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 from the radial growth of the oldest trees in Spain. With this research they want to know how the climate has been in previous centuries and be able to estimate the severity and progress of the effects of climate change.
We have to bear in mind that many climate changes have occurred throughout history, but they have not been as fast as the one that is occurring today. For an increase in average temperatures similar to what exists 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 through the study of the radial growth of trees such as pines. The Geophysical Research Letters journal now collects 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 the instrumental climatic records (data measured in meteorological stations) reaches at best 100 years, an insufficient time period to evaluate the possible exceptionality of the current 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.
Work has begun with summers of the XNUMXth century since it was the beginning of the industrial revolution in which greenhouse gases began to be emitted through the industrial revolution.
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), referred in this case to the months of July and August. Summers have become increasingly dry until, today, they are the ones that set historical records.
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 increasing further.
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 that does not allow the storms to enter Spain and, therefore, the rain. Furthermore, this increased recurrence of dry events is in line with the results of the latest report of the Intergovernmental Panel on climate change.