why is climate change happening?
The atmosphere and the sun are essential for life on earth – the different layers of gases around the earth trap the sun’s heat and maintain temperatures that allow life to thrive on this planet. The ‘natural greenhouse effect’ refers to a layer of gases that occur in the lower ten kilometres of the atmosphere (unlike the ozone layer which occurs in the outer ten to fifty kilometres of the atmosphere). These gases – water vapour, carbon dioxide, ozone, methane and nitrous oxide – are crucial for keeping the earth’s temperature at a global average of 16oC. Without this ‘natural’ amount of greenhouse gases the earth would be 30 degrees colder than it is today. Carbon dioxide for the earth is like salt for us. We cannot live without it, but too much is poison. Climate change (or global warming) is occurring because levels of all key greenhouse gases are rising as a direct result of human activity. Increased amounts of these gases mean that the atmosphere traps more heat than would usually
The climate is changing because the earth’s atmosphere is warming up. As we burn increasing quantities of fossil fuels (oil, gas, coal) to generate energy, we release carbon dioxide (CO2) into the atmosphere. This and other ‘greenhouse gases’ act like a blanket round the planet – just enough, and the earth is perfectly poised to sustain life; too heavy, and the temperature rises, causing major upsets to the world’s climate. Most scientists are convinced that climate change is real, and that it’s linked to human activity. In June 2005 the national Academies of Science of the USA, UK, France, Germany, Italy, Russia, Canada, Japan, India, Brazil and China issued a statement saying ‘The threat of climate change is clear and increasing.’ Click here to see more about what the Intergovernmental Panel on Climate Change said in its fourth assessment report in 2007 We’re the ones who’ve caused the problem and we need to do something about it.
In the past, some scientists thought that changes to the climate were just part of the Earth’s natural climate cycle, but it is now clear that it isn’t that simple. Today, most climate experts believe that human activity is the major cause of global warming and climate change. To understand why the experts now agree on this, we need to take a look at what is called the ‘greenhouse effect’.
There is consensus among the international community that human (anthropogenic) activities are the main cause of the recent global warming. In its latest AR4 Synthesis Report, the UN Intergovernmental Panel on Climate Change (IPCC) concludes that:- Most of the observed increase in globally-averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic (man-made) global greenhouse gas (GHG) concentrations. According to the IPCC:- • GHG emissions due to human activities have grown since pre-industrial times, with an increase of 70% between 1970 and 2004. • Global atmospheric concentrations of CO2, methane (CH4) and nitrous oxide (N2O) have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values determined from ice cores spanning many thousands of years. • Atmospheric concentrations of CO2 (379ppm) and methane (1774 ppb) in 2005 exceed by far the natural range over the last 650,000 years. • Globa
