Introduction The weather influences all of us either directly or indirectly. In rare circumstances it can threaten our lives with hazardous weather including gales, thick fog, flood-producing rain, lightning and more. Since most of us live and work in urban areas and travel by modern private or public transportation, we are less aware of, and less affected by, the weather than we would have been decades ago. I well remember my elementary school teacher saying that the weather is an Englishman's (or anyone's) standby, meaning that it was always a useful medium for striking up a conversation with a stranger. That was in the late 1950s. Since then, especially during the last decade or so, scientists have made us all aware of changes in our atmosphere that are potentially of great consequence to our lives. Nowadays, just about all of us are at least conscious of predicted future changes in our atmosphere that are linked to the way we live. The science of the weather has advanced dramatically over recent decades. Today, many national weather agencies can predict weather many days ahead, for the whole world. One major center, the European Centre for Medium-Range Weather Forecasts (ECMWF) in Reading, UK, is sponsored by over 20 European weather services to forecast the weather for the entire world out to ten days ahead. The continual improvement in weather forecasting is related to better observational networks, faster and better computers, and increased knowledge and understanding of how the atmosphere "works," including its interaction with the land and ocean surfaces. Nowadays there is also great international concern about global change and how it will impact upon our everyday lives. The discovery of the Antarctic Ozone "hole" stimulated rapid intergovernmental cooperation to tackle the main causes of the problem. The seasonal Ozone hole continues to occur and it is estimated that it is likely to do so until the middle of this century at least. Global change is principally related to the observed warming of the lower atmosphere in recent decades. Scientists are able to predict future climate change by using computer models. They look at changes over decades -- so that we can gain the best possible idea of what temperature and rainfall levels will be like globally, by the year 2050 for example. Work continues to improve these models and to compare them. They form the basis for concerted international effort through responsible governmental planning. That said, the Kyoto Protocol, which sets out the reduction in the emission of greenhouse gases by a certain target period and was signed by virtually all the world's nations in 1992, has yet to be ratified by a sufficient number to give it force in international law. As a result, the outlook for many island states is gloomy, their very existence seriously threatened by the measured and predicted increase in sea-level that is being forced by warming oceans and melting ice. Rising seas are likely to remain a significant problem for decades to come. Today's scientific methods of prediction haven't always been with us of course. For thousands of years humans have followed signs in the sky that would help to indicate how weather may progress during a day. Some would also have been aware of other natural guides to the possible character of an incoming season, for example the state of berries on a particular shrub or the timing of the migration of birds. Today we are aware of weather "lore," sayings that encapsulate such observational skill developed over long periods of time. "Red sky at night, shepherd's delight; red sky at morning, shepherd's warning" is one such saying still in circulation. The "red sky at night" rule works some of the time but only in regions where the weather systems arrive from the west, even so, the rule is obviously less reliable than today's computer predictions. The number and type of weather sayings in circulation globally is enormous. Some sayings are centuries-old seasonal indicators such as "If snow remains on the trees in November, they will bring out but few buds in the spring" (Germany) or "When birds and badgers are fat in October, expect a cold winter" (USA). Others are short-term, like "If the rain falls on the dew, it will fall all day" (Italy) or "If the wind is northeast three days without rain, eight days will pass before south wind again" (UK). Another tradition relates to changes in seaweed and pinecones, suggesting that changes in the bulk or shape of seaweed or pinecones indicate the likelihood of rain, It is based on the response of plant life to variations in relative humidity. When this increases with the approach of frontal rain, seaweed and pine cones will absorb some of the moisture, changing their appearance. Seaweed becomes more plump or less dry, and pine cones will partly close. Such humidity-related changes may simply reflect the daily variation in relative humidity under settled conditions, which occurs as the air temperature increases to a peak in the afternoon then decreases to a minimum during the night. True, there will be changes on the approach of moister air ahead of a depression, but for the vast majority of us, the sky is a far more reliable source of harbingers of a frontal system. The notion that the weather on a particular day of the year may indicate the nature of the weather to come over the following month, or more, is the basis of Groundhog Day in the USA, and St. Swithun's Day in the UK. Groundhog Day, on February 2, takes place at Punxsutawney, Pennsylvania, involving a captive groundhog known as Punxsutawney Phil. If he sees his shadow when he pokes his head out of his burrow, winter will last another six weeks; if he does not see it, spring is just around the corner. If the day is sunny and, therefore, probably cold and anticyclonic, local folklore has it that these conditions will persist. If there is no shadow, it is obviously cloudy and probably milder. However, there is no real evidence that this particular day is the key to forecasting long-term weather patterns. St Swithun's Day on July 15 in the UK is another example. Swithun died in 862, when he was bishop of Winchester, and he was buried at his own request in the cathedral grounds. After his canonization the following century, it was decided to move his remains to the choir of the cathedral on 15 July. The plan was abandoned, however, after 40 days of rain that began on that day. Lore has it the weather on St. Swithun's day is supposed to dictate the nature of the weather for the next 40 days. If it rains on July 15, it will rain for 40 days, if it remains dry, there will be no rain for 40 days. In the cold light of scientific reality, a wet St. Swithun's Day is extremely unlikely to start a run of wet weather lasting nearly six weeks in Winchester or anywhere else. In addition to looking at how forecasts are made today, this book provides an overview of meteorology for those who want to gain a basic understanding of what makes the weather "tick," and to appreciate what lies behind some of today's great atmospheric environmental issues. If you are interested, for example, in being more involved in taking your own observations, obtaining advice about using weather science in schools, linking up with others interested in the atmospheric environment or receiving magazines and newsletters, there are learned societies you can contact, all with regional centers. All welcome foreign members too. In Europe, the European Meteorological Society encourages anyone interested in weather and climate to join one of its member societies, for example the UK's Royal Meteorological Society. Similar societies exist in the USA, Australia, New Zealand and Canada. They can be contacted by mail or via the Web. In addition, the "Climatological Observers' Link" exists to promote the collection and exchange of weather observations by anyone interested to do so. Useful addresses and websites are listed at the end of the book. Excerpted from Guide to Weather by Ross Reynolds All rights reserved by the original copyright owners. Excerpts are provided for display purposes only and may not be reproduced, reprinted or distributed without the written permission of the publisher.
