Greenhouse effect and climate change: scientific basis and overview

Abstract

Climate change due to ‘enhanced greenhouse effect’, arising as a result of human activities is considered a major global environmental threat to mankind. A review of the topic including the physics of the greenhouse effect is given. The Earth provides a unique life-supporting environment. Solar radiation has been responsible for maintaining the Earth's climatic system, the biosphere and fuelling the present technological age. Earth's temperature is a result of the equilibrium between the solar energy absorbed by the Earth and the long wave (infra-red) radiation from the Earth escaping into space. The natural greenhouse effect arises due to some of the trace gases, called the greenhouse gases, which are nearly transparent to solar radiation but strongly absorb the infra-red radiation emitted by the Earth. This results in a warming of the Earth by about 30°C and makes it habitable. Since industrialization, human activities have resulted in steadily increasing concentrations of the greenhouse gases—carbon dioxide, methane, nitrous oxide and chlorofluorocarbons—in the atmosphere, leading to fears of the ‘enhanced greenhouse effect’. Carbon dixoide alone contributes roughly two-thirds to the ‘enhanced greenhouse effect’. Past records suggest that the Earth has warmed by 0.5°C and the global sea level has increased by 15 cm since the beginning of this century. Climate models predict a further warming of 0.3°C per decade if no efforts are made to decrease emissions of greenhouse gases. This warming rate is higher than that at any time during the past 10 000 years and is likely to cause global changes in agricultural patterns, precipitation, water resources, rise in sea levels and inundation of coastal areas, occurrence of more frequent and intense extreme events such as droughts and hurricanes. African nations will be particularly vulnerable to some of these changes. Uncertainties do remain in the predictions of climate change at regional level and the scale and timing of such changes. Limitation and adaptation strategies need to be developed and implemented. Decreasing use of fossil fuels and increasing use of alternative sources of energy—solar, wind, hydro, biomass—coupled with energy conservation strategies are needed to reduce emissions of greenhouse gases. Reducing deforestation and embarking on reforestation programs is needed to increase the sinks of carbon dioxide. More research is needed to enable better understanding of climate processes and decrease uncertainties in climate predictions. Climate data, analyses and information need to be utilised in planning processes.