Comoros - Climate

Small island state, the Union of Comoros is particularly vulnerable as other small island developing States (SIDS). The main hazards impacting the Union of the Comoros are: the increase in temperature; The rise of Sea level (erosion and submersion); Tropical cyclones, modification of the regime Precipitation; Changes in the wind regime; Ocean acidification and the modification of Cycles.

Comoros enjoys a humid tropical climate under oceanic influence characterized by two major seasons: a hot and humid season (austral summer) and a dry and cool season (austral winter). The mean rainfall is between 1500 and 5000 mm. However, it is necessary to take into consideration the decrease in temperature as a function of altitude. This climate is characterized by large local variations in relation to exposure to prevailing winds and altitude.

The country has a tropical humid climate. During the warm season or rainy season (mid-November to mid-April), the average air temperature is 27°C, with highs between 31 and 35°C and lows around 23°C. The temperature during the colder season, from June to September averages 23 to 24°C. Highs are around 28°C and lows are 4 to 5°C lover than those of the warm season. Mean annual rainfall for the islands is 1000 mm. In Grande Comore it varies between 1398 mm and 5888 mm, in Anjouan between 1371 mm and 3000 mm, and in Moheli between 1187 mm and 3063 mm. Comoros is known for its many microclimates.

There are three types of cyclone that can hit the Comoros. North of Madagascar and in the east between 55 and 65 degrees east longitude. Reinforced from May to August (the coolest month) by local currents in the South-West sector that come from the Mozambique Channel.

The water problem in Comoros is two-fold: access and quality. The islands of Anjouan and Moheli traditionally relied on surface water supply. In Anjouan, where forest clearing is paramount, there used to be over 40 rivers to supply the island population with water. Today, there are fewer than 20 rivers left. In Moheli, where some 20 rivers can be accounted for, surface water dries up during the warm season. In Grande Comore, 60% of the population relies on uncovered water containers and 40% on coastal aquifers. Coastal aquifers constitute the main underground water of Grande Comore. They rest on salted water, and their salt content varies from 2gr/litre to 6gr/litre, depending on the distance between the well and shore and/or sea level, which influences their overall salinity. Deforestation Of the Kartala forest mantle may eventually lead to the drying up of groundwater that supplies some of the island's major cities according to the latest estimates.

In April 2012, the Comoros was inundated by heavy rains, causing the worst flooding in decades. These downpours caused landslides, collapsed bridges, contaminated fresh water supplies and isolated many communities from evacuation. With approximately 46,000 people displaced, France and India, along with the Red Crescent and Red Cross and funding from the U.S.'s USAID, began sending disaster-relief teams and supplies to the affected regions of the country.

The studies made in the context of the Initial National Communication on Climate Change were based on the findings of the Intergovernmental Panel on Climate Change (IPCC) study on impacts and adaptation of Indian Ocean small island states. Changes in climate to be anticipated in Comoros by year 2050 are estimated to be a raise in mean annual air temperature to an average of 28°C, a change that represents a 1°C increase compared to the current situation. A sea level increase of 4 mm/year for a total increase of 20 cm by 2050 was also expected.

Expected impacts are the intrusion of salted water in the coastal aquifers; an increase in the occurrence of malaria and of collective food poisoning resulting from consumption of marine animals; a decrease in crop yields, agricultural production and fisheries; the displacement of 10% of the country’s coastal inhabitants whose habitat would be flooded; and lastly, the destruction of coastal infrastructure and habitat for an estimated value of 400 million USD, 2.2 times Comoros Gross Domestic product (GDP) for 2001.

The strengthening of the resilience of the Comorian communities to climate-related natural disasters will in a long term require a profound change in the current practices of development planning and implementation. This will first require greater awareness of decision makers and a better understanding of medium- to long-term climate change risks. This will also require that human settlements, community basic infrastructure and economic development infrastructure be made more resilient to disasters induced by climate change through designing and implementation of effective prevention against natural disasters and the integration of climate change and disaster risk management in the development.

Differences between islands necessitate their specific analysis in order to better identify the problems. There is great diversity in rainfall, Within each island and between the islands. Distribution affects all islands. The predictable consequences are a quantitative and qualitative decline in water (stagnation in all the islands) The phenomena of river drainage on Anjouan and Mohéli are generally associated with the clearing of the forest and the subsequent erosion of the soil.