Cook Islands - Climate
The islands have a humid, tropical climate, though this is less pronounced in the Southern Cooks, farther from the equator than the Northern Cooks. The prevailing winds are the trades, blowing from the southeast in the Southern Cooks and from the east in the Northern Cooks. Rarotonga's average annual temperature is 24°C and the average yearly rainfall 2,000 millimeters. Tropical storms occur durring the humid months from November to March.
Seasonal temperatures differ between the northern and southern Cook Islands. The Northern Cook Islands’ (Northern Group) position so close to the equator results in fairly constant temperatures throughout the year, while in the Southern Cook Islands (Southern Group) temperatures cool off during the dry season (May to October). Changes in temperatures are strongly tied to changes in the surrounding ocean temperature. The annual average temperature at Penrhyn in the Northern Group is 28°C and at Rarotonga in the Southern Group is 24.5°C.
Rainfall in the Cook Islands is strongly affected by the South Pacific Convergence Zone. This band of heavy rainfall is caused by air rising over warm waters where winds converge, resulting in thunderstorm activity. It extends across the South Pacific Ocean from the Solomon Islands to east of the Cook Islands. It is centred close to or over the Southern Group from November to May. This is when the South Pacific Convergence Zone is most active and furthest south. From November to March the South Pacific Convergence Zone is wide and strong enough for the Northern Group to also receive significant rainfall. The driest months of the year in the Cook Islands are from June to October.
The Cook Islands’ climate varies considerably from year to year due to the El Niño-Southern Oscillation. This is a natural climate pattern that occurs across the tropical Pacific Ocean and affects weather around the world. There are two extreme phases of the El Niño-Southern Oscillation: El Niño and La Niña. There is also a neutral phase. The El Niño-Southern Oscillation [ENSO] has opposite effects on the Northern and Southern Groups. In Rarotonga, El Niño events tend to bring drier and cooler conditions than normal, while in the north El Niño usually brings wetter conditions. Ocean temperatures warm in the north during an El Niño event so air temperatures also warm.
Droughts and floods are also a strong feature of the Cook Islands risk profile and these events may at times also be attributed to El Niño and La Niña conditions. For example, during El Niño the Southern Cook Islands experience drought conditions (40% less rainfall than average) and many households go without water for periods ranging from several weeks to some months. At the same time islands in the Northern Group may experience up to 300% more rainfall'. During the contrasting La Niña phase, flash flooding is a frequent problem for the volcanic and Makatea Southern Group islands, while the Northern Group islands suffer drought. It goes without saying that agriculture is severely affected by these extreme fluctuations in rainfall.
Being small islands, the retention of adequate fresh water resources for domestic and commercial use is a constant challenge, particularly during the dry season, when droughts of varying severity occur. This poses a serious constraint on people and the economy. On the flip side, some parts of the islands are prone to flooding including much of the central business district. In Rarotonga, this is particularly a problem when heavy rains coincide with equinoxal high spring tides which decreases the capacity of drainage canals and streams to discharge the runoff into the sea.
With a rise of 4mm per year since 1993, the sea level around the Cook Islands is increasing quicker than the global average of 2.8-3.6mm per year. This is problematic, as it further exposes private property, coastal communities, coastal ecosystems and public infrastructure already considered vulnerable to extreme weather events. Sea level rises combined with natural year to year changes will increase the impacts of such extreme events, like coastal flooding and storm surges.
cyclones constitute the most significant natural hazard for the people of the Cook Islands as they occur relatively frequently (an average of one every other year) and are often coupled with extremely strong winds and severe storm surges and flooding. Coastal settlements and infrastructure are most at risk during these events, with the smaller low -lying atoll islands often being completely exposed.
While it’s predicted that tropical cyclones may decrease in frequency, cyclones that do occur will be more intense, and potentially much more damaging. The Cook Islands sit at the heart of the “cyclone belt.” Between 1969 and 2010, the nation recorded 74 cyclones. Changing weather patterns mean the destructive storms will only intensify. In 2005, five consecutive cyclones over a two-month period blazed through the nation, causing damage estimated at $13.7 million. On average, destruction per cyclone totals $4.5 million, or 2 percent of the country’s GDP.
The country’s most isolated islands capture populations most vulnerable to the extreme changes in weather patterns. The Pa Enua islands, a cluster of isolated islands in the Cook Islands’ outer rings, lie 1,250 kilometers (775 miles) from the country’s capital. Persistent droughts and aggressive cyclones can leave households without access to fresh water for months on end. Many residents leave their homes, migrating to higher ground in the southern Cook Islands, or overseas.
Climate change and disasters affect the Cook Islands' economic, social, environmental and cultural progress. In this regard, our national and local development strategies give emphasis to Cook Island's heritage and resilience as a large ocean state promoting low carbon economic development alongside social and environmental benefits. Given the Cook Islands size, vulnerabilities, limited resources, and capacities while noting also its special circumstances, designating its entire EEZ of almost two million sq km as a marine park is evidence of national commitment to the global effort to building the resilience of marine ecosystems.
Globally, the Cook Islands contributes to only 0.00012% of GHG emission, which is an insignificant amount relative to the total global emission of 2004 (IPCC Report, 2007). Yet, collectively, the consequences of the global emission via climate change is detrimental to ecosystems, infrastructures, economy, and therefore the livelihood of Cook Islanders. The Cook Islands has carved a pathway of low carbon development to strengthen climate resilience and further reduce its carbon footprint to achieve its national vision, which is ‘to enjoy the highest quality of life consistent with the aspirations of our people, and in harmony with our culture and environment'.
The country has developed key plans and policies that articulate its priorities to reduce vulnerability and strengthen resilience. This includes the first 20 year national vision 'Te Kaveinga Nui', accompanied by the first National Sustainable Development Plan (NSDP) 2007-2010, and subsequently the second NSDP 2011-2015 with the latest 2015-2020 to follow. The Joint National Disaster Risk Management and Climate Change Adaptation Plan (JNAP) is a five-year (2011–2015) roadmap that being updated to 2020. The Climate and Disaster Compatible Development Policy 2013-2016, provide direction for more coordinated adaptation and mitigation actions within and across all sectors. The Renewable Energy Chart provides the pathway of transforming the electricity sector from diesel based to renewable energy sources.
The Cook Islands is confident that its existing frameworks and robust systems guiding ongoing climate change mitigation and adaptation measures are considerable, and its commitments are ambitious to the global goal despite its unique circumstances.
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