New paper finds the Sun controls Greenland climate

An important paper published today in Nature Geoscience finds a persistent link between solar activity and Greenland climate during the last ice age, and finds the link is similar to modern solar forcing of regional climate. 

According to the authors, 

"We suggest that solar minima could have induced changes in the stratosphere that favour the development of high-pressure blocking systems located to the south of Greenland, as has been found in observations and model simulations for recent climate. We conclude that the mechanism behind solar forcing of regional climate change may have been similar under both modern and Last Glacial Maximum climate conditions."

The authors describe a solar amplification mechanism by which solar minima favor the development of high-pressure blocking systems which block the jet stream and cause increased jet stream dips of the polar vortex [just like we have seen over the past few record cold winters in the US and Europe]. Many other papers have described this solar amplification mechanism via solar effects on the stratosphere, which in turn affect the QBO, which in turn affects large scale planetary waves such as Rossby Waves and the jet stream. This is only one of many solar amplification mechanisms described in the scientific literature. 

The authors also provide a new reconstruction of solar activity using the cosmogenic isotope 10Be, which shows a remarkable correlation over relatively short time-scales to ice core temperatures and precipitation: 

d18O [mean of 2 ice cores shown as blue line] is a proxy of temperature and precipitation. 10Be [orange line] is a proxy of solar activity [note 10Be is inversely correlated to solar activity]

Note 10Be concentration at end of 20th century was ~0.6, much less than mean of ~1 from first chart above, indicating solar activity was much greater at end of 20th century than during the last glacial maximum. 

Excerpt explaining the solar amplification mechanism

Climate alarmists such as Jennifer Francis and Heidi Cullen claim man-made CO2 from your SUV is the control knob of Greenland climate, and that increased CO2 causes jet stream dips and record cold weather. However, this new paper and many others provide a much more plausible explanation: it's the Sun. 

Persistent link between solar activity and Greenland climate during the Last Glacial Maximum

• Florian Adolphi,
• Raimund Muscheler,
• Anders Svensson,
• Ala Aldahan,
• Göran Possnert,
• Jürg Beer,
• Jesper Sjolte,
• Svante Björck,
• Katja Matthes
• & Rémi Thiéblemont

• Affiliations
• Contributions
• Corresponding author

Nature Geoscience

 

(2014)

 

doi:10.1038/ngeo2225

Received

 

26 June 2014 

Accepted

 

17 July 2014 

Published online

 

17 August 2014

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Changes in solar activity have previously been proposed to cause decadal- to millennial-scale fluctuations in both the modern and Holocene climates¹. Direct observational records of solar activity, such as sunspot numbers, exist for only the past few hundred years, so solar variability for earlier periods is typically reconstructed from measurements of cosmogenic radionuclides such as¹⁰Be and ¹⁴C from ice cores and tree rings^2, 3. Here we present a high-resolution ¹⁰Be record from the ice core collected from central Greenland by the Greenland Ice Core Project (GRIP). The record spans from 22,500 to 10,000 years ago, and is based on new and compiled data^4, 5, 6. Using ¹⁴C records^7, 8 to control for climate-related influences on ¹⁰Be deposition, we reconstruct centennial changes in solar activity. We find that during the Last Glacial Maximum, solar minima correlate with more negative δ¹⁸O values of ice and are accompanied by increased snow accumulation and sea-salt input over central Greenland. We suggest that solar minima could have induced changes in the stratosphere that favour the development of high-pressure blocking systems located to the south of Greenland, as has been found in observations and model simulations for recent climate^9, 10. We conclude that the mechanism behind solar forcing of regional climate change may have been similar under both modern and Last Glacial Maximum climate conditions.

Related: 

Paper finds solar activity explains climate change over past 200,000 years

Paper shows solar activity at end of 20th century was the highest in 1200 years

New paper shows 20th century solar activity was at highest levels of past 9,400 years

New paper finds Ireland climate controlled by natural ocean oscillations and Sun over past 5000 years

New paper finds another amplification mechanism by which the Sun controls climate

What is the Planetary Theory about? Why all the Fuss?

