Climate change has caused temperatures in the world to rise in the last few decades, and temperatures in Europe have risen twice as fast as the average change in the rest of the world. In Spain, which already has a hot and dry climate, extreme events such as heatwaves are becoming increasingly frequent. The country is also experiencing more episodes of drought and increased severity of these episodes. Water resources will be severely affected in various climate change scenarios. Also, the mediterranean climate (Köppen: Csa), as well as other temperate climates in the country, is becoming less and less common, being replaced by the semi-arid climate (Köppen: BSk/BSh) and even the expansion of desert regions. Some forecasts indicate that the semi-arid climate will be the most common in Spain by 2050.

To mitigate the effects of climate change, Spain is promoting an energy transition to renewable energies, such as solar and wind energy. In 2021, to support this process, the government approved a law on climate change and energy transition.

Spanish society as a whole is one of the most climate change conscious societies in the EU. Due to the effects of global warming, Spanish society is demanding stronger measures.

Greenhouse gas emissions

Four sectors generate 90% of emissions: transport, industry, agriculture and energy.

Per capita CO2 emissions (not including land use change) were 5 tonnes in 2021. Spain accounts for 9% of the total CO2 emissions in the European Union. CO2 emissions are dominated by the combustion of fossil fuels for transport and electricity generation, and by the industrial production of materials such as cement.

Fossil fuels A large part of Spain's energy demand comes from fossil fuels, which account for over 70% of the total. In 2021 oil was responsible for 60% of the emissions and natural gas 30% of emissions.

Transportation Greenhouse gas emissions are the highest in the transportation sector, accounting for 27% of total GHG emissions. Of that, 90% of emissions come from road transport, with light-duty vehicles, such as passenger cars and motorbikes, contributing 66% and heavy trucks and buses accounting for the remaining 34%.

Electricity generation Spain is considered an energy island, as its electricity import and export capacity is very limited, at 2.8 GW with France and 3.70 GW with Portugal.

In 2022 coal-fired power plants emitted 15% of the CO2 from electricity generation, but these will be shut down by 2030. Almost all the rest is from gas-fired power plants.

In the Balearic Islands electricity production is mainly natural gas and some solar energy, while the Canary Islands produce almost all their electricity with oil.

Agriculture and waste Agriculture produces two potent greenhouse gasses: nitrous oxide and methane.

Impacts on the natural environment

Temperature and weather changes

Between 1965 and 2015 the average temperature rose by . According to Aemet the frequency of heatwaves have doubled since 2010. Between 1980 and 2000 were 10 to 12 heatwaves per decade, whereas between 2010 and 2020 there were 24. The duration of these heatwaves will also be longer, with at least 41 days of extreme heat predicted in 2050 and, in the worst emissions scenario, 50 days. Compare this to heatwaves in 1971-2000 when the average number of days was 21 days annually.

Based on the IPCC reports, different scenarios have been developed in order to study the future climate. The AEMET (Spanish meteorology agency) has studied how three of these would affect the Spanish climate through the year 2100: RCP 4.5, RCP 6, and RCP 8.5. The first scenario (RCP 4.5) envisages an increase in greenhouse gas emissions for several more decades, before stabilising and then decreasing before the end of the century. The RCP 8.5 scenario models the most extreme case, with no regulation of greenhouse gas emissions.

In the best-case scenario (RCP 4.5), between 2081 and 2100 the annual maximum temperature would increase , with an uncertainty of . In RCP 6.0 that becomes an increase of 1-4 °C ± 0.5-1.5 °C ( ± ) between 2046 and 2065, and of between 2081 and 2100.

In the worst-case scenario (RCP 8.5), the annual maximum temperature increases of are expected for 2081–2100. In this scenario there is an uncertainty of .

Changes are also predicted regarding precipitation. In scenario RCP 4.5, predicted changes for the years 2081-2100 range from +10% (in specific localised regions) to -20% with an uncertainty of up to 30%. Whereas in scenario RCP 8.5 the expected annual precipitation change varies from +10% to -30% with uncertainties of 10-30% between 2081 and 2100.

Extreme weather events Heatwaves Of Spain's many heat waves, some that stand out are: 2017 for being the year with most heat waves, having had 5, totaling 25 days - 1991 and 2016 had 4 heat waves each. 2003 for having had the hottest summer ever recorded with an average national temperature of , and for having had the longest heatwave at the time. This 16 day heatwave caused thousands of deaths in Europe. 2015 for having the longest heat wave which lasted for 26 days, ten days more than the previous record holder. 2012 for having the most extensive heatwave. On August 10, it affected 40 out of 50 provinces.

Climate change made the April 2023 heatwave at least 100 times more likely. The previous year (2022) heatwaves killed almost 4,000 people in Spain.

