Climate Risks in Haiti

Tony Barnston: Haiti is a tropical island with daily temperatures that range, on average, from 19°C to 28°C (67°-83°F) in winter, to 23°C to 33°C (73°-92°F) in summer, in lowland areas. Average annual rainfall varies, from almost none in some areas to more than 127 centimeters (50 inches) in Port-au-Prince. The two rainy seasons that Port-au-Prince experiences are from April to June and from August to mid-November. The dry season runs from December to April. The country is subject to periodic droughts and floods, which are made worse by deforestation. Hurricanes also periodically threaten the country.

Tony Barnston: Haiti's rainy season is long. As I mentioned above, it actually has two peaks, with a brief period in July that has relatively lower rainfall. We expect the current El Niño to persist through at least March, and possibly through May. During times of El Niño, the region around Port-au-Prince tends to get above-normal rainfall from late winter to around May. But we can't be sure the El Niño will still exist in May. We'll have a better idea in the coming months.

Alessandra Giannini: Let's remember that we are talking about the impact of the El Niño-Southern Oscillation (ENSO) in its weakening phase, which is different from that in its growing phase. Right now, El Niño's impact on Haiti is mostly indirect, resulting from warming in the tropical North Atlantic over the past six months. That's why we also need to consider North Atlantic atmospheric circulation, captured in something called the North Atlantic Oscillation. The NAO was in its negative phase in December 2009, meaning that trade winds were weakened. This situation contributed to ocean warming, because there was less evaporation happening on the surface waters. So if the NAO lasts in its negative state from December to March, it will favor the continuation of these warm conditions, which are the basis for the above-normal rainfall predictions that Tony mentioned above.

Tony Barnston: The rainfall expectation for the second half of Haiti's rainy season will depend in part on the direction of the ENSO state this summer-- will it be toward another El Niño, La Niña or neutral? At this time of year we currently have poor predictability for ENSO beyond about May or June. An unfavorable scenario for Haiti would be for the development of La Niña during the summer. It would not only imply a wet second half of its rainy season, but also the chances for a tropical hurricane in the vicinity, or even a hurricane hit. As these maps show, La Niña conditions tend to not only increase the total number of hurricanes in the Atlantic, but also increase the number that cut across the Caribbean. In 2008, Tropical Storm Fay, Hurricane Gustav, Hurricane Hanna and Hurricane Ike pounded Haiti, leaving widespread destruction and displacing hundreds of thousands of people.

Tony Barnston: That's right, we'll have better information in forecasts we issue over the next few months.

Walter Baethgen: Information and forecasts are most useful when they can be added to existing practices or methods. Information may not help if there isn't a mechanism in place that can use it to improve preparedness and response, or if it reaches a population that is extremely vulnerable, as in Haiti's case. Haiti is an example where much work is needed in vulnerability reduction at many levels. Unless these vulnerabilities are reduced, climate information isn't going to do much good.

Before we get too far, it's very important we define what we mean by "risk". Simply put, risk has two components: hazards and vulnerability. Hazards are the things that threaten: hurricanes, heavy rains, earthquakes, etc. Vulnerability is how susceptible a society is to damage, loss of life, epidemics and other possible consequences of those hazards. Poor building codes, widespread malnutrition, poor sanitation, are all elements that can make a society more vulnerable. We can think of risk then as the likelihood that a society will suffer damages from hazards based on its overall vulnerability.

Walter Baethgen: Reducing risks could be achieved by reducing the hazards, but in the case of climate this usually isn't possible--one can't reduce the chances of having El Niño or a hurricane. Another way is work on reducing the vulnerability, for example, reducing the number of people who live on steep slopes, in flood plains and other areas sensitive to storms. We can also reduce vulnerability by having structures like early-warning and early-response systems and institutions that are well prepared and react fast in the event of a disaster.

Molly Hellmuth: The other thing about risks is that they vary by hazard, which means the way to reduce vulnerability of the population at risk also varies. An effective risk reduction strategy for Haiti must consider all the multiple hazards, stressors and risks that threaten the country.

Molly Hellmuth: Stressors such as endemic poverty, ineffective governance and institutions, limited access to capital, ecosystem degradation and conflicts. They all combine to exacerbate vulnerability to hazards. IRI's next Climate and Society publication will be about disaster risk management and how we can better inform disaster preparedness and response through improved understanding of climate information across time scales.

Walter Baethgen: Well, the information needs to be useful across time scales. For rebuilding, there's a need to consider the multiple hazards and risks that Molly mentioned. In the immediate future, the information should feed into the emergency and early warning/response systems that are available now in Haiti. It will be useful to the International Federation of Red Cross and Red Crescent Societies and other humanitarian organizations, for example. They need to be aware that as desperate as the conditions are right now, new hazards and socioeconomic damage are possibilities in the near future due to adverse weather and climate conditions that may affect food production, health conditions and water supplies. Going back to the concept of risk that we discussed before, any new hazard in the near future will find Haiti in a situation that is even more vulnerable than usual, given the devastating effects of the earthquake, and therefore the risks are huge.