The influence of solar variability on
North Atlantic climate
David Jackson*, Jeff Knight*, Adam Scaife*, Sarah Ineson*, Nick Dunstone*, Lesley
Gray†, Mike Lockwood #, and Amanda Maycock ‡
*Met Office Hadley Centre, †University of Oxford, #University of Reading,
‡University
11th European Space Weather Week
of Cambridge
Liege, Belgium, 17-21 November 2014
Contents
• The North Atlantic Oscillation and European
winter climate variability
• Observed and simulated solar links
• Upper stratospheric mechanism
• Solar UV perturbation experiments
• Lags between the solar cycle and the NAO
response
• Impacts of a possible “grand solar minimum”
Winter North Atlantic Oscillation
Northern Europe in Winter depends largely
on which way the wind blows:
Winter 1962/63
Weakened Pressure
Gradient
Cold advection
into Europe
Winter 2009/10
Cold, calm
and dry
Winter 1999/00
Strengthened
Pressure Gradient
Warm Europe
Mild, stormy and wet
North Atlantic Oscillation
Most important mode of year-to-year
variability in North Atlantic-European
winter climate
Linked to storminess:
NAO+: more active storm track, more westerly
advection of air
NAO-: less active, southward shifted, less
advection from the Atlantic
Regional climate effects of the solar
cycle in observations and models
Observed solar variability and NAO
related climate
11 year solar cycle
–ve NAO and more blocking
at solar minimum
2m temperature
Woollings et al., 2010, GRL
Observed solar variability
Solar maximum minus solar minimum from the 11 year cycle
Descending wind anomalies, Winter only, strongest in NH
N. Hemisphere winter
S. Hemisphere winter
Kuroda and Kodera, 2002, JMSJ
Lesley Gray
Models: some experiments have shown
encouraging signs: (eg Matthes et al, JGR, 2006)
But generally, models produce mixed
results
Results with more comprehensive upper atmosphere physics
No sign of westerly anomaly at solar maximum (Tsutsui et al.,
JGR, 1999)
UV perturbation experiments
Experiments
Generally previous model results are mixed
SIM measured a decline in ultraviolet
from 2004-2007 that is a factor of 4 to 6
times larger than typical previous
estimates
mesosphere
• Hadley Centre ocean-atmosphere climate model.
85 levels – well resolved middle atmosphere upper boundary at 85km
• Solar minimum (80 yrs): control run
stratosphere
• Solar maximum (20 x 4 yrs): perturbation of
+1.2Wm-2 to 200-320nm UV band. Only the UV is
altered. Based on apparent UV change in SIM
satellite data (Harder et al. 2009)
troposphere
• Climatological ozone
Ineson et al., Nat. Geosci., 2011.
Cooling of the equatorial stratopause
at solar minimum
Weaker meridional temperature gradient
Weakened westerly flow
Annual zonal mean temperature
Solar min –
Solar max
Solar Variability Effects – mainly winter
Solar min – Solar max
Oct
Nov
Dec
Jan
Feb
Mar
Similar to wave-mean flow interactions seen in other contexts
Ineson et al., Nat. Geosci., 2011.
Mechanism: descent through the stratosphere
zonal mean zonal wind (contours) and EP flux divergence (cols)
After Andrews and McIntyre 1978
increase in
planetary wave
driving F
 deceleration just
below easterly wind
anomaly
Solar min – Solar max
 descent of the
anomaly
Winter surface climate response
(solar min – solar max)
Sea level pressure
Surface temperature
Lags in the solar response
Observed relationship in NAO mslp,
SST LAGS solar cycle by ~2-3y
An
associated
signature in
the ocean
Perhaps this is the
source of the
memory…
Grey et al., JGR, 2013.
We performed transient experiments using the Hadley Centre atmosphereocean climate model (HadGEM3)
MSLP (UVmin-max - Constmin-max)
• Two 12-member 1960-2009 transient
ensembles:
• Constant solar forcing
• UV-only (230-320nm) solar variability with
amplitude based on SIM satellite observations
(1.2 Wm-2 peak to trough)
• Each uses other known forcings: GHGs,
aerosols, ozone, volcanoes
• By looking at the difference in responses in
the two ensembles, the solar UV influence
can be isolated.
Sub-Surface North Atlantic response
• Evidence of re-emergence of signals
below the summer mixed layer
• Oceanic memory for NAO lag
Climate response to a
‘Grand Solar Minimum’
Experiments
• Control: Hadley Centre IPCC RCP8.5
simulation (HadGEM2-CC) to 2100
• Scenarios based on most rapidly declining
Lockwood (2010) total solar irradiance (TSI)
scenario. Decline to approximately 2050
then level
• EXPT-A: relative proportion of changes in
each spectral band same as in CMIP5
control simulation
• EXPT-B: all the change is put into the UV
band (200-320nm)
• Overall, A and B have a very similar TSI
decline of about 1.75Wm-2
Effect on global mean
warming small. As is
effect on winter
European surface T
Climate effect of a long-term
decline in solar activity
Solar scenario minus RCP8.5, 2050-2099 average
MSLP
Surface Temperature
The climatic effect of a long-term decline in solar forcing appears to be very
similar to that for the minimum of the solar cycle
Ineson et al., 2015, submitted
Solar influence compared to
climate change in IPCC scenarios
2050-2099 average
} Grand solar min scenarios
In specific regions such as Southern Europe, future solar forcing could be nearly
as important as which emissions scenario is followed (here for winter rainfall).
Ineson et al., 2015, submitted
Summary
• Using a larger estimate of UV variability than has previously been used, it is possible to
reproduce the amplitude of the observed NAO response to the solar cycle in the Hadley
Centre climate model (HadGEM3)
• The model shows a ‘top down’ mechanism linking anomalies in the tropical upper
stratosphere and the NAO via interaction between planetary waves and zonal wind
anomalies
• Other effects, such as ozone changes and heating in the lower stratosphere remain as
candidates to modify or enhance these signals
• Using ensembles of simulations of the period 1960-2008 it is possible to reproduce the
observed lag of 3-4 years in the NAO response
• The solar cycle response is also seen following an early 21st century decline in solar activity
towards a ‘grand solar minimum’
• Regionally, the scale of the solar impact is a large fraction of the difference between
emissions scenarios. This argues for scenarios of natural forcing alongside anthropogenic
forcing
Proposal for “Carrington” – a UK Space Weather Mission
•
A Sun-Earth Sentinel at L5
•
First Operational Space Weather mission
•
Addresses MOSWOC requirements
•
High technology readiness, low risk, low cost
•
Fast transfer (<2 years) to L5 for a 10-year mission
•
24/7 operations, 100% coverage, continuous data
•
Excellent research output
•
Protects infrastructure hence growth
•
Excellent opportunity for UK/US bilateral
Instrument
Usage
Coronagraph
Identify Earth-directed CME
Heliospheric
Imager
Identify Earth-directed CME,
and image arrival at Earth
Particles/fields
Measurement of CIR
approaching Earth.
Magnetograph
Image the magnetic structure
of the photosphere and
assess the potential for
eruptions/flare.
For any queries:
markos.trichas@astrium.eads.net