Has solar forcing been an important influence on climate in the late Holocene?

Transcription

1 Has solar forcing been an important influence on climate in the late Holocene? Ray Bradley Climate System Research Center University of Massachusetts, Amherst

2 Forcing can be considered on several timescales: Tectonic (orogenic/eustatic/glacio-isostatic) Orbital Milankovic (eccentricity/obliquity/precession) ~100,000; 40,000; 23,000/19,000 years Millennial solar irradiance thermohaline oscillations ( internal variability?) Decadal-to-interannual volcanic ENSO/NAO/PDO ( internal variability?) Feedbacks? Vegetation/hydrological changes Snow/sea-ice cover

3 orbital thermohaline? greenhouse gases solar activity volcanoes Source: Bradley et al., 2003

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5 Source: Solanki et al., 2004

6 2.0 Genevev et al 250 Radiocarbon Record H/H D lt 14C Year 2.0 Nachasova & Burakov Year Genevev / C Correlation 14 H/H Yang / C Correlation C C Delta Delta Year Yang - Archeointensity VADM Nachasova / 14 St Onge / C Correlation VADM H/Ho 2 C Correlation Year St-Onge 1.2 C C NRM/IRM Delta Delta H/Ho NRM/RM Year

7 200 Measured & Predicted Delta 14 C C 14 Delta 50 0 Measured Delta 14C Yang Predicted Genevev Predicted Nachazova Predicted St-Onge Predicted Year

8 100 Residual Delta 14 C 50 0 C 14 Delta Yang Residual Genevev Residual Nachazova Residual St-Onge Residual Mean Solar activity increasing Year

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11 Alaskan glacier advances & solar activity minima Lower solar activity Glacier advances Source: Wiles et al.; 2004

12 U.S. northern Great Plains (40-50 year lag) Source: Yu & Ito, 1999

13 Lower solar activity Aletsch Glacier Switzerland 200 B.C- A.D.50 A.D.1856 Ice advance A.D.2000 A.D.2050? Source: Holzhauser et al., 2005

14 High lake levels W. Central Europe Ice advance Switzerland Source: Holzhauser et al., 2005

15 Source: Bond et al, 2001

16 Source: Bond et al, 2001

17 More ice-rafting 14 C Low solar 10 Be Less icerafting High solar Source: Bond et al, 2001

18 Weak SW monsoon North Atlantic ice rafting episodes Source: Gupta et al., 2003

19 Dongge Cave, China (25 17 N, E) Source: Wang et al., 2005

20 Dongge Cave, China 18 O 14 C Weaker monsoon Lower solar activity Source: Wang et al., 2005

21 Lower irradiance? Solar variability effects on Arabian monsoon rainfall? Drier Source: Neff et al., 2001

22 Lower solar activity Lake Naivasha, Equatorial East Africa Source: Verschuren et al., 2000

23 Lower solar activity Equatorial East African Lakes Higher lake level Source: Stager et al., 2005

24 Coba Quintana Roo Mexico

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26 Source: Hodell et al., 1995

27 Lake Chichancanab, Yucatan, Mexico Source: Hodell et al., 1995

28 Solar lower Yucatan, Mexico lake sediments? AD850 (~208 year periodicity) wetter Source: Hodell et al, 2001

29 More Upwelling (stronger Trades?) Lower solar activity Source: Black et al.,1999; 2004 Cooler &/or drier Lower Solar activity

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31 Lower solar activity (decreased total irradiance?) = cold wette r dry cold More sea-ice Cold,wet cold Wetter?? Cooler &/or drier dry Weaker monsoon Weaker monsoon Weaker monsoon wetter wetter Sources: Wiles et al., 2004; Hallett et al., 2003; Anderson 1992; Yu & Ito, 1999; Hodell et al., 2001; Black et al., 1999,2004; Verschuren et al., 2000; Neff et al., 2000; Bond et al., 2001; van Geel et al., 1996, 2000; Magny, 1993; Prasad et al., 2004; Agnihotri et al., 2002, 2003; Hong et al., 1999

32 Summary of climate signals associated with low solar activity Lower temperatures at high latitudes (expanded polar vortex) Reduced monsoon intensity (contraction of Hadley circulation) more restricted seasonal range of the ITCZ BUT! Data are limited; many records do NOT show any connection: Danger of reinforcement syndrome

