Page 31 - Earth's Climate Past and Future

CHAPTER 1 • Overview of Climate Science 7

Global temperature FIGURE 1-3 Time scales of climate
Cold Warm Cold Warm Cold Warm Cold Warm change Changes in Earth’s climate
0 0 0 0 span several time scales, arrayed
from longer to shorter: (A) the last
1900 300 million years, (B) the last 3 million
AD years, (C) the last 50,000 years, and
Age (Myr) Age (Myr) Age (yr) Age (yr) progressively smaller changes in
(D) the last 1000 years. Here
climate at successively shorter time
scales are magnified out from the
larger changes at longer time scales.

1400
AD

300 3 50,000 1000
10°C 10°C 3°C 1°C
A Tectonic B Orbital C Deglacial/millennial D Historical

comparison younger records tend to have progressively oceanographers explore the circulation of the ocean,
greater resolution, and Parts III through V look at suc- chemists investigate the composition of the ocean,
cessively shorter-term changes in climate that occur atmosphere and land, glaciologists measure the behav-
within intervals of thousands, hundreds, and finally ior of ice, and ecologists analyze life-forms on land or in
even tens of years. We will examine the resolution issue the water.
more closely in Chapter 2. Other scientists study changes in climate or climate-
related phenomena in Earth’s recent or more distant
past: geologists explore the broader aspects of Earth’s
Development of Climate Science
history; geophysicists investigate past changes in Earth’s
As scientists began to discover examples of major climatic physical configuration (continents, oceans, mountains);
changes earlier in Earth’s history, their curiosity naturally geochemists analyze past chemical changes in the ocean,
grew about why these fluctuations had happened. The air, or rocks; paleoeocologists study past changes in vegeta-
few amateur scientists and university professors who tion and their role in the climate system; climate modelers
studied climate in relative isolation during the nineteenth evaluate possible causes of climate change; and climate
and early twentieth centuries have now been replaced by historians comb written archives for information that
thousands of researchers with backgrounds in geology, will enable them to reconstruct past climates.
physics, chemistry, and biology working at universities, In recent decades, studies of Earth’s climatic history
national laboratories, and research centers throughout have begun to cross these traditional disciplinary bound-
the world (Figure 1-4). Today climate scientists use air- aries and merge into an interdisciplinary approach
craft, ships, satellites, sophisticated new biological and referred to as “Earth system science” or “Earth system
chemical lab techniques, and high-powered computers, history.” Such efforts recognize that the many parts of
among other methods, to carry out their studies. Earth’s climate system are interconnected so that inves-
Studies of climate are incredibly wide-ranging. They tigators of climate must look at all the parts to under-
vary according to the part of the climate system being stand the whole. This entire book is an example of this
studied, such as changes in air, water, vegetation, land Earth system approach.
surfaces, and ice. They also vary by the techniques used, Similarly, this book makes no special distinction
including physical and chemical measurements of the between studies of Earth’s past history and investigations
properties of air, water, and ice and of life-forms fos- of the current (or very recent) climatic record. Earth’s
silized in rocks; biological or botanical measurements of climatic history is a continuum from the distant past to
endless kinds of life-forms; and computer simulations to the present. The book is organized by time scale because
model the behavior of air, water, and vegetation. that is the way the continuum of Earth’s climatic history
This huge diversity of studies covers a broad array has developed and will continue to develop in the future.
of scientific disciplines. Some studies are directed solely Lessons learned about how the climate system has
at improving our understanding of the climate system: operated in the past can be applied directly to our under-
meteorologists study the circulation of the atmosphere, standing of the present and future, but the opposite is true