Page 17 - Earth's Climate Past and Future

PREFACE

even years after publication of the first edition of Earth’s Earth’s major systems (ice, water, air, vegetation, and
SClimate early in 2001, a new edition is needed because land) as they developed through Earth’s history. The
of recent evidence confirming the key role of greenhouse structure again follows time’s arrow, moving from the
gases in the ongoing warming of the last century. During earliest known climate history to historical, modern,
those seven years, climate has followed the course that cli- and future changes. The main reason for this structure
mate scientists predicted would result from increased con- is that this is the way Earth’s climate has actually devel-
centrations of greenhouse gases in the atmosphere. Sea ice oped, so it is the most natural way to tell the story. In
and snow have retreated in the polar north, melting of addition, shorter-term climate changes tend to ride on
mountain glaciers and ice caps has accelerated, and even the back of longer-term changes, and the longer-term
the supposedly sluggish Greenland ice has begun to show changes need to be understood first to provide context
evidence of rapid melting along its margins. to those that are of more recent origin.
A range of new evidence also adds to the conclusion
that human beings are the main cause of the recent Mystery-Solving Approach Another advantage of
warming: reanalysis of satellite temperature data that organizing the book by time scale is that students are
now show a warming comparable to that from surface given a coherent, integrated view within each time scale
stations, the realization that changes in visible and near- of both the evidence of climate change and the compet-
visible radiation from the Sun (“solar irradiance”) have ing hypotheses posed to explain the evidence. Because
had a much smaller effect on global temperature during the central dynamic of science is the interconnection
the last century than previously thought, and the discov- of data, theory, and theory testing, this integrated
ery that enormous brown clouds emanating from south- approach makes science come alive. The evidence of
ern Asia and other regions have masked (rather than past climatic changes summarized at the start of each
amplified) part of the full effect of greenhouse-gas warm- chapter leads to an obvious question: What caused the
ing. With this new evidence, the claim that humans are observed changes? The chapters then describe and eval-
playing the major role in warming the planet has gained uate the hypotheses proposed to explain the observa-
broad acceptance in the scientific community. This fun- tions. Students are invited to be detectives in the prob-
damental shift is reflected in this new edition of the book. lem-solving process by assessing the proposed hypothe-
ses against a range of data and other methods, including
experiments with climate models. From my own teach-
Building on the First Edition
ing experience, many of the best students are intrigued
This edition of Earth’s Climate retains several approach- to find out that much work still remains to be done in
es used successfully in the first edition. this young field of science.
The major themes of the book remain the same as
Multidisciplinary Scope The story of Earth’s cli- in the first edition:
mate draws on many disciplines—geology, ecology,
• Causes (forcing) of climate change
paleobotany, glaciology, oceanography, meteorology,
biogeochemistry, climate modeling, atmospheric chem- • Natural response times of the many components
istry, and hydrology, among others. This range of disci- of Earth’s climate system
plines is a large challenge, both to students for whom all
• Interactions and feedbacks among the numerous
the science in this field is new and to instructors who
components
may specialize in one or two of the many research fields
and time scales of climate change. This text eases the • Role of carbon as it moves within the climate
challenge through logical, step-by-step explanations of system at each time scale
critical material, accompanied by attractive color graph-
ics that summarize key points, and by including lists of Structure The structure of Earth’s Climate, Second Edi-
follow-up resources for background material. tion, is similar to its predecessor. Part I surveys the field
of climate science and the approaches used to unravel
Following Earth’s Timeline Like the first edition, Earth’s climatic history. Parts II through V describe how
the second edition explores the climatic responses of Earth’s climate has changed and are organized by time

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