Chemistry Reference
In-Depth Information
temperatures increase. There is also a general agreement over precipitation
decreases in the sub-tropics. Models agree to a lesser extent over an increase of
precipitation in the tropics, and cloud formation and wind patterns are areas
of uncertainty in model structure, as current understanding remains limited.
Natural climate variability (e.g. El Ni ˜ o Southern Oscillation (ENSO),
Pacific Decadal Oscillation (PDO), Atlantic Multi-decadal Oscillation (AMO))
and its impacts have been well documented for many regions of the world,
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but the understanding of the causes of shifts in teleconnections (related climate
anomalies) remains limited and thus difficult to include in climate models.
Extreme events (long, intense droughts, flood, hurricanes and typhoons) are
also difficult to predict from general circulation models. The latest report from
the Intergovernmental Panel on Climate Change (IPCC)
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warns about the
increased risk of more intense, more frequent and longer-lasting heatwaves, as
exemplified by the European heatwave of 2003 that killed several thousands of
people and caused widespread forest mortality.
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Along with a greater risk of
drought, there is an increased chance of intense precipitation and flooding due
to the greater water-holding capacity of a warmer atmosphere, such that both
wet and dry extremes should become more severe. Several modelling studies
are projecting that future cyclones could become less numerous but more
severe, with greater wind speeds, more intense precipitation, and higher ocean
waves.
These extreme events, while unpredictable, often shape our landscapes. Past
extreme events such as the drought of the 1930s that caused the Dust Bowl in
the USA, or the 1998 floods in China caused by heavy rainfall that affected 240
million people, certainly affected natural ecosystems and human land use.
Recently, reports of extreme events have been increasing. For example, a
drought in the of summer 2010 caused crop failure and huge fires in Russia,
while record rainfall caused extensive flooding and loss of life in both China
and Pakistan. These extremes might be evidence of climate destabilisation, but
they are at the very least consistent with what climate scientists have been
expecting. They certainly pose a challenge to the more comfortable prospect of
chronic linear change rather than abrupt and unpredictable change, yet these
events might be what people most need to take into account when they
consider preparing for change. In the past, the reliability of models was tested
in part by simulating large disturbances and observing the simulated system's
response.
d
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r
2
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It
may
be
necessary
for
practitioners
to
focus
on
disturbance
simulation to fully explore the resilience of their systems.
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Changes in Forest Dynamics
3.1 Introduction
Forests and woodlands account for approximately 30% of terrestrial land
cover
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and store about 45% (more than 1 trillion tonnes) of the carbon in
terrestrial ecosystems.
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Changes in vegetation cover are strong indicators of
