The Changing Debate on Global Warming

1. The Changing Debate on Global Warming by Dr. Eric J. Barron Hot Science - Cool Talks Volume 51 Produced by and for the Hot Science - Cool Talks Outreach Lecture Series of the Environmental Science Institute. We request that the use of any of these materials include an acknowledgement of Dr. Eric J. Barron and the Hot Science - Cool Talks Outreach Lecture Series of the Environmental Science Institute of the University of Texas at Austin. We hope you find these materials educational and enjoyable.

2. The Changing Debate on Global WarmingEric J. BarronJackson School of Geosciences

3. Incoming solar energy (hot sun, short wavelengths) largely pass through the atmosphere and heat the surface Earth’s surface radiates to space (cooler body, longer wavelength) Gases like carbon dioxide selectively absorb longer wavelengths – reradiate to space and back to the surface Without selective absorbers Earth is 5°F With selective absorbers Earth is 64°F Every credible scientist recognizes that increases in greenhouse gases promote warming

4. How much will it warm – in response to humans adding more greenhouse gases? How fast will it warm? How significant will be the impact? The first two questions will likely remain uncertain for decades. So, for decision-makers the last question is key. It is not just a science question. It depends on what you value. The Real Issue in the Debate

5. Suppose I got a contract to cut down all of the trees for lumber on the west side of Austin. Good or bad? My debate with an Economist

6. Suppose I got a contract to cut down all of the trees for lumber on the west side of Austin. Good or bad? GOOD – a product - brings in dollars; jobs bring in dollars My debate with an Economist

7. Suppose I got a contract to cut down all of the trees for lumber on the west side of Austin. Good or bad? GOOD – a product brings in dollars; jobs bring in dollars WAIT – what about beauty, habitat, ecosystem services (water)? My debate with an Economist

8. Suppose I got a contract to cut down all of the trees for lumber on the west side of Austin. Good or bad? GOOD – a product brings in dollars; jobs bring in dollars WAIT – what about beauty, habitat, ecosystem services (clean water)? But in one generation people won’t know what they have missed – it doesn’t have value My debate with an Economist

9. The Changing Debate on Climate ChangeWhat do scientists really believe about global warming?What are the predictions for the future?What are the potential impacts?

10. What do climate experts say about global warming?

11. Carbon dioxide is a selective absorber Greenhouse gases are increasing (due to burning oil, coal and deforestation) Increased greenhouse gases promote warming Draw down of gases will take centuries Aerosols have human sources Many aerosols promote cooling The planet has warmed 1°F in a century Foundations

12. 1 0.8 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 The Smoking Gun Temperature Change Temperature Change °F 380 360 340 320 300 280 260 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 1000 years of global CO2 and temperature change CO2 Concentrations CO2 Parts per Million by Volume (PPMV) 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 8 6 4 2 0 Carbon Emissions Billions of Metric Tons Land-use Change Fossil-fuels 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 U.S. Global Change Research Program Year

13. Global Land-Ocean Temperature Anomaly (°C) Base Period = 1951-1980 0.6 0.4 0.2 0 -0.2 -0.4 Annual Mean 5-year Mean 1880 1900 1920 1940 1960 1980 2000 Year J. Hansen, R. Ruedy, M. Sato, and K. Lo (NASA and Columbia University)

14. 2001-2005 Mean Surface Temperature Anomaly (°C) Global Mean = 0.54 -2 -1.6 -1.2 -.8 -.4 -.2 .2 .4 .8 1.2 1.6 2.1 J. Hansen, R. Ruedy, M. Sato, and K. Lo (NASA and Columbia University)

15. The stratosphere will cool. Predictions that are virtually certain Lower Stratosphere (13-19 km) Cooling Upper Troposphere (8-13 km) Warming Thickness of atmospheric layers exaggerated for clarity. Lower Troposphere (0-8 km) Slight Warming Earth’s Surface Warming NASA

16. Surface temperature will increase: •0.5 to 2.0°C by 2050 • 1.5 to 4.5°C for a CO2 doubling • 2.5°C most likely Global precipitation will increase Sea ice will retreat in Northern Hemisphere Arctic warming Predictions that arevery probable

17. Sea level will rise, 5 to 40 cm by 2050 The effects of solar variability will not be significant over the next 50 years compared to those of CO2 Predictions that are very probable

