水循环是一个常见的，浅显的自然现象。水蒸发后，水蒸气由风抬升，飞过高山，然而冷却，压缩，降水，流回再进入另一个循环。

地球每转动24小时就有14万亿吨的水被抬升到大气之中，其中约20%被降回我们生活的陆地上。位置、时机和温度是由我们现在开始了解的多个因素所决定的，其结果解释了最近奇怪的天气状况，警示我们地球变暖。

世界气象组织将反常天气定义为每25年或者更长时间内才发生一次的天气。在过去数年间，灾难性天气频繁登上世界各国和中国报纸的头条，如中国南方出现罕见的暴风雪，北方出现一个世纪以来最严重的干旱等。

现在是时候用崭新的现代视角来观察不可思议的水循环，分析世界的山地、河流和天空的观测数据，理解人类究竟正在怎样影响地球。

海洋表面“温和的烹饪”

光子以每秒30万公里行驶，以光子形式的电磁力被圆盘形的地球所拦截，拥有每秒162000万亿焦耳（162 petawatts）的能量。其中，约有一半的能量到达地表，一半加热了海洋和湖泊的水面，这能量足以产生蒸发作用。这一自然现象规模之庞大使人受到启发而仔细思考。例如160年前，詹姆斯.焦耳（James Joule）所发现的基础物理学表明，1卡路里的热量可以将1立方厘米的水加热1度。（国际标准单位中，4.148焦耳等于1卡路里）当地球缓慢地以每小时1000公里的速度转动时，在水表面产生温和的“烹饪效应”，一定程度上将水抬升到数公里的天空中。如果是一立方米的水，每天就被抬升24公里。

来自太阳的热量是经过大气过滤的。干洁大气有一种低抑制因子，水汽越重，到达地球表面的能量越少。其他气体也折射和反射光子，因而削弱了能量，加热了地表水。但这种效应不被经常讨论，在评论全球水循环如何对我们产生影响前，我们需要确切地阐述被我们认为是理所当然的基本自然功能。

我们应该感谢地球的两项活动，假定我们不打算改变它们，即使我们珍惜它们恒久不变的状态，而气候变化也可能将它们剥离。地球在真空中以每小时10多万公里的速度疾驰（假定其季节变化）并以每小时超过1000公里的速度转动，为我们降温和供暖，并将部分动力传递给转动着的海洋和大气。现在，前景光明的生态信息学界启发了我们对海洋和气流模式的认识。

就像空气动力学工程师在一个风洞中跟踪汽车周围的空气分子流一样，在模糊条件下，科学家团队能界定各种风型常规流向何处，并能跟踪最近在温暖的中低纬度地区出现暴风雪的某些极端反常天气（这让全球变暖的否认者幸灾乐祸）。这些新的反常风型也导致农民所依赖的季节性降水完全混乱。

这方面，中国走在新研究领域的前列，在开拓科学发展的国家政策激励下认识新的研究问题。水是不能被生产但也不会消失，只要人类简单地从水的自然循环中取用，然后再还回自然就能达到平衡。然而，用水最好能有个限度，比如，中国年度GDP的计划用水量限制在6700亿立方米。

物质流分析是一种相似的方法，由于水是一种市场化商品，就像棉花和铝，它的价格自然由供给和需求决定。水也有“生命周期”，就像铁，从自然界提取、冶炼、加工后配送到工厂，制成的产品进入千家万户，最后有的产品能再回收，有的则被废弃。北京师范大学和北京大学两位教授率领的一个团队正在尝试一种可能带有意义深远的革命性方法，即使用《火用》的概念作为统一资源核算口径，既包括质还包括量。

北极风“跳出城墙”吹向南方

过去的两年，北半球流体流动的一项引人注目的新现象已得到揭示。以前，北极上空的大气冷而密，形成的极涡非常紧，它几乎没干扰或中断海洋和墨西哥湾暖流的大气，墨西哥湾暖流是巨大的热量传递纽带，从赤道北部和大西洋北部一直到美国东北部、欧洲，太平洋北部，北美北部地区，乃至日本、朝鲜和中国北方地区。

