Earth's Climate Follows The Sun's UV Groove

That large changes in solar radiation can affect Earth's climate is widely accepted. However, the hypothesis of solar-induced centennial to decadal climate changes, which suggests feedback mechanisms in the climate system amplifying even small solar variations, has not found acceptance among orthodox climate scientists. The climate change clique would rather place their money on greenhouse gasses—human generated CO2 in particular. It is true that satellite-based measurements of total solar irradiance show that mean variations during solar cycles do not exceed 0.2 W m−2 (~ 0.1% of the Sun's energy output). It has also been noted that relatively large variations of 5–8% in the ultraviolet (UV) frequencies can occur, though how this could change global climate remained a puzzlement—but perhaps no longer. From studying a significant climate shift 2,800 years ago, a group of scientists have concluded that large changes in solar UV radiation can, indeed, affect climate by inducing atmospheric changes.

Ask a rational and scientifically literate person what might be the primary cause of climate change and they would be well justified in pointing out the large bright object that passes overhead daily. Humanity noticed that warmth came from the Sun long before it started keeping written records. A number of primitive cultures even worshiped the Sun as a deity. Fittingly, the Sun's possible influence on climate has not been ignored (see “Atmospheric Solar Heat Amplifier Discovered”). Climate scientists, however, have been loath to grant the local star primacy of place, at least when it comes to relatively short term climate variation.

It has been suggested by several scientists that centennial-scale climate variability during the Holocene epoch has been controlled by the Sun. While this sounds reasonable the problem has always been that the amplitude of solar forcing is small when compared with the climatic effects. Satellite measurements taken at the top of Earth's atmosphere indicate that observed solar fluctuations amount to less than 1/10th of a percent of total irradiance, though the data are limited and not reliable beyond the past 30 years or so. Without more extensive and reliable data, it is unclear which feedback mechanisms could have amplified the influence. That situation may have recently changed.

As reported in Nature Geosciences, “Regional atmospheric circulation shifts induced by a grand solar minimum,” Celia Martin-Puertas et al. took a meticulous look at annual sediment deposits in a German lake from 3,300 to 2,000 years ago. They analyzed the sediment layers—called varve—carefully measuring proxies for solar irradiance. This is what they found and their major conclusion:

Here we analyse annually laminated sediments of Lake Meerfelder Maar, Germany, to derive variations in wind strength and the rate of 10Be accumulation, a proxy for solar activity, from 3,300 to 2,000 years before present. We find a sharp increase in windiness and cosmogenic 10Be deposition 2,759  ±  39 varve years before present and a reduction in both entities 199  ±  9 annual layers later. We infer that the atmospheric circulation reacted abruptly and in phase with the solar minimum. A shift in atmospheric circulation in response to changes in solar activity is broadly consistent with atmospheric circulation patterns in long-term climate model simulations, and in reanalysis data that assimilate observations from recent solar minima into a climate model. We conclude that changes in atmospheric circulation amplified the solar signal and caused abrupt climate change about 2,800 years ago, coincident with a grand solar minimum.

The methodology involved employed a number of proxy sources aside from counting layers of sediment. 10Be is a so called cosmogenic radionuclide, an isotope of beryllium who's abundance is regulated by incoming cosmic radiation. Since the level of solar activity regulates the amount of incoming cosmic radiation, 10Be can be used as a gauge of the Sun's activity in times gone by.

“A less active Sun implies high cosmogenic radionuclide production rates in the atmosphere related to weaker shielding against galactic cosmic ray fluxes,” the authors state, “thus, the steep increase in 14C content of the atmosphere from 2,800–2,650 cal yr BP and the rise in the cosmogenic radionuclide 10Be flux archived in Greenland ice cores both point to a long-term (centennial) solar minimum from about 2,750–2,550 cal yr BP known as the Homeric minimum.”

What they were looking for were indications of “top-down” mechanisms that could translate long-term solar fluctuations into changes in climate. To accomplish this required very accurate dating, along with high resolution proxy readings for temperature and precipitation. Then they added in data for other climate parameters such as wind strength. An illustration of some of the measurements used in the study are shown below:

Lake Meerfelder Maar proxy data.

The methodology used here is not new or groundbreaking, but the conclusion the investigators reached is: they suggest a link between UV variability and atmospheric conditions. The report notes that significant shifts at the 200–300 nm (ie UV) part of the solar emission spectrum can have significant effects on heating and ozone chemistry in the middle atmosphere. This can induce indirect dynamical effects in the atmosphere down to the Earth’s surface and that could affect climate. Specifically:

This acts through disturbances of the stratospheric polar vortex that propagate by means of wave–mean flow interactions downwards, influence the tropospheric jet streams, which are connected to the Arctic Oscillation/North Atlantic Oscillation at Northern Hemisphere mid-latitudes and affect European winter variability. Other mechanisms for solar influence on climate concern the role of energetic particles from the Sun or galactic cosmic rays, but they are energetically smaller and their climate impact is much less understood than the mechanisms connected to electromagnetic radiation.