18. Climate variability changes Regional climate changes Tropical storms The next 25 years & biosphere feedbacks Predictions that are uncertain

19. What do climate models predict for the continental U.S. from 2090 to 2100?

20. Summer Maximum & Winter Minimum Temperature Change +15°F +10°F +5°F 0°F -5°F +15°F +10°F +5°F 0°F -5°F Canadian Model 21st Century Canadian Model 21st Century Summer Maximum Winter Minimum Hadley Model 21st Century Hadley Model 21st Century +15°F +10°F +5°F 0°F -5°F +15°F +10°F +5°F 0°F -5°F Summer Maximum Winter Minimum U.S. Global Change Research Program

21. Precipitation Change Canadian Model 21st Century 100% 75% 50% 25% 0 -25% -50% -75% -100% Observed 20th Century 100% 75% 50% 25% 0 -25% -50% -75% -100% Hadley Model 21st Century 100% 75% 50% 25% 0 -25% -50% -75% -100% U.S. Global Change Research Program

22. What are the potential impacts for ecosystems, water, agriculture and health?

23. Ecosystem ModelsCurrent Models Tundra Taiga/Tundra Conifer Forest Northeast Mixed Forest Temperate Deciduous Forest Southeast Mixed Forest Tropical Broadleaf Forest Savanna/Woodland Shrub/Woodland Grassland Arid Lands U.S. Global Change Research Program

24. Ecosystem Models Canadian Model Tundra Taiga/Tundra Conifer Forest Northeast Mixed Forest Temperate Deciduous Forest Southeast Mixed Forest Tropical Broadleaf Forest Savanna/Woodland Shrub/Woodland Grassland Arid Lands Hadley Model U.S. Global Change Research Program

25. Projected Changes in Distribution of Sugar Maple Trees Even Hadley model says no sugar maples in the U.S. Iverson et al. 1999

26. July Heat Index Change Canadian Model 21st Century Hadley Model 21st Century +25°F +20°F +15°F +10°F +5°F 0°F B. Felzer, UCAR

27. Heat Mortality and Climate ChangeHeat-related deaths in Chicago in July 1995 180 160 140 120 100 80 60 40 20 0 120 115 110 105 100 95 90 85 80 75 Heat Index Max Temperature Deaths Maximum Temperature (°F) or Max Heat Index Number of Heat-related Deaths 7/11 7/12 7/13 7/14 7/15 7/16 7/17 7/18 7/19 7/20 7/21 7/22 7/23 NOAA/NCDC

28. Vector-borne DiseaseReported Cases of Dengue 1980 - 1999 Texas: 64 Cases Border States: 62,514 Cases Mexico HIH, Mexico; TDH; U.S. PHS

29. High Precipitation and “Flashy” StreamsObserved changes in streamflow and precipitation (1939-1999) 20 15 10 5 0 -2.5 Percentage of Total Change - % per 100 years 0 20 40 60 80 100 Light/Low Moderate Heavy/High U.S. Global Change Research Program

30. Changes in Western Snowpack 20 0 -20 -40 -60 -80 -100 20 0 -20 -40 -60 -80 -100 Percentage Change from 1961 - 1990 Base Percentage Change from 1961 - 1990 Base 2023 2071 2083 2095 2023 2071 2083 2095 1999 2011 2035 2047 2059 1999 2011 2035 2047 2059 U.S. Global Change Research Program

31. More tendency towards drought Projected Trends in the PDSI 21st Century Hadley Model Trends Palmer Drought Severity Index / 100yr

32. More tendency towards drought Projected Trends in the PDSI 21st Century Canadian Model Trends Palmer Drought Severity Index / 100yr

33. Corn Yields and Weather EventsCorn Yields in U.S. 1950 - 1999 140 120 100 80 60 40 20 0 Bushels per Acre 1950 1960 1970 1980 1990 1999 Year U.S. Global Change Research Program

34. Projected Summer Sea Ice ChangeCanadian Model: An ice-free Arctic summer Current Sea Ice Extent 2030 Sea Ice Extent 2095 Sea Ice Extent U.S. Global Change Research Program

35. What do scientists really believe about global warming? What are the predictions for the future? What are the potential impacts? The Changing Debate on Global Warming