全球变暖正在两极地区发生是毋庸置疑的，自从1979年卫星照片记录出现以来，北冰洋30%的冰面消失了。过去，冰面能反射太阳光，现在，由于水吸收太阳光，气候变暖则加速了。过去冷而紧密的极涡现在不再那么紧密，向外扩大延伸与墨西哥湾暖流相撞，由此带给地区史无前例的暴风雪，加重了季风影响地区的干旱和多雨等极端天气。

多数情况的降水是一种只在当地的简单地形循环，陆地风将云吹向山地，凝结，降水之后流回大海。世界最高年年降水量和最高降雨量记录都是这个循环形成的。当然，情况也在变化，人们应该研究如何帮助农民规划种植进度，农民应该种什么、他们能多大程度依赖水库和水的输送渠道。而农田的水资源配置、贮存和输送的规划和执行将需要更多的科学支持。即使不谈农业的例子，随着水循环的改变，我们将需要重新考虑正在经受急剧气候变化的城市的未来。例如，工业发展正‘‘滥用’’经过多年变化达成的全球生态系统的平衡，全球生态系统已经发生巨大改变，而零增长的工业扩张（不可能的事）还将影响地球已遭受严重影响的水循环。也许在未来的冬天，暴风雪、洪水和干旱将发生在过去没有经历过这些恶劣天气的地方。因此，现在开始储备会是件明智的事。

Kids learn about the water cycle in middle school – water evaporates, uplifted by wind over mountains, cools, condenses, rains, and flows back down for another cycle. Beautiful and true. If we did not have our mind on other things in those puberty years we may have thought about it more and understand what it now means to our lives now.

14,000,000,000,000 tons of water are lifted into the air each 24 hour rotation of the Earth, and about 20% is dumped back on where we live, on the land. The location, timing, and at what temperature are decided by factors we are now beginning to understand and the results explain recent weird weather and warn us on global warming.

The World Meteorological Organization defines abnormal weather as that which occurs only once in every 25 years or more. In the last few years, disastrous weather has been frequent headlines around the world and certainly in China, with freak blizzards in southern China and the worst drought in a century in north China. It is time to take a modern, fresh look at the miraculous water cycle, analyse the buildings-full of data now monitored around the world on mountains and rivers and in the sky, and understand what on Earth humans are doing to impact on it.

“Gentle cooking” of the oceans’ surface

The electromagnetic forces in the form of photons traveling at 300,000 km per second that the disc shape of the Earth intercepts have an energy of 162,000,000,000,000,000 joules per second (162 petawatts). About half that reaches the Earth’s surface, and half of that warms the water surfaces of the oceans and lakes sufficient for evaporation. It is enlightening to reflect on the gigantic scale of this natural phenomenon. Basic physics explored by James Joule 160 years ago demonstrates that 1 calorie of heat can warm 1 cubic centimeter of water by 1 degree. In Standard International units we now use the unit of energy, joule, of which 4.148 equal a calorie. We have personal experience of water in the stove and observe it evaporating. As the Earth rotates “slowly” at over 1,000 kph, the photons, not like lasers, but as random very high speed jostling through the molecules of oxygen and nitrogen in the air (which explains where half the energy goes – bounced back and reflected into space or transmitted to warm the atmosphere), have a gentle “cooking effect” on surface water, to the extent of lifting the water several kilometers into the sky. If it was a cube of water it would have sides of 24 kilometers lifted each day.

The amount of heat applied from the sun is filtered by the atmosphere. Clean dry air has a low inhibiting factor and with heavy water vapor less energy reaches the Earths surface. Other gases also refract and reflect photons debilitating their power to heat surface water. This effect is not commonly discussed, compared with the volumes of scientific and common discussions on the second stage, return trip – how the Green House Gases trap heat that decades before industrial pollution were reflected back into space. Before we comment on how we might be impacted on by the global water cycle, we need to enunciate its fundamental natural functions which we have taken for granted.

