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Christmas Island - Climate

Unlike many tropical regions Christmas Island has a nearly ideal climate, such a climate as one dreams about and rarely finds. Most of the year the weather is much like that of a dry, hot English summer, though tempered nearly always by the steady tradewinds from the southeast, which are generally cool and always pure, having blown over miles of open sea. The temperature varies only a little during the year, often less than twenty degrees Fahrenheit. The average daily maximum is eighty-four degrees Fahrenheit, the minimum seventy-five degrees Fahrenheit. The island being high, and devoid of swampy places, and never having been contaminated by the filth of human habitation, it is practically free from all diseases, and the present inhabitants are astonishingly healthy. Rain falls only in the winter, with the exception of an occasional shower in the higher parts of the island during summer nights.

The climate is tropical and temperatures range from 21 C to 32 C. Humidity is around 8090 per cent and south-east trade winds provide pleasant weather for most of the year. However, during the wet season between November and April, it is common for some storm activity to occur producing a swell in seas around the Island. The average rainfall is approximately 2000 mm per annum.

The climate of Christmas Island is both pleasant and healthy. During the greater part of the year the weather is much like that of a hot, dry, English summer, tempered nearly always by a steady sea-breeze from the E.S.E., which is generally fairly cool, and keeps the temperature very even day and night. The maximum temperature (in the shade) recorded during my stay was 89 Fahr. on November 20th; the minimum (night) was 70 Fahr. on February 13th, when it was raining heavily. The greatest range in twenty-four hours was 14. The average daily maximum and minimum may be taken as about 84 Fahr. and 75 Fahr. respectively, the former occurring an hour or two after midday, the latter shortly before sunrise. The average temperature of the surface of the sea, deduced from several observations, is about 83.

The prevalent wind is the S.E., or rather E.S.E., trade-wind, which blows the greater part of the year (about 300 days on an average). From May to December it is almost uninterrupted, but during the earlier months of the year, which are the rainy season in the island, the wind occasionally shifts round to the N. and N.E., and sometimes blows hard from these directions, accompanied by heavy rains.

At such times Flying Fish Cove, which during the prevalence of the trade-wind forms a sheltered anchorage, is exposed to a heavy sea, which breaks on the reef with great violence, the spray filling the whole valley and drifting up the high cliff like smoke. The beach is piled up till it is nearly vertical, and at high tide a little water is sometimes spilled over its edge on to the platform behind. During these periods many birds of passage, such as wagtails, whimbrel, swallows, ete., reach the island, often in a very exhausted condition, and several new kinds of moths and butterflies, not seen at other times, were obtained. Even if the northerly wind only lasts a few hours swarms of dragon-flies nearly always arrive; after two or three weeks they disappear again.

Except for showers at night on the higher parts of the island, almost the whole rainfall occurs from December to May inclusive; during these months there are sometimes heavy downpours lasting several days, but as a rule the mornings are fine. At these times the rain nearly always comes when the wind shifts round towards the north. In the dry season (May-December) the vegetation is kept fresh by very heavy dews and occasional showers at night. These latter often occur on the uplands of the island, and seem to be caused by the chilling of the E.S.E. wind, which results in the formation of clouds over the high land.

The meteorological peculiarities of the island no doubt depend on its situation close to the southern limit of the monsoon. From towards the end of the year till May the northern horizon is nearly always marked by a cloud-bank, even when the trade-wind is blowing on the island, and, as shown above, it is only occasionally that the N. and N.E. wind extends as far south as the island, bringing with it unsettled weather.

The Intergovernmental Panel on Climate Change Fourth Assessment Report concluded that human induced climate change is expected to have a discernable influence on many physical and biological systems. The resilience of many ecosystems is likely to be exceeded over the course of the twenty-first century and approximately a quarter of all plant and animal species are likely to be at increased risk of extinction if increases in global average temperature continue to match current projections.

The projected effects of climate in the Indian Ocean Territories region include sea level rise, an increase in air and sea temperatures, increase in ocean acidity and changes in the frequency and intensity of extreme weather events.

While Christmas Island is characterised by its terraces, flat, low lying areas are at risk of sea level rise caused by increases in global average sea level. Any change in mean sea level, combined with the effects of storm surge, is likely to have a significant impact on a range of species living on these sites. It is unknown whether coral in the fringing reef will be able to grow fast enough to keep pace with sea level rise.

While Christmas Island is not officially considered to be a cyclone prone location projections suggest there will be fewer cyclones overall, but predict an increase in the frequency of high intensity cyclones. This may result in canopy loss and tree fall. Canopy gaps can take up to 10 years to close. Following Cyclone Rosie in 2008, canopy damage, tree fall and seabird chick mortality was recorded.

While future changes to rainfall patterns in Christmas Island National Park are uncertain, a decrease in annual average rainfall and an increase in air temperature and evaporation may impact many of the island's habitats and species.

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Page last modified: 26-07-2017 19:17:10 ZULU