Low solar activity shows little impact on climate

Press Release by the Potsdam Institute for Climate Impact Research (PIK)


Study on the Little Ice Age: Low solar activity just marginally cools the climate   

The weakening sun was not the determinant factor for the Little Ice Age. Strong volcanic eruptions in particular, but also a smaller amount of greenhouse gases in the atmosphere were important factors during this period of cooler climate in the 16th and 17th century, a new study shows. This implies that low solar activity, which is expected by some researchers for the coming decades, cannot considerably slow down global warming caused by humankind’s greenhouse gas emissions.

“The impact of variations in solar activity on the climate is often overestimated,” says Georg Feulner of the Potsdam Institute for Climate Impact Research (PIK). He is the author of the article just published in Geophysical Research Letters. “This is what our new analysis shows for the past – and we can learn from this to understand future climate change.”

Sun spots are a visible sign of solar activity. When their number is small, solar radiation intensity is measurably lower. In the late 17th century, after a slow decrease of solar activity that started around 1600, the sun entered an extended period of rest, the Maunder Minimum. This is often considered to be the dominant cause of the cooling of the Earth’s climate during the Little Ice Age.

Two studies published earlier this year found two very different estimates for solar radiation during the Maunder Minimum. One concludes that radiation intensity at that time was substantially lower than today. The other one says that solar activity was just as low as during the extraordinary solar minimum in the years 2008/09.

The impact of these two estimates of solar radiation on temperatures in the Northern hemisphere during the last 1000 years has now been determined for the first time. Feulner fed the data on solar intensity into a climate model – a computer-based complex system of equations simulating the most important climatic processes in the oceans and the atmosphere. Changes in greenhouse gas concentrations and the cooling effect of sulfate aerosols from volcanic eruptions are also considered. The temperature computed by the model was then compared to temperatures reconstructed from natural climate archives like ice cores, tree rings, sediments and corals.

The result is unequivocal. In the model’s calculations, the estimates from the study concluding that solar radiation in the Little Ice Age was extremely low result in temperatures which are significantly below observed temperatures in periods of low solar activity. The estimates of the other study which did not show big differences between radiation intensity during the Maunder Minimum and the recent solar minimum yield realistic temperatures. So the climatic data from natural archives support the second study. “To understand climate history, we certainly have to take into account all possibly relevant factors,” Feulner says. “However, the impact of solar activity on the climate is comparatively small. That is what the new study confirms.”

Now what do these findings mean for our century in case the sun enters a quiet period comparable to the Maunder minimum as some experts suggest? “This would bring a cooling effect of at most 0.3 degrees,” Feulner says. This could decrease anthropogenic global warming by roughly 10 percent or less. “Regrettably, this is too little to considerably slow down anthropogenic climate change.”

Article: Feulner, G. (2011): Are the most recent estimates for Maunder Minimum solar irradiance in agreement with temperature reconstructions? Geophysical Research Letters, Vol. 38, L16706 [doi:10.1029/2011GL048529]

Weblink to the article

More on this issue:

Weblink to another study on the effect of solar activity on the future climate on Earth (published 2010)

Weblink to the Solar and Heliospheric Observatory (ESA and NASA)

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2 opinions on “Low solar activity shows little impact on climate”

  1. Below please find an interesting article I read a couple of days ago. The Financial Post is an insert in the National Post, a Canadian national newspaper owned, for the record by the Asper family, prominent Liberal Party supporters. They bought it from Conrad Black, a prominent and imprisoned Conservative Party supporter. Just thought I’d add a little color to the piece. Seems there is still more to the story, depending upon who you read.

    Science now settled
    Lawrence Solomon, Financial Post · Aug. 27, 2011
    The science is now all-but-settled on global warming, convincing new evidence demonstrates, but Al Gore, the IPCC and other global warming doomsayers won’t be celebrating. The new findings point to cosmic rays and the sun – not human activities – as the controller of climate on Earth.

