Average air temperature
Air temperature is an indicator that measures heat in the atmosphere, measured in degrees Celsius (°C). This indicator describes the average air temperature trends in the Basque Country from 1971 to 2016.
- Since 1971 there has been an upward trend in the average air temperature in the Basque Country, with an increase of 0.25 °C per decade.
- The rates of change at spatial level are increasing, evenly distributed over a large part of the territory and are statistically significant.
- Spring is the season of the year with the highest increase, followed by summer and autumn, which are all statistically significant. However, winter temperatures remained the same over the study period.
Relationship of the indicator to climate change
The concentrations of greenhouse gases in the atmosphere are increasing. As a result, the Earth's average surface temperatures are also increasing and are expected to continue to do so in the future, although the evolution is different across the Earth. It is therefore of interest to know to what extent temperatures will increase in the Basque Country.
Air temperature is a basic indicator in climate description. It affects ecosystems, including human, in a crucial way. Thus, temperature rises may lead to more frequent and intense heat waves, which can cause illness and death, especially in vulnerable people. Temperature regimes throughout the year determine the types of flora and fauna that can survive in an area. Temperature changes can alter a wide range of natural processes, especially if these changes occur too rapidly for plant and animal species to be able to adapt.
Trends over time and indication of climate change
This section describes in detail the average rate of evolution of mean air temperature in the Basque Country since 1971. We identified jumps in the series and the warmest and coldest years on record.
Figure 1. Mean air temperature anomaly (°C) in the Basque Country - 1971-2016.
Figure 1 shows the annual anomalies compared to the mean temperature for the standard period 1971 - 2000. For example, an anomaly of +1 degree means that the average temperature was 1 degree higher than the average for the standard period.
The 70s was the coldest decade of the standard period considered, with 1972 being the coldest year. Significant positive anomalies are identified from 1989 onwards. After a clear slowdown in the first decade of the 2000s, the second decade saw a rapid rise again.
Figure 2. Rate of change of mean air temperature (°C per decade) in the Basque Country, 1971-2016.
The spatial variability in air temperature in the Basque Country since 1971 have been increasing, being evenly distributed over a large part of the territory and statistically significant. However, there are some areas with a negative trend, probably due to edge effects and problems in the characterisation of the altitude gradient in the spatial estimation process.
Figure 3. Evolution of the mean annual air temperature by season in the Basque Country, 1971-2016.
It is also worth considering whether this warm trend is uniform depending on the time of year. Analysing Figure 3, we can see spring is the season with the highest increase, followed by summer and autumn, all statistically significant. Winter, however, would have remained similar throughout the period.
Air temperature in the Basque Country is measured in both manual and automatic weather stations managed by different institutions (Basque Government, Provincial Councils, Central Government).
In manual stations readings are taken at 8:00 AM GMT and consists of measuring the temperature recorded at that time, and the maximum and minimum temperatures for the previous 24 hours, which is the time elapsed since the thermometer was reset at the station. Both the temperature at 8:00 AM GMT and the minimum temperature are recorded on the day of measurement, while the maximum temperature is recorded on the previous day. The daily mean temperature of these stations corresponds to the statistical average calculated adding daily maximum and minimum temperatures.
At automatic stations recording is continuous and averaged in 10-minute intervals. The average temperature then corresponds to the average of the 144 ten-minute readings for the day in question.
Data series have been fed into spatial prediction models to generate a daily resolution cartographic database, which is the starting point for the calculation of this climate change indicator. Static covariates, derived from digital terrain models, have been included in this prediction to explain air temperature.
The cartographic database comes from Phase II of the KLIMATEK project - "High Resolution Climate Change Scenarios for the Basque Country"escenariosklima.ihobe.eus/data
Based on these maps, monthly anomalies are calculated, in relation to the standard period 1971-2000, and then averaged to find an annual temperature anomaly for each year. These regional anomalies are then averaged for the territory as a whole.
Decadal trends (Sen’s slope), i.e. magnitude of mean temperature increases/decreases over a decade, is also calculated; and it is checked whether the trend is statistically significant or whether it is actually the result of the variability of the thermometric series itself using the Mann Kendall (MK) test.
Gaztelumendi S., Otxoa de Alda K., R. Hernández, M. Maruri, J.A. Aranda, P. Anitua (2018) “The Basque Country Automatic Weather Station Mesonetwork in perspective”. WMO/CIMO Technical Conference on Meteorological and Environmental Instruments and Methods of Observation (CIMO TECO-2018). 8 - 11 October 2018. Amsterdam, The Netherlands.
Hernández R., M. Maruri, K. Otxoa de Alda, J. Egaña, S. Gaztelumendi. (2012) “Quality Control Procedures at Euskalmet Data Center”. Advances in Science and Research – Topical Library, Volume 8, 2012, pp. 129-134.
Herrera, S., J. M. Gutiérrez, R. Ancell, M. R. Pons, M. D. Frías and J. Fernández. 2012. Development and analysis of a 50-year high-resolution daily gridded precipitation dataset over Spain (Spain02). Int. J. Climatology, 32, 74-85, doi: 10.1002/joc.2256.
Herrera, S., J. Fernández and J. M. Gutiérrez. 2016. Update of the Spain02 Gridded Observational Dataset for Euro-CORDEX evaluation: Assessing the Effect of the Interpolation Methodology. Int. J. Climatology, 36, 900-908, doi: 10.1002/joc.4391.
Klein Tank, A.M.G., Zwiers, F.W., Zhang, X. 2009. Guidelines on analysis of extremes in a changing climate in support of informed decisions for adaptation, climate data and monitoring WCDMP-No 72, WMO-TD No 1500, p 5.
Proyecto Klimatek 2016. Elaboración de escenarios regionales de cambio climático de alta resolución sobre el País Vasco. IHOBE. Gobierno Vasco.
The Basque Country
Global (1)
+1.2 ºC
For five-years averages
Europa (1)
+2.2ºC
For five-years averages
Euskadi (2)
+0.25 ºC
Per decade since 1971
(1) Copernicus