33 solar forcing produces feedbacks involving temperature gradient driven regional circulation regimes that can alter clouds. Over relatively cloud-free oceanic regions in the subtropics in areas of low-level moisture divergence (the moisture collection areas for the ocean precipitation convergence zones), the enhanced solar heating produces greater evaporation. This increased moisture then converges into the precipitation zones, intensifying the upward vertical motions of the regional Hadley and Walker circulations. The subsidence associated with this enhanced regional vertical motion results in fewer low clouds over the subtropical ocean regions, allowing even more solar energy to reach the surface, and so on... Source: Meehl et al., 2004

34 Multiple iterations reduce noise from other factors. Solar increase Solar decrease Climate parameter? Map differences>> (superposed epoch analysis)

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36 For accurate information about climate change & global warming, see:

37 The Holocene solar forcing enigma: a research strategy 1. Assume best proxy of solar forcing is 10 Be or 14 C 2. Select periods with extended intervals of + or cosmogenic isotope anomalies 3. Map paleoclimate anomalies (or differences) between these intervals 4. Repeat for several episodes 5. Identify common signals (if any!) 6. Compare with models (must have good stratospheric component) forced by solar irradiance changes; ensure there are multiple simulations

38 OR Examine solar-forced models v control; Select regions with largest signals (+, -) [what season, what parameter?] Seek proxies in these regions; Compare observed signals with model predictions (IPCC detection strategy what is the spatial fingerprint of solar forcing?)

39 10-30ºS 15ºS Source: Meehl et al., 2004

40 Lower solar activity Source: Hodell et al., 2001

41 N.W. India (NE Arabian sea): Upwelling indices: % C org & %N Biogenic proxies of surface water productivity, an indicator of monsoon intensity.

42 Speleothems

43 Maunder Minimum Solar activity LOW* O S D Solar activity HIGH *.assuming geomagnetic field strength properly known!

44 0m Qinghai Lake: 18 O in ostracods 1.7ka 2.5ka Weak monsoon Sampling interval: ~220years 9ka 11.5ka Strong monsoon 12.5ka ~5.6m Source: Wei & Gasse, 1999

45 Source: Solanki et al., 2004

46 DJF JJA Source: Meehl et al., 2004

47 Greenland Lake Lisan Cold episodes in Greenland & aridity in Lake Lisan (Dead Sea, Israel) Source: Prasad et al, 2004

48 Speleothems Historical Documents (& archeology) Tree rings Speleothems Ice (Varved) sediments

49 10,000 BP Today 90 N 90 S Wm -2

50 0m Qinghai Lake: 18 O in ostracods 1.7ka 2.5ka Weak monsoon Sampling interval: ~220years 9ka 11.5ka Strong monsoon 12.5ka ~5.6m Source: Wei & Gasse, 1999

51 Source: Bradley et al., 2003

52 Greenland Summit (GISP2): Holocene ice core volcanic sulfate record Year BP Source: Zielinski et al., 1995

53 ? 10 Be 14 C production? Sources: Carslaw et al., 2002 van Geel et al., 1999

54 Forcing factors over the last 2000 years Greenland volcanic SO 4 (N.E. Greenland; Summit) 0-40 Solar activity indices ( 14 C, 10 Be) 2 W/m ~ ~ ~ residual SO 6 4 nssso 4 Conc.( 2- Eq/L) μ Antarctic volcanic SO A.D Medieval Time----- Plateau Remote Law Dome Sources: Bigler et al., 2003; Zielinski 2000 Beer, 2002; Bard et al., 2001; Palmer et al., 2002; Cole-Dai et al.,

55 Source: Lean et al., 1995

56 (Energy balance model) (proxy-based paleotemperatures) instrumental Source: Crowley, 2000

57 Mean annual surface temperature anomaly over the Northern Hemisphere Model ± 1 (solar, volcanic forcing, CO 2 ) Mann et al, 1998 Crowley & Lowery,2000 Source: Goosse et al, 2004

58 Correlations between Mann et al (1998) mean annual temperatures & Lean et al (1995) total solar irradiance estimates, , Source: Waple et al., 2002

59 Temperature sensitivity to solar irradiance forcing ( ) Annual ºC/Wm -2 Decadal (9-25 year) Source: Waple et al., 2002

60 W/ Source: Shindell et al.; 2003

61 Winter NASA-GISS GCM: Temperature response to solar forcing Summer Cool in ~15-16 th centuries? Warm in ~12 th century? Source: Shindell et al.; 2003

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63 Source: Hodell et al, 2005