Has solar forcing been an important influence on climate in the late Holocene? Ray Bradley Climate System Research Center University of Massachusetts, Amherst
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
orbital thermohaline? greenhouse gases solar activity volcanoes Source: Bradley et al., 2003
Source: Solanki et al., 2004
2.0 Genevev et al 250 Radiocarbon Record 1.5 200 1.0 H/H 150 100 0.5 D lt 14C 50 0.0-10000 0-8000 -6000-50 -10000-4000 -2000 0 2000-2000 0 2000-2000 0 2000-2000 0 2000 Year 2.0 Nachasova & Burakov -8000-6000 -4000-2000 0 2000 1.5 Year 1.0 14 Genevev / C Correlation 14 H/H Yang / C Correlation 100 160 0.5 140 80 120 0.0-10000 60 100 80 C C Delta Delta 40 20-6000 -4000 Year 40 14 60-8000 14 20 Yang - Archeointensity 12 0 10 0 8-20 -20 6 7 8 9 10 11 0.6 12 0.8 1.0 1.2 VADM Nachasova / 14 St Onge / C Correlation 14 1.4 1.6 1.8 VADM -40-40 6 4 H/Ho 2 C Correlation 0-10000 120-8000 -6000-4000 120 Year 100 100 80 80 60 60 1.4 St-Onge 1.2 C 14 14 C 40 0 1.0 20 NRM/IRM Delta Delta 20 40 0-20 -20-40 -40-60 0.6 0.8 1.0 1.2 H/Ho 1.4 1.6 1.8 0.6 0.8 1.0 1.2 NRM/RM 1.4 1.6 0.8 0.6-10000 -8000-6000 -4000 Year
200 Measured & Predicted Delta 14 C 150 100 C 14 Delta 50 0 Measured Delta 14C Yang Predicted Genevev Predicted Nachazova Predicted St-Onge Predicted -50-10000 -8000-6000 -4000-2000 0 2000 Year
100 Residual Delta 14 C 50 0 C 14 Delta -50-100 Yang Residual Genevev Residual Nachazova Residual St-Onge Residual Mean Solar activity increasing -150-10000 -8000-6000 -4000-2000 0 2000 Year
Alaskan glacier advances & solar activity minima Lower solar activity Glacier advances Source: Wiles et al.; 2004
U.S. northern Great Plains (40-50 year lag) Source: Yu & Ito, 1999
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
High lake levels W. Central Europe Ice advance Switzerland Source: Holzhauser et al., 2005
Source: Bond et al, 2001
Source: Bond et al, 2001
More ice-rafting 14 C Low solar 10 Be Less icerafting High solar Source: Bond et al, 2001
Weak SW monsoon North Atlantic ice rafting episodes Source: Gupta et al., 2003
Dongge Cave, China (25 17 N, 108 5 E) Source: Wang et al., 2005
Dongge Cave, China 18 O 14 C Weaker monsoon Lower solar activity Source: Wang et al., 2005
Lower irradiance? Solar variability effects on Arabian monsoon rainfall? Drier Source: Neff et al., 2001
Lower solar activity Lake Naivasha, Equatorial East Africa Source: Verschuren et al., 2000
Lower solar activity Equatorial East African Lakes Higher lake level Source: Stager et al., 2005
Coba Quintana Roo Mexico
Source: Hodell et al., 1995
Lake Chichancanab, Yucatan, Mexico Source: Hodell et al., 1995
Solar lower Yucatan, Mexico lake sediments? AD850 (~208 year periodicity) wetter Source: Hodell et al, 2001
More Upwelling (stronger Trades?) Lower solar activity Source: Black et al.,1999; 2004 Cooler &/or drier Lower Solar activity
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
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
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
Multiple iterations reduce noise from other factors. Solar increase Solar decrease Climate parameter? Map differences>> (superposed epoch analysis)
www.paleoclimate.org
For accurate information about climate change & global warming, see: http://www.realclimate.org
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
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?)
10-30ºS 15ºS Source: Meehl et al., 2004
Lower solar activity Source: Hodell et al., 2001
N.W. India (NE Arabian sea): Upwelling indices: % C org & %N Biogenic proxies of surface water productivity, an indicator of monsoon intensity.
Speleothems
Maunder Minimum Solar activity LOW* O S D Solar activity HIGH *.assuming geomagnetic field strength properly known!
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
Source: Solanki et al., 2004
DJF JJA Source: Meehl et al., 2004
Greenland Lake Lisan Cold episodes in Greenland & aridity in Lake Lisan (Dead Sea, Israel) Source: Prasad et al, 2004
Speleothems Historical Documents (& archeology) Tree rings Speleothems Ice (Varved) sediments
10,000 BP Today 90 N 90 S Wm -2
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
Source: Bradley et al., 2003
Greenland Summit (GISP2): Holocene ice core volcanic sulfate record 1000 800 600 400 200 0 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000 Year BP Source: Zielinski et al., 1995
? 10 Be 14 C production? Sources: Carslaw et al., 2002 van Geel et al., 1999
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 1370 1365 ~500-610 ~1110-1240 ~920-970 200 400 600 4residual SO 6 4 nssso 4 Conc.( 2- Eq/L) μ -20 0 800 2 20 Antarctic volcanic SO 4 1360 A.D. 1000 800 600 1200 0 200 400 600 800 1000 1200 1400 1600 1800 2000 -----Medieval Time----- Plateau Remote Law Dome 1000 0 40 Sources: 400 200 2000 1500 1000 Bigler et al., 2003; Zielinski 2000 Beer, 2002; Bard et al., 2001; Palmer et al., 2002; Cole-Dai et al., 2000 500 0
Source: Lean et al., 1995
(Energy balance model) (proxy-based paleotemperatures) instrumental Source: Crowley, 2000
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
Correlations between Mann et al (1998) mean annual temperatures & Lean et al (1995) total solar irradiance estimates, 1650-1850, Source: Waple et al., 2002
Temperature sensitivity to solar irradiance forcing (1650-1850) Annual ºC/Wm -2 Decadal (9-25 year) Source: Waple et al., 2002
1368 1367 1366 1365 W/ 1364 1363 1362 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 Source: Shindell et al.; 2003
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
Source: Hodell et al, 2005