What is global warming?
Global warming is a term used to describe the increase over time in the earth’s average temperatures as a result of what are now commonly known as ‘greenhouse gases’ (such as carbon dioxide and methane). These gases cause pollution that builds up in the earth’s lower atmosphere and prevents heat escaping into space. Scientists predict that global average temperatures will rise by between 1.8 and 4.0 degrees Celsius this century.
How do we know humans have contributed to global warming?
Scientists now believe that most of the warming that has taken place in the past 50 years has been caused by humans burning fossil fuels (such as coal, oil and natural gas) combined with widespread land clearing.
Carbon dioxide is the main contributor responsible for 80% of emissions from industrialised countries. The gas is released into the atmosphere primarily from burning fossil fuels: oil, petrol and natural gas. A growing population coupled with increasing demands on transport and energy, has led to emissions increasing at dramatic rates.
Other greenhouse gases which arise from a range of industrial and agricultural sources are:
- Methane
- Nitrous oxide
- Hydrofluorocarbons (HFCs)
- Perfluorocarbons (PFCs)
- Sulphur Hexafluoride (SF6)
Combined, these greenhouse gases absorb infrared radiation in the atmosphere and thus change the dynamic balance between energy arriving from the sun and energy escaping.
Present carbon dioxide and methane concentrations are the highest they have been for at least 420,000 years. In many places throughout the world, the hottest days ever recorded have occurred in the past decade. Eleven of the past 12 years have ranked among the dozen warmest on record. Meanwhile, over the past 30 years, small groups of like-minded people have started planting trees and changing the way they use energy. More and more people are changing their behaviour every day. Humans can have the most impact on global warming by reducing the amount of carbon dioxide, methane and nitrous oxide that is released into our atmosphere.
What are the predicted impacts of global warming?
The real impact of climate change remains worryingly uncertain, with consequences for all communities, species and environments across the world. Effects include:
- Changing weather bringing drought and flooding, affecting drinking water supplies and agriculture.
- Irreversible loss of many species of plants and animals.
- Rising sea levels, threatening freshwater supplies because of salt water intrusion.
- Melting glaciers, threatening freshwater supplies for millions of people who depend on glacier meltwater for their water supply and irrigation.
We will all experience these effects but an appalling injustice of climate change will be that those people in the developing world, who have contributed little towards the problem, are at greatest risk and will be the hardest hit. They have fewer resources for coping with storms, floods, droughts, disease outbreaks, and disruptions to food and water supplies. This is an issue with the welfare of humans at its heart.
Predicted impacts in Developing Countries
The Intergovernmental Panel on Climate Change predicts that "the effects of climate change are expected to be greatest in developing countries in terms of loss of life, and relative effects on investment and economy". Livelihoods built for generations on particular patterns of farming may quickly become impossible. If not addressed, climate change is likely to place an additional 80-120 million people at risk of hunger; 70 to 80 per cent of these will be in Africa¹.
In Africa it is predicted that by 2050:
Land areas may warm by as much as 1.6°C over the Sahara and semi-arid regions of southern Africa. This could mean people having to move from their home due to prolonged drought. In southern Africa and parts of the Horn, rainfall will fall by about 10 per cent. Sea level will rise by around 25cm, threatening low-lying areas of West Africa and coastal fisheries. Climate variability and the frequency and intensity of severe weather events will increase³.
In Latin America and the Caribbean it is predicted that:
Hurricanes and tropical storms will increase in intensity. With 26 tropical storms and 14 hurricanes, the 2005 hurricane season is rated as one of the most active and destructive in history. Sea level rise is likely to hit coastal areas, leading to loss of coastal land, infrastructure, and biodiversity, as well as the intrusion of soil-contaminating saltwater. Sixty of Latin America's seventy seven largest cities are located on the coast. Warming in high mountain regions is melting glaciers, snow and ice, affecting farming and the availability of water to coastal cities and tourist activities. It is estimated that by 2025 about 70 per cent of the population in South America and Mexico will live in regions with low water supply.
In Asia it is predicted that:
Rainfall will become more variable during the Indian summer monsoon. The timing and intensity of rainfall will become more erratic and between seasons; Heavy rainfall and tropical cyclone intensity may increase due to disruption of the El Nino cycle and increasing sea surface temperature. A 1°C increase in sea surface temperatures in the Bay of Bengal could increase tropical cyclone intensity by 10%. Other extreme events such as heat waves are also likely to increase as the climate becomes unstable through climate change. The principal consequences of these changes in climate are greater risks to food and water security, and greater health risks, which will affect the poor and vulnerable the most.
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