Page 378 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

342 part II The Water, Weather, and Climate Systems
TABLE AQS 11.2
IGBP Climate-Change Index for 2001–2013
Year
Scaled Difference Values (dimensionless)
Annual Index
Cumulative Index
Temperature
CO2
Sea Level
Sea Ice
2001
57.9
60.5
50.5
−26.5
+36
+36
2002
2004
2006
2008
2010
2012
57.9 −47.4 −52.6 −105.3 68.4 −10.5
78.6 37.9 64.7 28.5 78.9 11.1 68.8 26.1 93.2 6.6 82.3 100.0
48.8 +56 +91 6.2 +13 +127 −21.6 +4 +198 −26.5 −9 +241 28.4 +49 +326 61.7 +58 +385
2003
−10.5
95.9
18.5
−11.7
+23
+114
2005
100.0
86.8
49.1
29.6
+66
+194
2007
42.1
69.9
−1.7
100.0
+53
+250
2009
73.7
66.9
44.5
−40.7
+36
+277
2011
−78.9
66.9
−3.8
18.5
+1
+327
2013
36.8
100.0
24.2
−106.2
+14
+399
concepts review
key learning
■ Describe scientific tools used to study paleoclimatology.
The study of the causes and consequences of changing climate on Earth systems is climate change science. Growing human population on Earth has led to an ac- celerating use of natural resources, increasing the re- lease of greenhouse gases—most notably CO2—into the atmosphere.
The study of natural climatic variability over the span of Earth’s history is the science of paleoclimatol- ogy. Since scientists do not have direct measurements for past climates, they use proxy methods, or climate proxies—information about past environments that rep- resent changes in climate. Climate reconstructions span- ning millions of years show that Earth’s climate has cycled between periods both colder and warmer than today. One tool for long-term climatic reconstruction is isotope analysis, a technique that uses relative amounts of the isotopes of chemical elements to identify the com- position of past oceans and ice masses. Radioactive iso- topes, such as 14C (carbon-14), are unstable and decay at a constant rate measured as a half-life (the time it takes half the sample to break down). The science of using tree growth rings to study past climates is dendroclimatology. Analysis of mineral deposits in caves that form speleo- thems and the growth rings of ocean corals can also iden- tify past environmental conditions.
climate change science (p. 308) paleoclimatology (p. 310) proxy method (p. 310)
isotope analysis (p. 311) radioactive isotope (p. 315)
dendroclimatology (p. 316) speleothem (p. 317)
1. Describe the change in atmospheric CO2 over the past 800000 years. What is the Keeling Curve? Where do its measurements put us today in relation to the past 50 years?
2. Describe an example of a climate proxy used in the study of paleoclimatology.
3. Explain how oxygen isotopes can identify glacials and interglacials.
4. What climatic data do scientists obtain from ice cores? Where on Earth have scientists drilled the longest ice cores?
5. How can pollen be used in radiocarbon dating?
6. Describe how scientists use tree rings, corals, and
speleothems to determine past climates.
■ Discuss several natural factors that influence Earth’s climate, and describe climate feedbacks, using examples.
Several natural mechanisms can potentially cause cli- matic fluctuations. The Sun’s output varies over time, but this variation has not been definitely linked to climate change. The Maunder Minimum, a solar minimum from about 1645 to 1715, corresponded with one of the coldest periods of the Little Ice Age. However, other solar mini- mums do not correlate with colder periods. Earth’s orbital cycles and Earth-Sun relationships, called Milankovitch cycles, appear to affect Earth’s climate—especially gla- cial and interglacial cycles—although their role is still under study. Continental position and atmospheric aero- sols, such as those produced by volcanic eruptions, are other natural factors that affect climate.
Climate feedbacks are processes that either am- plify or reduce climatic trends toward warming or cool- ing. Many climate feedbacks involve the movement of