Transcript Chapter 20

Chapter 20.3:
Global Warming
Reminder: Carbon Footprint Calculation due
on Tues. 17th
http://www.nature.org/initiatives/climatechange
/calculator/?src=l12
Bring results of your calculation to class
Natural and Anthropogenic Factors in Climate
Variations in:
 Insolation intensity
 Land surface changes
 Earth’s orbit
 Atmospheric and aerosol composition
Natural Cycles in Global
Temperatures:
Variations in the earth’s orbit
 Milankovitch theory: explanation of how
natural changes in the earth’s climate can
be explained by changes in the Earth’s orbit
around the Sun.
1. Eccentricity
2. Precession
3. Obliquity
Eccentricity
Changes in the shape of the earth’s orbit.
Change from circular to elliptical and back takes
~100,000 years.
Precession of the earth’s axis of rotation:
“wobble”
Today, earth is closest to sun ‘
in July
January
July
In 11,000 years
January
Always about ~23.5 degree tilt
Closest in July
Obliquity
Changes in Tilt
Today
23.5 degrees
Max 24.5 degrees
Min 22 degrees
Changes from max to min
In 41,000 years
Climate Change (IPCC report)
FIGURE 17a: Global energy balance: The influx of solar radiation and its
fate
FIGURE 17b: Global energy balance: Carbon dioxide and other
greenhouse gases radiate heat back to Earth
FIGURE T02: Major Greenhouse Gases and Their Characteristics
Source: Data from World Watch Institute, U.S. EPA, and Journal of
Geophysical Research.
FIGURE 18: Natural Cycles
Reproduced with kind permission from Springer Science+Business
Media: Clim. Change, A slippery slope: How much global warming
constitutes "dangerous anthropogenic interference?" vol. 68, 2005, pp.
269-279, J. E. Hansen.
FIGURE 19a: Annual Carbon emissions from fossil fuel
burning, 1751-2004
Data from UN, BP, DOE, and IEA
FIGURE 20: Comparing the average sea surface temperature during 19511980 to the average temperature during 2001-2005
Courtesy of GISS/NASA
FIGURE 21: Loss of arctic sea ice
Courtesy of Josefino Comiso and NASA/Goddard Space Flight Center
Scientific Visualization Studio
FIGURE 22: The number of tornadoes each year is on the rise
FIGURE 23: Category 1, 2, and 3 hurricanes are on the decline while more
violent and destructive category 4 and 5 hurricanes are on the rise
Adapted from P.J. Webster, et al., Science 309 (2005): 1844-1846.
FIGURE 26: This tiny Island in Tuvalu is losing ground to rising sea levels
caused by global warming
© Ashley Cooper/Alamy Images
FIGURE 28: Surface and deep water circulation
FIGURE 29: Computer projections of sea ice (blue) and actual
measurements (red), indicating that the computer models underestimate
melting
© 2008 University Corporation for Atmospheric Research, illustration by
Steve Deyo.
FIGURE 30: Dangerous feedback
FIGURE T03: Major Greenhouse Gases and Their Characteristics
Source: From L.R. Brown, C. Flavin, and S. Postel (1991). Saving the
Planet: How to Shape an Environmentally Sustainable Economy. New
York: Norton.
Texas A&M Climate Change Statement
It is virtually certain that the climate is warming,
and that it has warmed by about 0.7 deg. C over
the last 100 years.
It is very likely that humans are responsible for
most of the recent warming.
If we do nothing to reduce our emissions of
greenhouse gases, future warming will likely be
at least two degrees Celsius over the next
century.
Such a climate change brings with it a risk of
serious adverse impacts on our environment and
society.
Solving the Problem Sustainably
 Redesigning human systems according to sound principles of
sustainability could help alleviate the problem of global warming.
 Recycling and energy efficiency greatly reduce energy demand
and cut greenhouse gas emissions.
 Renewable energy technologies can provide us with muchneeded power, with little or no impact on global climate.
 Population stabilization can help reduce our demand for fossil
fuels and other greenhouse-enhancing activities such as
deforestation.
 Restoring forests, especially in the tropics, could have a
profound effect on global carbon dioxide levels.