… Still seasonal weather, but with slight variations

By M Margaret Burke

IN TODAY’S world climate change is everybody’s business. Things are happening even at this very moment across the globe and by now, while Irma is becoming a household name, so will be two other tropical storms if they have their way – Jose and Katia, which are now rolling in the Atlantic basin.

Komalchand Dhiram of the Office for Climate Change (Guyana), explained that climate change is a continuing present day issue. He said that floods, heat waves, strong winds and their impact on society reach us almost every day and these reports imply a threat to our present way of living, urging for responsibility, pro-environmental behaviour and ecologically sustainable progress.

“There is an increasing awareness that climate change is not only an ecological and economic dilemma but also a social and psychological one. Guyana can expect prolonged dry spells, flash floods and rising sea level,” he said.

THE VERY HOT DAYS ARE NORMAL
In an explanation for the very hot days that many Guyanese are complaining of; many feel that it is unusual and that something else might be in the ‘air’, Dhiram said that during this time of the year from, June to August the northern hemisphere of the globe experiences summer, while the southern hemisphere should be experiencing winter.

He noted, however, that because Guyana is located within 10 to 70 latitudes north, the atmosphere above Guyana experiences its highest Net Radiation during this time of the year, using the imagery with figures below to provide further explain the details:

Guyana, he said, has transitioned into the primary (longer) dry season, which will last until mid-November. During this period, there will be long dry spells (days without rain fall) and short wet spell will peak in October, the reason being because of the position of Guyana relative to the sun, hence this is normal.

According to Dhiram, another cause for the very hot days is the global and environmental change that Guyana, as well as people in many parts of the world, are experiencing. He explained that human activities have further contributed towards the increasing heat waves during the hot days, by the increasing global emission of greenhouse gases. “In Guyana, we may not have the mega factories that produce significant amount of greenhouse gases, but the increasing use or air condition units (ACUs) along with an increased number of motor vehicles urbanisation of the cities and villages may well interfere with the atmospheric chemistry.

Other results show a warming of the surface air temperature at land stations. In general, he said, the indices based on minimum temperature show stronger warming trends than indices calculated from maximum temperature. The frequency of warm days, warm nights and extremely high temperatures have increased, while fewer cool days, cool nights and extremely low temperatures were found.

CHANGE IN CLIMATE AND DIRECT EFFECTS
Climate change, Dhiram said, is a change in the statistical properties of the climate system that persists for several decades or longer, usually at least 30 years. These statistical properties include averages, variability and extremes. Climate change may be due to natural processes, such as changes in the sun’s radiation, volcanoes or internal variability in the climate system, or due to anthropogenic (human influences) such as changes in the composition of the atmosphere or land use. Over the past two decades, Guyana has experienced its most extreme meteorological and hydrological disasters on record, which are to some extent related to the increasing climate variability and change.

He noted that research showing local data have indicated an increase of 0.8 C of the difference between night time and day time temperature for northern Guyana and 0.6 C for southern over the last 50 years. The frequency of extreme rain events and prolonged dry spells have also increased throughout Guyana (e.g. 2015 coastal flood, July 15, 2015, and December 23, 2016 floods in Georgetown, and May 16, 2017 flood in Region Seven and Eight;1997/98 and 2015/16 drought episodes, etc.). Meteorologically, the increasing variability of floods and dry spells are having severe impacts on the livelihoods of all Guyanese, he said.

SEASONAL WEATHER PATTERN
Northern Guyana has two rainy seasons while the south has one. The first rainy season in the north starts around the last week of April to the first week of May and ends around the last week of July to the first week of August. The second rainy season in the north starts around the second week of November and ends around the first week of February. The dry seasons are between the rainy seasons. There is no definite start and end dates of the rainy and dry season because it depends on the dynamics and thermodynamics of the atmosphere. Hence close monitoring is being practiced, Dhiram said.

He noted that the rainfall seasons in Guyana are found to be associated with the Inter-Tropical Convergence Zone (ITCZ). The ITCZ is located between the borders of the northern and southern hemispheres, the behaviour of the atmosphere in this zone results in an uplift of air and generation of heavy convective rainfall and thunderstorms moves north and south with the progression of the seasons. The seasons are associated with the varying position of the Earth relative to the Sun, hence, the behaviour of the atmosphere is highly correlated with the radiation from the Sun.

The rainy seasons in Guyana are also influenced by the El Niño Southern Oscillation (ENSO) because of the high correlation between the temperature irregularities in the Eastern and Central Pacific (ENSO Region) and northern South America and other regions across the globe. ENSO refers the interaction between the atmosphere and ocean in the tropical Pacific Ocean that results in a somewhat periodic variation between below-normal and above-normal sea surface temperatures and dry and wet conditions over the course of a few years.

It also has three phases: El Niño (above normal temperature) and La Niña (below-normal temperature – with high intensity and longer rainy season); and Neutral (temperature that is close to normal). “There is still seasonal weather in Guyana but with a slight variation because of the increasing occurrence of El Nino and La Niña and another forcing,” Dhiram said.

He further explained that the Hydro-meteorological Service has been developing capacities to mitigate the impacts of climate variability and change, mainly through the Global Framework for Climate Service (GFCS), which is a global partnership of governments and organisations that produce and use climate information and services.

GFCS seeks to enable researchers, producers and users of information to join forces to improve the quality and quantity of climate services worldwide, particularly in developing countries. It also seeks to build on continued improvements in climate forecasts and climate change scenarios to expand access to the best available climate data and information. (mercilinburke2017@gmail.com)