Evidence
for global warming - and why we need to take action
The
following statement was prepared
by Professor Peter Barrett FRSNZ (Director of the Antarctic Centre,
Victoria University of Wellington), and is a slighly amended version
of an article originally published in the "Evening Post".
We still
see letters and articles in our newspapers claiming that global
warming has nothing to do with human activity,
and that there is no need to do anything about it. This claim
is echoed and promoted by
business interests, and risks deflecting Government
efforts to reduce our greenhouse gas
pollution. Do we really need to be concerned
about this? I believe we do on
two counts:
1. The
claim denies a huge body of contrary published scientific
evidence amassed over the last 15 years.
Thus it trivialises this effort, and
by implication all science.
2. Earth scientists have a better understanding than most of
earth history and behaviour, and can appreciate the magnitude of
effects that are bound to follow the 3-4 degree C global temperature
rise projected for the next 100 years - giving a temperature as warm
as the Eocene.
How can we be so sure of
this? For the last few years I have been following the work of the
UN-sponsored Intergovernmental Panel on Climate Change (IPCC). It
consists of three Working Groups:
* WG I to get the best possible evidence on present and past
climate from many places on the earth's Surface;
* WG II to check out the consequences of possible changes for
Communities; and
* WG III to advise governments on how to deal with the
issue.
They first reported in 1990, and again in 1995 and 2000. Working
Group I alone comprises just under 1000 climate scientists from 100
countries. Their work consists of reviewing knowledge of climate
change, analysing and summarising data from thousands of relevant
published and peer-reviewed scientific articles. Tedious but
unassailably sound and comprehensive. To ensure that their findings
can be understood, they have produced summaries for policy makers
that are approved by government representatives of IPCC countries
line by line. This is advice unbiased by individuals or special
interests and the best we can get.
What have they said? IPCC concluded in 1995 that "The balance of
evidence suggests a discernible human influence on global climate",
and then in 2000 with "There is new and stronger evidence that
most of the warming observed in the last 50 years is attributable to
human activities". But they also provide figures and graphs so
that we can see for ourselves. The upper graph (below) shows that
average temperature has been steady for most of the last millenium,
but has risen dramatically in the last few decades. And why? The
lower graph shows an equally dramatic rise in CO2.
A few people are saying
that the recent warming could be part of a natural cycle. But a
further fact from IPCC. "The present CO2 concentration has not
been exceeded in the last 420,000 years." This is based on CO2
concentrations measured directly from Antarctic ice cores, which also
record 4 glacial-interglacial cycles over this time period. In fact,
IPCC think that there is more CO2 in the air we are breathing now
than at any time in the last 20 million years. This is long before
our ancestors first stood upright (about 5 million years ago) and
shows what a significant global climate event is taking place. In the
face of these observations, and the well-established effects of
increasing greenhouse gases (GHGs), it is hard to escape the
conclusion that if we do nothing we face a continuing rise in global
temperature that will lead to global ecological disaster by the end
of this century.
So why aren't we doing something? The GHG problem is extremely
dangerous to our civilization because we are predisposed to ignore
it. We are visual animals, and have evolved over the last few million
years to respond to immediate and visible threats (predators or
enemies). Indeed, the success of your ancestors in dealing with these
threats has allowed you to read this column. GHGs, however, are an
invisible and slowly increasing threat, and they are all the more
dangerous because their inevitable consequences come decades after
the pollution itself.
The GHG problem is all the more difficult because it requires us to
focus not on creating new wealth, but on preserving the environment
in which we live (and have largely taken for granted). An
effective response will require long term vision and planning at
international and national levels, so that the costs of the remedies
are spread equitably through the community. A huge and complex task,
but now the message is clear. The problem is rapidly becoming
critical, and we will need our best intelligence and technology to
restore our lifestyle to one that is sustainable for our children and
their children.
The international community has already shown, through the Montreal
Protocol of 1987, that we can recover from global atmospheric
pollution - in that case leading to the loss of stratospheric ozone
and UV protection. The Kyoto Protocol deals with a more complex
problem, and is a small step forward, but it is also a necessary step
in the right direction.
A final thought. The earth has experienced around 40 glacial and
interglacial cycles over the last two million years, and our
ancestors survived all of these living a fairly basic life style in
small communities. Our oldest civilizations developed a little over
6000 years ago, around the time that sea level and climate stabilised
after the most recent glaciation. Maybe this was because the last
6000 years has been the longest period of climate stability in the
last 2 million years - grand irony with the threat of climatic
instability from our technological success.
Peter
Barrett
10 May 2002
More information on the
information produced by IPCC can be seen on their web site at:
http://www.ipcc.ch
GSNZ
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