Geoscience Reference
In-Depth Information
13
CHAPTER THIRTEEN
Climate change
Mark C. Serreze and Roger G. Barry
LEARNING OBJECTIVES
When you have read this chapter you will:
n
understand the difference between climate variability and climate change and know the
characteristic features that may constitute a change of climate
n
be aware of the different timescales on which past climate conditions are studied and the
sources of evidence that may be used
n
recognize the major climate forcing factors and feedback mechanisms and the timescales over
which they operate
n
understand the anthropogenic contributions to climate change
n
appreciate the possible impacts of climate change on environmental systems.
in the 1950s (see
Box 13.1
). Instrumental records
for most parts of the world span only the past
100 to 150 years, and are typically assembled at
monthly, seasonal or annual time resolution.
However, proxy indicators from tree rings, pollen
in bog and lake sediments, ice core records of
physical and chemical parameters, and ocean
foraminifera in sediments provide a wealth of
paleoclimatic data. Tree rings and ice cores can
give seasonal or annual records. Peat bog and
ocean sediments may provide records with 100 to
1000-year time resolution.
In any study of climate variability and change,
one must pay careful attention to possible artifacts
in the records. For instrumental records, these
include changes in instrumentation (e.g., rain
gauge types), observational practices, station
A GENERAL
CONSIDERATIONS
In this final chapter we examine climate variability
and change, climate forcing factors, feedbacks and
projected future states of the climate system. In
many parts of the world, the climate has varied
sufficiently within the past few thousand years to
affect patterns of agriculture and settlement. As
will become clear, the evidence is now over-
whelming that human activities have begun to
influence climate.
Realization that climate is far from being
constant came only during the 1840s, when
indisputable evidence of former Ice Ages was
obtained. Studies of past climate began with a few
individuals in the 1920s and gained momentum
