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/D001684/1
• 负责人: Paul Valdes
• 金额: $ 5.65万
• 依托单位: University of Oxford
• 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%2FD001684%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.

在过去的两万年中，地球的气候从整个冰河时代变成了温暖的时期。在冰河时代，欧洲和北美有大型冰盖，冬季的海洋寒冷，海冰地区很大，冰冰地区很冷，通常干燥，全球森林大大降低，气候被非常低的二氧化碳和其他“温室气体”和其他大量的空气中的粉尘保持在寒冷。最后一个冰河时代的气候也不稳定，被大量的冷却和持续数十年至数百年的突然变暖所刺破。冰河时代后的变暖突然被持续一千年的寒冷时期打断了。从那时起，气候一直更加温暖，更稳定，但是气候，植被和气氛仍然存在变化。例如，在工业革命始于急剧上升之前的大约八千年中，二氧化碳浓度的增长缓慢。一些气候变化是戏剧性的，例如撒哈拉沙漠的形成。这些事实已经建立得很好，但是要了解它们背​​后的机制仍然是科学的挑战。气候变化以及温室气体和灰尘的工业前变化的原因（反过来影响气候）尚不完全了解。唯一已知的外部原因是地球轨道的变化，这逐渐改变了在不同纬度和季节收到的太阳能量的数量。地球显然以非常复杂的方式，有时突然以非常复杂的方式对这种变化做出反应。尤其是气候变化不仅是物理问题的线索，尤其是大气的变化。它们还涉及“生物地球化学周期” /大气，海洋和土地之间的碳和其他元素的交换，这些元素受到活生物体的调节。了解这些过程尤其重要，因为人类活动现在正在改变气氛和气候，我们需要能够预测长期后果。对“反向”进行预测是测试我们使用的模型的一种方法。该项目的目的是对从最后一个冰河时代到最近的时期驱动气候变化，大气成分和生物地球化学周期的变化的全面了解。我们将结合两种通常是分开的工作方式。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，包括动态的全球植被模型，该模型可以预测湿地，沙漠和森林大火的变化。这将使我们能够模拟许多影响气候的重要物质的土地 - 大气交换，例如二氧化碳，甲烷，挥发性烃，灰尘和烟灰。我们将使用这些模型的版本非常有效，因为它们仅模拟大规模模式。这样，我们可以进行比通常这样做的更多和更长的模拟。另一方面，我们将使用现有的数据库和新的数据分析方法来重大综合世界各地沉积物核的数据，包括花粉计数（过去的植被的指标），木炭计数（过去火灾的指标）和碳同位素测量值。这项工作将首次提供从最后一个冰河时代到最近的地球状态状态的连续图片。我们将评估气候模型的工作状况，并通过对我们的计算机生成的地球“虚拟历史”进行详细比较，从而了解植被变化如何与气候和大气组成相互作用。