What computer simulations can tell us about the success of international treaties

International negations on climate change
sometimes give the impression that a lot of hot air is raised for nothing:
Politicians, policy makers and scientists alike gain air miles on their way to countless
conferences, thereby emitting non-negligible amounts of greenhouse gases, only
to arrive at the lowest common denominator satisfying none of the parties. International
treaties resulting from these negations suffer a rather bad reputation.

Recent computer simulations may smoothen the
ruffled feathers of all those who see international regulations as the sole
remedy to global environmental problems. At the annual
of the international research program
SCOUT-O3 that ends tomorrow, researchers
presented simulation
showing how the Montreal
– originally ratified in 1992 to reduce the emissions of CFCs and
other ozone-damaging substances –has contributed to a healthier environment
(see newspaper

Why do we need simulations to evaluate the
success of the Montreal Protocol? The
protocol is known to have reduced global emissions of CFCs and other ozone-damaging
substances virtually to zero – Kofi Annan famously referred to it as "Perhaps the single most successful international
agreement to date […]"
. Although often necessary, reducing
emissions may not be sufficient to solve some environmental problems. The
reasons for this are multi-layered: Our deficient understanding of atmospheric processes
and relevant parameters (cp. Steve
Clarke’s post on climate change
); the nature of research within the earth
sciences, which distinguishes itself from `classical hard sciences’ such as
physics, chemistry or astronomy in a number of relevant ways; the fact that a
lot of ozone damaging substances, just like greenhouse gases, are long living –
the dispensation of CFCs will show its results in the stratosphere only after a
long time. Maybe it is already too late to stop major damages from anthropogenic
greenhouse gas emission, maybe it was too late when the protocol forbade the emissions of
ozone. Indeed, in most parts of Europe,
the UV-impact has
increased over the last 30 years – the Montreal Protocol could not change this.

However, the simulation results presented at
the current conference reassure us: The world would indeed have been a worse
place if the Montreal Protocol had never been ratified. Not only would the
expected increase in skin cancer within middle Europe
be six to ten times the currently predicted value; the ozone depletion in the
polar regions would also added to global warming. The results of simulations
are not merely reassuring or interesting. Their ‘necessity’ points to the
general difficulties we have in predicting earth science systems – if not
impossible, it is at least extremely difficult to isolate single single
cause-effect relations.

But can these simulations tell us anything
about success or failure of the Kyoto Protocol that was ratified by 175 nations
only last November? Unfortunately they cannot tell us much. Even setting
questions regarding model or parameter uncertainty aside, the Montreal Protocol
is unusual as the lowest common denominator in this case was fairly large – arguably
because international consensus was sought-after in a time of relaxation between
East and West.

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