伦敦极端天气与全球变暖有什么关系呢？
Today we have more data. But now science has provided a theory, a model of the weather system. Fronts and anticyclones are individual weather events, which brings up the next question: what then is climate? Climate is the long-term average of all the weather events if you like. So if we look at a period of 30 years or 50 years, if we then take all the weather that’s occurred over those periods, the rainfall on a particular day, the sunshine, the warmth, whatever it might be, including the extreme events, and we average those data over a long period, and that’s what we describe as climate, but it’s not just a single figure, which says a long-term average of 10 degrees or whatever it might be. It also represents the variability that would occur during that long period on a day-to-day, year-to-year or decade-to-decade basis. So climate is average weather. But what drives this weather system? Solar energy warms the earth’s surface and this warms the air above. The air rises and moves away from the equator towards the poles. As it rises, the air cools, and then it sinks back towards the surface. This process is called atmospheric convection. These great convection systems drive the wind. But the atmosphere is only one factor contributing to the climate system. Another very important component is the ocean. Most of the radiation coming onto the earth falls in the equatorial regions, and that has to be redistributed around the globe. That job is shared between the atmosphere and the ocean. Water is very efficient at storing and moving heat around. That’s why you have water in your radiators at home and not the air. You can store as much heat in the top three meters of the ocean as you can in the whole of the atmosphere above it. Water in polar regions is cooled. Cold water is more dense than warm water, and so it sinks. In fact, cold water is continuously sinking in both polar regions. Meanwhile, the winds are driving the surface currents. The so-called gyro form of this current system results partly from the earth’s rotation and partly from the shape of the ocean basins. If we look at the surface and deep currents together, we can think of them as a kind of global ocean conveyer system. It carries cold, deep water through all the main ocean basins and returns warm, surface water back to the polar oceans, especially the North Atlantic. The atmosphere and oceans are intimately connected. Together they are the main driving forces of the climate system. So how could humans really have an impact on such a gigantic global system? Climate change has been a cause of concern for well over a hundred years now. In fact in the late 19th century the Swedish scientist, Arrhenius, warned quite explicitly that burning coal could lead to global warming. Climate change has been a cause of concern for well over a hundred years now. In fact in the late 19th century the Swedish scientist, Arrhenius, warned quite explicitly that burning coal could lead to global warming.