Current warming and likely future impacts - Climate Change: Biological and Human Aspects - page 266

climatic change. First, regionally, part of a climatic cycle may go with the direction
of longer-term climatic change, so that part of the cycle can provide insights into
the regional manifestations of longer-term climatic change. Second, understanding
the biological impact of climatic cycles is intrinsically important to regional biomes.
Third, longer-term climatic change may result in changes in ocean and atmosphere
circulation (see section 6.6.6) and these circulation changes can themselves change
the characteristics (or even existence) of regional climatic oscillations. If we are
unaware of the current effects of regional oscillations then it will be difficult to
discern what biological changes are due to contemporary regional climate systems
and what changes are due to longer-term climatic change.
Climate change also has some surprisingly unexpected effects on biological sys-
tems. Just as the IPCC urge us to be aware of 'climate surprises' when considering
their gradual warming scenario forecasts, so biologists need to be alert to surprise
biological responses to climate change. Climate change can alter things in ways that
one might not normally consider important and this includes changing to the wrong
type of snow falling. The millions of Britons who regularly travelled into and out of
London at the start of the 21st century will be aware of the seemingly joke excuse
that rail operators used one winter when they said that the 'wrong type of snow' had
prevented their track de-icing equipment from working. This made the national head-
lines. For some species the right type of snow is of crucial importance. Norwegian
lemmings ( Lemmus lemmus ) need the right type of snow, of the kind that ground
warmth melts a small layer immediately above it so leaving a gap between the ground
and the underside of the snow layer. This subnivean space not only provides warmth,
it allows some protection from predators. Climate change can mean that such spaces
do not exist for as much of each year as they used to. Worse, with warmer condi-
tions the snow immediately above the ground can melt more than it otherwise would
have done during the day and then refreeze at night, producing a thicker layer of ice
that prevents the lemmings feeding on the underlying moss. In 2008 a small team of
Norwegian and French researchers led by Kyrre Kausrud and Atle Mysterud published
the results of a long-term study and an ecological analysis. They collected dispar-
ate sets of long-term records to reveal how changes in snow type not only affected
the lemming population but had wider ecological implications too: lemmings are
noted for their population cycles and these have often (not without good cause) been
attributed to predator-prey interactions. They got university students taking winter
ecology courses to collect data on snow condition. The researchers also gathered
hunter-reported bird catches, drew on meteorological records, and used long-term
rodent trap records and bird census data, and other records from the period 1970-94
and subsequent years. They began to see a pattern as to how climate affected the
lemmings, and in turn other species, and used these associations to make a predictive
model that forecast an absence of rodent peaks after 1994. By 2007 they were able
to look back and compare the actual lemming population, as revealed by trap catch
rate, with that predicted by their model. It was clear that the model not only reflected
lemming numbers before 1994 and importantly their peak years, but also the absence
of lemming population booms after that year. This provided them with compelling
evidence that changing snow conditions are indeed a major factor changing lem-
ming population dynamics. What appears to be happening is this. The North Atlantic