Frequency of heat waves shows change

Climate change is no longer seen as a future scenario. In Greece, the first signs were seen last winter and then again in the summer. How these phenomena develop is largely up to us, and depends on the models of growth we choose, which will determine the future increase of greenhouse gas emissions. It is not the heat waves that show the climate has changed, but the frequency at which they occur. Between 1961 and 1990, Athens had a total of 28 days of temperatures over 40 degrees Celsius. According to scientists’ estimates, between 2071 and 2100, these will total 580-1,078 days, depending on the increase in emissions. The world increase in greenhouse gas emissions (mainly carbon dioxide, which is produced in all combustion processes) by 2100 is expected to be of the order of 62-520 percent depending on what measures are taken to reduce emissions. In practice, this means concentrations of 850-950 parts per million of CO2 in the atmosphere, compared to 380 ppm today. This is a realistic scenario according to the researchers. These emissions will result in an increase of at least 3.5 degrees Celsius in the average temperature and a rise in sea levels of 0.35 to 0.45 meters. These figures refer to climatic change over the planet as a whole, according to figures from the Intergovernmental Panel on Climatic Change (IPCC). The group’s estimates for Greece show a considerable increase in the average maximum temperature throughout the region, but above all in the Balkans, where the average maximum temperature for July is expected to increase by up to 11 degrees Celsius. In Greece, that increase will be from 6.1 to 8.9 degrees Celsius in the southern areas, and from 6.5 to 10.7 in central and northern parts. Lower increases are expected for the months of June and September, to range from rises of 3.9 to 8.9 in the south and 3.4 and 9.9 in central and northern Greece. In Athens, the average maximum temperature in July is estimated to rise from the 33 degrees it is today to 41 degrees Celsius. Drastic reductions in the amount of rainfall are also expected – about 20 percent, which will be as much as 80 percent in summer months. In December, the month with the highest amount of rainfall, there will be a considerable reduction, particularly in the Eastern Mediterranean but also in Western Greece, where the average rainfall figures for 2071-2100 are expected to be 60-70 percent lower than at present. In northeastern Greece, however, the islands of the eastern Aegean and Crete, the difference will not be as marked. There will be even less rain during summer months, particularly in northern Greece and the Balkans, where rainfall is expected to be 20-30 percent lower than today. «Particularly in parts of the former Yugoslavia, Bulgaria and Romania, the reduction in rainfall during summer months is causing great concern as the rain there feeds the major river systems that flow into Greece,» said Elena Georgopoulou, a researcher in the observatory group. The average rainfall per month will decrease considerably, particularly in July and August (by 64-77 percent) with the greatest reduction in Athens and the lowest in Thessaloniki. So the future is likely to be much hotter and definitely drier. «This summer we got a taste of what is to come,» said Georgopoulou. «Imagine July with temperatures over 40 degrees, and occasionally temperatures of around 50 degrees,» added Dimitris Lalas of Athens University’s Department of Physics, who explained that urban populations will want to move to cooler regions. «There will be greater demand for homes on Mt Parnitha, for example, which is 1,000 meters above sea level, and therefore has temperatures that are 6-7 degrees lower.»