None of these events are truly remarkable when considered individually. But together they represent a clear and alarming trend towards wilder weather conditions. "These extreme events all go into calculating the monthly and annual averages which, for temperatures, have been gradually increasing over the past 100 years," says Kenneth D Davidson, director of the World Climate Programme, wmo. According to recent reports of the Intergovernmental Panel on Climate Change, the global average surface temperature over the 20th century has increased by around 0.60c. This value is about 0.15c more than the previous estimates. Global average land and sea surface temperatures in May 2003 were the second highest since 1880. "Soon 2003 may be the hottest year ever recorded," asserts Davidson.
To date, the 10 hottest years in the 143-year-old global temperature record have all been after the 1990, with the three hottest being 1998, 2002 and 2001. Extreme weather events also increased during this period -- there were 63 weather-related disaster declarations in 1998, far more than the average 21.7 disaster announcements made per year during the 1980s. For instance, there were 26 flood disasters worldwide in the 1990s, but just 21.7 per year during the 1980s. The frequency and intensity of extreme weather increases due to a change in the distribution of heat, which disrupts the flow of energy through the climate system, altering the circulation patterns of the atmosphere and oceans, and modifying the Earth's hydrologic cycle. Higher temperatures also increase evaporation and transpiration, and raise the air's capacity to hold moisture, making more of it available to fall as rain and snow.
With the weather becoming unpredictable, both human casualties and economic losses have increased over the years. In the 1980s, the world's property insurers lost an average of us $2 billion annually to extreme weather events. But in the 1990s, losses exceeded us $12 billion annually. For just the first 10 months of 1998, weather-related expenses (us $89 billion) far exceed the losses for the entire decade of the 1980s.
Poor nations tend to suffer far more than wealthier ones -- while flooding in Mozambique cut the country's gross domestic product (gdp) by 45 per cent in 2000, floods of the same scale in Germany last year were blamed for just a one per cent decline in the nation's gdp. Hopefully, wmo's warning will help save numerous lives and minimise losses worth billion of dollars this year.