The last week of April 2023 is likely to be a historic one due to the high maximum temperatures forecast, with record highs for this time of year. The latest forecasts indicate that this week we will reach record highs for several consecutive days in a large part of the Iberian Peninsula, with up to 40ºC in the Guadalquivir valley. The warm mass of subtropical Atlantic origin will be warmer in the vertical of the peninsula - exceeding 20 ºC at 1,500 metres above sea level in the south and 25 ºC in the eastern third - due to an anticyclonic ridge at medium-high levels of the atmosphere and extending from North Africa.
The characteristics of the ridge, favoured in part by a North Atlantic squall, are more typical of late June, resulting in a warm spell two months ahead of the climatology of the 1990s. This points in the same direction as the most recent climate change studies already on record. For example, according to the Spanish Meteorological Agency (AEMET), with each passing decade, summers start about a week earlier and end about three days later. This means that, over the last 50 years, summer has gained a month on spring.
In addition to the high temperatures in April and even in March, there was a rainfall drought, characterised by its extent and duration, known as a compound event. The anomalous temperatures increase evapotranspiration values, aggravating the lack of available humidity and water, reaching anomaly values (quarterly SPEI below -4) never recorded before. With each week of insufficient rainfall prior to summer, the severity of the drought increases in already critical regions.
To illustrate the extraordinary magnitude of the event, it is sufficient to see that the historical record in April for Cordoba is 34.0 ºC (18 Apr. 2017). Between Tuesday and Wednesday it is expected to exceed 35 ºC (more than 1 ºC difference), and by the end of the week it could exceed 38 ºC (more than 4 ºC difference from the previous record, only five years ago). Statistically, this is impossible to explain without the current scenario of particularly accelerated climate change. We know that extremes will increase in intensity, duration and spatial extent with significantly increasing trends.
Moreover, future climate change projections not only confirm the observed trend, but also point to a likely worsening of extreme heat conditions. The number of warm spring days (>30°C) will double or triple in most cases.
In the springs at the end of the century, Ourense could have more hot days than those currently recorded in Malaga, and Valencia could exceed the current number recorded in Cordoba. In general, by the middle of the century we will have in many places in the south almost two to three weeks on average with maximum temperatures above 30ºC in spring.
This will mean that springtime heat extremes will be 4 or 5 ºC higher than at present, thus adding 1 or 2 more months to the already extended summer. We can see how future extremes will be what we now consider practically impossible. In the month of April alone there will be extremes of 32ºC to 35ºC in several Andalusian cities, when historically the first maximum temperature was observed at the beginning of May in cities such as Seville, reaching mid-April or even the end of March in Seville, Cordoba or Malaga by 2050 and the end of the century.
The current situation is only the beginning of what may come in the coming decades, which should lead us to increase our efforts in mitigation and adaptation strategies (more green and shaded areas, energy efficiency in buildings, avoiding working outdoors in extreme temperatures). There must also be proper management of these multi-risk situations, with greater prevention and preparation of all our warning and emergency systems.
