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Figure 4.27
Time series of minimum ozone
concentration over Antarctica (Credit: NOAA)
SOUTH POLE OZONESONDES
Total Column Ozone
400
350
300
250
200
1967-71
1986
1993
1999
2006
2009
2010
150
100
50
Jul 1
Aug 1
Sep 1
Oct 1
Nov 1
Dec 1
Dec 31
limit and eventually phase out the production of CFCs. This protocol has begun to
show signs of taking effect, with a decrease in CFCs in the stratosphere since 1997.
Given the long lifetime of CFCs in the atmosphere a reversal of the ozone hole is
not expected immediately, but may begin to become evident by as early as 2015.
It is possible that the spring ozone hole will no longer develop by the end of the
twenty-
s nations were able to act to reverse a
global environmental problem like the ozone hole provides hope that a solution
for global warming can be achieved as well.
rst century. The fact that the world
'
Global climate modelling and global warming
Observations of carbon dioxide at Mauna Loa observatory in Hawaii and at the South
Pole in Antarctic, since 1957, have shown a 20% increase in the amount of carbon
dioxide in the atmosphere. Scientists have become increasingly concerned over the
last two decades about the possible impacts of increasing greenhouse gases (carbon
dioxide, methane and others) on the climate system. The concern is that an increase in
greenhouse gases in the atmosphere, primarily due to the burning of fossil fuels, will
alter the radiation balance of the atmosphere since these gases are effective in
absorbing longwave radiation. In doing this these gases trap longwave radiation
emitted from the surface of the Earth, resulting in a warming of the lower atmosphere
and an increase in surface temperature. Further, there is reason to believe that these
changes in temperature will also be accompanied by changes in precipitation and
atmospheric circulation patterns. These changes will also impact other aspects of the
climate system, such as monsoons, hurricanes, sea ice and ice sheets.
The United Nations Intergovernmental Panel on Climate Change (IPCC) has
been tasked with evaluating observed climate change, assessing what role human
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