There are two activities about the Earth that we should acknowledge and assume we are not going to change, even though we need to appreciate their constancy on which climate change may spin off. The Earth is hurtling through a vacuum at over 100,000kph (giving its seasonal change) and rotating at over 1,000kph, cooling and heating us and imparting partial momentum to the swirling oceans and atmosphere. A bright new world of Ecological Informatics now lights up our understanding of the basic ocean and air current patterns.

Just like aerodynamic engineers tracking streams of air molecules around a car in a wind tunnel, teams of scientists can define, within fuzzy limits, where wind patterns normally flow, and can track some radical recent anomalies that seem to turn cause blizzards in warm latitudes (and cause Global Warming deniers to gloat). These new wind pattern anomalies also cause havoc to the seasonal rainfall farmers rely on.

China is at the forefront of new research and understanding through encouragement by the national policy of pioneering new outlooks on Scientific Development. Water is a chemical compound, a molecule of three atoms, and is subject to the principle of Material Balance, a scientific approach applied by Professor Ma Zhong, Dean of the Environment Faculty, Renmin University. Water is not produced or consumed, but simply taken out of its natural cycle by humans and then returned. The numbers must add up, and, for example, the volume of water used in the annual GDP of China is planned to be limited to 670,000,000,000 cubic meters. A similar approach, Substance Flow Analysis, is being pioneered by Professor Shi Lei, Department of Environmental Science and Engineering, Tsinghua University. Water is a market commodity and just like cotton and aluminium, has a natural price dependent on supply and demand. The “life cycle” of water, can be likened to that of iron, extracted from nature, processed and refined, delivered to industry and households, and then treated for recycling or as “waste”. A brave and radical approach which may revolutionize the science is being trialed by a team led by Professor Chen Bin, Beijing Normal University, and Professor Chen Guoqian, Peking University using the concept of exergy as a unified measure of resource accounting encompassing both matter and energy, and both quantity and quality. Quality of water is increasingly more critical as pollutants make assessments more complex. This new approach was applied to a comprehensive study of the Yellow River and results shed new understanding on water flows through human habitat.

The Arctic wind “leaps the wall” to the south

The past two years have revealed a remarkable new phenomenon in northern hemisphere fluid flows. Previously the air over the Arctic was so cold and dense that it formed a vortex so tight that it barely interfered or interrupted the ocean and air of the Gulf Stream that acts as a giant conveyor of heat from the equator north, north in the Atlantic to the north-eastern US and to Europe, and north in Pacific to northern North America, and Japan, Korea and northern China. There is no doubt that Global Warming is occurring at the poles, with 30% of the ice surface on the Arctic Ocean disappeared since satellite photo records commenced in 1979. The warming is accelerated by the water absorbing sunlight as opposed to the previous ice surface reflecting it. The previous cold dense vortex is not so tight and now spins out wider to clash with the Gulf Steam, bring blizzards where they are unprecedented, and exacerbating the extremes of dry and wet in the monsoon-influenced regions.

Most rainfall is a simple fairly local orographic cycle where onshore winds blow clouds up hills to condense and flow back to the sea. The world’s highest annual rainfalls and most record downpours are attributed to this cycle. Understanding how new human-induced effects on global fluid flows interfere with previously established water cycle patterns will be necessary for success in future living. This is certainly the case for farmers planning their planting schedule, in terms of what they plant, and to what extent they can rely on water reservoirs and delivery channels. More science will need to go into the planning and implementation of water allocation to farmland, in storage and in delivery flows. And beyond the obvious case for agriculture, cities experiencing drastic climate change as the water cycle alters will need to reconsider their future. The sad fact in no need of elaboration is that the rising crescendo of industrial abuse to our finely tuned global ecosystem means it has already changed and zero increase now of industrial expansion (impossible) would still us leave the water cycle significantly affected. In the coming winter there will be blizzards, floods and droughts in places where such severity have not been experienced in the past. It would be wise to take stock now.