Geography Reference
In-Depth Information
The neoglacial events were a response to either a decrease in
summer temperatures, which leads to enhanced melting of the
glacier ice, or an increase in winter (snow) accumulation, which
leads to glacier growth. Glacier variations in effect fi lter out
the year-to-year climatic variability and have revealed that the
climate often differed appreciably from that of today. Some of
the features of the record are named in Figure 8, including the
likely absence of glaciers during the so-called 'climatic optimum'
of the mid-Holocene, around 7,000 years ago (characterized by
temperatures 2-3 degrees Centigrade warmer than today); the
re-growth of glaciers (conventional neoglaciation) between about
6,000 and 5,000 years ago; and the 'Little Ice Age' of the last
500 years (with temperatures 1-2 degrees Centigrade colder than
today).
There are at least two wider implications of both the long-term
and the short-term record of past climates that provide strong
reasons for physical geographers to continue to investigate the
environments of the past. First, similar natural variations in
climate will almost certainly continue to occur in the future. It is
therefore vital to understand the natural background onto which
anthropogenic global warming is being superimposed. Second,
climatic variations are the drivers of changes in so many other
aspects of the geo-ecosphere that are central to physical geography
and so important to humanity.
Human impacts: from Holocene to Anthropocene
As the 20th century drew to a close, human impacts on the
geo-ecosphere and, in particular, on global climate became
a priority, both for science and for society. The extent and
intensity of the impacts, and rates of change in the biosphere,
pedosphere, hydrosphere, and toposphere became signifi cant
from the mid-Holocene, around 5,000 years ago. Since then,
from Neolithic times onwards, a succession of increasingly
advanced technologies has enabled the increasing exploitation
of the Earth's resources with accompanying intentional and
