Climate Change - what are
the underlying facts?
The greenhouse effect issue concerns the
warming of the lower part of the atmosphere, the troposphere
which is about 10-15 kilometers thick, by increasing concentrations
of the so-called greenhouse gases (carbon dioxide, methane,
nitrous oxide, ozone, and others). This warming occurs because
the greenhouse gases, while they are transparent to incoming
solar radiation, absorb infrared (heat) radiation from the
Earth that would otherwise escape from the atmosphere into
space. The greenhouse gases then re-radiate some of this heat
back towards the surface of the Earth.
The natural balance of the greenhouse gases ensures that the
earth's temperature is maintained within a limit. Some activities
of man also produces greenhouse gases upsetting the balance
of the greenhouse gases. Because of higher emission of greenhouse
gases in the atmosphere, more heat is trapped which makes
the Earth warmer. This is known as GLOBAL WARMING.
We have witnessed unprecedented warming of
the planet in the past 25 years but for rapid change in human
activities. The years 2005 and 1998 were probably the warmest
years of the last millennium. The 1990s was the warmest decade
and the 20th century the warmest century.
scientific evidence supports the conclusion that the observed
changes in the global climate are, in large part, due to human
activities and primarily related to fossil fuel consumption
patterns. Climate change is caused by increased levels of
carbon dioxide and other gases in the Earth's atmosphere as
a result of human activities such as burning coal, oil and
gas for transport and energy, and cutting down forests. Greenhouse
gases include methane, nitrous oxide, ozone and water vapour,
but environmentalists are concentrating on carbon dioxide,
as it is the one that can be controlled even at the level
of individuals and institutions.
Carbon Dioxide is a global problem, but the
countries that produce the greatest amount per person are
in North America, Europe and Australasia.
'The United Nations Intergovernmental Panel on Climate Change
(the IPCC - a high level, independent, scientific advisory
body) has published studies which state that unrestrained
greenhouse gas emissions could drive global temperatures up
as much as 6 degrees centigrade by 2100, triggering raised
sea levels, species destruction, economic devastation in tropical
zones and mass human migrations.
The graph above, which has been produced
by the IPCC shows that most of the change has been in the
past century as the world industrialised and population has
grown rapidly. From fluctuating in a narrow band around 0.5°C
below the average 1990 temperature, it has started to rise
sharply and is most likely to be between 1.5°C and 5.5°C
above current temperatures by 2100.
This would have a catastrophic effect on the earth, with widespread
melting of glaciers and ice-sheets, and a highly probable
rise in sea level that could lead to the inundation of countries
such as the Netherlands and Bangladesh. Latest scientific
concern is focused on melting ice lowering salinity in the
North Atlantic Ocean, which could lead to the reversal of
the "Great Atlantic Conveyor" - better known as
the Gulf Stream. If this were to happen, we could find that
temperatures in NW Europe, including Britain, drop by up to
10°C, despite temperatures elsewhere in the world rising.