Geoscience Reference
In-Depth Information
signed the Protocol, the
final UN country to do so. Another interpretation
would be that it took 22 years for all countries to sign an international agreement
which was relatively simple, and had little economic impact compared with the
complex challenges of climate change today.
CFCs are non-toxic, non-
ammable chemicals developed in the 1930s to
replace ammonia. Although the concentrations of CFCs are just beginning to fall
through the actions of the Montreal Protocol, they have lifetimes of ~20 to 100 years
in the stratosphere. The recovery of the ozone hole is predicted to be around 2070.
There is some uncertainty in the timing, as recovery is also affected by the
concentration of carbon dioxide in the atmosphere. Carbon dioxide is a greenhouse
gas that warms the troposphere, but acts to cool the stratosphere, and a colder
stratosphere will delay the recovery of the ozone hole. The concentration of carbon
dioxide through the twenty-
rst century is the largest unknown in climate change
projections and hence the uncertainty.
The replacement for CFCs was initially hydrochloro
uorocarbons (HCFCs)
but now hydro
uorocarbons (HFCs) are the major class of replacement substance.
These chemicals have low ozone depleting potential but they are very effective
indeed as greenhouse gases. The global warming potential (GWP) of carbon dioxide
(100-year) is 1; the corresponding GWPs for the principal HFCs vary between 1000
and 4500. Speci
cally the GWP of HFC-125 is 3500, HFC-134a is 1430 and HFC-
143a is 4470. Predictions suggest that the developing countries will increase their
demand for HFCs by 800% by 2050. This is likely to add ~15% additional warming
to that of carbon dioxide
equivalent to just a little less than the impact of the
carbon dioxide produced today by the United States or China. There are no
international regulations or agreements on HFC and HCFC gases despite the
likely increase in demand for refrigeration in the future. There is a pressing need to
-
find substances that have no ozone depleting potential and low global warming
potential, as well as very low
flammability and toxicity.
Impacts on the marine environment around Antarctica
The marine ecosystem of the Southern Ocean is often considered as relatively
simple compared with those of other oceans. It covers not only 10% of the global
seas but also a tremendous size range from microbial organisms (bacteria) to
the largest animal that has ever lived on Earth, the blue whale.
A key element of the Antarctic marine ecosystem is the presence of sea ice,
which provides higher predators with a platform for giving birth and for foraging, as
well as a specialised habitat at the sea surface. Sea ice formation and its melting have
a major in
uence on the timing, location, and intensity of biological production.
Sea ice affects light and nutrient availability and ultimately food availability for
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