The Maunder minimum in a 400 year history of sunspot numbers
Volver a la lucha contra el
cambio climático
Calentamiento global y cambio
climático
¿Calentamiento global?
LD Walter E. Williams 13.01.2009 © Creators Syndicate Inc.
A los estadounidenses les han metido en la sesera que el calentamiento global va a acabar destruyendo el planeta. En cuanto a los científicos que se han mostrado escépticos con las tesis del calentamiento global antropogénico, han sido tachados de traidores o de vendidos a las petroleras.
El Washington Post afirmó el 28 de mayo de 2006 que sólo había "un puñado de escépticos" en lo relacionado con la amenaza del calentamiento global originado por el hombre. El 30 de agosto de ese mismo año Bill Blakemore decía: "Luego de una investigación exhaustiva, ABC News no ha podido dar con debate [científico] alguno". El secretario ejecutivo de la Convención sobre Cambio Climático de Naciones Unidas, Yvo de Boer, dijo en su día que era "criminalmente irresponsable" ignorar la urgencia del calentamiento global. En mayo de 2007, la enviada especial para el clima de Naciones Unidas, Gro Harlem Brundtland, dio por "zanjado" el debate y advirtió que era "completamente inmoral" el mero cuestionamiento del "consenso" científico de la ONU. Un par de meses más tarde, Miles O'Brien, de CNN, afirmó: "El debate científico ha terminado". Previamente había dicho que los científicos escépticos solían estar "comprados y sobornados por la industria de los combustibles fósiles". La histeria desatada a cuenta del calentamiento ha brindado una nueva oportunidad a todos aquellos que quieren controlar nuestras vidas. Después de todo, sólo la imaginación es capaz de poner límites a las leyes y restricciones que pueden promulgarse al amparo de la salvación de la Tierra. Ahora bien, cada vez son más los científicos que están reuniendo el valor necesario para alzar la voz. Así, Stanley B. Goldenberg, de la División de Investigación de Huracanes de la Administración Nacional Atmosférica y Oceánica, ha declarado: "Lo de que sólo hay un puñado de científicos que no comparte la tesis del calentamiento antropogénico es una mentira descomunal, propagada por los medios". "Más de 650 científicos internacionales disienten del discurso del calentamiento antropogénico: los científicos siguen poniendo en entredicho el consenso", puede leerse en un reciente informe de la minoría en el Senado norteamericano. Entre esos 650 científicos se cuentan, por ejemplo, el Nobel de Física Ivar Giaever ("Soy escéptico ... El calentamiento global se ha convertido en una nueva religión"), el químico Kiminori Itoh ("[Estamos ante] el peor escándalo científico de la historia ... Cuando la gente descubra la verdad, se sentirá engañada por la ciencia y los científicos"), el ingeniero químico de la Universidad Abo Akademi de Finlandia y ex miembro de Greenpeace Jarl R. Ahlbeck ("Hasta ahora, las mediciones no muestran signos alarmantes de que vaya a producirse un calentamiento catastrófico") y el físico atmosférico James A. Peden, que en tiempos trabajó en el Centro de Coordinación e Investigación Espacial de Pittsburgh ("Muchos [científicos] buscan ahora la forma de distanciarse discretamente [del ecoalarmismo] sin ver arruinadas sus carreras profesionales"). Lo cierto es que cada vez son más las investigaciones que sugieren que podría producirse un enfriamiento global. El geólogo Don J. Easterbrook, profesor emérito de la Western Washington University, dice: "Los cambios registrados en el Sol últimamente sugieren que podría ser [un enfriamiento] bastante severo, quizá más parecido al de 1880-1915 que al de 1945-1977. Un enfriamiento como el mínimo de Dalton y Maunder podría sumir al planeta en una nueva Pequeña Edad del Hielo, pero sólo el tiempo dirá si esto es una posibilidad". El geólogo Dr. David Gee, presidente del comité científico del Congreso Geológico Internacional de 2008, que actualmente trabaja en la Universidad de Uppsala (Suecia), se pregunta: "¿Durante cuánto tiempo ha de enfriarse la Tierra para que nos demos cuenta de que no se está calentando?". He aquí una pregunta trascendental que los americanos han de plantearse. Las leyes, una vez promulgadas, es muy difícil, por no decir imposible, echarlas abajo. Si el hielo se enseñoreara de Nueva Jersey y demás zonas septentrionales del país, como lo hizo en tiempos remotos, a mí no me extrañaría que un Congreso manejado por fanáticos conservara toda la legislación aprobada para prevenir el calentamiento global. Lo que es yo, no les daría tanta manga ancha.
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El mínimo de Dalton y Maunder
From Wikipedia, the free encyclopedia mínimo de Dalton y Maunder
Maunder Minimum
The Maunder minimum in a 400 year history of sunspot
numbers
The Maunder Minimum is the name given to the period roughly from 1645 to 1715, when sunspots became exceedingly rare, as noted by solar observers of the time. It is named after the solar astronomer Edward W. Maunder (1851–1928) who discovered the dearth of sunspots during that period by studying records from those years. During one 30-year period within the Maunder Minimum, for example, astronomers observed only about 50 sunspots, as opposed to a more typical 40,000–50,000 spots.