New paper describes another solar amplification mechanism that affects low clouds

A paper published today in Geophysical Research Letters finds another potential solar amplification mechanism by which tiny changes in the solar wind affect clouds and pressure [geopotential height anomalies] in the lower troposphere. 

The authors find this new mechanism to be distinct from previously described solar amplification mechanisms involving 

"downward propagation of atmospheric effects to the lower troposphere from the stratosphere due to solar-variability-driven mechanisms involving ultra-violet radiation or energetic particle precipitation."

The newly described solar-wind-driven amplification mechanism is also distinct from the solar-wind-driven mechanism of Svensmark's cosmic ray theory of climate, and adds to many other potential solar amplification mechanisms described in the scientific literature. 

Solar-wind-driven geopotential height anomalies originate in the Antarctic lower troposphere

Mai Mai Lam et al

We use NCEP/NCAR reanalysis data to estimate the altitude and timelag dependence of the correlation between the interplanetary magnetic field component, By, and the geopotential height anomaly above Antarctica. The correlation is most statistically significant within the troposphere. The peak in the correlation occurs at greater timelags at the tropopause (~6–8 days) and in the mid-troposphere (~4 days), than in the lower troposphere (~1 day). This supports a mechanism involving the action of the global atmospheric electric circuit, modified by variations in the solar wind, on lower tropospheric clouds. The increase in timelag with increasing altitude is consistent with the upward propagation by conventional atmospheric processes of the solar-wind-induced variability in the lower troposphere. This is in contrast to the downward propagation of atmospheric effects to the lower troposphere from the stratosphere due to solar-variability-driven mechanisms involving ultra-violet radiation or energetic particle precipitation.

New paper finds another solar amplification mechanism by which solar activity & cosmic rays control climate

A paper published today in the Journal of Atmospheric and Solar-Terrestrial Physics finds another potential solar amplification mechanism mediated by galactic cosmic rays [GCRs] (and distinct from Svensmark's cosmic ray theory of climate). The author demonstrates:

Solar modulation of GCR [Galactic Cosmic Rays] is translated down to the Earth climate.

•

The mediator of solar influence are energetic particles.

•

GCR impacts the O₃ [ozone] budget in the lower stratosphere.

•

O₃ influences the temperature and humidity near tropopause, and greenhouse effect.

•

Effectiveness of this mechanism depends on geomagnetic field intensity.

---

"In this paper we show that bi-decadal variability of solar magnetic field, modulating the intensity of galactic cosmic ray (GCR) at the outer boundary of heliosphere, could be easily tracked down to the Earth's surface. The mediator of this influence is the lower stratospheric ozone, while the mechanism of signal translation consists of: (i) GCR impact on the lower stratospheric ozone balance; (ii) modulation of temperature and humidity near the tropopause by the ozone variations; (iii) increase or decrease of the greenhouse effect, depending on the sign of the humidity changes. The efficiency of such a mechanism depends critically on the level of maximum secondary ionisation created by GCR (i.e. the Pfotzer maximum) − determined in turn by heterogeneous Earth's magnetic field..."

The paper adds to over 100 potential solar amplification mechanisms described in the literature.

As to the false belief that solar activity does not correlate to global temperatures, the sunspot 'integral', the accumulated mean sunspot activity, and Fourier analysis all demonstrate this belief to be false:

Graphics from the paper and abstract below:

Bi-decadal solar influence on climate, mediated by near tropopause ozone

• N.A. Kilifarska 

•

Solar modulation of GCR [Galactic Cosmic Rays] is translated down to the Earth climate.

•

The mediator of solar influence are energetic particles.

•

GCR impacts the O₃ budget in the lower stratosphere.

