From Toxics Link, an environmental non-govt organization headquartered in New Delhi.
Climate Change is said to be caused when there is a statistically significant variation in either the mean state of the climate or its variability, persisting for an extended period due to increasing emissions of greenhouse gases (GHG) such as carbon di-oxide, methane, nitrous oxide and chlorofluoro carbons. In simple terms as these gases trap the solar heat within the earth's atmosphere, the earth's surface temperature increases, leading to changes in the weather patterns and the earth's ecological balance. The concentration of atmospheric carbon dioxide in the atmosphere has increased by 31 % since 1750, to a level which has been not been exceeded during the past 420,000 years and most likely not even during the past 20 million years. This implies severe, unforeseen weather changes resulting in massive all round effects. Climate change will lead to the melting of polar ice, changing weather patterns in complex ways causing events such as frequent storms, floods, invasion of seawater inundating low-lying islands. Other disastrous effects will be on biodiversity, changes on cropping patterns and the rise of disease vectors. Even mountain glaciers have retreated dramatically in the non-polar regions and the global average sea level has risen between 0.1 and 0.2 meters during the 20th century. In addition, the number of heavy rainfall events has increased in the mid latitudes in the northern hemisphere, while parts of Africa and Asia have experienced increases in the frequency and intensity of droughts. Instrumental records of recent climate show that the global mean temperature has increased by 0.6 to 2 degrees Celsius over the last century. They also indicate that, globally the 1990s was very likely the warmest decade, while 1998 and 2001 were the warmest and the second warmest years respectively since the start of the instrumental records in 1861. Since 1958, there has been a 17 % increase in atmospheric CO2 levels. Climage change effects
Climate change will lead to the melting of polar ice, changing weather patterns in complex ways causing events such as frequent storms, floods, invasion of seawater inundating low-lying islands. Other disastrous effects will be on biodiversity, changes on cropping patterns and the rise of disease vectors. Even mountain glaciers have retreated dramatically in the non-polar regions and the global average sea level has risen between 0.1 and 0.2 meters during the 20th century. In addition, the number of heavy rainfall events has increased in the mid latitudes in the northern hemisphere, while parts of Africa and Asia have experienced increases in the frequency and intensity of droughts. Instrumental records of recent climate show that the global mean temperature has increased by 0.6 to 2 degrees Celsius over the last century. They also indicate that, globally the 1990s was very likely the warmest decade, while 1998 and 2001 were the warmest and the second warmest years respectively since the start of the instrumental records in 1861. Since 1958, there has been a 17 % increase in atmospheric CO2 levels. Natural and Man-Made causes
Climate change can take place due to either natural processes or persistent anthropogenic (man-made) changes. The earth's climate is controlled by the balance of energy from the sun and the amount of energy it releases back to space. Causes of climate change involve any process that can alter this global energy balance. There are two processes external and internal that force the climate to change. External processes take place outside the earth and includes changes in the earth's orbit around the Sun, or in the amount of energy the sun emits. Internal processes occur within the earth's climate system involving oceans, atmosphere and biosphere etc. and include change in the global energy balance due to changes in the composition of the atmosphere or ocean circulation. Some sources of green house gases
November 2002 Toxics Link is based at H-2 Jungpura Extension, New Delhi 110 014. Tel: +91 11 4328006/0711.