无法解释它们。对这种差异的一种可能解释是，Budyko模型将地球视为一个均匀的“水世界”，两个半球是相等的。地球是高度不对称的，南北半球之间的陆地和海洋分布明显不同。将两个半球之间的不同反照率结合起来或许可以解释这种差异，但需要从一开始就重新制定模型。本博士的主要目标是开发能够解释冰川旋回的新模型，并利用它们为未来的预测和改进gcm提供信息。1 .重新制定不对称地球的Budyko模型。对该模式的许多其他扩展是可能的，例如使用经验观测到的反照率关系。

This project is looking at long term climatic behaviours with the intention of gaining insights into both past and future environmental changes. This relates to the LWEC research area of EPSRC as I will be investigating environmental effects that result from both orbital and geological phenomena, as well as the impact that humans have had.Earth's climate is constantly changing, with some changes taking millions of years and others just a decade. The current climate emergency, predominantly caused by significantly increased carbon dioxide emissions, has sparked an increased concern for the future of our climate. A global climate model (GCM) uses large datasets to make predictions about Earth's state with a timescale of the order of 100 years. GCMs are large-scale complex models that attempt to simulate the interacting behaviour of the oceans, atmosphere, cryosphere, biosphere and anthroposphere. Most current GCMs are highly tuned for accurate predictions over a decade timescale. These are important for vulnerable areas such as The Netherlands, with its flat, low altitude landscape, to prepare for climate events such as a rise in sea-level. There are also larger scale changes occurring, of the order of 100,000 years, most notably the regular glacial cycles or "ice ages". These changes may be relevant for short to medium term climate change but are not yet understood making them an important target for future research. The Milankovich cycles describe periodic variations to Earth's movement, including its axial tilt, varying with a period of 41, 000 years, and the eccentricity of its orbit, with a period of 100, 000 years. For the last million years, Earth's average temperature, and the surface area of its ice caps, has fluctuated with a reliable 100,000 year cycle. Although the consensus is that the eccentricity of Earth's orbit drives this climate variation, it is not entirely responsible. Before the last million years these climate cycles had a period of around 41,000 years, seemingly linked to Earth's axial tilt. Explaining this transition, from one periodicity to the other, is referred to as the '100,000 year problem' as it is not yet understood by climate scientists. Additionally, data shows that Earth's average temperature does not respond linearly to the Milankovich cycles suggesting that Earth has non-linear feedback mechanisms interacting with the Milankovich cycles. This PhD will explore and develop fundamental models of the whole-Earth system focusing on the known past behaviour the Earth's glacial cycles and possible future climate change on a 1,000 year timescale. The Budyko energy balance model developed in the 1950s provides a simple way to estimate the effect of parameters such as atmospheric CO2 concentration and the effect of the Milanovich cycles on global temperature over a timescale ranging from 1,000 to 1,000,000 years. Recently, Widiasih adapted the Budyko model to incorporate polar ice caps making it a candidate for investigating glacial cycles [3]. However, the resulting model does not reproduce the known past history of glacial cycles as the direct effect of the eccentricity cycle is too small to account for them. A possible explanation for this discrepancy is that the Budyko model treats the Earth as a homogeneous "waterworld" with both hemispheres being equivalent. The Earth is highly asymmetric with a significantly different distribution of land and ocean between the Northern and Southern hemispheres. Incorporating differential albedo between the hemispheres might account for the difference but will require reformulating the model from the beginning. The main objectives of this PhD are to develop novel models that can account for glacial cycles and use them to inform future predictions and improvements to GCMs. In particular: 1 Reformulate the Budyko model for an asymmetric Earth. A number of other extensions to the model are possible such as using the empirically observed albedo-larelationship.