    The research, published with little fanfare this week in the prestigious journal Nature, comes from über-prestigious CERN, the European Organization for Nuclear Research, one of the world’s largest centres for scientific research involving 60 countries and 8,000 scientists at more than 600 universities and national laboratories. CERN is the organization that invented the World Wide Web, that built the multi-billion dollar Large Hadron Collider, and that has now built a pristinely clean stainless steel chamber that precisely recreated the Earth’s atmosphere.

    In this chamber, 63 CERN scientists from 17 European and American institutes have done what global warming doomsayers said could never be done – demonstrate that cosmic rays promote the formation of molecules that in Earth’s atmosphere can grow and seed clouds, the cloudier and thus cooler it will be. Because the sun’s magnetic field controls how many cosmic rays reach Earth’s atmosphere (the stronger the sun’s magnetic field, the more it shields Earth from incoming cosmic rays from space), the sun determines the temperature on Earth.

    The hypothesis that cosmic rays and the sun hold the key to the global warming debate has been Enemy No. 1 to the global warming establishment ever since it was first proposed by two scientists from the Danish Space Research Institute, at a 1996 scientific conference in the U.K. Within one day, the chairman of the Intergovernmental Panel on Climate Change, Bert Bolin, denounced the theory, saying, “I find the move from this pair scientifically extremely naive and irresponsible.” He then set about discrediting the theory, any journalist that gave the theory cre dence, and most of all the Danes presenting the theory – they soon found themselves vilified, marginalized and starved of funding, despite their impeccable scientific credentials.

    The mobilization to rally the press against the Danes worked brilliantly, with one notable exception. Nigel Calder, a former editor of The New Scientist who attended that 1996 conference, would not be cowed. Himself a physicist, Mr. Calder became convinced of the merits of the argument and a year later, following a lecture he gave at a CERN conference, so too did Jasper Kirkby, a CERN scientist in attendance. Mr. Kirkby then convinced the CERN bureaucracy of the theory’s importance and developed a plan to create a cloud chamber – he called it CLOUD, for “Cosmics Leaving OUtdoor Droplets.”

    But Mr. Kirkby made the same tactical error that the Danes had – not realizing how politicized the global warming issue was, he candidly shared his views with the scientific community.

    “The theory will probably be able to account for somewhere between a half and the whole of the increase in the Earth’s temperature that we have seen in the last century,” Mr. Kirkby told the scientific press in 1998, explaining that global warming may be part of a natural cycle in the Earth’s temperature.

    The global warming establishment sprang into action, pressured the Western governments that control CERN, and almost immediately succeeded in suspending CLOUD. It took Mr. Kirkby almost a decade of negotiation with his superiors, and who knows how many compromises and unspoken commitments, to convince the CERN bureaucracy to allow the project to proceed. And years more to create the cloud chamber and convincingly validate the Dane’s groundbreaking theory.

    Yet this spectacular success will be largely unrecognized by the general public for years – this column will be the first that most readers have heard of it – because CERN remains too afraid of offending its government masters to admit its success. Weeks ago, CERN formerly decided to muzzle Mr. Kirby and other members of his team to avoid “the highly political arena of the climate change debate,” telling them “to present the results clearly but not interpret them” and to downplay the results by “mak[ing] clear that cosmic radiation is only one of many parameters.” The CERN study and press release is written in bureaucratese and the version of Mr. Kirkby’s study that appears in the print edition of Nature censored the most eye-popping graph – only those who know where to look in an online supplement will see the striking potency of cosmic rays in creating the conditions for seeding clouds.

    CERN, and the Danes, have in all likelihood found the Holy Grail of climate science. But the religion of climate science won’t yet permit a celebration of the find.

  2. Ah, Feulner fed the data on solar intensity into a climate model. Well that proves it then. We know how good climate models are.

    “Changes in greenhouse gas concentrations…”
    For years they have been using a 1% per annum increase in CO2, for simulations, when in reality it has been around half that.

    “The temperature computed by the model was then compared to temperatures reconstructed from natural climate archives like ice cores, tree rings, sediments and corals.”
    “Tree Rings”? Haven’t we been there before?

    Svensmark has them worried, so they now have to set about trying to neutralise him.

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