The UB leads a study with the most precise reconstruction of the climate in the Iberian Peninsula for the last 700 years

The study shows the most precise synthesis conducted so far on the peninsular climate evolution for over the last 700 years to contextualize this cold period and its previous development, and is based on the analysis of several historical documents and natural records (glacier behaviour, lake sediments, tree rings, etc.).

Other participants in this study are the UB researchers Mariano Barriendos, from the Department of Modern History, and Antonio Gómez Ortiz, from the Department of Geography, as well as experts from the Meteorological Service of Catalonia, the Institute of Earth Sciences Jaume Almera (ICTJA-CSIC), the Pyrenean Institute of Ecology, the University of Oviedo, the National Museum of Natural History, the University of Zaragoza, the University of Lisbon, University of Santiago de Compostela, University of Granada, University of Valladolid and the Institute History (CSIC).

The longest cold period over the last 10,000 years

The results of this study allowed researchers describe the peninsular climate evolution of this period known as the little ice age, “which is the longest and most intense cold period of the last 10,000 years”, says researcher Marc Oliva. The researchers focused their work on the study of mountain areas, the areas that were less affected by human activity, and they collected all evidence on the clime from the last 700 years in the Iberian Peninsula.

Although the coldness and its implications were known in other areas of the European continent, its translation to the Iberian Peninsula and its impact on natural ecosystems were not known about. “One of the main new aspects of the study is to show the high climate variability with a higher recurrence of extreme climate events (cold waves, snowfalls, droughts, floods, etc.). It was known to be a colder period than the current one but we did not know it had such a high variability and extreme episodes with determining repercussions on the daily life of the societies of that time”, says the researcher.

Episodes of extreme floods such as the ones recorded in the peninsular coast in November 1617 or in the Atlantic front in January 1626 led to a loss of harvest, destruction of paths and bridges, and severe damage in the economy. The repeated cold waves caused an increase of deaths and these even defined some changes in the daily diet of north-western peninsular societies. Moreover, low temperatures came with snowfalls that caused dramatic avalanches, such as the big snowfall in 1888 in Asturias.

This impact can be specially seen through the large quantity of documentary resources, from which the climate data has been taken, such as city administrative files, journals, reports, memoirs, files on public buildings, ground plans, and maps or reports of climate risk damages.

11C temperature rise due natural causes

The study also enabled researchers to quantify the climate warming and evaluate its magnitude over the last 700 years. According to the researchers, since the beginning of the Industrial Revolution the temperature rose by 1ºC, the same that took place due natural causes over the coldest stage in the little ice age (1675) until the latest stages, which coincide with the beginning of industrial human activity.

“The temperature rose by 1ºC since the start of the industrial activity (1850-2017), a similar rise to the one recorded in the coldest stages of the little ice age, around 1675, until the start of the industrial age. However, in this case, this rise took place because of natural reasons, without any anthropic interference, due several factors related to the solar activity, volcanic eruptions, etc.”, says Oliva.

According to the authors, these results require us to be careful when relating -in a reductionist way- any climate variability-related phenomenon to the concept of climate change. “The climate responds to many variables, of which we do not know their behaviour completely, and the level of uncertainty is underestimated”, says the researcher, and provides the example of the accelerated fusion of glaciers in the Pyrenees: “Natural records say that glaciers in the Pyrenees are an anomalous phenomenon over the last 10,000 years, there had been some only in certain stages. It was more common to see Pyrenees without ice in summer than those preserving ice permanently. And this has happened over time when there was not human impact on the climate. Therefore, glaciers disappearing would be linked to natural warming in the late little ice age, which would be promoted by warming due the greenhouse effect gases linked to human activity”, he concludes.

“Only by understanding which is the ecosystem response in the past can we predict what can happen in the future”, says Marc Oliva.

Reference

Oliva; M.; Ruiz-Fernández, J.; Barriendos, M.; Benito, G.; Cuadrat, J. M.; García-Ruiz, J. M.; Giralt, S.; Gómez-Ortiz; A.; Hernández, A.; López-Costas, O.; López-Moreno, J. I.; López-Sáez, J. A.; Martínez-Cortizas, A.; Moreno, A.; Prohom, M.; Saz, M. A.; Serrano, E.; Tejedor, E., Trigo, R., Valero-Garcés, B. i Vicente-Serrano, S. (2018). «The little ice age in Iberian mountains», Earth Science Reviews, 177: 175-208.