Small Islands – Precipitation in the Future

Abstract

<p>For most islands, there is very little published literature documenting the probability, frequency, severity,or consequences of climate change impacts, such as an decrease in precipitation. Some times, projections of future climate change impacts are limited by the lack of model skill in projecting the climatic variables that matter to small islands. The Azores are an archipelago formed by nine high volcanic islands, presenting a relatively small land area where precipitation is of orographic origin. Relatively projections up to the end of the 21st century, they were used for the same geographic region - the Azores region between 37 °N - 40°N and 32°W - 25°W - the results of the CMIP5 project for the RCPs (Representative Concentration Pathways) scenarios; trajectories describe four possible future climate scenarios, which depend on the amount of greenhouse gases emissions that may be emitted in the coming years. The four RCP scenarios (RCP 2.6, RCP 4.5, RCP 6.0 and RCP 8.5), correspond to four radiative forcing intervals for the year 2100, to pre-industrial values ​​(+2.6, +4.5, +6.0 and +8.5 W/m<sup>2</sup>, respectively). Most of the CMIP5 climate data and projections used in this work they are freely available on the Climate Ex plorer portal (https://climexp.knmi.nl/) of the KNMI (Koninklijk Nederlands Meteorologisch Instituut). Anomaly of the average annual precipitation for the Azores was calculated in the 1979-2019 period and its projections are estimated up to 2100, according to the RCP scenarios (Figure 1). In this case, the average variation calculated for the three scenarios for annual precipitation is -7.8 mm; in the case of the scenario more pessimistic (RCP 8.5), the models show for the Azores a decrease in average annual precipitation of about 9.8 mm/day until the end of the century, compared to the average of the last 30 years. According to the RCP4.5 scenario, a decrease is observed which is accentuated from the northwest to the southeast in the region under consideration, especially affecting the islands of the central and eastern groups. Of the calculations results for the average of the models an increase of the maximum number consecutive days with low rainfall (<1mm) from + 0.2 to 4.8 days / year until the year 2100. The demand for water affects basically four activities: the agriculture, energy production, industrial uses and consumption human. The projections found for the Azores of a decrease in precipitation are in line with other small island regions, such as the Caribbean and Mediterranean region. Thus, these regions become more vulnerable to social, economic and environmental impacts.</p>