Introduction - Climate Change Impacts on Freshwater Ecosystems - page 1

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Introduction
Brian Moss, Richard W. Battarbee and Martin Kernan
Changing climate and a changing planet
In June 2008, one of us chanced upon a shepherd repairing his five-ft high (he
didn't deal in metres) dry limestone walls on the uplands near Asby Scar in
Cumbria, north-west England. We exchanged pleasantries that inevitably, this
was Britain after all, embraced the weather. It was a bright warm day. But 'Bleak
in winter up here' I said. 'Not so much in the past fifteen years' he replied,
'Before that the snow lay in drifts hiding the walls, but not any more'. It was yet
another anecdotal sliver of evidence to complement the mass of information
assembled by the Intergovernmental Panel on Climate Change (IPCC 2007) on
the reality of global warming.
That Fourth Report of the IPCC summarized changes to date (Fig. 1.1) that
included an almost 1°C increase in the northern hemisphere mean air temperature,
over the years since the industrial revolution accelerated the yet unabated burning
of fossil fuels. It presented evidence that these processes were related and that we
could have high confidence that the temperature rise was largely human-induced.
Linked with it have been changes in the distribution of rainfall, with generally
more falling in winter or wet seasons and less in the summer and dry seasons.
There has been an increase in sea level of about 20 cm, largely due to thermal
expansion of the huge mass of oceanic water, to which the melting of the mountain
and polar glaciers is now making a contribution. And there has been an increase
in the frequency of extreme weather events, such as cyclones, droughts and
floods. In turn, there have been numerous records of changes in the phenology
of species (Sparks & Carey 1995; Roy & Sparks 2000; Parmesan & Yohe 2003;
Hays et al . 2005; Adrian et al . 2006) and a steady migration polewards of a
variety of the more mobile species (Walther et al . 2002; Root et al . 2003).