Page 534 - Environment: The Science Behind the Stories

change first made news on January 31, 2008, when over 1900 Conclusion
schools participated in the Focus the Nation teach-in on global
warming. Young people have played a large part in subse- Many factors influence Earth’s climate, and human activi-
quent grassroots events and organizations, including 350.org’s ties have come to play a major role. Climate change is well
International Day of Climate Action on October 24, 2009. This underway, and further greenhouse gas emissions will inten-
event—kicked off by the Maldives’ underwater cabinet meet- sify global warming and cause increasingly severe and diverse
ing—featured 5200 events in 181 nations and was called “the impacts. Sea level rise and other consequences of global cli-
most widespread day of political action in the planet’s history.” mate change will affect locations worldwide from the Maldives
Global climate change may be the biggest challenge to Bangladesh to Alaska to New York to Florida. As scientists
we face, but halting it would be our biggest victory. With and policymakers come to better understand anthropogenic
concerted action, there is still time to avert the most severe climate change and its environmental, economic, and social
impacts and sustain a livable climate. Through outreach, consequences, more and more of them are urging immediate
education, innovation, and lifestyle choices, today’s youth action. Reducing greenhouse gas emissions and taking other
have the power to turn the tables on climate change and help steps to mitigate and adapt to climate change represent the
bring about a bright future for humanity and our planet. foremost challenges for our society in the coming years.

Reviewing Objectives

You should now be able to: • Direct measurements of temperature, precipitation, and other
conditions tell us about current climate. (pp. 507–508, 510)

Describe Earth’s climate system and explain the • Climate models serve to predict future changes in climate.
factors influencing global climate (pp. 508–509, 512–513)
• Earth’s climate changes naturally over time, but it is now
changing rapidly because of human influence. (p. 502)
Outline current and future trends and impacts of
• The sun provides most of Earth’s energy. Earth absorbs global climate change
70% of incoming solar radiation and reflects 30% back
into space. (pp. 502–503) • Climate science is a huge body of research. The
Intergovernmental Panel on Climate Change (IPCC)
• Greenhouse gases such as carbon dioxide, methane, water synthesizes current research, and its periodic reports represent
vapor, nitrous oxide, ozone, and halocarbons warm the the consensus of the scientific community. (pp. 510–511)
atmosphere by absorbing and re-emitting infrared radia-
tion. (pp. 502–503) • Temperatures on Earth have warmed by an average of 0.74°C
(1.33°F) over the past century and are predicted to rise 1.8–
• Earth is experiencing radiative forcing of 1.6 watts/m of 4.0°C (3.2–7.2°F) over the next century. (pp. 510–511, 514)
2
thermal energy above what it was experiencing 250 years
ago. (p. 505) • Changes in precipitation have varied by region. (pp. 514–515)
• Extreme weather events are becoming more frequent,
• Milankovitch cycles, solar radiation, ocean absorption, and
ocean circulation all influence climate. (pp. 505–506) likely in part as a result of modification of the jet stream.
(pp. 514–515)
Characterize human influences on the atmosphere • Melting glaciers will diminish water supplies, and melting
and on climate ice sheets are adding to sea level rise. (p. 516)
• By burning fossil fuels and clearing forests, people are • Sea level has risen an average of 21 cm (8.3 in.) over the
increasing atmospheric concentrations of greenhouse past 130 years, and will rise by more in the coming century.
gases. (p. 504) (pp. 516–518)
• Increased greenhouse gas emissions enhance the green- • Storm surges worsened by higher sea levels threaten the main- CHAPTER 18 • Glob al Cli M aT e Chan G e
house effect. (p. 504) land United States, and not just oceanic islands. (pp. 516–519)
• Input of aerosols into the atmosphere exerts a variable but • Ocean acidification may be one of the most far-reaching
slight cooling effect. (p. 505) impacts of our greenhouse gas emissions. (p. 519)
Summarize how researchers study climate • Climate change exerts impacts on organisms and
ecosystems, as well as on agriculture, forestry, health, and
• Proxy indicators—such as data from ice cores, sediment economics. (pp. 519–521)
cores, tree rings, packrat middens, and coral reefs—reveal
information about past climate. (pp. 506–509) • Climate change and its impacts vary regionally. (pp. 521–523)
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