Climate Outlook Raises Concerns for Haiti

The already challenging humanitarian relief and rebuilding efforts in earthquake-ravaged Haiti may become even more difficult, if a recent climate outlook verifies.

Significantly above average sea surface temperatures (SSTs) in the Atlantic Ocean combined with a waning El Nino in the Pacific may make for a wetter than average rainy season in Haiti, potentially complicating already difficult humanitarian relief operations following the devastating 7.0 magnitude earthquake on January 12.

The current Haiti rainfall outlook issued by Columbia University's International Research Institute for Climate and Society (IRI) shows a 50 percent chance that rainfall will be above average during the period from May through July, and a 55 percent chance of above average rainfall from June through August. This compares to just a 15 percent chance that rainfall will be below average during both periods. The rainy season in Haiti lasts from April through the first half of October.

Humanitarian experts fear that a particularly wet rainy season could significantly worsen the situation on the ground in Haiti, where thousands of people are currently living in tent cities after losing their homes in the quake. Excessive rainfall would bring with it an increasing threat of disease and mudslides, among other hazards.

There are two primary reasons why Haiti, as well as the Caribbean in general, is projected to receive above average rainfall during the next few months, said Tony Barnston, lead forecaster at IRI. The first factor, he said, is the presence of much above average SSTs in the Atlantic Ocean, stretching from Africa westward through the Caribbean. The warmer water is expected to provide additional fuel for the thunderstorms that typically form in the region during the rainy season, as well as tropical storms and hurricanes.

Sea surface temperature anomaly map, showing warmer than average waters in the main hurricane developing region of the Atlantic Ocean off of Africa, into the Caribbean Sea. Source: CPC/NCEP/NOAA

"Year-to-year changes in sea surface temperatures in this region are not large," Barnston said. "So even one or two degrees is a big deal in the Atlantic because the amount of convection, or thunderstorm activity, is very sensitive to the sea surface temperature." He noted that in some areas, water temperatures are currently two degrees Celsius above average.

"It's really impressive," he said.

Studies have linked higher SSTs to manmade climate change. However, natural factors such as El Nino and the Arctic Oscillation, which is a climate pattern in the North Atlantic Ocean, may be to blame for much of the current record warmth, according to Barnston.

The presence of the warm water, as well as a weakening El Nino in the Pacific Ocean, is projected to result in a more active hurricane season this year, with more tropical storms, hurricanes and major hurricanes than normal.

Jeff Masters, chief meteorologist for Weather Underground, noted in a blog post on May 17 that SSTs in the Atlantic's Main Development Region for hurricanes had their warmest April on record. “The high April SST anomaly does not bode well for the coming hurricane season. The three past seasons with record warm April SST anomalies all had abnormally high numbers of intense hurricanes,” Masters wrote.

Although the likelihood of a direct hurricane strike on Haiti is rather low — below 50 percent according to IRI’s Barnston — a more active season increases the odds of heavy rainfall.

The IRI produced the Haiti outlook in response to requests from international assistance groups and agencies that are seeking to incorporate climate information into their operational planning, according to Haresh Bhojwani, IRI’s international development officer.

Bhojwani said a key challenge is for climate and weather experts to provide information in a form that is useful and understandable for international development experts, who may not have expertise in using climate data. Training people to interpret climate information is not always feasible, since in urgent situations such as in Haiti, "People are way too busy and have way too many crises going on for us to be able to take them aside and train them on these kinds of issues," he said.

The IRI's Haiti outlook is an example of what the federal government, which is in the process of forming a National Climate Service, refers to as "climate services." Although global climate change earns most of the headlines these days, climate science is not limited to studies of long-term man-made and natural climate change. Shorter-term climate variability can have profound consequences for society, particularly for vulnerable populations.

Source:
Climate Central, "Climate Outlook Raises Concerns for Haiti", By Andrew Freedman, accessed May 19, 2010