Global Warming and its possible impacts on Essex
11
Figure 3. Oxygen isotope variation as an indicator of temperature change during the last
interglacial, based on data from the GRIP Summit ice core. (Derived from Lowe and Walker, 1997)
However, it is clear that humans are making an impact.
Records of methane and carbon dioxide show sharp
rises since pre-industrial revolution times (Fig. 4). The
rates of increase are beyond any others in the last 1000
years and beyond those in the Ipswichian, though
admittedly not by much. More convincing is the close
parallel between the increases and industrial activity,
with increased values coinciding with the inputs that
can be calculated from industrial activity. However,
the estimated human impacts are measured in degrees
or fractions of a degree.
Thus the degree of natural change is way beyond the
impacts humans may be having on climate, but this docs
not mean we can be complacent about our activities.
Some short term changes may be operated by triggers
and by altering our climate we may activate a trigger.
Arguably it may take only a few degrees increase in
temperature to release large quantities of methane from
the oceanic oozes, possibly with catastrophic effects.
Also the evidence is that changes in the earth's
atmosphere can amplify astronomical effects. It is wise
to operate the precautionary principle.
Neither can we ignore global warming. Whatever the outcome from the arguments about the degree
of human input into global warming, it is a fact that global warming is occurring.
Figure 4. Carbon dioxide and methane concentrations in the atmosphere over the last 250 years.
(Derived from J.T. Houghton, G.J. Jenkins and J.J. Ephraums, 1990, 'Climatic Change: The IPCC Scientific
Assessment', Cambridge University Press)
Essex Naturalist (New Series) 17 (2000)