1. Earth’s radiative balance or, how I learned to stop worrying and love the greenhouse effect If the Earth had no atmosphere: T  T 4 = S / 4 (1 — A) T = 255 K -18 ˚C 0 ˚F Albedo (reflectivity) Solar constant (1370 W/m 2 ) Stefan-Boltzmann constant (5.67x10 -8 ) reflected Absorbed and re-radiated as heat

4. 288 - 255 = 33 ˚ of ‘normal’ greenhouse warming Actual surface No atmosphere Sunlight Infra-red radiation Air

5. 0 -0.4 0.4 1900194019801860 Temperature anomaly (˚C) Global Temperatures for the last 150 years (5-year running average; as of ~2005) Civil war Model T World War II Al Gore invents the internet

6. After Jones and Wigley, 1980 “... a global deterioration of climate, by order of magnitude larger than any hitherto experienced by civilized mankind, is a very real possibility and indeed may be due very soon.” Climate change in the age of Disco

7. The last ~10 years: another plateau resembling ~1950

8. Currently favored explanation of the plateaus is that these are periods when accumulated heat gets preferentially stored in ocean instead of atmosphere…

9. Warming has a strong geographic bias (2000-2009 avg. vs. 1950-1980 mean) ±2.5 ˚C scale

10. A long-suspected driving force — rise in CO 2 Global average 1700-2000 AD Mauna Loa 1958-2004 AD

11. The CO 2 Greenhouse Effect What should physical principles lead me to expect of global warming? Complications Solar ‘constant’ is a variable Water-vapor feedback Albedo Ice Clouds Aerosols and dust Ground cover 33 ˚ of warming = 20˚ from H 2 O v + 10 ˚ from CO 2 + 3 ˚ from other things CO 2 has risen 10’s of %, so T should have risen by a degree or more Arrhenius, 1896 Doubling CO 2 = 5-6 ˚C warming

12. Cylon invasion happens here

15. Reid, 1999; by way of www.oar.noaa.gov Sunspots and early 20th century temperatures

28. So what factor is to blame for 20 th century T rise? Wrong question — lots of things are to ‘blame’ but some are more important than others, and at different times