•

O₃ influences the temperature and humidity near tropopause, and greenhouse effect.

•

Effectiveness of this mechanism depends on geomagnetic field intensity.

---

Abstract

The Sun's contribution to climate variations was highly questioned recently. In this paper we show that bi-decadal variability of solar magnetic field, modulating the intensity of galactic cosmic ray (GCR) at the outer boundary of heliosphere, could be easily tracked down to the Earth's surface. The mediator of this influence is the lower stratospheric ozone, while the mechanism of signal translation consists of: (i) GCR impact on the lower stratospheric ozone balance; (ii) modulation of temperature and humidity near the tropopause by the ozone variations; (iii) increase or decrease of the greenhouse effect, depending on the sign of the humidity changes. The efficiency of such a mechanism depends critically on the level of maximum secondary ionisation created by GCR (i.e. the Pfotzer maximum) − determined in turn by heterogeneous Earth's magnetic field. Thus, the positioning of the Pfotzer max in the driest lowermost stratosphere favours autocatalytic ozone production in the extra-tropical Northern Hemisphere (NH), while in the SH − no suitable conditions for activation of this mechanism exist. Consequently, the geomagnetic modulation of precipitating energetic particles – heterogeneously distributed over the globe – is imprinted on the relation between ozone and humidity in the lower stratosphere (LS). The applied test for causality reveals that during the examined period 1957–2012 there are two main centers of action in the winter NH, with tight and almost stationary ozone control on the near tropopause humidity. Being indirectly influenced by the solar protons, the variability of the SH lower stratospheric ozone, however, is much weaker. As a consequence, the causality test detects that the ozone dominates in the interplay with ULTS humidity only in the summer extra-tropics.

New paper finds another solar amplification mechanism by which the Sun controls climate

A paper published today in Environmental Research Letters finds another potential solar amplification mechanism by which changes in solar UV activity over 11-year solar cycles are amplified to large-scale effects upon climate via modulations of the North Atlantic Oscillation [NAO]. 

The authors model a mechanism whereby large changes (up to 100%) in solar UV over solar cycles affect heating rates of the upper stratosphere, which in turn affect winds and temperature gradients in the troposphere, and heat storage in North Atlantic Ocean. This results in a lagged effect of 3-4 years in the amplitude of the North Atlantic Oscillation, which in turn affects Arctic sea ice extent, other ocean oscillations, the jet stream, and weather patterns around the globe. The paper corroborates several others demonstrating solar influence upon the NAO, as well as other ocean oscillations. 

According to the authors,

Numerous studies have suggested an impact of the 11 year solar cycle on the winter North Atlantic Oscillation (NAO), with an increased tendency for positive [NAO signals to occur at maxima of the solar cycle, and negative NAO signals to occur at minima of the solar cycle]. Climate models have successfully reproduced this solar cycle modulation of the NAO, although the magnitude of the effect is often considerably weaker than implied by observations.  

A leading candidate for the mechanism of solar influence is via the impact of ultraviolet radiation variability on heating rates in the tropical upper stratosphere, and consequently on the meridional temperature gradient and zonal winds...On reaching the troposphere this produces a response similar to the winter NAO. Recent analyses of observations have shown that solar cycle–NAO link becomes clearer approximately three years after solar maximum and minimum. Previous modelling studies have been unable to reproduce a lagged response of the observed magnitude. 

In this study, the impact of solar cycle on the NAO is investigated using an atmosphere–ocean coupled climate model. We show that the model produces significant NAO responses peaking several years after extrema of the solar cycle, persisting even when the solar forcing becomes neutral. This confirms suggestions of a further component to the solar influence on the NAO beyond direct atmospheric heating and its dynamical response. Analysis of simulated upper ocean temperature anomalies confirms that the North Atlantic Ocean provides the memory of the solar forcing required to produce the lagged NAO response. These results have implications for improving skill in decadal predictions of the European and North American winter climate.

