The weather and climate of Macaronesia: past, present and future

This paper discusses the historical record and the characteristics of the present day climate and weather phenomena of the Macaronesian islands (Figure 1). It will also assess the projected global climate model (GCM) changes for the region. Macaronesia is the collective name for the archipelagos of the Azores, Madeira, the Savage Islands, the Canary Islands and the Republic of Cape Verde and is a biogeographical rather than a political region. It should not be confused with the similarly named Micronesia, which comprises thousands of small islands in the western Pacific Ocean. The region is an important transitional climatic zone that encompasses a large part of the eastern north Atlantic. The semi-permanent Azores high-pressure system forms the anchor around which many of the southwesterly weather systems that affect the British Isles and western Europe originate. Conversely, just to the west of the Cape Verde islands lies the birthplace of some of the most intense hurricanes that have the potential to severely affect the Caribbean and eastern United States (recent Cape Verde-originated hurricanes Ivan (2004) and Ike (2008) were, respectively, the sixth and third most financially costly Atlantic hurricanes of all time (updated from Blake et al., 2011)). However, the climate of the islands within Macaronesia itself is typically quite stable. The name, ‘Macaronesia’, was devised by ancient Greek scholars and literally translates as the Islands of the Fortunate/Blessed. The scholar Plutarch (46–120 AD), in his biography of notable Grecian individuals, remarkably makes the first climatic observations of Macaronesia: These [islands] are two in number, separated by a very narrow strait; they are ten thousand furlongs [just over 2000km – probably an exaggeration] distant from Africa.They enjoy moderate rains at long intervals, and winds which for the most part are soft and precipitate dews. Moreover, an air that is salubrious, owing to the climate and the moderate changes in the seasons, prevails on the islands. For the north and east winds which blow out from our part of the world plunge into fathomless space, and, owing to the distance, dissipate themselves and lose their power before they reach the islands; while the south and west winds that envelope the islands sometimes bring in their train soft and intermittent showers, but for the most part cool them with moist breezes. From this description we can see it is most likely that the islands that Plutarch was referring to are Madeira and Porto Santo. The north and east winds are the trade winds and his description of precipitation events and the small differences between seasons is still an accurate description today. This is due to the aforementioned stability of the islands’ climate, which is largely moderated by the influence of the north Atlantic. A feature of this stability is the potential for a high signal-to-noise ratio in meteorological observations – that is, it is relatively easy to determine an actual ‘trend’ over time as the background fluctuations do not vary significantly. This, if we have a historically-rich observational record, puts a high value on these islands in a climatological context.