Page 32 - Earth's Climate Past and Future

8 PART I • Framework of Climate Science

FIGURE 1-4 National research
centers The National Center for
Atmospheric Research (NCAR) in
Boulder, Colorado, is one of several
national laboratories and university
centers at which Earth’s climate is
studied. (NCAR.)

as well. The broad term climate science refers to this secrets slowly, and many important questions still
vast multidisciplinary and interdisciplinary field of research remain to be answered, but the revolution in knowledge
and to its linkage of the past, the present, and the future. has been immense, as this book will show.
This revolution has reached the point where it is
taking its place alongside two great earlier revolutions
How Scientists Study Climate Change
in knowledge of Earth history. The first was the devel-
Climate science moves forward by an interactive mix of opment by Charles Darwin and others in the nine-
observation and theory. Climate scientists gather and teenth century of the theory of evolution, which led to
analyze data from the kinds of climatic archives an understanding of the origin of the long sequence of
reviewed in Chapter 2, and the results of this research life-forms that have appeared and disappeared during
are written up and published. Progress in science the history of this planet. The second was the synthesis
depends on the free exchange of ideas, and climate during the 1960s and 1970s of the theory of plate tec-
researchers publish in order to tell the scientific com- tonics, which has given us an understanding of the slow
munity what they have discovered. motions of continents across Earth’s surface through
These scientists interpret their research results and time, as well as associated phenomena such as volca-
occasionally come up with a new hypothesis, an idea noes, earthquakes, and mountain ranges.
proposed as an explanation for observed data. Science
moves forward in part by disproving and discarding the
less worthy hypotheses. Many hypotheses are eventu- Overview of the Climate System
ally discarded, either because they are found to disagree In this section we take a first look at Earth’s climate
with basic scientific principles or because they make system, consisting of air, water, ice, land, and vegeta-
predictions that subsequent observations contradict. tion. At the most basic level, changes in these compo-
A hypothesis that succeeds in explaining a wide array
of observations over a period of time becomes a theory. nents through time are analyzed in terms of cause and
effect, or, in the words used by climate scientists, forcing
Scientists continue to test theories by making additional and response. The term “forcing” refers to factors that
observations, developing new techniques to analyze drive or cause change; the responses are the climatic
data, and devising models to simulate the operation of changes that result.
the climate system. Only a few theories survive years of
repeated testing. These are sometimes called “unifying 1-4 Components of the Climate System
theories” and are generally regarded as close approxima-
tions to “the truth,” but the testing still continues. Figure 1-5 provides an initial impression of the vast array
Taken together the many expanding efforts to of factors involved in studies of Earth’s climate. It shows
understand climate change have led to a scientific revo- the air, water, ice, land, and vegetation that are the major
lution that has accelerated through the late 1900s and components of the climate system, as well as processes at
early 2000s. The mystery of climate change yields its work within the climate system, such as precipitation,