A simulated lagged response of the North Atlantic Oscillation to the solar cycle over the period 1960–2009

OPEN ACCESS

M B Andrews 1, J R Knight 1 and L J Gray 2
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M B Andrews et al 2015 Environ. Res. Lett. 10 054022
doi:10.1088/1748-9326/10/5/054022Published 22 May 2015

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Abstract

Numerous studies have suggested an impact of the 11 year solar cycle on the winter North Atlantic Oscillation (NAO), with an increased tendency for positive (negative) NAO signals to occur at maxima (minima) of the solar cycle. Climate models have successfully reproduced this solar cycle modulation of the NAO, although the magnitude of the effect is often considerably weaker than implied by observations. A leading candidate for the mechanism of solar influence is via the impact of ultraviolet radiation variability on heating rates in the tropical upper stratosphere, and consequently on the meridional temperature gradient and zonal winds. Model simulations show a zonal mean wind anomaly that migrates polewards and downwards through wave–mean flow interaction. On reaching the troposphere this produces a response similar to the winter NAO. Recent analyses of observations have shown that solar cycle–NAO link becomes clearer approximately three years after solar maximum and minimum. Previous modelling studies have been unable to reproduce a lagged response of the observed magnitude. In this study, the impact of solar cycle on the NAO is investigated using an atmosphere–ocean coupled climate model. Simulations that include climate forcings are performed over the period 1960–2009 for two solar forcing scenarios: constant solar irradiance, and time-varying solar irradiance. We show that the model produces significant NAO responses peaking several years after extrema of the solar cycle, persisting even when the solar forcing becomes neutral. This confirms suggestions of a further component to the solar influence on the NAO beyond direct atmospheric heating and its dynamical response. Analysis of simulated upper ocean temperature anomalies confirms that the North Atlantic Ocean provides the memory of the solar forcing required to produce the lagged NAO response. These results have implications for improving skill in decadal predictions of the European and North American winter climate.

1. Introduction

The variability of the Sun's output influences the heating of the stratosphere via the absorption of ultraviolet (UV) by ozone (Haigh1994, Gray et al 2009). Observational studies of the influence of the 11 year solar cycle show warm temperature anomalies in the equatorial upper stratosphere at solar maximum compared to solar minimum (Frame and Gray 2010, Mitchell et al 2014). Significant changes in the extratropical atmospheric circulation have been linked to these temperature anomalies (Kodera 1995, Kodera and Kuroda 2002), and this is supported by modelling studies (e.g. Matthes et al 2004, 2006, Ineson et al 2011). One of the mechanisms for 'top-down' solar influence (Gray et al 2010) involves equatorial stratospheric warm anomalies at solar maximum which increases the mean meridional temperature gradient, resulting in an increase in the mean Westerly wind in the mid-latitude stratosphere. This positive zonal wind anomaly is then amplified by forcing from planetary waves propagating upwards from the troposphere. Along with meridional advection, this wave feedback causes the poleward and downward migration and amplification of the wind anomaly to the mid- and high-latitude lower stratosphere, where it is able to influence tropospheric circulation. The resulting surface response involves sea-level pressure changes at solar maximum which are very similar to the positive phase of the Arctic Oscillation (AO), with anomalous low pressure over the North Pole bordered by anomalous high pressure in mid-latitudes (Thompson and Wallace 1998). Conversely, at solar minimum, a negative AO response results from reduced stratospheric meridional temperature gradients and the downward and poleward propagation of negative zonal wind anomalies. This top-down mechanism occurs on seasonal timescales since planetary wave propagation in the stratosphere is limited to the winter half-year.