Sunspot observations
The Maunder Minimum occurred between 1645 and 1715 when only about 50 spots appeared as opposed to the typical 40,000–50,000 spots. The minima counts for 10-year periods from 1610–1681 are as follows:
| Decade | Sunspots |
|---|---|
| 1610 | 9 |
| 1620 | 6 |
| 1630 | 9 |
| 1640 | 2 |
| 1650 | 3 |
| 1660 | 1 |
| 1670 | 0 |
| 1680 | 1 |
During the Maunder Minimum enough sunspots were sighted so that 11-year cycles could be extrapolated from the count. The maxima occurred in 1674, 1684, 1695, 1705 and 1716.
The sunspot activity was then concentrated in the southern hemisphere of the Sun, except for the last cycle when the sunspots appeared in the northern hemisphere too.
According to Spörer's law, at the start of a cycle spots appear at ever lower latitudes, until they average at about lat. 15° at solar maximum. The average then continues to drift lower to about 7° and after that, while spots of the old cycle fade, new cycle spots start appearing again at high latitudes.
The visibility of these spots is also affected by the velocity of the sun's rotation at various latitudes:
| Solar latitude |
Rotation period (days) |
|---|---|
| 0° | 24.7 |
| 35° | 26.7 |
| 40° | 28.0 |
| 75° | 33.0 |
Visibility is somewhat affected by observations being done from the ecliptic. The ecliptic is inclined 7° from the plane of the Sun's equator (latitude 0°).
Little Ice Age
The Maunder Minimum coincided with the middle — and coldest part — of the Little Ice Age, during which Europe and North America, and perhaps much of the rest of the world, were subjected to bitterly cold winters. Whether there is a causal connection between low sunspot activity and cold winters is the subject of ongoing debate (e.g., see Global Warming).
Other observations
Solar activity events recorded in radiocarbon.
The lower solar activity during the Maunder Minimum also affected the amount of cosmic radiation reaching the Earth. The resulting change in the production of carbon-14 must be taken into account when radiocarbon dating is used to determine the age of archaeological artifacts.
Graph showing proxies of solar activity, including
changes in sunspot number and cosmogenic isotope production.
Solar activity also affects the production of beryllium-10, and variations in that cosmogenic isotope are studied as a proxy for solar activity.
Other historical sunspot minima have been detected either directly or by the analysis of carbon-14 in ice cores or tree rings; these include the Spörer Minimum (1450–1540), and less markedly the Dalton Minimum (1790–1820). In total there seem to have been 18 periods of sunspot minima in the last 8,000 years, and studies indicate that the sun currently spends up to a quarter of its time in these minima.
One recently published paper, based on an analysis of a Flamsteed drawing, suggests that the Sun's rotation slowed in the deep Maunder minimum (1666–1700).[1]
During the Maunder Minimum auroras had been observed normally. Detailed analysis has been published by Wilfried Schröder (1992)[2] and J. P. Legrand et al. (1992).[3]
The fundamental papers on the Maunder minimum (Eddy, Legrand, Gleissberg, Schröder, Landsberg et al.) have been published in Wilfried Schröder (Ed) Case studies on the Spörer, Maunder and Dalton Minima.[4]
See also
References
Further reading
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This figure summarizes the 400 years of regular sunspot number observations. Since ~1749, continuous monthly averages 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 figure 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 ~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 and earlier periods may be among the principal causes of the Little Ice Age. Similarly, the Modern Maximum is partly responsible for global warming, especially the temperature increases between 1900 and 1950. One study (Stott et al. 2003), argues that residual warming due to the sustained high level of activity since 1950 is responsible for 16 to 36% of recent warming.
Copyright
This figure was prepared by Robert A. Rohde and is part of the Global Warming Art project.
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Description
This figure shows two different proxies of solar activity during the last several hundred years. In red is shown the Group Sunspot Number (Rg) as reconstructed from historical observations by Hoyt and Schatten (1998a, 1998b) [1]. In blue is shown the beryllium-10 concentration (104 atoms/(gram of ice)) as measured in an annually layered ice core from Dye-3, Greenland (Beer et al. 1994).
Both of these proxies are related to solar magnetic activity. Sunspots are darker, cooler regions of the sun's surface associated with high magnetic flux. Higher numbers of sunspots indicate a more active sun with stronger and more complicated magnetic fields. The dominant change in sunspots reflects the quasi-11 year solar magnetic cycle. The quiet period observed from 1645 to 1710 is known as the Maunder Minimum and is associated with a near zero abundance of sunspots.
Beryllium-10 is a cosmogenic isotope created in the atmosphere by galactic cosmic rays. Because the flux of such cosmic rays is affected by the intensity of the interplanetary magnetic field carried by the solar wind, the rate at which Beryllium-10 is created reflects changes in solar activity. A more active sun results in lower beryllium concentrations (note inverted scale on plot). Since the atmospheric residence time for beryllium is not more than a few years, it is also possible to resolve the solar magnetic cycle in beryllium concentrations. Beryllium measurements, such as these, are the best evidence that the solar magnetic cycle did not cease even during the period with no evident sunspots.
The dark curves are 30 year averages of the data.
Copyright
This image was produced by Robert A. Rohde from previously published data and is incorporated into the Global Warming Art project