New paper shows solar activity is linked to the Greenland climate even 20,000 years ago

This new paper by Adophi et al uses beryllium, oxygen and carbon isotopes from Greenland ice cores right back as far as the depth of the last ice age, 22,500 years ago, and finds there is a link between solar activity and the climate. It follows these proxies of temperature and solar activity as the planet warmed to the start of the Holocene 10,000 years ago.

It is gaining attention in The Daily Mail, with the headline:

Is the SUN driving climate change? Solar activity – ‘and not just humans’ – could be increasing global warming, study claims During the last glacial maximum, Sweden was covered in a thick ice sheet that stretched all the way down to northern Germany and sea levels were more than 330ft (100m) lower than they are today, because the water was frozen in the extensive ice caps.

‘The study shows an unexpected link between solar activity and climate change,’ Dr Muscheler said in a press release.

‘It shows both that changes in solar activity are nothing new and that solar activity influences the climate, especially on a regional level. Dr Joanna Haigh, Professor of Atmospheric Physics at Imperial College London, tells MailOnline that the research is interesting but people should not jump to any conclusions. ‘This is a very nice careful piece of work which provides evidence from Greenland, over a period 10,000-25,000 years ago, consistent with a picture that has emerged from other studies looking at changes over more recent times,’ she says.

‘This shows that when the sun is less active winters are likely to be warmer in Greenland and colder in Northwest Europe.

‘It is not easy to draw any conclusions from this work with regard to the sun’s role in global warming or the recent slowdown in warming of global air temperature.’ – The Daily Mail, The grudging acknowledgement comes couched in odd terms. The sun might be a little bit more important, but it’s not the most important factor, it just does something to this odd incidental thing called atmospheric circulation. There is still a lot of uncertainty as to how the sun affects the climate, but the study suggests that direct solar energy is not the most important factor, but rather it indirectly affects atmospheric circulation. ‘Reduced solar activity could lead to colder winters in Northern Europe,’ said Dr Muscheler. ‘This is because the sun’s UV radiation affects the atmospheric circulation. We can’t draw any conclusions except this small last note: ‘The study also shows that the various solar processes need to be included in climate models in order to better predict future global and regional climate change.’ What about that 95% certainty then? Getting down to the nuts and bolts, Adolphi et al find that the climate in Greenland appears to be influenced by solar cycles. They theorize the mechanism involves those very wiggly “meridional” wind patterns (which swing in loops far to the south or north, and drag hot weather up from the tropics or send cold blasts down from the arctic.) During solar minima there appear to be more of those “blocking” type wave patterns, and they remark that this is similar to what we see today during solar minima, even though the climate regime would be quite different in an ice age.

Greenland is not global of course. But in terms of national billion-dollar policies, it’s yet another paper suggesting that the reason modern climate models don’t work is that they don’t understand the sun’s role in the climate. Which scientist says they are 95% sure CO2 caused the modern warming? Of course, it’s a trick question.

Here we present the first reconstruction of solar activity variations for the end of the last glaciation from 22.5 to 10 kyr BP (thousand years before present, AD 1950) based on new and published 10Be data from the GRIP and GISP2 ice cores 4,6 supported by independent estimates of atmospheric 14C concentrations 7,8. In addition, we provide the first evidence for a solar forcing of Greenland climate during Greenland Stadial 2 (GS-2, 22.9-14.7 kyr BP; ref. 14) that seems coherent with increased frequencies of high-pressure blocking patterns south of Greenland during low-solar-activity winters a relationship that has been reported previously from modern observations and climate model experiments. 9,15

This sun climate relationship is accompanied by increased inputs of sea salt, higher snow

accumulation, and a decrease in terrestrial aerosols (Supplementary Fig. 10). This pattern is interpreted as episodes of a more meridional atmospheric circulation during solar minima advecting relatively moist North Atlantic air masses to Greenland. Modern observations indicate that this type of flow pattern is enhanced during winters with high-pressure blocking situations south of Greenland, which in turn have been found to occur more often during solar minimum periods9. On synoptic scales these high-pressure blocking situations can be described as cyclonic Rossby wave breaking events over the North Atlantic, often accompanied by a southward displacement of the eddy-driven jet and negative North Atlantic Oscillation anomalies24,25. Both are connected to solar variability in reanalysis and model experiments (Fig. 4).

BACKGROUND

Why does 18O correlate with temperature? Most oxygen is 16O and only 1 part in 500 is 18O. During warm weather slightly more of the lighter Oxygen-16 type evaporates with more of the Oxygen 18 left behind in the ocean. Hence the ratio of the two types tells us something about the temperature of the air. – See Oregon Uni for info

How significant?

An R2 of 0.3 – 0.2. p <0.01, details here:

“Comparing the solar activity reconstruction to 18O from the GRIP (ref. 21) and GISP2 (ref. 22) ice cores reveals a significant positive correlation (r2 D 0.3 and 0.2, p < 0.01, for 10Be concentrations and flux, respectively) during GS-2 (Fig. 3 and Supplementary Fig. 9). Significant (95%) spectral coherence of 18O and the solar activity proxy 10Be at known solar cycle wavelengths (Supplementary Fig. 5) strengthens the hypothesis of a solar influence on climate.”

ABSTRACT

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 as 10Be and 14C from ice cores and tree rings2,3. 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 data4–6. Using 14C records7,8 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 18O 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 climate9,10.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.

From the supplementary file, the power spectra suggests that there are similar cycles within these isotope deposition records.

Figure S4: Multiple Taper Method

Power spectra of 14C and 10Be

production rates during the Holocene

(top 2 panels) and Greenland Stadial 2

(lower 2 panels). Black lines indicate 90

(solid), 95 (dashed), and 99 (dotted) %

significance level inferred from fitting

1/f noise to each respective power

spectrum. The yellow bars highlight

dominant periodicities which are present

during Holocene and Glacial in the

production rate records. Amongst them

the well known Gleissberg (80-90 years)

and deVries (200-230 years) solar

cycles, as well as previously discussed

solar periodicities around 150 and 340

years37. All data has been linearly

detrended and resampled to 20 year

resolution before power spectrum

estimation. Note the spectral similarity

of 10Be during GS-2 and Holocene 14C

and 10Be.

When analyzing the cycles of Be (solar activity) and 18O (temperature) there appears to be an anti-correlation (meaning when one is up on a certain cycle, the other is down).

In further support for the reliability of our solar activity reconstruction we see a coherent amplitude modulation of the well-known solar de Vries cycle (207 yr) in both 10Be and

14C production rates (Fig. 2d), closely resembling the Holocene modulation pattern (Supplementary Fig. 8).

REFERENCE

Adolphi, Florian, and Muscheler R., Svensson, A., Aldahan, A., Possnert, G., Beer, J., Sjolte, J., Björck, A., Matthes, K., Thiéblemont, R. (2014) Persistent link between solar activity and Greenland climate during the Last Glacial Maximum. Nature Geoscience; DOI: 10.1038/ngeo2225

h/t to Joffa, ScienceDaily and The HockeySchtick. H/t to Eric Worral for the Daily Mail article. Thanks to Robbo to.

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