Climate in the Past and the Future

Vesselin Alexandrov

Аbstract

 

Since the late 1970's climate in Bulgaria has been warming. In the second half of XX century, winters are milder.18 of the past 21 years after 1989 are characterized with positive anomalies of mean annual temperature relative to the climate norms of the reference period 1961-1990. The average annual temperature in 2009 was 1,2°C above the climate norm. This is the 12th consecutive year with temperatures higher than usual for the country. The annual amplitude between maximum and minimum air temperature decreased - the minimum temperature rises faster than the maximum one; Periods of drought have been longest in the 1940's and the last two decades of the XX-th century. The most significant droughts were in 1945 and 2000; Precipitation tends to decrease at the end of last century. Since mid-1990's annual precipitation tend to increase in most regions of the country. In recent years, increased frequency of extreme weather and climatic events are observed: storms, intense rainfall and flooding, hail, drought and forest fires, heat waves and others. The snow cover tends to decrease at the end of last century. The upper limit of the deciduous forests are shifting to higher altitudes. There is a trend of increasing water scarcity in the soil as a result of increased consumption of water that evaporates from the soil surface and transpirates by vegetation. When talking about possible changes in climate over the next 100-200 years, we have no kind of weather forecast, and examine different scenarios for climate change, based on various models and perceived changes in the factors on which climate depends. Most models include such factors and human activities. Many processes in nature are still not included in these models. According to simulations of climate change, drawn from the main emission scenarios, the expected temperature rise in Bulgaria are between 2 and 5 degrees by the end of the XXIst century.