Anyone in the US who experienced this past winter's mild temperatures and is now suffering through the Midwest's sweltering summer can attest to the influence of upper-level air currents like the jet stream. The same can be said for the record cold in some parts of eastern Europe, a weather pattern blamed on the Arctic Oscillation and North Atlantic Oscillation being stuck in their plus phases. This winter’s AO/NAO pattern stands in stark contrast to what occurred the previous two winters, when we had the most extreme December jet stream patterns on record, caused by a strongly negative AO/NAO. The negative AO conditions suppressed westerly winds over the North Atlantic, allowing Arctic air to spill southwards into eastern North America and Western Europe, bringing unusually cold and snowy conditions.

“Climate models are generally too crude to make skillful predictions on how human-caused climate change may be affecting the AO, or what might happen to the AO in the future,” states Dr. Jeff Master on his WunderBlog. “There is research linking an increase in solar activity and sunspots with the positive phase of the AO. Solar activity has increased sharply this winter compared to the past two winters, so perhaps we have seen a strong solar influence on the winter AO the past three winters.”

Even NASA—at least the part not filled with climate change doomsayers like James Hansen—recognizes that UV radiation can have a big impact on the upper atmosphere. The National Center for Atmospheric Research (NCAR) in Boulder, Colorado, put out a NASA funded report that implicated solar UV radiation in expanding and contracting the upper atmosphere, possibly hastening the decay of satellite orbits.

As background, Martin-Puertas et al. cite an earlier paper by Sarah Ineson et al., “Solar forcing of winter climate variability in the Northern Hemisphere,” also published in Nature Geoscience. In that paper it was proposed that solar UV variation contributes a substantial fraction of typical year-to-year variations in near-surface circulation, with shifts of up to 50% of the interannual variability. That report concluded:

Our result has important implications for regional climate prediction in the northern extratropics. Fluctuations in the NAO often dominate the seasonal and decadal winter climate but its predictability on seasonal and decadal timescales is low. If the recent satellite data are typical of the variation in ultraviolet fluxes in other solar cycles then our results suggest shifts in the NAO of a sizeable fraction of the interannual variability. Given the quasiregularity of the 11-year solar cycle, our results therefore suggest significant decadal predictability in the NAO.

Here is recent research by two independent groups of investigators that have suggested plausible mechanisms for variation in the Sun's ultraviolet radiation to affect climate. This should surprise no one who is aware of the Maunder Minimum and the corresponding Little Ice Age—a time of advancing mountain glaciers in the Alps, failed crops and cold weather around the world. It is generally agreed that there were three temperature minima, occurring around 1650, 1770, and 1850. Each minima separated by slight warming intervals. These periods coincide closely with times of solar inactivity, with some of the worst weather occurring squarely during the Maunder Minimum. Of course, this blog has reported on such findings before, but as usual, the warm-mongering climate alarmists have ignored these data.

A NASA video of the Sun in UV—this is what changes Earth's climate.

Science has linked UV radiation to both decadal and century long timescales, yet the climate science establishment continues to pursue GHG emissions as the primary cause for recent climate change. It should be noted that not knowing the precise mechanisms by which GHG emissions amplify the Sun's power to cause global warming has not silenced the climate change alarmists. Lack of linkage has in no way diminished the shrillness or fervor with which they trumpet their unsubstantiated claims. We now know that the Sun calls the tune for earthly climate change, so the eco-extremist crowd can no longer blame global warming primarily on humans.

Let me emphasize the research paper's central conclusion: “changes in atmospheric circulation amplified the solar signal and caused abrupt climate change.” In other words, small changes in the Sun's output can and have driven rapid climate change in the recent past. Too bad for the warmists, because science has shown that Earth's climate does groove to the Sun's UV tune. No CO2 emissions need apply.

Be safe, enjoy the interglacial and stay skeptical.

Thanks to Henrik Svensmark

I think Svensmark nailed it. The sun is the heating element but also controls the "Pella blinds". Just as the sun goes quieter with a fraction less UV out, there is also less magnetic output to the heliosphere. More cosmic rays are allowed in, each spawning millions of muons to catalyze moisture rich, more densely solar reflective low level clouds right at the crucial 2000 to 3000 foot climate cooling level. One thing I'm wondering about, hoping it will be elucidated. Is there or is there not, an increase in vulcanism when the sun goes quiet? An estimated 3 million sub oceanic sites could drive a LOT of atmospheric moisture increase. Added ash and SO2 from surface sites could have an added effect. If that's how it works it is a very multi- pronged attack to bring on cooling. Some solar experts are now predicting a solar hibernation ahead.

