Influence of Solar Cycles on Climate Change: Evidence from Tree-Ring Records
- This study examines the linkage between solar cycles and climate change based on tree-ring carbon-14 records.
- The results show that solar cycles have a persisting influence on climate beyond the period of instrumental observations.
- Temperature variations over the 22-year cycles appear to be more significant, especially during grand solar minima like the Maunder Minimum.
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Abstract The linkage between multi-decadal climate variability and activity of the sun has been long debated based upon observational evidence from a large number of instrumental and proxy records. It is difficult to evaluate the exact role of each of solar parameters on climate change since instrumentally measured solar related parameters such as Total Solar irradiance (TSI), Ultra Violet (UV), solar wind and Galactic Cosmic Rays (GCRs) fluxes are more or less synchronized and only extend back for several decades. Here we report tree-ring carbon-14 based record of 11-year/22-year solar cycles during the Maunder Minimum (17th century) and the early Medieval Maximum Period (9–10th century) to reconstruct the state of the sun and the flux of incoming GCRs. The result strongly indicates that the influence of solar cycles on climate is persistent beyond the period after instrumental observations were initiated. We find that the actual lengths of solar cycles vary depending on the status of long-term solar activity, and that periodicity of the surface air temperatures are also changing synchronously. Temperature variations over the 22-year cycles seem, in general, to be more significant than those associated with the 11-year cycles and in particular around the grand solar minima such as the Maunder Minimum (1645–1715 AD). The polarity dependence of cooling events found in this study suggests that the GCRs can not be excluded from the possible drivers of decadal to multi-decadal climate change.
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要旨（※1） 数十年規模の気候変動と太陽の活動との関係については、多くの、計器による記録ならびにプロキシの記録（※2）などの観測証拠に基づいて長らく議論されてきた。計器を使って測定された太陽総放射強度（TSI：※3）、紫外線（UV）、太陽風および銀河宇宙線（GCR:※4）流束といった太陽光に関するパラメーターは、多かれ少なかれ同期化されたり（※5）、わずか数十年間さかのぼるだけなので、気候変動における太陽光パラメーター各々の正確な役割を評価することは難しい。本稿で（※6）我々は、太陽とこれからやってくる銀河宇宙線の流束の状態を再構築する為に、マウンダー極小期（17世紀：※7）と早期中世温度極大期（9-10世紀）の間における11年と22年の太陽活動周期の記録を元に、年輪に含まれる炭素14（※8）を報告する。研究結果は、気候における太陽活動周期の影響は計器による観測が開始された後の期間をすぎても継続していることを強く示唆している。太陽活動周期の実際の長さは長期的太陽活動の状態によって異なり、表面大気温度の周期性もそれに同調して変化していることがわかる。一般的に、22年周期での温度変化は11年周期に伴うものよりもずっと顕著であり、特にマウンダー極小期（西暦1645年～1715年）のような太陽の黒点がほとんど消えていた時期あたりでは顕著だと思われている。本研究でわかった寒冷化事象の地磁気の極性依存性は、GCRが数年から十数年規模の気候変動における要因として考えられることを示している。 ※1：abstruct 論文の最初の段落は「要旨」と訳すのがお決まりです。 ※2：proxy record 気象観測において、proxy dataと呼ばれるものがあります。これは「代理データ」とも訳されますが、何を意味するかというと気象観測時代以前の気象データの代わりに、気象の指標となるデータのことを指します。従いまして、ここでのproxyも同様に「指標」という意味になります。ですが、一般的には「プロキシの記録」と言いますので、そのように訳しました。 ※3：TSI 地球大気表面の単位面積に入射する太陽のエネルギー（電磁波）のこと。 ※4：GCR 天の川銀河内の超新星残骸から発生している高エネルギーの荷電粒子のこと。 ※5：synchronized（同期化された） 意図的ではなくとも2つ以上のデータなどの内容を一致させたという意味です。 ※6：Here we report 「本稿で我々は～～を報告する」という決まり文句です。 ※7：Maunder Minimum 下記をご参照ください。 http://ja.wikipedia.org/wiki/%E3%83%9E%E3%82%A6%E3%83%B3%E3%83%80%E3%83%BC%E6%A5%B5%E5%B0%8F%E6%9C%9F ※8：tree-ring carbon-14 太陽の磁場は、宇宙線から地球を守るバリアの役割を果たしていますが、太陽活動がよわくなると、バリアが薄くなり、たくさんの宇宙線が地球に到達します。すると大気中に炭素14がつくられ、それが木の年輪に取り込まれます。太陽活動が活発になるとその逆です。つまり年輪に含まれる炭素14の量を調べれば過去の太陽活動の推移がわかるという仕組みです。
