In Spain droughts are a fairly recurring natural phenomenon and even more so in all Mediterranean environments. The frequency and intensity of the same is increased by the effects of climate change And, although economic activities and natural systems have adapted to this characteristic of the climate, they cannot do so in this scenario, which affects sustainability.
This situation of drought and increased temperatures has led to the hottest and driest summers in the last three centuries in recent decades. What effects does this situation have?
More heat, less water
For two decades, members of the research group Climate, Water, Global Change and Natural Systems of the Department of Geography and Spatial Planning They reconstruct the climate of the past based on the radial growth of the oldest trees in Spain. With this research, they hope to understand what the climate has been like in previous centuries and estimate the severity and progression of the effects of climate change.
We must bear in mind that many climate changes have occurred throughout history, but they have not been as rapid as the one currently occurring. For an increase in average temperatures similar to that of today, millions of years passed. However, current climate change is happening on a human scale, that is, in just a few centuries.
This information can be obtained by studying the radial growth of trees such as pines. The journal Geophysical Research Letters now includes the analysis of samples from 774 trees of the species Pinus sylvestris and Pinus uncinata Located in the Iberian mountain range, since the length of instrumental climate records (data measured at meteorological stations) reaches 100 years at best, a time period insufficient to assess the possible exceptionality of the current climate. You can read more about the driest summers in Spain in the context of these changes, as well as consult Spain's climate classification to better understand variations in climate.
Study of tree growth
Thanks to the information that is collected from the measurements of the growth of the trees, it is possible to know how the climate has evolved. When each tree gives rise to the late wood, that is, the darkest that is generated in the final stages of annual growth, it is possible rebuild the effects of the drought in the summers since the first decades of the XNUMXth century.
We began working with summers from the 18th century, since this was the beginning of the Industrial Revolution, when greenhouse gases began to be emitted through the Industrial Revolution. In this sense, it is interesting to see how The rain in Spain has decreased in recent years, severely affecting the drought. Studies on temperature records in Spain They also reveal worrying changes that align with this trend of historical droughts.
It is the first time that scientists have been able to reconstruct the climate of past centuries in this way. The technique is called Standardized Evaporation and Transpiration Index (SPEI), referring in this case to the months of July and August. Summers have become increasingly drier, and are now record-breaking. This phenomenon has also been studied in relation to .
Something that is taken into account in these measurements and that is important for the elaboration of results and conclusions is that this index used in the measurements takes into account the additional stress experienced by natural systems in the event of a possible abnormal decrease in rainfall, in a context where, due to global warming, annual temperatures are rising furtherIn this regard, it is important to highlight how they have influenced this situation.
The results that have been obtained have been pointed out by other authors from Europe and North Africa, who refer to the exceptionality that extreme droughts that have occurred at the end of the XNUMXth century and those that occur now in the last years.
Changes in atmospheric patterns caused by climate change act on a large scale and are capable of alter the position and persistence of the Anticyclone in the Azores which prevents storms and, therefore, rain from entering Spain. This situation, combined with the current weather conditions, is also related to the Azores anticyclone and how it influences drought in Spain. Furthermore, this increased frequency of drought events is consistent with the results of the latest report from the Intergovernmental Panel on Climate Change.
