Southern Hemisphere climate change in an era of ozone recovery

在过去的三十年里，南大洋周围的西风变得越来越强，这种大气环流的变化导致南极洲大部分地区变冷，南极半岛和南美洲南部变暖。最近的研究表明，这一趋势还影响了海洋的环流和温度，以及海洋对温室气体二氧化碳的吸收。气候模型表明，大气循环的这种变化部分是由温室气体的增加引起的，部分是由臭氧空洞造成的。温室气体水平很可能在未来50年内继续增加，但由于国际上对破坏臭氧的化学品的排放进行监管，预计臭氧空洞将开始恢复。然而，臭氧空洞何时以及以多快的速度开始恢复是非常不确定的，不同的计算机模拟产生了截然不同的结果。以前的气候模型对未来气候变化的预测通常要么假设臭氧层空洞不会恢复，要么使用对未来臭氧变化的单一预测。我们计划使用英国气象局开发的最先进的气候模型，来推导出一系列对未来气候变化的预测，其中考虑到我们对未来臭氧变化的不确定性。我们将首先将过去25年大气环流的模拟变化与气候观测进行比较，以帮助我们了解过去趋势的原因。我们还将研究这些趋势对南半球气候和南大洋环流的影响。然后，我们将测试臭氧变化的一系列预测。这些预测是使用对大气化学变化的计算机模拟做出的，我们将通过将过去臭氧变化的模拟与卫星和气球的观测进行比较来检验它们。一旦我们确定了过去臭氧变化的四个最现实的模拟，我们将使用最新的气象局气候模型来模拟未来45年未来臭氧变化的四个相应情景中的每一个的气候响应。未来的温室气体变化也将在气候模型中具体说明。我们将使用这些气候模型模拟来预测南半球未来可能发生的环流变化的可能范围，以及这些变化对大气和海洋的影响。如果臭氧恢复逆转了历史上的环流趋势，这种影响可能包括南极洲变暖加剧，从而加快冰川融化和海平面上升；澳大利亚变暖和变干加剧；海洋对二氧化碳的吸收发生变化。

Over the past thirty years, the westerly winds blowing around the Southern Ocean have grown stronger, and this change in the circulation of the atmosphere has led to a cooling over most of Antarctica, and a warming of the Antarctic Peninsula and southern South America. Recent research suggests that this trend has also influenced the ocean circulation and temperature, and its absorption of the greenhouse gas carbon dioxide. Climate models indicate that this change in atmospheric circulation has been caused partly by the increase in greenhouse gases, and partly by the ozone hole. Greenhouse gas levels are very likely to continue to increase over the next fifty years, but the ozone hole is expected to start to recover, due to international regulation of emissions of the chemicals which destroy ozone. However, it is very uncertain when and how quickly the ozone hole will start to recover, and different computer simulations produce very different results. Previous climate model predictions of future climate change have generally either assumed no recovery of the ozone hole, or they have used a single prediction of future ozone change. We plan to use a state-of-the-art climate model, developed at the Met Office, to derive a range of predictions of future climate change which take account of our uncertainty in future ozone change. We will start by comparing simulated changes in atmospheric circulation over the past 25 years with climate observations to help us understand the causes of past trends. We will also examine the effects of these trends on the climate of the Southern Hemisphere, and on the circulation of the Southern Ocean. We will then test a range of predictions of ozone change. These predictions are made using computer simulations of changes in atmospheric chemistry, and we will test them by comparing simulations of past ozone changes with observations made by satellite and balloon. Once we have identified the four most realistic simulations of past ozone change, we will use the latest Met Office climate model to simulate the climate response to each of the four corresponding scenarios of future ozone change over the next 45 years. Future greenhouse gas changes will also be specified in the climate model. We will use these climate model simulations to predict the likely range of possible future circulation changes in the Southern Hemisphere, and the impacts of these changes on the atmosphere and ocean. If historical circulation trends are reversed by ozone recovery, such impacts could include enhanced warming over Antarctica, and hence faster ice melt and sea level rise; enhanced warming and drying of Australia; and changes in the absorption of carbon dioxide by the ocean.