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- Nakay702
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以下のとおりお答えします。 概要 重畳的な10年間統計による気候変動と太陽活動との間の関連が、多くの機器を駆使した代用記録からの観測的証拠に基づいて、長期間討議されました。気候の変化に関する、太陽の各パラメーター（媒介変数）の正確な作用役割を評価するのは難しいことです。というのも、「太陽の放射束密度総計」(TSI)、紫外線(UV)、太陽風および「銀河宇宙線」(GCR)の流動などの、手段として測定された太陽関連のパラメーターは、多かれ少なかれ、同期しながらも数十年間後ろに延びるからです。ここで我々は、太陽の状態と地球にやって来るGCRの流動状況を再構築するために、太陽の不規則活動期（17世紀）と初期「中世の最高限度値期間」（9-10世紀）との間の、11年／22年の太陽活動周期の記録に基づいて、年輪による炭素14を報告する。その結果は、機器観察が始められた後、気候に対する太陽活動周期の影響が期間を越えて持続していたことを強く示しています。我々は、太陽活動周期の実際の長さが、長期的な太陽活動の状態に依存して変わることや、表面温度の周期性もそれに同期して変化することを知るに至りました。22年の周期にわたる温度ゆらぎは、一般に11年の周期に関連したものより大きく、「太陽の不規則活動期」（紀元1645-1715年)のような、重大な太陽活動極小期のあたりでは、特に大きいように見えます。この研究で見つかった冷却事象の極依存は、10年間の重畳統計が示す気候変動における可能な動因から、GCRを除外することはできない、ということを示唆しています。
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3. Results and discussions Our new annual carbon-14 data for the EMMP not only confirm the relationship between the cycle length and solar activity level but also provide some important insights on the state of solar activity during this period. Fig. 1 shows the signal of solar cycles detected in the carbon-14 data and Fig. 2-a shows the frequency analysis of the data, exhibiting the change in solar cycles and their amplitude. The power spectrum remarkably indicates a 9-year cyclicity (± 1 for the 68% confidence level against the high-frequency noise (< 3 years) through 880–960 AD, together with an 18-year period of solar polarity reversals. The overall significances of the two signals are 3 sigma and 2.7 sigma, respectively. The length of the 11-year solar cycle is ~ 2 years shorter than that observed for the last 150 years, and ~ 5 years shorter than those during the Maunder Minimum.
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Although the magnitude of the variations of carbon-14 is strongly attenuated through the carbon cycle after being produced by the GCRs in the atmosphere (Siegenthaler and Beer, 1988), carbon-14 in tree-rings preserve the information on the variations in solar cycles and the magnetic dipole polarity of the sun. Therefore, the variability of the “11-year” solar cycle in association with the century-scale variations of solar activity can be monitored to asses its influence on climate. The lengths of sunspot periods have been modulated by a few years since the 11-year sunspot cycle was firstly found by Schwabe (1843). The maximum range observed so far is ~ 9 to ~ 14 years, but most of the cycles fit in ~ 10–12 years with the overall average being 11 years. However, we have previously found a change in average cycle length during the Maunder Minimum ((Miyahara et al., 2004); see Supplementary Fig. S1). The sunspots were scarce through 1645–1715 AD due to the anomalous weakening of the magnetic activity at this time, yet the carbon-14 abundances show the appearance of significant cyclic changes in magnetic activity. The average length of the cycles through the 70 years was about 14 years with the 28-year period of magnetic polarity reversals. The relationship between the cycle length of the “11-year” variation in sunspots and its magnitude has been investigated in several papers (Clough, 1905, Solanki et al., 2002 and Rogers et al., 2006). A consistent feature is the inverse correlation between cycle amplitudes and cycle lengths that maybe related to the change of the meridional flows inside the convection zone of the sun (Hathaway et al., 2003).