This 'top-down' mechanism cannot explain the recently identified lag of approximately 3 years between solar maximum (minimum) and an increased tendency of a positive (negative) North Atlantic Oscillation (NAO) signal superimposed on the intrinsic year-to-year NAO variability (Gray et al 2013). The ability of the climate system to produce a multi-year lag in the winter NAO response necessitates the persistence of solar signals within the climate system from one winter to the next. Scaife et al (2013) showed that the North Atlantic Ocean is a prime candidate for the source of the lag. Model simulations have demonstrated that the sub-surface North Atlantic Ocean can be influenced by NAO changes related to the internal variability of stratospheric circulation (Reichler et al2012) and changes in multidecadal solar irradiance (Menary and Scaife 2014). On interannual timescales, Scaife et al (2013) presented a mechanism involving coupled atmosphere–ocean feedbacks. The NAO is known to be correlated with a tripole pattern in the North Atlantic sea-surface temperatures (SST), (Visbeck et al 2003), which extends below the surface into the ocean mixed layer. Due to the seasonal cycle in surface heat and turbulent fluxes, the mixed-layer-depth (MLD) is deeper in winter than in summer. This suggests that a winter sub-surface ocean signal, linked to solar variability, could persist by being isolated underneath the shallower summer mixed layer from the modifying influence of surface fluxes from the atmosphere. In autumn, as the summer mixed-layer erodes and the deeper winter mixed layer becomes established, any sub-surface solar signal would reconnect with the surface, giving it the potential to influence the atmosphere. This sequestration and re-emergence of signals from one winter to the next has been shown to operate in other contexts (Alexander et al 1999, Timlin et al 2002, Deser et al 2003, Taws et al 2011), and would give rise to a forcing of the NAO by the ocean (Rodwell and Folland 2002). Hanawa and Sugimoto (2004) identified several regions of re-emergence including areas of the North Atlantic relevant to this study. Scaife et al (2013) argue that a weak solar-related AO/NAO signal could build up over a number of years in the tripole region of the North Atlantic Ocean and feedback onto the atmosphere to produce a peak in the NAO signal after a few years.

Several studies have examined the simulated NAO response to solar forcings. Gray et al (2013) and Mitchell et al (2015) showed that Coupled Model Intercomparison Project Phase 5 (CMIP5) simulations were unable to reproduce the observed NAO response. On the other hand, Ineson et al (2011) were able to simulate a realistic amplitude of the NAO response by imposing a higher level of variability in UV-band irradiance. They reproduced the UV-induced 'top-down' mechanism, connecting the upper-stratosphere and the tropospheric NAO. The simulations from Ineson et al (2011) were further analysed by Scaife et al (2013), who showed that the implied ocean–atmosphere coupling in the model used by Ineson et al (2011) was too weak to produce the observed delay.

In this study we use historical simulations of the period 1960–2009 with CMIP5 evolving forcings to explore the influence of solar variability on the NAO. This is different to the experiments of Ineson et al (2011) which use constant forcings within their solar maximum and solar minimum scenarios. We use two ensembles, the first with solar irradiance held constant and the second with time-varying spectrally resolved solar variability. The difference in response of the ensembles should reveal the influence of the varying solar cycle on the atmosphere and oceans.

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Figure 1. (a) Time-series of imposed TSI anomaly (black line), and UV-band irradiance anomaly (dashed blue line) with respect to the 1960–2009 mean. (b) Composites of upper stratospheric zonal mean temperature (dashed red line) and DJF NAO-index (black line) as a function of lag with respect to solar maximum minus solar minimum. The upper stratospheric temperature is calculated as the annual average of the region bounded by 0.5–5 hPa (approximately 40–55 km), and 30 °S–30 °N. The NAO-index is defined as the DJF surface pressure difference between the Azores and Iceland. The points where the NAO-index is significant at the 95% level are highlighted with squares.

...

