3. Introduction
The recent interest in global warming and sustainable development has become a
global talk.
Climate has from the very beginning regulated by human in practically every aspect of life
and has played a very important role in the development of civilizations all around the
world.
Human’s impact on climate began 5000 to 9000 years ago, as they was able to alter the
environment by burning and felling forest and tilling the earth. The most extensive change
brought by human prior to our own times was the gradual conversion of most of the temperate
forest zone to crops that is an artificial steppe or savanna. Thus until the industrial revolution
and probably until the present century, man had little effect on the climate except on a very
local scale.
Presently global warming has emerged as one of the most important environmental
issues ever to confront humanity.
Climate Change
4. What is climate change?
Climate change is a newcomer to the international political and environmental
agenda, having emerged as a major policy issue only in the late 1980s and
thereafter. But scientists have been working on the subject for decades.
They have known since the nineteenth century that carbon dioxide in the
atmosphere is a ‘green house gas’, that is, its presence in the atmosphere helps
to retain the incoming heat energy from the sun, thereby increasing the earth’s
surface temperature. Of course, carbon dioxide is only one of several such
greenhouse gases in the atmosphere.
5. Others include methane, nitrous oxide and water vapour. However,
carbon dioxide is the most important greenhouse gas that is being affected
by human activities.
Carbon dioxide is generated by a multitude of processes
ranging from animal and plant respiration to the burning of any kind of
fuel containing carbon, including coal, oil, wood and cow dung. For a long
time, human activities that generated carbon dioxide caused only a small
perturbation in the natural cycle of the gas. However, since the Industrial
Revolution, when our usage of fossil fuels increased dramatically, the contribution
of carbon dioxide generated from human activities has grown
large enough to constitute a significant perturbation of the natural carbon
cycle.1 Since the early 1950s, when regular measurements of the atmospheric
concentrations of carbon dioxide were started, it has been conclusively
established that these concentrations are increasing rapidly, driven by
human activities.
6.
7. Human impacts on the carbon cycle
Humans, just like all other living organisms, have impacted the global carbon cycle
since the dawn of our species. However, the magnitude of our impacts has changed
dramatically throughout history. The Industrial Revolution, which occurred around
the turn of the 19th century, began to make major changes in the use of resources
around the world. Beginning in Britain, industrialization eventually affected the
whole world. The development of coal-fueled steam power, and later transportation
following the discovery of large oil deposits, had enormous influence on the
economic and social structure of the world. As the world accelerated in the
production and transportation of manufactured goods, the production and
consumption of fossil fuels grew. As economic growth continued to increase, so did
the production of carbon dioxide through fossil fuel combustion.
8. Since the Industrial Revolution, when our usage of fossil fuels
increased dramatically, the contribution of CO2 from human
activities has grown large enough to constitute a significant
perturbation of the natural carbon cycle.
The concentration of CO2 in the Earth’s atmosphere was about
280 parts per million by volume (ppmv) in 1750, before the
Industrial Revolution began. By 1994 it was 358 ppmv and rising
by about 1.5 ppnw per year. If emissions continue at the 1994
rate, the concentration will be around 500 ppmv, nearly double
the pre-industrial level, by the end of the 21st century.
9. In many less-industrialized countries, combustion of biomass such as
wood or animal dung is still the primary energy source that many
citizens, particularly in rural areas, depend on for domestic use
(heating, sanitation, and cooking) as it is inexpensive, relatively efficient,
and readily available. Figure 7.3c shows the global distribution of
biomass fires in the world. While the burning of biomass for domestic
use contributes to some of these fires, it is the so-called slash-and-burn
agriculture that makes up a larger contribution. Take a minute to
compare the areas highlighted in Figure 7.3c to the countries of the
world that are currently experiencing rapid population growth
(Chapter 3). If you need a refresher, use the CIA World Factbook
website to view current global population growth values by country:
https://www.cia.gov/library/publications/the-world-
factbook/rankorder/2002rank.html.
10. Rising temperature :
0.3 to 0.6 °C since the late 19th century; 1 to 3.5 °C by the year 2100
global mean sea level by about 15 to 95 cm
Habitat Extinction
