Adam Scaife - 30-Second Weather: The 50 Most Significant Phenomena and Events, Each Explained in Half a Minute

Tackling the greenhouse effect will test human ingenuity, making scientific knowledge and understanding of our planet and its atmosphere even more pressing during this century.

Professor Adam A. Scaife

The atmosphere is inextricably linked with human endeavour. There are countless examples: the early loss of ships at sea in fierce storms; fortuitous Trade Winds that aided the crossing of vast oceans; devastating droughts, floods and hurricanes that still take thousands of lives even today; and the reliance on the regular onset of rainy seasons that sets the timing of agriculture the weather has an enormous impact on us all. It has shaped cultures and is even responsible for key turning points in history, such as the failure of Napoleons march into Russia in the grip of winter in the nineteenth century or the mass displacement of farmers in America due to the Dust Bowl drought of the 1930s.

These events and their consequences come about because the atmosphere is constantly changing. It varies on all timescales from the afternoon sunshine that brings us outdoors to the prolonged rains of the tropical monsoons. There are even decades where the weather keeps reverting back to similar behaviour summer after summer or winter after winter, only to change and be followed by years of the opposite. This apparently mysterious behaviour arises because the atmosphere is actually a constantly circulating fluid; trapped in a thin layer at the surface of our rotating Earth it swirls and flows just like the water in your bath tub. Apart from a lack of internal friction, the equations that govern the future behaviour of our weather and climate are almost the same as the equations that apply to the swirling fluid in your morning cup of coffee.

There are just six mathematical equations that encapsulate all of this and they can be written so concisely that they fit onto the back of a postcard. In fact, given their enormous significance, it is surprising they are not printed on T-shirts! These few equations that determine the fate of our weather also stem from well-established, or even old physics: they derive from Newtons laws of motion, the physics of heat and gases that was uncovered more than a century ago and the fact that air is neither created nor destroyed as it blows around with the wind. Yet despite the fact that we know so well the equations that govern what the future weather will be, they are still shrouded in uncertainty. This is because the problem is not like your school maths exercise where pencil and paper will do, instead the equations are intractable: they simply cannot be solved precisely. Even worse, they show that small changes can eventually give rise to big impacts through chaos and the revelation that a seagull flapping its wings can actually result in a hurricane months later fundamentally puts limits on any forecast. This is what makes meteorology so challenging and yet so compelling, and understanding the fluid that is our atmosphere is one of the most active remaining areas of terrestrial physics.

Harnessing the power of the wind, constantly circulating the planet, is one early example of how the human race propelled itself towards becoming a global society.

Modern advances in understanding and the production of improved forecasts from hours to years ahead are now completely dependent on modern technology. A suite of scientific instruments measures various parameters of the Earths atmosphere. Arrays of environmental satellites continuously monitor the behaviour of the atmosphere and oceans and relay their measurements back to Earth: polar orbiters constantly circle the Earth in an almost northsouth orbit at 800 kilometres altitude and geostationary satellites are sited 36,000 kilometres above the surface.

These vital observations, along with terrestrial measurements from weather stations, radar, aircraft and weather balloons are automatically incorporated into vast databases that constantly update our changing picture of the global weather. Some of the most powerful computers on the planet are used to pick up this latest information, combine it with computerized representations of the underlying equations and calculate what will happen next. The results are remarkable: the computer models produce virtual simulations of the Earths global weather that contain just about everything we see, from jet streams and hurricanes to multi-year climate oscillations between the ocean and atmosphere like El Nio. All of these features emerge spontaneously from the few fundamental equations at the core of the computer models. The results of this daily application of basic science drive everything from the forecast made this evening by your local TV weather forecaster to the century-long projections that affect government policies on climate change.