Summary

We have investigated the NAO response to solar variability using a state-of-the-art atmosphere–ocean coupled model. Historical ensembles for the period 1960–2009 were performed with constant and time-varying solar irradiance. Analysis of the differences between the ensembles was performed to identify solar cycle responses in the atmosphere and ocean. The results demonstrate tropical upper stratospheric heating in response to the imposed UV change at solar maximum compared to solar minimum, and confirm the results of Ineson et al (2011), showing a subsequent surface winter NAO response via a 'top-down' mechanism. The response of the NAO peaks 3–4 years following the extreme phase of the solar cycle. This finding is consistent with a recent re-evaluation of observed responses to the solar cycle (Gray et al 2013) which shows the largest NAO signal at a similar lag. The in-phase response of the Aleutian Low is also in agreement with observational analyses.

We diagnose the source of the NAO lag in the model by examining its surface and sub-surface solar responses in the North Atlantic Ocean. We find evidence for amplification of 'top-down' solar-related NAO changes via an ocean feedback over a period of several years, as suggested by Scaife et al (2013). This feedback is analysed by examining solar cycle responses in the different nodes of the North Atlantic tripole SST pattern, as this pattern reflects NAO–ocean coupling. The Northern and Middle nodes of the tripole show temperature responses in the surface and sub-subsurface ocean with a similar lag to the NAO. The Southern node, however, does not show any lag. In the Middle node we find re-emergence of solar signals imprinted on the ocean from the previous winter. By remaining intact below the shallow ocean mixed-layer that forms in summer, these signals can re-emerge in winter and reinforce the 'top-down' forcing of the NAO via coupling with the atmosphere. This mechanism is not evident in the Northern and Southern nodes. The simulated re-emergence in the North Atlantic Ocean causes an accumulation of the solar signal, allowing the NAO to grow over several years. This growth is limited by the reversal of the solar cycle, resulting in a lag approximately equal to one quarter of its period. Although we do not explicitly demonstrate here that the growth in the NAO response arises through feedback from the solar SST signal in the Middle node the existence of this feedback is supported by previous studies (Rodwell and Folland 2002, Timlin et al 2002) that show the influence of tripole SSTs on the NAO.

The NAO (Hurrell et al 2003) is a key mode of regional climate variability that strongly influences the wintertime weather of Northern Europe and Eastern North America. The ability to reproduce the lagged NAO response to solar forcing in atmosphere–ocean coupled models offers the possibility of increased NAO predictability and hence skill in seasonal forecasts (Scaife et al 2014) and decadal forecasts up to a few years ahead (Smith et al 2012).

New paper explains solar amplification mechanism controlling North Atlantic climate

A new paper published in Annales Geophysicae finds another solar amplification mechanism by which solar activity controls sea level pressures, mid-tropospheric geopotential heights (which in turn controls the lapse rate and surface temperatures), the North Atlantic Oscillation (NAO) and atmospheric circulation in the North Atlantic, as well as the Pacific/North American pattern. The authors

"concentrate on the Northern Hemisphere and North Atlantic in the period 1948–2012. Composite and correlation analyses point to a strengthening of the North Atlantic Oscillation and weakening (i.e. becoming more zonal) of the Pacific/North American pattern. The locations of points with lowest and highest sea level pressure in the North Atlantic change their positions between low and high solar activity."

and discuss in the conclusion the potential solar amplification mechanism:

"The solar effect on atmospheric circulation in the North Atlantic can be described as a tripole mechanism. During solar maximum conditions the differences between the Icelandic Low and Azores High increase, while the Greenland High decreases. Solar minimum conditions reinforce the high pressure above Greenland together with a weakening of the other two North Atlantic pressure centres."

The paper adds to over 200 others published since 2010 alone which explain numerous mechanisms by which tiny changes in solar activity may be amplified to large-scale changes in atmospheric circulation and climate change. In addition, many papers corroborate solar control of the NAO found in this paper, which may in turn be the primary influence upon Arctic climate and Arctic sea ice extent. 

