Potential Impacts of Global Warming

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Lecture 16

• Potential Impacts of Global Warming

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IPCC Reports

• Three working groups ? 3 reports
• WG1 Science
• (What weve been talking about)
• WG2 Impacts and Adaptation
• Impacts Changes in society, ecosystems, etc.
• Adaptation Learning to live with climate change
• WG3 Mitigation
• Reducing the rate of climate change

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Arctic Impacts

• Large reduction in summer sea ice
• Arctic could be ice-free in summer by end of
  century

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Permafrost

• Permafrost soil that remains frozen throughout
  the year
• Warming ? softening of permafrost

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Permafrost landslide in Yukon
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Alaska
Softening of ground makes it more vulnerable to
erosion by waves
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China-Tibet Railway
Some scientists question whether the 4-billion
rail line will survive as is or require major
reconstruction.
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Glaciers and Ice Sheets

• Mountain glaciers will continue to shrink
• Greenland ice sheet will very probably lose mass
• Antarctica (?)
• West Antarctic Ice Sheet www.realclimate.org

BBC Video
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Sea Level

• Melting glacial ice and thermal expansion will
  cause sea level to rise
• Estimated rise
• Low-emission scenario 18 38 cm
• High-emission scenario 26 59 cm
• Estimates are probably too low
• Contribution from ice sheets was not taken into
  account!

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Impact of Rising Sea Level

• Greatest in countries with heavily populated
  coastal regions, e.g. Bangladesh and in
  small-island nations

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• 6 million people live within one meter of sea
  level!
• Problem aggravated by sinking of land

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Small Island Nations
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Highest Point 5 m above sea level
Population 11, 000
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Fresh Water Supplies

• Warming ? shrinking glaciers, reduced snowfall in
  mountains
• Problem 1/6 of world population depends on
  glacial snow melt for drinking water

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Precipitation

• Models project increases in precipitation in some
  regions, decreases in others
• Regions of decrease include
• Southwestern U. S., Mexico, Central America,
  Caribbean
• Mediterranean
• Regions of increase include
• Canada, most of Asia

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Soil Moisture, Runoff

• ?precip. ? ?soil moisture and runoff
• But, can have ?soil moisture even with ?precip.

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Effect on California

• Warming ? less snowfall in mountains
• ? less summer runoff
• ? less water in summer for
• irrigation
• hydroelectric power
• drinking water
• Loss of salmon habitat

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More about precipitation

• Models project increased variability
• ? increased flooding and increased droughts!
• Another problem increased demand for water.

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Agriculture

• Reductions in soil moisture ? reduced crop yields
• However, areas with increased soil moisture
  could benefit
• (If warming isnt too large.)

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Other Potential Agricultural Benefits of Warming

• Increased growing season in higher latitudes
• Could benefit Canada, Russia
• Beneficial effects of increased CO2 could offset
  damaging effects of reduced soil moisture
• Called CO2 fertilization
• Only works if warming is relatively small

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Ecosystems

• In past, ecosystems have been able to adapt, but
  
• resilience of many ecosystems is likely to be
  exceeded by 2100
• Effects of climate change aggravated by
• increased human demands
• fragmentation of habitats

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Ecosystems, continued

• Up to 30 of species at increasingly high risk
  of extinction if average global temp increase
  above 2 -3?C
• Oceans becoming more acidic
• Will hurt organisms that make shells

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Carbon Cycle

• Now, biosphere is a net sink of carbon
• i.e., carbon uptake gt carbon released
• By mid-century, biosphere likely to become a net
  source of carbon
• i.e., carbon release gt carbon uptake
• (mainly due to increased rate of decay)
• Ocean carbon uptake will diminish
• Result Faster rise of CO2

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Impacts on U. S. Forests

• Each tree species requires a specific environment
  for optimum growth
• Climate change will cause a shift in tree
  habitats
• Projections of habitat changes
• http//www.fs.fed.us/ne/delaware/atlas/web_atlas.h
  tml

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Northward Habitat Shift Example 1
White Ash
Yellow lost habitat
Note northward shift
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Northward Shift Example 2
Sugar Maple
Prediction It will disappear from the U. S.
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Northward Expansion - 1
Laurel Oak
Green Current habitat Blue Additional habitat
Range increases
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Northward Expansion - 2
Southern Red Oak
Range increases
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No Change Example
Red Maple
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Complex Pattern Example
Black Oak
Yellow Lost Habitat Blue Expanded habitat
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Forest Fires

• In western U. S., warming ? more forest fires

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Tropical Cyclones basic info

• Called hurricanes in Atlantic, eastern Pacific
• Called typhoons in western Pacific (north of
  equator)
• Energy source heat stored in oceans
• Theory warmer oceans ? stronger storms
• (There is evidence this already happening)

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Human Health

• More deaths from heatwaves
• Like 1995 Chicago heat wave
• Increases in some tropical diseases