Headlock
Sales of sparkling water at a high, rivers at a low: The hot July 2006 breaks (almost) all records. But is it just an exception or is climate change already making its mark?
"Finally!" many would almost like to exclaim, the heat is finally over: being able to sleep rested at night, not being completely sweaty on the bike ride to the office in the morning or standing in traffic jams on glowing asph alt roads because the constant sun has upset the concrete slabs of the motorway. Maybe finally rain, which saves the crops of potato and corn farmers or at least spares the domestic lawn from an ignominious brown end.
A comprehensive change in the general weather conditions responsible for Central Europe makes it possible. Where previously stable and powerful high pressure areas with memorable names such as "Bruno" romped about, now low "Xaviera" is displacing the last patches of the heat wave. It all began on June 9, on the day of the opening game of the soccer World Cup, when a so-called anticyclonic south-east situation set in over Central Europe, which brought permanently dry and, above all, too warm weather: from south-eastern Europe to the B altic Sea and southern Scandinavia to the North Sea - sometimes also as far as Iceland - high air pressure extends, the descending air masses of which dissolve the clouds. Only occasionally did small disturbances move across Germany as the foothills of a low over the East Atlantic, which then sometimes brought very strong but only brief downpours.
This penetrance of the nice weather phases gave Germany a sunny and hot July, which even put the last exceptional summer of 2003 in the much sought-after shadow: "In the archives of the German Weather Service we cannot find a month that was hotter or sunnier than July 2006. This month is beating all records," says Wolfgang Kusch from the German Weather Service (DWD). Since Germany-wide weather records began in 1901, there has not been a July that weighed more than this year's average of 22.1 degrees Celsius.
Instead of the 16.9 degrees Celsius of the long-term average, this time the values were a full 5.2 degrees higher. In some places like Karlsruhe, Trier or Jena, every single day of the month went down in the annals as a so-called summer day with maximum temperatures above 25 degrees Celsius. In the southwest of the republic and in Brandenburg, the threshold of 30 degrees Celsius was often exceeded on more than twenty days. And at numerous stations, new record highs were also set - for example in Kalkar on the Lower Rhine with 38.6 degrees Celsius on July 19 or in Wernigerode in the Harz Mountains with 36.4 degrees Celsius the day after. However, the absolute temperature record of 40.2 degrees Celsius in Karlsruhe from August 2003 remained untouched, Bernburg an der Saale only reached 38.9 degrees Celsius.
To the suffering of farmers
Precipitation, on the other hand, was rare, so that only a little more than half of the usual rainfall in July wetted the dry soil in Germany. East Germany and parts of the north and extreme west were particularly affected, where in some cases not even a fifth of the usual amount of water came down after June had already affected these areas with drought. But when the floodgates opened, it could rain down violently: On July 7, Karlsruhe reported more than 76 liters of rain per square meter - more than in any other monitored July before.
And where the sky was mostly a flawless blue, the sun was able to shine undisturbed - much to the delight of solar power producers, who have been enjoying the summer so far. Because while normally almost 200 hours of sunshine represent the normal value of the month, this year the average duration of sunshine was more than 330 hours, on the B altic Sea coast even 400 hours.
But certain branches of the economy such as inland shipping or agriculture were less happy about this. The last hot, dry weeks meant enormous stress for plants in particular, as Günter Delfs from the DWD notes, while animal pests found optimal conditions. In the case of grain, for example, the ears of corn did not continue to grow in many places during the ripening period, so that losses are to be expected here. It was even worse for corn, which starts flowering later in the year and cob development fell in the middle of the worst drought. Bottlenecks are also to be expected with the hay, since the second cut often had to be cancelled. The forest may also have suffered, but according to Delfs, the consequences can usually only be foreseen later.
But not only Germany moaned – or was happy – about the hot days, large parts of North America also recorded one of the warmest June months since climate data collection began. In general, 2006 has been the warmest year since 1895, and according to preliminary data, July seems to be no exception. Almost half of the land area of the United States now suffers from drought. Drought is also the keyword for the southern Amazon Basin, which has suffered for the second year in a row from too high temperatures, lack of rain and rapidly falling river levels, as well as for southern England, where, in addition to pronounced heat, water shortages are making headlines.
All of this fits into the global picture, because according to the US National Oceanic and Atmospheric Administration (NOAA), last June was the second warmest ever recorded worldwide and the first half of the year was always the sixth warmest. The fever curve of the planet thus continues to show a rising trend, as the temperature deviations have increased considerably over the last 10 to 15 years - even if climatologists are unanimous in their opinion that a single summer like this is still not definitive proof of the projected climate change.
No surprise for climate researchers
But this July is no longer a surprise for Peter Werner from the Postdam Institute for Climate Impact Research, because it corresponds to all the forecasts of his profession. Since the mid-1970s, such periods of fine weather have been occurring more frequently, because at that time there was a new heat surge in the earth's atmosphere, which caused the general weather patterns to change spatially and temporally over Europe as well. This is why the stationary subtropical highs – such as the famous one around the Azores – are meanwhile strengthening in summer and expanding their influence further north. Rainy low-pressure areas, on the other hand, are now more common further north, according to the researcher. The result: stable, long-lasting sun phases in Germany, which, according to Werner, had never been seen before in this frequency in this country.
Summers like those of 2003 or 2006 should therefore become the norm in the future if the earth's temperatures continue to rise - even if there will always be downward peaks and a cold, wet July or August annoys people. However, according to the Potsdam researcher and Günter Delfs, these events are becoming rarer, which may make it easier for the population to remember them. In terms of climate, last winter wasn't as extreme as everyone assumed: "Rather, the memory of normal winters with ice and snow is fading," notes Peter Werner.
Maybe the beginning of August will also soon suppress thoughts of the hot July. According to Günter Delfs, it now looks as if dynamic Atlantic lows could dominate in this country: The low "Xaviera" is slowly moving from the East Atlantic towards the North Sea, transporting fresh sea air as well as individual showers and thunderstorms. At least in northern Germany, the weather that is actually typical for the time of year will soon prevail again, with a mix of sun, clouds and rain. But a small consolation on the side: Because of the heated North Sea, even with North Atlantic air currents, only mild things flow to Central Europe - so nobody has to freeze yet.
