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Climate Changeis geared toward a variety of students and general readers who seek the real science behind global warming. Exquisitely illustrated, the text introduces the basic science underlying both the natural progress of climate change and the effect of human activity on the deteriorating health of our planet. Noted expert and author Edmond A. Mathez synthesizes the work of leading scholars in climatology and related fields, and he concludes with an extensive chapter on energy production, anchoring this volume in economic and technological realities and suggesting ways to reduce greenhouse-gas emissions.Climate Changeopens with the climate system fundamentals: the workings of the atmosphere and ocean, their chemical interactions via the carbon cycle, and the scientific framework for understanding climate change. Mathez then brings the climate of the past to bear on our present predicament, highlighting the importance of paleoclimatology in understanding the current climate system. Subsequent chapters explore the changes already occurring around us and their implications for the future. In a special feature, Jason E. Smerdon, associate research scientist at Lamont-Doherty Earth Observatory of Columbia University, provides an innovative appendix for students.

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You can also view a pdf of Chapter 6: Learning from Climates Past

1. CLIMATE IN CONTEXT

"Rain, heavy at times, will begin in late morning and continue into the evening hours as a cold front sweeps across the area...." Ah, the weather forecast—what would we do without it? There is no shortage of conversation about the weather, which, after all, touches our daily lives. For some, the weather is pretty important—especially if their harvest depends on it. For others, it is more tangential. I'm thinking of myself here—most days I just want to know about my trek in and out of New York City, where I work. Will rain or snow make it impossible or just more miserable than usual? And climate? What would a climate forecast be like? "The next decade will bring persistent showers and mild temperatures in January to March, and extensive periods of no rainfall at all throughout the summer months." Hmm... that seems a bit remote from my immediate worry of getting to work.

Weather and Climate

The musings here illustrate the essential difference between weather and climate, the topic of this book. It also illustrates one of the conundrums in reducing carbon dioxide (CO2) emissions from the use of fossil fuels, the main culprit in global warming. Weather refers to conditions in the atmosphere at any one time. The now familiar radar images on television show that local weather systems develop and dissipate rapidly over the course of hours to a day. On a continentwide scale, weather systems form and decay over days to perhaps a week. A persistent weather system, such as a warm spell, may last for a couple weeks, especially in midlatitudes where the tracks of the systems are commonly determined by the position of the polar jet stream, as chapter 2 explains.

Climate, in contrast, can be thought of as the "average weather" for a particular region over some time. Region here can mean the entire globe, as in global warming; it can mean a large land area, say, eastern North America; or it can even mean a small one, as in the "microclimate" of a wine-producing valley near Bordeaux, France. Over all these scales, however, climate implicitly refers to the long term. One conundrum, therefore, is that it is difficult to marshal either the individual or the collective will to make the changes necessary to avoid negative impacts of global warming because they generally do not affect our immediate lives.

Although we have become adept at forecasting weather over hours to days, predictions beyond that become progressively more uncertain with distance into the future. Weather is inherently chaotic. Strictly speaking, the term chaotic means that small differences in initial conditions result in large differences in how a system will eventually develop. In other words, to predict weather accurately, one would have to know the temperature, humidity, barometric pressure, wind velocity, precipitation, and other characteristics of a weather system everywhere across an affected region; the more information at hand, the farther out in time a reliable forecast becomes possible.

Being an average condition, climate is more stable and displays distinctive patterns of change on distinctive timescales. Examples include annual changes such as monsoons, which are shifts in winds that bring seasonal rains to a number of regions in the tropics and subtropics. They also include fluctuations that occur only every several years, the most notable of which is El Nino, referring to the periodic warming of the equatorial eastern Pacific Ocean that commonly infl ences climate across much of the globe.

The Climate System

Climate is a dynamic system resulting from the combined interactions of various parts of Earth with one another and with the Sun. The parts are the atmosphere; the ocean (the hydrosphere); glaciers, terrestrial ice sheets, and sea ice (collectively known as the cryosphere); the living biomass (the biosphere); and even the solid Earth (the lithosphere ) (figure 1.1). Think of it as your body, with all of its parts interacting in a pulsating whole. And like your body, the climate system is not just a set of physicals interactions. It is also a dynamic chemical system, with matter flowing through its various parts.

The atmosphere, being the medium that we live in, is the part of the climate system that affects us most directly. It plays a major role in transporting heat around the planet. Because Earth is a sphere, the Sun's heat is more intense near the equator than near the poles. This uneven distribution generates winds that carry heat from the equator to the poles and from the surface to the upper atmosphere. The atmosphere is not isolated from the ocean, however. The ocean circulates, in part driven by the winds and guided by the positions of continents, and thereby also transports heat toward the poles. Indeed, the ocean holds far more heat than the atmosphere, but it flows much more slowly.