GLOBAL WARMING: THE BIOLOGICAL DIMENSION

Transcription

1 FOCUS THE NATION GLOBAL WARMING: THE BIOLOGICAL DIMENSION Thomas W. Sherry Department of Ecology & Evolutionary Biology Tulane University, New Orleans, Louisiana

2 Environmental misconceptions rampant Global warming is our number one enemy Global warming doesn t exist Technology will save us We (humans) won t have to sacrifice much Mother Earth will take care of herself

3 Organization/Assertions 1. Global warming in perspective Global change more than climate change Global climate change more than warming 2. Biological impacts of global climate change Global change impacts more than humans Global warming more than hot air 3. Generalizations Interaction of global change phenomena Tipping points (thresholds)

4 Global change more than just climate change (from Vitousek et al., Science 1997)

5 Global climate change much more than just warming Warming (drought) Local cooling Altered precipitation Increased intensity of storms Floods Hurricanes Tornadoes

6 What are biological dimensions of global warming? It depends Figure based on Nobel-prize winning Intergovernmental Panel on Climate Change (IPCC) 2007 report

7 Warming impacts: terrestrial Glaciers melt & retreat Tan area in greenland (right) Accelerated retreat in warmer ocean water (Antarctica), lubricated by melt water Corresponding sea level rise Red (right) areas inundated given 6 m sea level rise Within 1-3 centuries? Or much faster?

8 Warming impacts: greatest in Arctic Alaska warmed 2-3º C in past 30 years (1º C global ave.) Fairbanks, AK, today averages -2º C Another 2 degrees warming will melt permafrost on which it sits More mosquitoes further north Warm summers, Kenai Peninsula -> spruce bark beetle outbreaks, killing 40 million spruce trees (illustration) Affected area 2Xs Yellowstone Park

9 Warming impacts: Arctic Ocean melting 2007 = extraordinary melt in annual sea ice (September) Consequences of melting? Bad news for polar bears, Inuits Increased coastal erosion Tipping point #1: Accelerated Warming?

10 Tipping points Box 10.1, Figure 1 Tipping points involve thresholds = non-linear system (e.g., climate) change Familiar example: heating item to point of combustion Because of sudden, rapid change these are hard to predict, model

11 Warming impacts: species ranges shift to formerly cooler locales Move to higher latitude? But high latitude species have no place to go! Hot spots for decline based on mammal study (2006)

12 Warming impacts: species shift to higher elevation? NE trade -> clouds -> cloud forest in Central America Warming trend -> fewer cloudy days, higher cloud layer Frogs swampy habitat in Costa Rica disappeared off mountain Extinction of Golden Toad, Monteverde Harlequin Frog Extirpation of 20 frog species Increased infection of frogs by parasitic Chytrid fungus?

13 Warming impacts: disappearance of coral reefs What is coral? Why is it vulnerable? Global change impacts Increased temperatures Increased CO 2 content of atmosphere Increased diseases, local water pollution, harvesting of fish that protect coral

14 Global mechanisms of coral destruction Acidification of oceans Increased ocean temperature We already see conditions not seen in past 420,00 years

15 Warming impact: disappearance of coral reefs

16 Implications of coral reef destruction? Loss of extraordinary biological diversity Reduced oceanic productivity Reduced fisheries (impacting 10s of millions of humans) Reduced protection from hurricanes, tsunamis

17 Western U.S. experiencing drought From 1970 to 2003, areas with greatest water deficit (left, below) had largest forest fires (right, below) These warming impacts already here, in our own back yard Warming impacts: drought & forest fires

18 Fig. 1. (A) Annual frequency of large (>400 ha) western U.S. forest wildfires (bars) and mean March through August temperature for the western United States (line) (26, 30) A. L. Westerling et al., Science 313, (2006) Published by AAAS

19 Warming impacts: drought & forest fires IPCC Report (2007) projects June-August temperature increases in Western U.S. of 2-5 ºC by ~2040; 15% precipitation decrease This means lots more forest fires! Forest fires put huge amounts CO 2 into atmosphere: Tipping Point: More greenhouse gas -> more forest fires -> more greenhouse gas

20 Drought impacts in Western U.S. 20% decline in snow melt since 1950 Reduced water Agriculture (irrigation) Human residences (e.g., Los Angeles, Phoenix) Wildlife (e.g., salmon)

21 Projected changes in rainfall Models project both winter (left) and summer (right) rainfall to increase at high latitudes, decrease in tropics Illustration of Dal Lake, India (Kashmir), has shrunk to half its former area in 40 years, due to changing temperature & rainfall

22 El Niño-La Niña Southern Oscillation (ENSO) Survival in migrant birds that winter in Caribbean basin Linked to ENSO (=SOI) in winter (Sillett, Holmes, & Sherry, Science 2000)

23 Intensification of ENSO? Historical record of ENSO events, Increasing El Niño intensity since 1975 (red line) Data from NOAA-CIRES climate diagnostics center, University of Colorado at Boulder Intensification of El Niño forecast in warmer climate!

24 Impacts of warming, drying on tropical forest productivity Less CO 2 -> plants close stomates -> less transpiration (evaporation from plants) By yr. 2100, Hadley model predicts 20% reduction in rainfall in Amazon basin Additional decline in rainfall due to predicted El Niño conditions Rainfall will go from 0.2 to 0.08 inches per day Average temperatures to increase by 10 ºF Vegetation will change from rainforest to savanna (grass & scattered trees) and desert?

25 Reduced growth of tropical trees in Costa Rica with increased temperature Clark, D. A. et al. (2003) Proc. Natl. Acad. Sci. USA 100, Copyright 2003 by the National Academy of Sciences

26 Reduced tree growth corresponds with increased CO2 flux (loss to atmosphere) Tipping Point! Clark, D. A. et al. (2003) Proc. Natl. Acad. Sci. USA 100, Copyright 2003 by the National Academy of Sciences

27 Conclusions Weve seen just a few biological consequences of global warming (and CO 2 increase) Every part of globe impacted Many tipping points that could speed up the changes dramatically Problem is more than just climate change, including diverse global change phenomena

28 Whom to believe about climate change? Greg Craven on U- Tube com/watch?v=ploo6 qyov08&feature=rela ted com/watch?v=9hpno BfEsLw&feature=relat ed