Page 503 - Environment: The Science Behind the Stories

plan for carbon-neutrality through a voluntary tax on tourists cities such as San Francisco and New York City. Superstorm
that could fund carbon offsets and investment in renewable Sandy in 2012 was a wake-up call for the eastern United States.
energy. The lost lives and billions of dollars of damage brought by this
Residents of the Maldives are not alone in their predica- massive hurricane and its storm surge in New York, New Jersey,
ment. Other island nations, from the Galápagos to Fiji to the and other states made clear that the costs of rising seas could
Seychelles, also face a future of encroaching seawater. These be enormous.
island nations have organized themselves to make their con- Storm damage from rising seas is just one of the many
cern over climate change known to the world through AOSIS, imminent consequences of global climate change. In one way
the Alliance of Small Island States. or another, climate change will affect each and every one of us
Mainland coastal areas across the world will face simi- for the remainder of our lifetimes. Putting solutions into action
lar challenges from sea level rise—from the hurricane-battered stands as a central challenge for our society right now and for
coasts of Florida, Louisiana, Texas, and the Carolinas to coastal the foreseeable future.

Our Dynamic Climate Three factors influence climate

Three natural factors exert the most influence on Earth’s cli-
Climate influences virtually everything around us, from the day’s mate. The first is the sun. Without it, Earth would be dark and
weather to major storms, from crop success to human health, and frozen. The second is the atmosphere. Without it, Earth would
from national security to the ecosystems that support our econo- be as much as 33°C (59°F) colder on average, and temperature
mies. If you are a student in your teens or twenties, the accelerat- differences between night and day would be far greater than
ing change in our climate today may well be the major event of they are. The third is the oceans, which store and transport
your lifetime and the phenomenon that most shapes your future. heat and moisture.
Climate change is also the fastest-developing area of envi- The sun supplies most of our planet’s energy. Earth’s
ronmental science. New scientific studies that refine our under- atmosphere, clouds, land, ice, and water together absorb about
standing of climate are published every week, and policymakers 70% of incoming solar radiation and reflect the remaining
and businesspeople make decisions and announcements just as 30% back into space (Figure 18.1). The 70% that is absorbed
quickly. By the time you read this chapter, some of its informa- powers many of Earth’s processes, from winds to waves to
tion will already be out of date. We urge you to explore further, evaporation to photosynthesis. We will assess how each major
with your instructor and on your own, the most recent informa- factor influences climate, focusing first on the atmosphere.
tion on climate change and the impacts it will have on your future.

What is climate change? Greenhouse gases warm the lower
atmosphere
Climate describes an area’s long-term atmospheric condi-
tions, including temperature, precipitation, wind, humidity, As Earth’s surface absorbs solar radiation, the surface
barometric pressure, solar radiation, and other characteristics. increases in temperature and emits infrared radiation (p. 49),
Climate differs from weather (p. 471) in that weather specifies radiation with wavelengths longer than those of visible light.
conditions at localized sites over hours or days, whereas cli- Atmospheric gases having three or more atoms in their mol-
mate describes conditions across broader regions over years, ecules tend to absorb infrared radiation. These include water
decades, or centuries. Global climate change encompasses an vapor, ozone (O ), carbon dioxide (CO ), nitrous oxide (N O),
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2
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array of changes in aspects of Earth’s climate, such as temper- and methane (CH ), as well as halocarbons, a diverse group of
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ature, precipitation, and storm frequency and intensity. People mostly human-made gases that includes chlorofluorocarbons
often use the term global warming synonymously in casual (CFCs; p. 487). Such gases are known as greenhouse gases.
conversation, but global warming refers specifically to an After absorbing radiation emitted from the surface, green-
increase in Earth’s average surface temperature. Global warm- house gases subsequently re-emit infrared radiation. Some of
ing is only one aspect of global climate change, but warming this re-emitted energy is lost to space, but some travels back
does in turn drive other components of climate change. downward, warming the lower atmosphere (specifically the
Over the long term, our planet’s climate varies naturally. troposphere; p. 469) and the surface in a phenomenon known
However, today’s climatic changes are unfolding at an exceed- as the greenhouse effect.
ingly rapid rate, and they are creating conditions humanity has Greenhouse gases differ in their ability to warm the
never experienced. Scientists agree that human activities, nota- troposphere and surface. Global warming potential refers to
bly fossil fuel combustion and deforestation, are largely respon- the relative ability of one molecule of a given greenhouse gas
sible. Understanding how and why today’s climate is changing to contribute to warming. Table 18.1 shows global warming
requires understanding how our planet’s climate functions. Thus, potentials for several greenhouse gases. Values are expressed
we first will examine Earth’s climate system—a complex and in relation to carbon dioxide, which is assigned a value of 1.
502 finely tuned system that has nurtured life for billions of years. Thus, a molecule of methane is 25 times more potent than a

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