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natural variability could be the reason for the existence of a ‘significant’
global warming trend – contributing to rising levels of greenhouse
gases in the atmosphere is highly contentious. These views are pushed
by those who still remain sceptical about the link between climate
change and human activity.
Temperature
changes over the past 400 000 years reconstructed from the Vostok
ice core, the longest continuous ice-core record to date. Introduction
to Climate Change, UNEP/GRID, Arendal, Norway; Figure 3.5 Kunsthistorisches,
Museum, Vienna/ Bridgeman Art Library;
This
record tells us, for example, that the Earth entered into the most
recent comparatively cold period of its history (known as the Pleistocene
Ice Age) around 2.6 million years ago. On a geological time-scale,
these Ice Ages are relatively rare, covering only 2–3% of
the history of our planet. The characteristic feature of the current
one (and there is no reason to suppose that it is finished) is evident
in the above graph. Drilled in Antarctica, the Vostok ice core provides
a temperature record that goes back several hundreds of thousands
of years. Beyond about 10 000 years ago, it tells a story of an
unstable climate oscillating between short warm interglacial periods
and longer cold glacial periods about every 100 000 years –
with global temperatures varying by as much as 5 to 8 °C –
interspersed by many more short-term fluctuations
By contrast, global temperatures over the
last 10 000 years or so seem to have been much less variable, fluctuating
by little more than one or two degrees. In short, the interglacial
period in which we live, known as the Holocene, appears (on available
evidence) to have provided the longest period of relatively stable
global climate for at least 400 000 years. It is almost certainly
no coincidence that this is also when many human societies developed
agriculture and when the beginnings of modern civilisations occurred.
We now shift the focus to the more recent past – the period
during which human population growth and the coming of the industrial
age began to make their mark on the composition of the atmosphere.
Contested
science: a case study
For complex issues such as global climate change, there
are many opportunities for scientists to take issue with
the findings of their colleagues. They can disagree about
the procedures for gathering data, the completeness or coverage
of the data, how the data are analysed and interpreted,
and then finally the conclusions. The assumptions that shape
a particular piece of research and inform the kind of questions
that will be asked can be no less contentious than the quality
of the data gathered.
Such contention is not unique to climate science, of course.
Fuelled in part by very human concerns such as a desire
to protect one's reputation, competition for funding, etc.,
vigorous debate is the lifeblood of science; it helps to
drive further investigation and innovation. In scientific
areas where society has pressing concerns, however, influences
beyond the normal cut and thrust of scientific debate come
into play. Scientists are typically aware of the potential
policy implications of their research, and may shape their
work accordingly. Often, such research is stimulated or
funded by organisations with an interest in the outcome
of the policy debate. In turn, interest groups and policy
makers tend to adopt a ‘pick n' mix’ approach
to the available scientific evidence, promoting research
that reinforces their existing arguments and beliefs, and
neglecting or criticising more uncomfortable findings. Equally,
the influence of individual scientists sometimes owes more
to their access to decision makers or the media than to
the reliability of their knowledge.
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‘Global
Warming’. An OpenLearn chunk used/reworked by permission of
The Open University copyright © (2007).’ http://creativecommons.org/licenses/by-nc-sa/2.0/uk/
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