1 Lecture 16 Potential Impacts of Global Warming

2 IPCCIPCC Reports IPCC Three “working groups”  3 reports WG1: Science (What we’ve been talking about) (What we’ve been talking about) WG2: Impacts and Adaptation Impacts: Changes in society, ecosystems, etc. Impacts: Changes in society, ecosystems, etc. Adaptation: Learning to live with climate change Adaptation: Learning to live with climate change WG3: Mitigation Reducing the rate of climate change Reducing the rate of climate change

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

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5 Permafrost Permafrost = soil that remains frozen throughout the year Warming  softening of permafrost

6 Permafrost landslide in Yukon

7 Softening of ground makes it more vulnerable to erosion by waves Alaska

8 China-Tibet Railway China-Tibet Railway Some scientists question whether the $4-billion rail line will survive as is or require major reconstruction.

9 Glaciers and Ice Sheets Mountain glaciers will continue to shrink Mountain glaciers will continue to shrink Greenland ice sheet will very probably lose mass Antarctica (?) West Antarctic Ice Sheet BBC Video

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

11 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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13 6 million people live within one meter of sea level! Problem aggravated by sinking of land

14 Small Island Nations

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18 Highest Point: 5 m above sea level Population: 11, 000

19 Fresh Water Supplies Warming  shrinking glaciers, reduced snowfall in mountains Problem: 1/6 of world population depends on glacial & snow melt for drinking water

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

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22 Soil Moisture, Runoff  precip.   soil moisture and runoff But, can have  soil moisture even with  precip.

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25 Effect on California Warming  less snowfall in mountains Warming  less snowfall in mountains  less summer runoff  less summer runoff  less water in summer for  less water in summer for irrigation irrigation hydroelectric power hydroelectric power drinking water drinking water Loss of salmon habitat

26 More about precipitation Models project increased variability  increased flooding and increased droughts!  increased flooding and increased droughts! Another problem: increased demand for water.

27 Agriculture Reductions in soil moisture  reduced crop yields However, areas with increased soil moisture could benefit However, areas with increased soil moisture could benefit (If warming isn’t too large.) (If warming isn’t too large.)

28 Other Potential Agricultural Benefits of Warming Increased growing season in higher latitudes Could benefit Canada, Russia Could benefit Canada, Russia Beneficial effects of increased CO 2 could offset damaging effects of reduced soil moisture Called “CO 2 fertilization” Called “CO 2 fertilization” Only works if warming is relatively small Only works if warming is relatively small

29 Ecosystems In past, ecosystems have been able to adapt, but … 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 increased human demands fragmentation of habitats fragmentation of habitats

30 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 Will hurt organisms that make shells

31 Carbon Cycle Now, biosphere is a net “sink” of carbon i.e., carbon uptake > carbon released i.e., carbon uptake > carbon released By mid-century, biosphere likely to become a net source of carbon i.e., carbon release > carbon uptake i.e., carbon release > carbon uptake (mainly due to increased rate of decay) (mainly due to increased rate of decay) Ocean carbon uptake will diminish Result: Faster rise of CO 2

32 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 Projections of habitat changes _atlas.html# _atlas.html# _atlas.html# _atlas.html#

33 Northward Habitat Shift: Example 1 White Ash Yellow = lost habitat Note northward shift

34 Northward Shift: Example 2 Sugar Maple Prediction: It will disappear from the U. S.

35 Northward Expansion - 1 Laurel Oak Green: Current habitat Blue: Additional habitat Range increases

36 Northward Expansion - 2 Southern Red Oak Range increases

37 No Change: Example Red Maple

38 Complex Pattern: Example Black Oak Yellow: Lost Habitat Blue: Expanded habitat

39 Forest Fires In western U. S., warming  more forest fires

40 Tropical Cyclones – basic info Called hurricanes in Atlantic, eastern Pacific Called hurricanes in Atlantic, eastern Pacific Called typhoons in western Pacific (north of equator) Energy source: heat stored in oceans Energy source: heat stored in oceans Theory: warmer oceans  stronger storms Theory: warmer oceans  stronger storms (There is evidence this already happening) (There is evidence this already happening)

41 Human Health More deaths from heatwaves Like 1995 Chicago heat wave Like 1995 Chicago heat wave Increases in some tropical diseases