rainfall chart 2

The Inter-governmental Panel on Climate Change (IPCC) has said that for the Caribbean and other small island developing states, it has observed that warming in small islands was attributed to human influence.

In addition, it said that this increase in temperature will continue in the 21st century in all modelled scenarios.

In Trinidad and Tobago, rainfall is primarily driven by heat, whether that be the temperature of the land during the day and during the wet season when moisture is present, or the temperature of the ocean surrounding the country.

Warmer temperatures result in more intense showers and thunderstorms.

The IPCC noted in its latest report, “The intensity and frequency of extreme precipitation and pluvial floods are projected to increase (with medium confidence) for 2°C of global warming level and above.”

However, while extreme rainfall is projected to increase, overall rainfall may suffer. The report explained there was high confidence in a dominant increase in dry days and drought frequency.

For the Caribbean region, the declining trend in rainfall during June through August will continue in the coming decades, particularly if global warming reaches 2°C and above.

With a warmer climate, scientists also note that higher evapotranspiration will result in increased aridity and more severe agricultural and ecological droughts but at medium confidence. Many Lesser Antilles islands, including Trinidad and Tobago, derive their drinking water from groundwater supplied by rainfall. These droughts can produce catastrophic agricultural impacts and threaten the water supply for small islands where tourism is the main driver of their economy.

Climate Change is here

Scientists have been sounding the climate change alarm bells for decades. For Trinidad and Tobago, the impacts of climate change have been felt in the last two decades. In 2018, one of the worst floods in modern history affected up to 80 per cent of the country. Two years later, water levels in the nation’s largest reservoir, the Caroni/Arena Dam, reached the lowest ever recorded. The country, even with short-term droughts, continues to see severe flash flooding events with torrential rains.

The Trinidad and Tobago Meteorological Service (TTMS) is responsible for collecting and maintaining the country’s climate records. TTMS Chief Climatologist Kenneth Kerr explained, “Climate change is the single biggest challenge for Trinidad and Tobago as an island, developing state.”

He added that there was evidence of changes happening more quickly than previously estimated.

“It can no longer be framed as a distant threat. It is an ongoing threat and a disaster risk multiplier. Our planning must be based on climate extremes, being made worse because of climate change,” Kerr said.

Using Arouca as an example, the area that rarely saw the level of flooding it did until 2020, with multiple significant flash flooding events, Kerr explained this could have resulted from climate change or our “bad behaviour as humans.”

He posed the question – will the residents now use these extremes to plan for the future?

In line with the IPCC report, on average, rainfall at Piarco has decreased very slightly over the last 80-odd-years.

The year 2019 was the third driest on record since 1960. Over the last decade, eight of the ten years produced less than average rainfall.

Kerr said, “It should be noted that some parts of Trinidad and Tobago have experienced greater decreases than others.”

Trinidad and Tobago’s new climate normal regarding rainfall, shows an overall (but slightly) drier average for 1991-2020 compared to 1981-2010. The only marginally wetter month is March, which is still the driest month of the year in T&T.

Average rainfall for January, February and December remains unchanged. Notably, all the wet season months are drier in the new climate normal.

The annual extreme (maximum) one-day rainfall totals at Piarco from 1960 to 2020, show an increase in extreme rainfall.

Extreme rainfall is also on the increase, as projected by the IPCC. Kerr explained that a larger percentage of rainfall at Piarco has come in the form of intense precipitation in recent years. There has been a steady increase of rain accumulating in the highest annual daily rainfall totals. According to Kerr, six of the highest top ten years for the highest one-day maximum rainfall totals at Piarco have occurred since 1990. Based on the records from the TTMS, in the last 35 years, 2020 tied 2008 and 1993 for the highest number of extreme single-day rainfall events in T&T, with seven extreme rainfall days.

The new normal for floods

With more intense, short-duration rainfall, severe street and flash flood events will become more common.

For areas along the Northern Range like Maraval, St Ann’s, Cascade, and from Port-of-Spain to Arima, an afternoon thunderstorm in a warmer climate could spell disaster. For already flood-prone areas near major rivers like the South Oropuche and Caroni River, residents may have to increase preparedness and flood mitigation measures to protect life and property.