Air temperature changes until now

The climate of the Maltese islands is typically Mediterranean, with a mild wet winter invariably followed by a long dry summer. The air temperature generally ranges between 9.5 °C and 33 °C; exceptional extremes of 1.4 °C and 43.8 °C having been recorded (1). Annual mean temperature is 18.6 °C; mean maximum and minimum temperatures are 22.3 °C and 14.9 °C, respectively (2).

The overall trend in air temperature over the period 1923-2005 indicates an increase at the rate of 0.71°C every 100 years. The post-1970 period has a clearly exacerbated rate of warming at around 1.5°C over 30 years, especially over the last two decades of the twentieth century. The overall rate of warming is by far strongest in the summer period at around 1.5°C every 100 years. The warming trend can also be traced from the incidence and magnitude of extreme temperature events. Yearly recorded maximum temperatures have gone up by about 3°C over 100 years (3).

Observed extremes in the maximum and minimum temperatures are typical of desert regions. Trends towards these conditions in Malta lead one to conclude that a process of desertification is already occurring (1). During the period 1967-2014 annual maximum and minimum temperature by increased by 0.09 °C and 0.02 °C per annum, respectively. Summer heat waves are becoming more frequent  (2).

Precipitation changes until now

Rainfall records have been maintained systematically for over 100 years. Annual rainfall is highly variable from year to year. Over the period 1840 to 2000, the highest maximum was 1031 mm (in 1859) and the lowest minimum was of 148.8 mm (in 1977). Rainfall is seasonal, with 70% of the annual precipitation occurring from October to March. During the short winters sufficient rain falls for crop irrigation but soil retention does not suffice for the relatively warm and dry spring seasons. The hot, dry summers are followed by warm and showery autumns, normally also with a rainfall deficit (1).

The 30-year average of annual precipitation from 1951 to 1980 was 580 mm, from 1961 to 1990 it was 553 mm and from 1971 to 2000, 568 mm. There are no perennial surface streams in Malta and rain water only flows along the bed of major valleys for a few days after heavy downpours, with about 6% of the total precipitation finding its way directly into the sea via this surface runoff (1).

Since 1923, there has been little change in rainfall during winter and summer, whereas there has been a decrease of 0.14 mm per year during spring and an increase of 0.8 mm per year during autumn. During the rainy season, the number of days per year with thunderstorms has increased by nine since 1950. The existence of convective rainfall is corroborated by the positive trend in the daily maximum rainfall between 1923 and 2000, since this type of rainfall is of short duration and often heavy. An increase in the daily maximum rainfall is observed notwithstanding the fact that, over a full year, the absolute number of days with rainfall in the range 1–50 mm is decreasing (1). During the period 1967-2014 no statistically significant change in total yearly precipitation was observed (2,3).

Sea water temperature changes until now

Sea surface temperature of the coastal waters has been steadily increasing at an average rate of 0.05°C per year over the last 40 years. This rise is most evident during summer and is comparable to Mediterranean averages, which are well above the global average of 0.01°C per year (3). 

Air temperature changes in the 21st century

The Maltese islands will suffer a moderate impact from climate change. A potential rise in annual average temperature in the range 0.53 - 1.32⁰C is projected by 2030 (3). 
There is a 50% probability that the mean annual temperature over the Maltese islands will rise by a further 3⁰C by the end of the century. The temperature seasonal pattern is expected to be retained with an approximately uniform warming across all months (1).

Precipitation changes in the 21st century

The projections for precipitation are less reliable than those for temperature. The scaled precipitation values give an estimated decrease of around 17% (to a best guess with 50% probability) amounting to a reduction of about 60 mm in the annual mean rainfall by 2100. The major decrease in rainfall is expected for autumn, with an increase during winter and little change during the rest of the year. The overall result is that the shift to less rain in autumn will have the greatest impact and will exacerbate dryness due to higher temperatures and the combined effect of enhanced evapotranspiration (1).

The current observed trends may be the opposite of projections. Most probably, this is because of the high natural variability in precipitation, which masks anthropogenic-induced changes. The mean winter precipitation observed between 1971 and 2001 was 568 mm, with a maximum of 895 mm and a minimum of 304 mm. The standard deviation of the series is 28% of the mean. Thus, the predicted range of possible changes lies well within the range of climate variability (1).

References

The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Malta.

1. Republic of Malta, Ministry for Rural Affairs and the Environment and the University of Malta (2004)
2. Galdies et al. (2016)
3. Climate Change Committee for Adaptation, Malta (2010)