The rugged terrain and geographic location bring in variety in Spain’s climate. In the last century, the average temperature has increased more in Spain compared to rest of Europe. The average annual temperature is over 18ºC and has been increasing since the mid-1970s, making the country warmer. Since 1850, both maximum and minimum temperatures have risen by an average of by 0,12 and 0,10⁰C/decade. The warmth has increased during spring and summers, with fewer cool nights since the 1960s.
From the beginning of 20th century to today, the annual temperature of the northern part of Iberian Peninsula rose by 0.13°C per decade. There has been a variation of about 0.09 and 0.16°C every decade. This has gone higher since the 1970s, with a central estimate of trend having 0.51°C increase per decade. The interval has shifted from 0.36 to 0.69°C per decade.
The coast has a decrease in the frequency of frost days by 0.6 days/decade since the 1960s. The frequency of summer tropical nights has increased towards the south-east of Spain by about +3.8 days/decade since the 1980s. The frequency of summer days towards the south has increased by +2.3 days/decade.
Since the 1960s, the warm events in winters have increased at the Ebro basin. The average count of warm days, have increased by 3 to 8 days at the beginning of winter months, with 14 to 22 days towards the end of the period. There was also a marked and statistical increase in melting of altitudes lower than 2000m above sea level.
Since the 1950s, the changes in the global climate system have unprecedented over decades to millennia. The main cause of this climatic change has been global warming. It is unequivocal on the ground, in the oceans and in the air. Even a pause of 15 years is too little to make a difference in long-term trends. The emissions of greenhouse gases cause more warming and disrupts the climatic system. To sum up, the atmosphere and the oceans have warmed, the snows and ice have diminished, the sea level has risen and greenhouse gases have increased.
The retreating glaciers in eight out of the nine European glacial regions are causing a major change all around. The most notable among these is the Pyrenees which have lost about 90% of their ice in the last century. The temperature of Catalan Sea has increased by about 1.1°C at the uppermost waters and 0.7°C at 80m from 1974 to 2008. This is similar to the observations of western Mediterranean. Again, towards the northwestern Mediterranean Sea the temperature increase has been at par with the global scale. In the last 40 years, the increase in warmth has been at a very similar rate.
It is predicted that the average temperature in Spain is likely to increase by 4 degrees by 2080. The extreme summers, just as experienced in 2003, are four times likelier to repeat in Spain, compared to other parts of southern Europe. Under the emission scenarios, every second summer in the continent will be as hot or even hotter like 2003. These changes are more projected to occur towards the south, and the effects will start showing by as early as 2020. The excepted rise in temperature of Europe is likely to go from 2 to 6.3 degree by 2100.
The temperature in Spain is steadily rising by 0.6-0.7ºC in summer and 0.4ºC in winter, every decade. By 2100, the temperature in the hinterland of the peninsula will go higher than 5-7ºC during summers and 3-4 ºC during winters. The temperature on the coasts is likely to rise by 2ºC lesser than that of the hinterland. The probable temperature rise by the end of the 21st century can differ by 3ºC according to the control of greenhouse gas emissions. The temperature rise is expected to be comparable for every region during winters, central and south during spring, and more in the interior than on coast for summers and autumns.
For the Basque country, it is predicted that there will be 50% decrease in the count of frost days by the end of the century. The episode of cold waves, defined by 6 consecutive days, has lowered from seasonal temperature by 5ºC since 1978 and is expected to disappear by 2020. On the other hand, the number of heat waves during summers is supposed to increase from 12% to 16% by 2050 and 22% by the entry of the century.
In general, there is supposed to be less precipitation all over Spain, and will accelerate by 2100. With regard to the current scenario, the annual precipitation is known to decrease by 5% in the centre, northeast and eastern regions, and 10% at south-west from 2011 to 2040. In 2070 to 2100 the probable low emission scenario of 15% is to go up to 25% of high emission scenario towards the centre and northern regions. 20% of low emission scenario is to increase about 30% or below, towards the south.
However, for specific regions and seasons, there are different estimates reported. For Andalusia and upland parts of Cataluna climate, the model calculation suggests that there will be a significant annual precipitation reduction from 6% to 14% b the end of 21st century. On the contrary, there is an increase of about 14% by the coasts between Almeria and the French border. This suggests that winter rainfalls are likely to increase in the northeast. The Pyrenees would experience milder winters, with more of precipitation, and hotter summers. This condition might lead to the reduction of snow covers on mountains. In most temperate mountain regions, the snows are close to melting and that is a sensitive issue for the change in temperature.
There is no consensus for extreme change in precipitation at the Iberian Peninsula from 2070 to 2100. The results of climate model suggest that there are extreme changes in the Basque country, and that might increase by 10% until the end of the century. The climate changes also show the increase in mean length of dry spells and largest dry spells and is related with a 2 year return period.