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Here we examine the relationship between the sun and climate by measuring the carbon-14 content in tree-rings with annual time resolution. The GCR flux and hence the activity level of the sun can be monitored by carbon-14. Our particular focus is around the period of the Maunder Minimum and the early Medieval Maximum Period (EMMP) in the 9–10th century. Sunspot numbers and the activity levels of the sun gradually change in time with quasi-cycles of about 11 years (Schwabe cycle).The polarity of the solar intrinsic magnetic field, which is more or less a simple dipole at every activity minima, reverses at every activity maximum. It changes the track of protons, the positively charged main constituent of GCRs, due to the spirally expanding interplanetary magnetic field formed by solar wind (Kota and Jokipii, 1983) and hence changes the attenuation level of GCRs in the heliosphere. Bulk of the GCRs comes from the polar region of the heliosphere when the polarity of the sun is positive, while GCRs come from the horizontal direction when negative.The attenuation of GCRs in the heliosphere is, therefore, more sensitive when the polarity is negative to the intensity of solar magnetic field and the tilt angle of the current sheets which expand horizontal direction. Thus the variation of the GCR flux on the earth has a “22-year” cyclic component, and will be transferred to the variations in carbon-14.
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These include the Little Ice Age (LIA) between the 14th and the 19th centuries and the so called Medieval Warm Period (MWP) around the 9th to the 12th century. The history of solar activity, on the other hand, has been investigated through cosmogenic radionuclides, such as carbon-14 and beryllium-10, embedded in the tree-rings and ice cores for decadal (Beer et al., 1998) and centennial changes (Stuiver and Quay, 1980, Stuiver and Braziunas, 1989 and Usoskin et al., 2004). The reconstructed records show that the sun has gone through several prolonged activity minima as well as maxima roughly in sync with the cold and warm spells such as the LIA and the MWP (Eddy, 1976 and Stuiver and Braziunas, 1989), although it is still difficult to evaluate solar variations quantitatively. The patterns of climate and solar variations are similar, but the global warming trend has not leveled off during the last few decades when the activity of the sun has peaked (Lockwood and Fröhlich, 2007), pointing that the anthropogenic greenhouse gasses are the major factor responsible for the global warming.
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1. Introduction The role and exact extent of natural and anthropogenic forcing for the climate evolution has been under much debate and one of the major sources of external forcing can be through solar variability. As is well summarized by Hoyt and Schatten (1997), several meteorological phenomena, such as temperature variations, cloud coverage, frequency of lightning strikes, and droughts, seem to be responding to solar variables over a wide range of time scales such as the 27-day solar rotation period, 11-year activity cycle, 22-year polarity reversal cycle and the other longer quasi-cyclic periods. Although the most straightforward mechanism of the sun–climate connection is the direct heating of the earth by solar radiation, it is unlikely that the entire solar influence on climate can be attributed simply to the variation of TSI (Foukal et al., 2004 and Foukal et al., 2006).
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Most scientists now fear that the massive amount of carbon dioxide humans are pumping into the air will lead to a catastrophic rise in Earth's temperatures, dramatically raising sea levels as glaciers melt and leading to extreme weather worldwide. Abdussamatov remains contrarian, however, suggesting that the sun holds something quite different in store. "The solar irradiance began to drop in the 1990s, and a minimum will be reached by approximately 2040," Abdussamatov said. "It will cause a steep cooling of the climate on Earth in 15 to 20 years."
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We study the evolution of meridional flows in the solar convection zone extending to a depth of 0.793R☉ in the period 2000-2003 with helioseismic data taken with the Taiwan Oscillation Network(TON) using the technique of time-distance helioseismology.The meridional flows of each hemisphere formed a single-cell pattern in the convection zone at the solar minimum.An additional divergent flow was created at active latitudes in both hemispheres as the activity developed.The amplitude of this divergent flow correlates with the sunspot number:it increased from solar minimum to maximum(from 1996 to 2000), and then decreased from 2000 to 2003 with the sunspot number.The amplitude of the divergent flow increases with depth from 0.987R☉ to a depth of about 0.9R☉, and then decreases with depth at least down to 0.793R☉.
