INTRODUCTION TO GLOBAL CLIMATE CHANGE

The Earth’s climate is affected by the interaction of radiation from the sun and the Earth’s atmosphere. The atmosphere consists of nitrogen and oxygen and a number of natural greenhouse gases (including carbon dioxide, methane, nitrous oxide, ozone gas, and chlorofluorocarbons (“CFCs”)).

The atmosphere and the surface of the Earth absorb part of the sun’s radiation but the remainder is reflected back into space. The greenhouse gases have the important function of trapping this radiation in the lower layers of the Earth’s atmosphere. This process is called the “greenhouse effect” without which the Earth would be as cold as the moon. It is now understood that increased concentrations of greenhouse gases in the atmosphere will increase this greenhouse effect and lead to changes in the Earth’s climate.

Natural events can also cause changes in the climate. For example, volcanic eruptions or variations in ocean currents can alter the distribution of heat and precipitation. The periodic warming of the central and eastern Pacific Ocean (better known as the “El Niño” phenomenon) can affect weather patterns around the world, causing heavy rains in some places and drought in others.

Human activities are now recognized as contributing to climate change. During recent years, scientists have been able to collect evidence of changes in temperature, rainfall and other weather variables. This data suggests that over the twentieth century the average world temperature increased by 0.6º Celsius. The data also demonstrates an increase in the quantity of greenhouse gases in the atmosphere of up to 30%, especially carbon dioxide.

Carbon dioxide (“CO2”) is partly produced as a result of human activities such as burning coal, oil and natural gas (“fossil fuels”), as well as agricultural activities and deforestation. CFCs and methane are also being emitted to the atmosphere as a result of human activities. The increase in the emission of these greenhouse gases can be attributed to the general economic growth which has taken place since the industrial revolution, especially after the 1950s, as well as increased levels of consumption, including the increased demand for electricity and the use of cars.

Oceans and forests can absorb CO2 and other greenhouse gases, and are therefore referred to as greenhouse gas “sinks.” Deforestation, however, releases previously stored greenhouse gases, thus contributing further to the increase of greenhouse gases in the Earth’s atmosphere.

Most greenhouse gases remain in the atmosphere for a long period of time. This means that even if emissions from human activities were to stop immediately, the effects of the emissions already accumulated may persist for centuries. Though the temperature increase over the last century has been relatively moderate at around 0.6º Celsius, scientists estimate that the global average surface temperature could rise by between 1.4º to 5.8º Celsius over the next 100 years.

Such a significant increase in the average world temperature will lead to serious impacts on the environment. Climate change experts predict that this global warming will cause increased rainfall in many areas, increased desertification in others, and the loss of ice cover in the Polar Regions. The average sea level is predicted to rise by up to eighty-eight centimetres by the end of the twenty-first century, posing a serious threat to low lying delta systems and small island states.

Global warming will also have impacts on natural vegetation and fauna. Seasonal patterns will change, leading to longer and hotter summers. Some species will not be able to adapt well to this change of environment and may slowly die out. The most serious consequence is likely to be the impacts on agriculture and thus food safety, especially due to increased water shortages.

While there has been some debate over the degree to which human influenced emissions have contributed to climate change, there is now general consensus that concerted action needs to be taken to minimize and mitigate the problems which global warming is starting to cause.