Ann. Geophys., 33, 207-215, 2015 www.ann-geophys.net/33/207/2015/ doi:10.5194/angeo-33-207-2015 The influence of solar activity on action centres of atmospheric circulation in North Atlantic

L. Sfîcă¹, M. Voiculescu², and R. Huth^3,4
1Faculty of Geography and Geology, Alexandru Ioan Cuza University, Iaşi, Romania
²Faculty of Science and Environment, Dunărea de Jos University, Galaţi, Romania
³Faculty of Science, Charles University, Prague, Czech Republic
⁴Institute of Atmospheric Physics, Academy of Sciences of the Czech Republic, Prague, Czech Republic
Abstract. We analyse the response of sea level pressure and mid-tropospheric (500 hPa) geopotential heights to variations in solar activity. We concentrate on the Northern Hemisphere and North Atlantic in the period 1948–2012. Composite and correlation analyses point to a strengthening of the North Atlantic Oscillation and weakening (i.e. becoming more zonal) of the Pacific/North American pattern. The locations of points with lowest and highest sea level pressure in the North Atlantic change their positions between low and high solar activity.

New paper finds solar UV varies up to 100% during solar cycles, confirms solar amplification mechanism

A paper published today in Atmospheric Chemistry and Physics notes that solar UV radiation can vary up to 100% during solar cycles, that it is "well accepted" these large changes in UV significantly affect stratospheric ozone production, and thereby act as a solar amplification mechanism on temperatures. 

The IPCC dismisses the role of the Sun in climate change by only modelling the tiny changes of the Total Solar Irradiance [TSI], while ignoring the large changes of up to 100% in the most energetic portion of the solar spectrum, the ultraviolet [UV] region. The UV spectrum also penetrates the deepest of any portion of the solar spectrum into the oceans [up to 100 meters] to heat the bulk of the oceans, unlike longwave infrared radiation from greenhouse gases, which can only penetrate a few millionths of one meter to cause evaporative cooling of the ocean 'skin' surface. 

From the Introduction to the paper:

The Sun is the primary source of energy to the Earth’s atmosphere, so it is essential to understand the influence that solar flux variations may have on the climate system. This can be studied by investigating the effect of 11 yr solar flux variations on the atmosphere. Although total solar irradiance (TSI) shows only a small variation ( 0.1% per solar cycle), significant (up to 100 %) variations are observed in the ultraviolet (UV) region of the solar spectrum. In a “top-down” mechanism, these UV changes are thought to modify middle atmospheric (lower mesospheric and stratospheric) O3 [ozone] production, thereby indirectly altering background temperatures (for a review see Gray et al., 2010). These temperature changes can then modulate upward propagating planetary waves, and amplify the solar signal in stratospheric O3 and temperatures. The temperature changes will also affect the rates of chemical reactions which control ozone. This mechanism has been well accepted.

Atmos. Chem. Phys., 13, 10113-10123, 2013 www.atmos-chem-phys.net/13/10113/2013/ doi:10.5194/acp-13-10113-2013 Stratospheric O3 changes during 2001–2010: the small role of solar flux variations in a chemical transport model

S. S. Dhomse¹, M. P. Chipperfield¹, W. Feng¹, W. T. Ball², Y. C. Unruh², J. D. Haigh², N. A. Krivova³, S. K. Solanki^3,4, and A. K. Smith^5
1School of Earth and Environment, University of Leeds, Leeds, UK
²Physics Department, Blackett Laboratory, Imperial College London, London, UK
³Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau, Germany
⁴School of Space Research, Kyung Hee University, Yongin, Gyeonggi, South Korea
⁵National Center for Atmospheric Research, Boulder, CO, USA
Abstract. Solar spectral fluxes (or irradiance) measured by the SOlar Radiation and Climate Experiment (SORCE) show different variability at ultraviolet (UV) wavelengths compared to other irradiance measurements and models (e.g. NRL-SSI, SATIRE-S). Some modelling studies have suggested that stratospheric/lower mesospheric O₃ changes during solar cycle 23 (1996–2008) can only be reproduced if SORCE solar fluxes are used. We have used a 3-D chemical transport model (CTM), forced by meteorology from the European Centre for Medium-Range Weather Forecasts (ECMWF), to simulate middle atmospheric O₃ using three different solar flux data sets (SORCE, NRL-SSI and SATIRE-S). Simulated O₃ changes are compared with Microwave Limb Sounder (MLS) and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite data. Modelled O₃ anomalies from all solar flux data sets show good agreement with the observations, despite the different flux variations. The off-line CTM reproduces these changes through dynamical information contained in the analyses. A notable feature during this period is a robust positive solar signal in the tropical middle stratosphere, which is due to realistic dynamical changes in our simulations. Ozone changes in the lower mesosphere cannot be used to discriminate between solar flux data sets due to large uncertainties and the short time span of the observations. Overall this study suggests that, in a CTM, the UV variations detected by SORCE are not necessary to reproduce observed stratospheric O₃changes during 2001–2010.