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Climate change is often associated with extreme weather events, melting glaciers and rising sea levels. But it could also have a major impact on human, animal and plant health by making it easier for diseases to spread. Various germs and parasites may find the coming years a time to live longer and prosper. Rising temperatures are changing environments and removing some of their natural impediments. Sonia Altizer is an associate professor at the University of Georgia’s Odum School of Ecology and lead author of the study. She said it’s a review of research done over the past 10 years to see what trends and new information on climate change have emerged. “One of the big themes that has emerged is that there’s a lot of diseases, especially in natural systems, where there as a pretty clear signal that either the prevalence or severity of those diseases has increased in response to climate change.” She said some of those natural systems where the signal is strongest are in the arctic and in warmer oceans. “So in the arctic there are parasitic worms that affect muskox and reindeer, for example, that are developing faster and becoming more prevalent and expanding their ranges. And then in tropical oceans, like Caribbean coral reefs, there’s a large amount of evidence that has mounted that shows that warming interferes with the symbiosis of corals – makes them more vulnerable to disease and at the same time increases the growth rate of some lethal bacteria,” she said. But a second theme emerged indicating that sometimes climate change may have no effect at all. “The other main point that we focused on is that knowing why different pathogens respond differently to climate change is what’s needed to help us predict and ultimately manage disease outbreaks in people and animals and plants,” she said. Some countries will be much better prepared to handle the disease threat than others, like those in Europe and North America. . “Surveillance, vector control, modern sanitation, drugs, vaccines can be deployed to prevent outbreaks of a lot of diseases, especially vector borne disease or diarrheal disease that are much more problematic in the developing world. And so these can counter the effects of climate change and make it hard to detect increases in those pathogens,” said Altizer. Controlling vectors means controlling such things as mosquitos and ticks, which can carry malaria or dengue fever. In developing countries, pathogens affecting agriculture and wildlife could adversely affect food security and the livelihoods of indigenous peoples. So how concerned should health officials be? Altizer said there’s no simple answer. “I think that the answer to it really depends on the location. So where, when and what pathogen? So I think we’re at a stage now where in the next five to ten years scientists will be able to move towards a predictive framework that will be able to answer questions about where in the world and what pathogens are responding and will continue to respond most strongly to climate change.” Altizer says the effects of climate change will unfold over decades. So it’s vital to follow long-term standardized data for many diseases and pathogens. She said crop management may be a good example to follow. It has a long history of tracking disease outbreaks, forecasting potential threats and responding to those threats early.
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From the time that life first appeared on Earth, species have gone extinct. Extinction is a natural part of evolution. Species that are best at adapting to their environment survive. Other species are unable to adapt quickly enough – so they die off. So, why do endangered species get so much attention today? One reason is much of the extinction happening these days is unnatural. The leading reason for a species to become endangered is loss of habitat. As humans cut down forests for farmland, expand cities, or pollute waterways, to name a few ways that habitat is destroyed, animals, plants, and insects find it harder and harder to survive. Thus, the effect of humans on the natural world is causing species to become endangered, and, ultimately, go extinct. Another leading reason for a species to become endangered is climate change. For example, the lizards in this article could probably adapt to a gradual change in temperature. However, the rapid change in the climate, and the consequent decrease in lizard birthrate, threaten to doom many lizard species. If human activity is a major reason for climate change, then it would seem that we are changing our world far too rapidly for species to naturally adapt. Humans are highly adaptable, but most species need a lot of time to get used to changing conditions.
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The sunspot numbers since the prolonged sunspot minimum occurred 1645–1715 AD so called the Maunder Minimum (Eddy, 1976) indicate gradual increasing trend in addition to the ~ 88-year quasi-periodicity. Solanki et al. (2004) concluded that the sun is currently experiencing one of the most active periods over the past 8000 years as estimated from a thousand year long records of carbon-14 dated tree-rings. However, the original interpretation by Solanki et al. is strongly model dependent (Muscheler et al., 2005) and there is a discrepancy with the long-term trend in beryllium-10 from a Greenland ice core (Vonmoos et al., 2006). The difficulty of interpreting the carbon-14 data is partly due to the complexity of the global carbon cycle. This is particularly true for the period since anthropogenic CO2 has been released to the atmosphere and for which instrumental climate records are available. Therefore, careful evaluation of long term and high resolution carbon-14 records is necessary to understand the possible sun–climate linkages especially from GCRs flux variations.
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