The Sun s Role in Climate Change. Philip R. Goode Big Bear Solar Observatory Center for Solar-Terrestrial Research New Jersey Institute of Technology

Transcription

1 The Sun s Role in Climate Change Philip R. Goode Center for Solar-Terrestrial Research New Jersey Institute of Technology

2 Changes in Earth s Climate In the most basic sense, it depends on changes in The solar constant (irradiance) The Earth s reflectivity (Bond albedo) Atmospheric Greenhouse gasses Moon provides the ideal perch from which to measure each.

3 Sunspot Number Sunspot number

4 The Sun s Irradiance Variations are Small, but Hard to Explain

5 Irradiance Changes Blue curve is solar cycle Red curve adds purported longterm variation Temperature changes from NCAR model Yellow line limit from physics of irradiance change Foukal, North and Wigley, Science 2004

6 Origin of Sun s Variable Output Seismic data provide most precise measure of solar variability (SoHO( SoHO/MDI f-modes) Physical picture is that rising solar activity blocks heat and convective flows, while corregating the solar surface making it a more effective radiator Active sun is cooler, corregated,, slightly smaller and more irradiant Inactive sun is warmer, smoother, slightly larger and minimally irradiant Dziembowski and Goode, ApJ, 2005

7 Implications of Limit Earth is responding to more subtle changes in Sun, which imprint the solar cycle and longer term wanderings of solar activity Changes in solar wind induces some unknown changes at the Earth Look for changes in net sunlight reaching Earth Motivates measurements of Earth s reflectance A new burden on the climate models

8 The Albedo Sets the Input to the Climate Heat Engine -Global and seasonal average is A ~ Shortwave input (visible, 0.5 µ m, T ~6000 K) -Longwave output (IR, 15 µ m, T ~255 K) TOA P = C! R (1 $ A); P = 4! R " # T = 4! R " # (1 $ g) T ; in E out E TOA E s Solar constant Albedo T 4 s C = (1 $ A); 4 "# (1 $ g) Greenhouse Gas

9 The Effective and Bond Albedos On any one night, earthshine measures p *, the effective (or apparent) albedo (one direction - different Sun-Earth-Moon reflection angle). To obtain the Bond albedo, A, we integrate over all phases of the moon at monthly/yearly time scales 2 A = " p * fl(! )sin(! ) d! 3

10 Decadal Variations in Reflectance ES Measurements ISCCP-based proxy Interannual variation: Smooth decline & recovery Palle et al., Science, 2004

11 The Proxy Implications Confidence in our results based on: earthshine data agreement Positive/negative phases are similar Scrambling the data in mock reconstructions time/space support the trend Variation is large Albedo change is 6 W/m 2 ; GHG until now is 2.4 W/m 2 Equivalent to 2% increase in solar irradiance, a factor 20 more than typical maxima to minima variations Reversibility suggests natural variations. GCM do not show such variations What is the climatic impact? Recent warming acceleration?

12 ISCCP Updated through Dec 2004! A 0.01" 10 # effect of! C 0.001

13 Comparison of ES and TOMS

14 The Bond Albedo of Earth

15

16 BBSO1.7 m Off-Axis Solar Telescope First Light Summer 2007

17 Thanks! The End

18 Changes in Earth s Climate In the most basic sense, it depends on changes in The Sun s output The Earth s reflectivity Atmospheric Greenhouse gasses Earthshine provides a global measure of reflectivity and greenhouse gasses Precise, cheap and global Satellites are expensive, degrade and can fail

19 The Albedo Sets the Input to the Climate Heat Engine -Global and seasonal average is A ~ Shortwave input (visible, 0.5 µ m, T ~6000 K) -Longwave output (IR, 15 µ m, T ~255 K) TOA P = C! R (1 $ A); P = 4! R " # T = 4! R " # (1 $ g) T ; in E out E TOA E s Solar constant Albedo T 4 s C = (1 $ A); 4 "# (1 $ g) Greenhouse Gas

20 Sunspot Number Sunspot number

21 Origin of Sun s Variable Output - Dziembowski and Goode (ApJ 2005) Seismic data provide most precise measure of solar variability Physical picture is that rising solar activity blocks heat and convective flows, while corregating the solar surface making it a more effective radiator Active sun is cooler, corregated,, slightly smaller and more irradiant Inactive sun is warmer, smoother, slightly larger and minimally irradiant

22 Implications of Limit Earth is responding to more subtle changes in Sun, which imprint the solar cycle and longer term wanderings of solar activity (confirm Foukal,, North and Wigley,, Science, 2004) Changes in solar wind induces some unknown changes at the Earth A new burden on the climate models

23 Earthshine Measurements of the Earth s Large-scale Reflectance The Earthshine is the ghostly glow on the dark side of the Moon Origin of Earthshine first explained by Leonardo da Vinci First measured by Danjon beginning in and by Dubois ES/MS = albedo (+ geometry and moon properties) Waning / morning

24 Coverage during One Night 15/10/99 Phase = /09/99 Phase = +110

25 Current Earthshine Team Phil Goode Steven Koonin Pilar Montañés Rodriguez Enric Pallé Bago

26 Albedo Changes

27 Decadal Variations in Reflectance ES Measurements ISCCP-based proxy Interannual variation: Smooth decline & recovery Palle et al., Science, 2004

28 The Proxy Implications Confidence in our results based on: earthshine data agreement Positive/negative phases are similar Scrambling the data in mock reconstructions time/space support the trend Variation is large Albedo change is 6 W/m 2 ; GHG until now is 2.4 W/m 2 Equivalent to 2% increase in solar irradiance, a factor 20 more than typical maxima to minima variations Reversibility suggests natural variations. GCM do not show such variations What is the climatic impact? Recent warming acceleration?

29 ISCCP Updated through Dec 2004

30 Comparison of ES and TOMS

31 Hourly Variations Cloudy Asia Dark Arabian Sea Global albedo can change by 10% in an hour! Model covers whole day Difficult to obtain an average A Need network to get better coverage and redundancy

32 Network --Monthly Average Coverage One, Two, Three and 5 Stations

33 Can Earth s Reflectance Increase while Earth Warms? Earthshine and other results point to an increasing reflectance over the past five years, which reverses a fifteen year trend of decline Taken in isolation, less sunlight would imply a reversal of global warming Recently updated ISCCP data reveal a change in clouds, so both reduced sunlight and increased global warming are possible Results also confirm earlier Earthshine results of an increasing Earth albedo

34 Cloud Amount & Distribution Cloud Amount from ISCCP Five year Bands of higher clouds (red) and lower clouds (blue) Unexplained change in last five years

35 Ocean Warming Lyman, Willis & Johnson

36 Ocean Warming Josh Willis

37 Spectra

38 Earth s apparent spectral albedo for a single night (11/19/2003) as Sun rises over South America Montañés Rodriguez et al. (ApJ, 2005) Rayleigh Scattering Chappuis Ozone band B-O 2 A-O 2 Atmospheric Water vapor

39 Thanks! The End