Paper finds solar amplification mechanism via clouds at the South Pole, amplifies surface solar irradiance up to 24 times

A paper published in Atmospheric Chemistry and Physics finds evidence of a solar amplification mechanism via cloud cover at the South Pole. According to the authors, at solar cycle minimums, cloud cover increases which further decreases solar radiation reaching the surface of the South Pole by 1.8% - 2.4%, depending on the wavelength, and vice-versa for solar cycle maximums. This begs the question: Could the current record high Antarctic sea ice extent be related to the current weakest solar cycle in 100 years rather than AGW? ;)

The paper adds to many other peer-reviewed papers describing solar amplification mechanisms by which tiny 0.1% changes of total solar irradiance can be amplified to produce large effects on climate. According to this paper, 0.1% changes in solar irradiation over solar cycles are amplified by a factor of 18 to 24 times at the surface of the South Pole, dependent upon wavelength. As noted by Dr. Roy Spencer, a mere 1-2% change in global cloud cover [such as the 1.8% - 2.4% found by this paper] can alone account for global warming - or global cooling.

The current solar cycle is the weakest in 100-200 years.

Atmos. Chem. Phys., 11, 1177-1189, 2011 www.atmos-chem-phys.net/11/1177/2011/ doi:10.5194/acp-11-1177-2011 Full paper available here: Solar irradiance at the earth's surface: long-term behavior observed at the South Pole

J. E. Frederick and A. L. Hodge
Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois, USA
Abstract. This research examines a 17-year database of UV-A (320–400 nm) and visible (400–600 nm) solar irradiance obtained by a scanning spectroradiometer located at the South Pole. The goal is to define the variability in solar irradiance reaching the polar surface, with emphasis on the influence of cloudiness and on identifying systematic trends and possible links to the solar cycle. To eliminate changes associated with the varying solar elevation, the analysis focuses on data averaged over 30–35 day periods centered on each year's austral summer solstice. The long-term average effect of South Polar clouds is a small attenuation, with the mean measured irradiances being about 5–6% less than the clear-sky values, although at any specific time clouds may reduce or enhance the signal that reaches the sensor. The instantaneous fractional attenuation or enhancement is wavelength dependent, where the percent deviation from the clear-sky irradiance at 400–600 nm is typically 2.5 times that at 320–340 nm. When averaged over the period near each year's summer solstice, significant correlations appear between [ground level] irradiances at all wavelengths and the solar cycle as measured by the 10.7 cm solar radio flux. An approximate 1.8 ± 1.0% decrease in ground-level irradiance occurs from solar maximum to solar minimum for the wavelength band 320–400 nm. The corresponding decrease for 400–600 nm is 2.4 ± 1.9%. The best-estimate declines appear too large to originate in the sun. If the correlations have a geophysical origin, they suggest a small variation in atmospheric attenuation [clouds] with the solar cycle over the period of observation, with the greatest attenuation [more clouds] occurring at solar minimum.