Winter of 2022-2023 The winter of 2022-2023 was, in general, hot and humid. December 2022 was the hottest December in the historical record, with the winter being the fifth hottest of the 21st century.

Meteorological drought In March 2022 AEMET analysed the previous 12 months and found that peninsular Spain has been in a meteorological drought since January 2022. These events are probably made more likely by climate change.

Water resources The annual precipitation was between 1991 and 2020, and may decrease by in 2040–2059. The effect that climate change has on water resources can be worse in regions that already have low water resources levels and recurring droughts.

According to existing climate change scenarios, Spain's water resources will be severely affected. However, these effects are difficult to accurately measure due to the natural variability of the water cycle and the impact of water usage on flow rates. As a result, enhancing the assessment of climate change impacts by hydrological simulation models is needed.

River basin districts with a higher water exploitation index appear to experience more significant reductions in mean annual runoff. If the predicted climate change scenarios in Spain materialize, the traditional measures used to combat water scarcity must be applied more intensely and in ways consistent with regional effects on water resources. Policymakers in Spain face the challenge of understanding the impact of climate change and devising and executing policies that guarantee the best adaptation to the expected decrease in water resources in the most impacted regions, particularly those already facing water scarcity.

Water resources in Spain are expected to experience temperature increases, more frequent and severe droughts and floods, and decreases in river flows, resulting in reduced water availability. These impacts may aggravate existing conflicts between Spanish regions and further elevate water as a potential powerful political tool.

Sea level rise

The Ebro Delta is a significant wetland area in the western Mediterranean, about 40% of the delta plain is less than above mean sea level, and parts of the southern margin are at mean sea level but protected by dikes. The delta may see a sea level rise of at least per year. The government is investing millions of euros into shifting sediments to alleviate the impacts of erosion, however this is not seen as a long-term solution.

To offset negative impacts from waterlogging and saltwater intrusion, and to maintain land elevation, future management plans should consider the relative sea level rise. Plans will also need to regulate freshwater and sediment flows from the river. Doing this will entail the partial removal of sediments trapped behind the Ribarroja Dam and Mequinença Dam, as the stocks and inputs of sediments in the corresponding reservoirs are sufficient to elevate the delta plain by around .

Coastal measurements indicate that the global mean sea level has risen at a rate of per year from 1950 to 2000, with regional variability. Gauge records in the Bay of Biscay indicate that sea-level rise is accelerating, which is in line with rates observed from satellite imagery in the open ocean since 1993.

Coastal habitats have been mapped via historical airborne photography since 1954 and via high-resolution imagery since 2004. The analysis of tide gauge records from Santander in northern Spain shows that relative mean sea level has been rising at a rate of per year from 1943 to 2004, consistent with trends from measurements elsewhere in the region. Using a LIDAR-based DTM, the study predicts an sea-level rise in the Gipuzkoan coast within a 50-year period. However, only change was detected from historical and recent orthophotography, possibly due to sea-level rise. While were transformed by human impacts, suggesting that human impact poses a greater threat to Basque coastal and estuarine habitats than natural erosive processes and global climate change.

Biodiversity A study conducted in northeast Spain concluded that the disappearances of white-clawed crayfish, Mediterranean barbel, chub, European eel, and southern water vole were clearly related to the hydrological changes of the studied stream. The study suggested that no other factors could explain their disappearance: there is no industrial or agrarian sewage in the Olzinelles valley that could cause water quality to deteriorate; the industrial pollution in the river Tordera has been reduced by the construction of sewage treatment plants and other administrative measures; these species had no market value in the study area, and fishing and capturing were occasional, making it unlikely that negative effects on their populations resulted from these activities. Additionally, the human pressure on these species has decreased over the years, as the valley's population dropped by 76% from 1924 to 2007.

The disappearance of white-clawed crayfish in the Olzinelles stream may have been due to the loss of water flow or from the impact of red swamp crayfish. The red swamp crayfish became one of the most widespread invasive species in Spain after its introduction to streams in the Montnegre Mountains in 1989. Though as of 2011 surveys conducted in the Olzinelles stream had not found the crayfish, which was believed related to the absence of water.

Impacts on people

Economic impact Tourism Although the scientific community has made significant progress in predicting the magnitude and regional variation of climate change in upcoming decades, it is remains challenging to estimate the economic costs of climate change. The challenge mainly lies in the uncertainties of future climate change and economic projections, as well as the intricacies of connecting physical impacts and economic processes.

As many of the tourist activities in Spain are weather-dependent, the industry may be strongly impacted by climate change. It has been projected that the Tourist Climate Index (TCI), which was 'excellent' and 'very good' during the summers (June–August) of 1961 through 1990, will become 'acceptable' around Spain, and 'good' and 'very good' in the north of the country for the years 2051–2080.

Agriculture impact