Is Our Climate Changing Mercury is the planet closest to the sun It has virtually no atmosphere and as a result the temperature on the planet’s surface fluctuates wildly The average temperature on the side of Mercury that faces the sun is 800 F 427 C on the side that faces away it is 300 F 184 C Because Mercury spins very slowly on its axis each day on Mercury is longer than the planet’s year of 88 earth days Effects of climate change You might not think that you would notice a difference of only 1 5 F 0 9 C in the temperature and if the only effect were to make the air a little warmer you would probably be right But a rise in temperature even a small one has significant effects on the world around us Weather systems are very sensitive to even the slightest changes A small rise or drop in temperature can be enough to trigger a tropical storm instead of a wind a drought instead of a dry spell or a flood instead of a rainy period Extreme weather events such as heat waves and tropical storms are becoming more frequent These events can have serious direct impacts people often die in heat waves floods and tropical storms but they also have other more indirect effects They change conditions for farming for example sometimes causing crop failures that can lead to famines Even weather that appears less severe can create problems A winter that is milder than normal with fewer frosts and less snow means that more pests can survive to damage crops or cause disease in the following year Drought causes crops to fail In this field of corn between 70 and 90 percent of the crop was lost because there was not enough rain 10
FORUM People hold different views about the human contribution to climate change The human contribution is not significant and observed increases in carbon dioxide and other greenhouse gases make only a negligible contribution to climate warming Professor David H Douglass University of Rochester International Journal of Climatology 2007 Humans are changing the earth and it’s a big effect we’re having Mike MacCracken chief scientist for climate change projects at the Climate Institute in Washington D C What do you think What is climate change Extreme weather can eventually make some areas uninhabitable In some places desertification is already a problem As populations increase people put more demands on the land clearing it to grow crops and taking more water from wells These actions often combined with less than average rainfall result in the land drying out As the land turns into desert the types of plants that can survive also change grassland and crops are replaced by tough scrub that needs little water These plants cannot support people or livestock and make the land unusable by humans How we use the weather In many parts of the world people have built their livelihoods on known and reliable weather patterns Crops and livestock are especially weather dependent as the climate changes people may have to think again about the crops they grow and the foods they eat Areas that depend on tourism may also find that their income is affected as the weather changes Some low lying ski resorts may have less snow and some seaside resorts may become too hot and dry or too prone to storms to attract customers In some ski resorts snowfall has decreased to such an extent that artificial snow is used to cover the runs
Chapter 2 Has the climate changed in the past Climate change is not new The climate has changed throughout history and prehistory sometimes in very extreme ways Hot and cold There is plenty of evidence for climate change in the past Some historical documents are good sources of information about the climate of a particular period even if they do not record actual temperatures For example we know from written accounts that there was a period during the Middle Ages when temperatures were warmer than they had been in previous centuries at least in the area around the North Atlantic Ocean Between the ninth and thirteenth centuries people could grow grapes for wine making in quite northern areas of Europe The ice-free northern seas also allowed the Vikings to explore Iceland from AD 874 and Greenland from AD 985 This contemporary engraving of a frost fair on the Thames River in England in the winter of 1683 to 1684 shows that winters were colder in the seventeenth century than they are today This trend reversed during the sixteenth to nineteenth centuries when Europe experienced the Little Ice Age In about 1300 Arctic pack ice started to expand and the reliable warm summers of the Middle Ages ended By the mid-seventeeth century some glaciers in the Alps had extended far enough to crush villages in their paths 12
Has the climate changed in the past Winters became colder causing rivers and canals in northern Europe and North America to freeze over Since the mid-nineteenth century the climate has been warming again Few scientists dispute that warming is happening but there is no universal agreement about why it is happening Prehistoric climate change We know that in the distant past there have been several true ice ages when temperatures over the entire planet fell far lower than they are today The last ice age ended about 10,000 years ago at a time when humans were well established on earth but had not yet begun to build civilizations The well-preserved remains of this mammoth were recovered from the permafrost in Siberia Mammoths lived during the last ice age Some scientists believe that mass extinction events may be caused by climate change Mass extinctions occur on average every 26 30 million years and wipe out many of the species living on earth A mass extinction event ended the era of the dinosaurs 66 million years ago It is likely that this event was caused by climate change possibly triggered by an asteroid hitting earth or a series of massive volcanic eruptions Either of these cataclysmic natural disasters could have caused climate change on a vast scale either because dust in the air blocked heat energy from the sun and made the earth colder or because a thick blanket of greenhouse gases trapped heat and made the earth warmer FOCUS Salty water David and Mary Mallia have an organic fruit farm in Malta an island in the Mediterranean Sea Like other people on Malta they draw fresh water from a well which is usually replenished by rain In recent years there has been less rain and the sea level has risen The water in the well is now becoming salty and can no longer be used for irrigating the Mallias’s crops If you water your trees with this water it will kill them David says 13