Cold European winters and solar activity

The past two years have seen unusually cold winters in central European. Scientists have long suspected that the Sun’s 11-year cycle influences climate of certain regions on Earth, yet records of average, seasonal temperatures do not date back far enough to confirm any patterns. A new report in Geophysical Research Letters suggests a link exists between cold European winters and atmospheric circulation anomalies caused by weak solar activity. Frank Sirocko of the Johannes Gutenberg University of Mainz, Germany, and his team compared historical records of freezing of the river Rhine with a time series of observed sunspot activity.

The researchers found that 10 of the 14 major freezing events that have occurred since 1780 took place in or around years with minimal numbers of sunspots, when solar activity was weak. The effects of weak solar activity may propagate to the lowest layer of Earth's atmosphere, leading to changes in pressure systems over the North Atlantic. According to the researchers, these changes would favor the sustained flow of chilly Arctic air to central Europe during winter months. Quoting from the AGU press release:

When sunspot numbers are down, the Sun emits less ultraviolet radiation. Less radiation means less heating of Earth’s atmosphere, which sparks a change in the circulation patterns of the two lowest atmospheric levels, the troposphere and stratosphere. Such changes lead to climatic phenomena such as the North Atlantic Oscillation, a pattern of atmospheric pressure variations that influences wind patterns in the North Atlantic and weather behavior in regions in and around Europe.

Amazing how long it has taken modern science to realize that the Sun has a big part in determining Earth's climate.

Top down solar effects on air circulation

Been there, done that:

"How The Sun Could Control Earth's Temperature"

November 2010

Ain't done this

You evidently missed the essential point that it is the variation in UV irradiance, not total irradiance, that makes the difference. Global warming groupies have argued for years that the small variation in total solar irradiance is insufficient to explain the observed variation in the atmosphere. I have written about previous work in the area as well (see “Atmospheric Solar Heat Amplifier Discovered”). This new paper explicitly identifies solar UV as the driving factor, by way of changing upper-level atmospheric flow in the Arctic region. I'm not dismissing Wilde's work, just saying that this new research extends and modifies his hypothesis. As usual, the devil is in the details.

Missing the essential point ?

Note that I initially referred to solar proton reactions as affecting ozone quantities but later shifted my position to involve all chemical reactions that would affect the balance between ozone destruction and creation.That obviously includes the UV effects which you rely on pretty exclusively. I think it is prudent to take the wider view at this stage. See my comment after the article:

"Following a lengthy exchange with solar specialist Dr. Leif Svalgaard I am inclined to the view that pinning the entire phenomenon on solar protons may be overly simplistic.

Nonetheless the creation of ozone depleting reaction products from a number of solar linked causes does, to me, seem likely to be the cause of cooling of the mesosphere when the sun is active and warming when the sun is quiet which would give the required reversed sign solar effect to support the propositions in my article.

To resolve the issue we need to await updated data concerning the temperature trends in mesosphere and stratosphere since 2007. "

Anyway, the whole point of my article is that raw TSI s NOT the culprit so your comment seems ill founded.

Furthermore I explain how and why the solar changes alter the global circulation patterns to create global climate zone redistribution as part of a negative system response. Who else has gone that far ?

I agree however that the paper you highlight does indeed provide empirical support for my hypothesis.

My key concept is the variability of the GRADIENT of the tropopause height from equator to poles. Change that gradient and the climate zones are free to slide to and fro beneath the tropopause as a thermal regulatory process altering the rate of energy flow from surface to space as a negative system response to ANY forcing process.

In violent agreement

It would seem that we have been talking past one another, for which I apologize. I take it by inference that you are the author of the referenced paper, Stephen Wilde (it is hard to tell from an anonymous posting). I scanned the paper and did not notice a specific reference to the greater variability in the UV portion of the Sun's output, where as the Martin-Puertas et al. paper explicitly mentions UV variability. Also note that these are their conclusions, I am merely reporting on their findings as I have on a number of other studies. My point is that a number of plausible, physical mechanisms for the Sun to influence climate change have been proposed and more or less ignored by mainstream climatologists. I certainly welcome your views on the subject.

Yes it is me (Stephen Wilde)

Yes it is me (Stephen Wilde) but my page display provided nowhere to indicate identity hence the apparently anonymous posting.

Our ideas overlap to some degree and I look forward to real world events clarifying the issues for us.

Best wishes,



That video of the suns surface is just awesome! You see something like that and have to wonder who came up with this CO2 nonsense anyway!

SPF 30 anyone?

Now you know why you should always wear sun block :-)

Video Credit

Give credit for the video to NASA, credit for the subject to nature.