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सारांश

This figure summarizes sunspot number observations. Since c. 1749, continuous monthly averages^{[dead link]} of sunspot activity have been available and are shown here as reported by the Solar Influences Data Analysis Center, World Data Center for the Sunspot Index, at the Royal Observatory of Belgium. These figures are based on an average of measurements from many different observatories around the world. Prior to 1749, sporadic observations of sunspots are available. These were compiled and placed on consistent monthly framework by Hoyt & Schatten (1998a, 1998b).

The most prominent feature of this graph is the c. 11 year solar magnetic cycle which is associated with the natural waxing and waning of solar activity.

On longer time scales, the sun has shown considerable variability, including the long Maunder Minimum when almost no sunspots were observed, the less severe Dalton Minimum, and increased sunspot activity during the last fifty years, known as the Modern Maximum. The causes for these variations are not well understood, but because sunspots and associated faculae affect the brightness of the sun, solar luminosity is lower during periods of low sunspot activity. It is widely believed that the low solar activity during the Maunder Minimum may be among the principal causes of the chilly Little Ice Age, circa 1350-1850 A.D.

Copyright

This figure was prepared by Robert A. Rohde and is part of the Global Warming Art project.

Image from Global Warming Art

This image is an original work created for Global Warming Art. Please refer to the image description page for more information.

यस दस्तावेजलाई स्वतन्त्र सफ्टवायर फाउन्डेसन द्वारा प्रकाशित जी॰एन॰यू फ्रि डक्यूमेन्टेशन लाइसेन्स को संस्करण 1.2 वा नयाँ (बिना कुनै इन्वेरियेन्ट अनुभाग र पछिल्लो वा पहिलो आवरणका पाठका) को अन्तर्गत कपी, वितरित एवं/अथवा परिवर्तित गर्ने अनुमति प्रदान गरिन्छ । यस लाइसेन्सको एक प्रति जी॰एन॰यू फ्रि डक्यूमेन्टेशन लाइसेन्स नामक अनुभागमा शामिल छ ।http://www.gnu.org/copyleft/fdl.htmlGFDLGNU Free Documentation Licensetruetrue

	यो फाइल क्रिएटिभ कमन्स एट्रिब्युसन-सेयर एलाइक ३.० अनपोर्टेड लाइसेन्स अनुसारको अनुमति प्राप्त छ।
	तपाईं स्वतन्त्र हुनुहुन्छ : साझेदारी गर्नुहाेस् – रचनालाई कपी, वितरित तथा संचारित गर्नको लागि रिमिक्स गर्नको लागि – काम अनुकूलित गर्नको लागि निम्नलिखित कारणहरूको अन्तर्गत: एट्रिब्युसन – तपाईंले रचनाको श्रेय अनुमतिपत्रकर्ता अथवा लेखकले बताएको माध्यमले दिनु पर्नेछ (तर यस प्रकार हैन, जसमा लागोस् की उ तपाईंलाई अथवा तपाईंको रचनाको प्रयोगलाई समर्थन गर्छन्)। शेयर अलाइक – यदि तपाई यस रचनामा कुनै परिवर्तन अथवा संसोधन गर्नुहुन्छ या यसमा आधारित केही रचना गर्नुहुन्छ भने तपाई निष्कर्ष स्वरूप बनेको रचनालाई मात्र यहाँ अथवा यसको समान कुनै अनिमति पत्र अन्तर्गत वितरित गर्न सक्नुहुन्छ।
	This licensing tag was added to this file as part of the GFDL licensing update.http://creativecommons.org/licenses/by-sa/3.0/CC BY-SA 3.0Creative Commons Attribution-Share Alike 3.0truetrue

References

• Hoyt, D. V., and K. H. Schatten (1998a). "Group sunspot numbers: A new solar activity reconstruction. Part 1.". Solar Physics 179: 189-219.
• Hoyt, D. V., and K. H. Schatten (1998b). "Group sunspot numbers: A new solar activity reconstruction. Part 2.". Solar Physics 181: 491-512.
• Stott, Peter A.; Gareth S. Jones and John F. B. Mitchell (15 December 2003). "Do Models Underestimate the Solar Contribution to Recent Climate Change". Journal of Climate 16: 4079-4093.