Global Warming and Climate Change
As Earth started to take its shape from a fire ball to a planet, many gases were released. These gases did not escape into outer space because of the Earth's gravitational pull and it still holds them back. The result? A thin layer of gases surrounds the Earth and provides us several important benefits. For example: the oxygen that we breathe, the ozone that protects us from harmful ultraviolet rays from the sun, the nitrogen that our plants use to make proteins that we need. This layer of gases is the medium through which fresh water is circulated and it also keeps us warm (take a look at the image from Class IX Chapter 4).
Keeping us warm is one of the most important things that the atmosphere does for us. It is like a light, but effective, blanket enveloping Earth. You will recall from Class IX that the atmosphere traps a lot of solar energy that reaches the Earth by preventing it from totally escaping back into space. This is called Green House Effect. This is important and vital for life to survive on this planet. If the Earth did not have this atmosphere, it would be very cold indeed.
However, since the 19th century, the planet has been warming up very rapidly. There is an increasing concern about this. Why this concern? After all, Earth has been through many cycles of warming and cooling (in fact, freezing!). So what is so special about it now?
Earlier, cycles of cooling and warming happened over very long periods of time. This allowed most of the life on Earth the time to adapt to the changes. The problem now is that the heating is much more rapid and could lead to catastrophic changes. Much of the warming that has been occurring since the Industrial Revolution is because of human activities. Hence, the current global warming trend is called AGW (Anthropogenic Global Warming; anthropogenic means caused by humans).
More recently, scientists are discovering large volumes of methane under the frozen tundras of the far northern latitudes (mainly in the vast expanses of northern Russia). As global temperature increases, the ice in the tundra melts more. The methane that is trapped under the ice escapes into the atmosphere, increasing the global temperatures. In turn, this causes even more ice to melt, releasing even more methane and so on. Methane is said to be even more powerful than Carbon dioxide as a greenhouse gas.
AGW and climate change
AGW is causing many changes in the distribution of heat in the Earth system. Remember how atmospheric and oceanic circulations keep re-distributing the heat in the world? AGW disturbs this and the re-distribution system. The disturbance itself is not so much of a problem. It is the rapidity with which it is happening.
When the redistribution system is disrupted, weather and climate patterns change. Long-term changes (climatic changes) happen from accumulations of short-term changes (weather changes).
An international effort to form an agreement whereby all countries try to reduce their emission of greenhouse gases has so far not been achieved. An international organization called Inter-governmental Panel on Climate Change (IPCC) was formed to address this issue. It has held many conferences to work out a treaty among the nations of the world to reduce AGW and try to slow down the process of climate change. None of these have been successful. The IPCC 2015 Paris Summit came to an agreement to reduce greenhouse gas emissions in order to limit the rise in global average temperature to well below 2°C above pre-industrialisation level. On this agreement total 195 countries signed.
Broadly, the disagreements are between the developed countries (mainly industrialised, economically more advanced countries of the West) and 'developing' countries (countries that are not as industrialised). Developed countries want developing countries to cut down on burning coal and other activities that add greenhouse gases to the atmosphere. Developing countries argue that developed countries developed precisely by burning fossil fuels when they were developing. Developing countries say that their economic development will be seriously damaged if they don't burn fossil fuels (mainly coal), and that. developed countries should do their fair share of work to help find alternatives that can help the developing countries to progress.
Most scientists from around the world agree on this much: AGW is real, it is happening, and it is leading to rapid and drastic climate change. They warn that severe weather and other changes will increase in the coming years and threaten life as we know it.
One of the human activities that contribute to global warming is deforestation.
Discuss this with your teacher and your classmates and try to answer the questions given above in a few sentences.
Impact of climate change on India
Though a rise of 2º C in average temperature may appear to be small, it would result in a rise of one meter in sea levels by early next century. This would affect large portions of our coastal areas and millions of people would have to be shifted. They would lose their livelihood.
Nearly 200 squatter families living in Nonadanga in east Kolkata for the past few years are in the process of being evicted by the Kolkata Metropolitan Development Authority (KMDA). Many of the families came to Kolkata in search of work, after the 'Aila super-cyclone' ravaged Sundarbans in 2009.
On March 30, the slum was bulldozed amid heavy police presence and some hutments were set on fire. The recurrent thunderstorms over the past few days have meant sleepless and soiled nights for nearly 700 people who have been rendered homeless. They work as house helps, rickshaw pullers and construction labourers.
The other effect would be on rainfall. This is likely to be more erratic and lead to greater imbalances: some places are likely to receive excess rainfall whereas others would get less than normal. Hence droughts and floods are expected to increase. This would affect the agriculture pattern and people's livelihood to a great extent.
The faster melting of Himalayan glaciers would disturb the livelihood of fresh water fisher folk as their natural habitat of fish is affected. Similarly, freak weather conditions that you read about are likely to increase. Climate change is something that happens at a global level. Therefore, it affects all of us.
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