QUEST Deglaciation: Climate and Biogeochemical Cycles during the last deglaciation.

QUEST 冰消期：末次冰消期期间的气候和生物地球化学循环。

• 批准号: NE/D001781/1
• 负责人: Paul Valdes
• 金额: $ 12.42万
• 依托单位: University of Edinburgh
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2006
• 资助国家: 英国
• 起止时间: 2006 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FD001781%2F1
• 关键词: QUEST; Deglaciation; Climate; Biogeochemical; Cycles

During the past twenty thousand years the Earth's climate has changed from a full ice age to a warm period. During ice ages there are large ice sheets in Europe and North America, the oceans are cold with large areas of sea-ice in winter, the continents are cold and generally dry, forests worldwide are much reduced, and the climate is kept cold by very low concentrations of carbon dioxide and other 'greenhouse gases' and by enormous amounts of dust in the air. The climate of the last ice age was also unstable, punctuated by large coolings and sudden warmings lasting tens to hundreds of years; and the warming after the ice age was suddenly interrupted by a cold period lasting a thousand years. The climate has been warmer and rather more stable since then, but there have still been changes in climate, vegetation and the atmosphere. For example, there was a slow rise in carbon dioxide concentration during some eight thousand years before the dramatic rise that began with the Industrial Revolution. Some climate changes were dramatic, like the formation of the Sahara desert. These facts are well established, but to understand the mechanisms behind them is still a challenge to science. The causes of changes in climate, and of pre-industrial changes in greenhouse gases and dust (which in turn affect the climate), are not fully understood. The only known external cause is the variation of the Earth's orbit, which gradually alters the amount of the Sun's energy received at different latitudes and seasons. The Earth apparently responds to this variation in a very complex way, and sometimes abruptly. The changes in the atmosphere, especially, give a clue that climate changes are not just a matter of physics; they also involve changes in 'biogeochemical cycles' / the exchanges of carbon and other elements between the atmosphere, ocean and land, which are regulated by living organisms. Understanding these processes is particularly important because human activities are now changing the atmosphere and climate, and we need to be able to predict the long-term consequences. Making predictions 'in reverse' is one way to test the models we use. The aim of this project is a fuller understanding of what has driven changes in climate, atmospheric composition and biogeochemical cycles during the period from the peak of the last ice age until recent times. We will combine two ways of working, which have usually been separate. On the one hand, we will try to predict the past. We will use computer climate models with extra features, including a dynamic global vegetation model that can predict changes in wetlands, deserts and forest fires. This will enable us to us simulate the land-atmosphere exchanges of many important substances that affect climate, such as carbon dioxide, methane, volatile hydrocarbons, dust and soot. We will use versions of these models which are very efficient because they only simulate large-scale patterns. In this way we can do many more and longer simulations than is usually done. On the other hand, we will use existing data bases and new data-analysis methods to make a major synthesis of the data from sediment cores around the world, including pollen counts (an indicator of past vegetation), charcoal counts (an indicator of past fires) and carbon isotope measurements. This work will provide, for the first time, a continuous picture of the state of the Earth's land surface from the last ice age up to recent times. We will assess how well the climate models are working, and get insights into how the vegetation changes are interacting with the climate and the composition of the atmosphere, by making a detailed comparison of this reconstruction with our computer-generated 'virtual history' of the Earth.

在过去的两万年里，地球的气候已经从盛冰期转变为暖期。在冰河时代，欧洲和北美有大片冰盖，冬季海洋寒冷，有大片海冰，大陆寒冷且普遍干燥，世界各地的森林大大减少，气候因二氧化碳和其他温室气体的极低浓度以及空气中大量的灰尘而保持寒冷。上一次冰河时代的气候也不稳定，不时出现持续数十至数百年的大降温和突然变暖；冰河时代后的变暖突然被一段持续一千年的冷期打断。自那以后，气候变得更加温暖和稳定，但气候、植被和大气仍然发生了变化。例如，在工业革命开始的二氧化碳浓度急剧上升之前的大约8000年里，二氧化碳浓度有一个缓慢的上升。有些气候变化是剧烈的，比如撒哈拉沙漠的形成。这些事实是确凿的，但要理解它们背后的机制仍然是对科学的挑战。气候变化的原因以及工业化前温室气体和尘埃(进而影响气候)的变化的原因还没有完全弄清楚。唯一已知的外部原因是地球轨道的变化，这逐渐改变了太阳在不同纬度和不同季节接收的能量。显然，地球对这种变化的反应非常复杂，有时甚至是突然的。特别是大气的变化，给出了一个线索，即气候变化不仅仅是一个物理问题；它们还涉及受生物有机体调控的“生物地球化学循环”/大气、海洋和陆地之间的碳和其他元素交换的变化。了解这些过程尤为重要，因为人类活动现在正在改变大气和气候，我们需要能够预测长期后果。“反向预测”是检验我们使用的模型的一种方式。该项目的目的是更全面地了解是什么推动了从上一次冰河时代高峰期到最近这段时间内气候、大气成分和生物地球化学循环的变化。我们将结合两种通常分开的工作方式。一方面，我们将尝试预测过去。我们将使用具有额外功能的计算机气候模型，包括可以预测湿地、沙漠和森林火灾变化的动态全球植被模型。这将使我们能够模拟许多影响气候的重要物质的陆地-大气交换，如二氧化碳、甲烷、挥发性碳氢化合物、尘埃和烟尘。我们将使用这些模型的版本，它们非常高效，因为它们只模拟大规模的模式。通过这种方式，我们可以进行比通常情况下更多、更长时间的模拟。另一方面，我们将利用现有的数据库和新的数据分析方法，对世界各地沉积物岩心的数据进行重大综合，包括花粉计数(过去植被的指标)、木炭计数(过去火灾的指标)和碳同位素测量。这项工作将首次提供从上一个冰河时代到最近的地球陆地表面状态的连续图像。我们将评估气候模型的工作情况，并通过将这种重建与我们的计算机生成的地球虚拟历史进行详细比较，深入了解植被变化如何与气候和大气组成相互作用。