What is Climate Change?
Climate describes the average weather conditions in a particular place over an extended period of time. It is based on data such as average monthly rainfall, average monthly temperatures and average hours of sunshine over periods as long as 10, 20 or more years. The climate in Barbados would be described as being tropical, which means it is hot all year round with a dry sunny season followed by a wet season with more cloud cover. Climate variability refers to the changes that occur from time to time relative to these average conditions. For example, some summers are wetter or drier than the average.
Climate change is a long-term continuous change, either an increase or decrease, in average weather conditions OR in the range of weather conditions (for example, more frequent and severe extreme storms). The Earth’s climate has always varied over long periods of time due to various natural causes. Records show that since the Industrial Revolution in the early 1900s, the average annual temperature has been steadily going up when compared with a longer-term average. This suggests that human activity has played a significant role in these recent increases.
Causes of Climate Change
There are various phenomenon that cause changes in the earth’s climate including:
The sun goes through natural periods of variation in the amount of energy emitted. The earth’s axis varies between 22° and 24° over about 41,000 years, which affects the influence of solar radiation.
Volcanic eruptions spew sulphur dioxide (SO2) gas, water vapour, dust, and ash, high into the atmosphere, which can cool the earth by blocking incoming radiation from the sun.
The Greenhouse Effect
There is a layer of gases that surrounds the earth. These gases create a liveable atmosphere for life on earth. This is often referred to as a greenhouse effect, because these atmospheric gases – also known as the greenhouse gases – act like the glass of a greenhouse, keeping life on earth at the right temperature. Radiation from the sun enters the earth’s atmosphere and is absorbed by the air, oceans, land and plants. This energy is either converted to food by plants (photosynthesis) or re-emitted as heat. Some of this heat escapes through the atmosphere, and some is reflected back to earth again by atmospheric gases, thereby having a warming effect.
Human activities are causing an increase in the amount and concentration of Greenhouse Gases (GHG), which lead to trapping of heat in our atmosphere. Of particular concern is the increase in Carbon Dioxide (CO2), which for hundreds of thousands of years remained below a level of 300 parts per million.
The burning of fossil fuels such as coal, oil and natural gas, as well as agriculture and land clearing influence the climate by increasing the concentrations of greenhouse gases. When fossil fuels are burned, the process combines carbon with oxygen in the air to make CO2 contributing to changes in the Earth’s climate.
Land-use changes, such as the cutting down of forests to create farmland, have changed the amount of sunlight reflected from the ground back into space. The trees that are lost can no longer absorb CO2. When trees are burned the carbon they stored is released into the atmosphere as CO2. When the cut trees decompose they produce methane – another GHG.
This video from NASA shows changes in global air temperature:
Predication of Climate Change for Barbados
The body of data collected by scientists over many years reveals the signals of a changing climate and that the global evidence for warming of the climate system is indisputable. Key points to evidence include: rising air temperatures, shrinking ice sheets, declining arctic ice, and glacial retreat. In Barbados, average air temperatures have risen by almost a degree over the last 45 years.
The Intergovernmental Panel on Climate Change (IPCC) is the international body for assessing the science related to climate change. The IPCC has developed future climate change predictions based on trends in observational data as well as the use of general circulation models (GCMs) to simulate the response of the Earth-climate system to increasing greenhouse gas concentrations, termed Representative Concentration Pathways (RCPs). These models represent advanced knowledge of the coupled hydrological processes in the atmosphere, ocean and land surface to provide projections of future climate change. Four different future scenarios have been modelled by the IPCC with different views of changes in society and the emission of GHGs.
Key predicted changes for Barbados over the next 50 years are:
-Air temperature is expected to rise 1º to 2º C
-Overall rainfall is expected to reduce
-Rainfall intensity may increase by up to 45%
-Sea level rise of 0.2 to 0.4 metres.
-A possible increase in hurricane intensity of 2% to 11%
The implications of these projected changes to Barbados are significant. Sea level rise will lead to reduced beach widths at many locations and increased saline intrusion (migration of seawater) into the freshwater aquifers from which Barbados draws its drinking water. Reduced rainfall amounts may lead to increased frequency and severity of drought, but increased rainfall intensity may lead to increased flooding.