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Here is a primer on climate change – basic reading if you will. Once you have understood the basics, you will be able to explore climate change in greater depth. India Climate Portal will be glad to help you learn about climate change, take action, and reduce your impact.
EARTH’S CHANGING CLIMATE Throughout Earth’s history, the climate has changed over long periods of time (thousands or millions of years). In the last 650,000 years there have been seven cycles of glacial advance and retreat. These changes have been gradual, and attributed to small changes in the amount of energy the earth received from the sun1. About seven thousand years ago, the last ice age ended, marking the beginning of the modern climate era and of human civilization1. Earlier in our history, humans hunted and gathered food, roaming over vast areas of the planet. Gradually, we learned to grow our food in one location or other, and started to settle down. With the progress of agriculture, use of advanced tools and assured food supply, our population grew. Soon we started producing cloth, machinery, and living together in villages, towns and cities. The Industrial Revolution got underway and coal (a fossil fuel) was burned to generate energy. Prosperity started to increase. As prosperity increased, lifestyles changed, and we started using more and more machinery to do our work. We soon discovered petroleum (or crude oil), invented many ways of processing it and producing several products from it (petrol, diesel, aviation fuel, LPG and most of our primary energy sources). We started to use petroleum and coal for a sizeable proportion of our work; from running industrial machines, to transporting ourselves, paving roads, packaging goods and generating electricity. Today, our modern civilization depends on industrial activities, which use large quantities of energy; and our biggest source of energy is fossil fuels. Over the years, we have been burning fossil fuels at faster and faster rates. When we do this, different kinds of gases and particles are released into the atmosphere. These are called emissions, and are gases like carbon dioxide and methane. These gases allow sunlight to enter, but block the heat from escaping: much like a greenhouse, causing a natural greenhouse effect. However, here’s the catch! Since 1751, roughly 351 billion tons of carbon dioxide (and other ‘greenhouse gases’), have been released into the atmosphere. Half of these emissions have occurred since the mid 1970s2, and the primary source of these emissions has been fossil fuels.
Today, there are more of these gases in the atmosphere than ever before, and emissions of carbon dioxide are accelerating. Since these gases trap heat, the Earth’s atmosphere is getting overloaded with these gases. We are also cutting and burning the earth’s natural sinks of carbon – the world’s tropical forests – at an estimated rate of 13 million hectares per year (deforestation). This is causing the Earth to warm in response1. HOW DO WE KNOW? We know that there is an overload of emissions in the Earth’s system from measurements of atmospheric carbon dioxide: CO2 levels are higher today than at anytime in the past 650,000 years1!
Source: NOAA; NASA
WHY SHOULD WE CARE? A result of so much carbon dioxide is a heating of the earth, or ‘global warming’. In effect, our climate is changing. Scientists have found many serious changes in Earth’s environment. There is also little doubt that human beings are the cause of this current warming trend. Global average surface temperatures: 1880 to 2005
Depending on how much and how soon emissions are reduced, the Intergovernmental Panel on Climate Change (IPCC) predicts an additional 1.8- 4.0 degrees Celsius rise in temperature.
Global sea levels rose about 17 cm in the last 100 years. In the last ten years, the rate of increase per year has nearly doubled, from a rate of change of 2 mm per year, to 3.4 mm per year. The graphs below show the rate of change of sea level.
Source: NASA The rate at which land ice is being lost is shown in the illustration to the left. Areas where melt occurred for longer periods of time is shown in red. Each year, ice extent has decreased by 36-60 cubic miles in Greenland. The extent of arctic sea ice has decreased by 38% as compared to 1979 to 2000 levels, as shown by the illustration on the right.
Source: NASA
Precipitation and evaporation patterns over the oceans have changed. We know this from increased salinity near the equator, and decreased salinity at higher latitudes4. Biological systems are strongly affected by climate change3. In the terrestrial systems, there is evidence of earlier timing of spring events, leaf unfolding, bird migration and egg-laying; and a poleward and upward shift in ranges in plant and animal species. In marine and freshwater systems, the ranges and abundance of algae, plankton and fish are changing, and increasing evidence of impacts on coral reefs4 WHAT IS THE CAUSE? Scientists have identified the kinds of human activities that are contributing to climate change. The major sectors that emit greenhouse gases are energy supply, industry, deforestation, agriculture, transport, and waste incineration.
Adapted from: IPCC report 2007
These activities release three major greenhouse gases: carbon dioxide, methane and nitrous oxide. Carbon dioxide is the largest contributor to climate change, as you can see from the chart below.
Adapted from: IPCC report 2007 WHAT ARE THE EFFECTS? The expected impacts of an unstable climate and rising sea levels are increased droughts, decreased availability of drinking water, displaced populations, salinisation of soil and freshwater, massive extinctions of wildlife, decreased forest cover, coral bleaching, reduced crop yields, increased epidemics and increased intensity of tropical storms. People living below the poverty line and dependent on land-based (agriculture) and marine occupations (fisheries) are likely to be the most seriously affected. As you can see, these consequences don’t affect just others. It affects ALL of us in some way or other.
WHO IS TO IMPROVE THINGS? We! That’s who. YOU can be a very important part of the efforts to reduce climate change. You can become a leader of efforts at different levels. Here are some links that will help you learn more about climate change. References: 1. California Institute of Technology, NASA: http://climate.jpl.nasa.gov/; 2. Carbon Dioxide Information Analysis Centre: http://cdiac.ornl.gov/; 3. State of the World report 2009; 4. IPCC Fourth Assessment Report, Summary |
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