QUOTE(Theodore @ Apr 30 2007, 11:29 PM) [snapback]1653285[/snapback]
The scientific proof of solar-forced climate change is overwhelming... certainly global warming, and planetary climate change is not the fault of human activity.
Hmmmm, overwhelming maybe to you, but not to everybody:
Changes in Solar Brightness Too Weak to Explain Global Warming, September 13, 2006
Changes in the Sun's brightness over the past millennium have had only a small effect on Earth's climate, according to a review of existing results and new calculations performed by researchers in the United States, Switzerland, and Germany.
The review, led by Peter Foukal (Heliophysics, Inc.), appears in the September 14 issue of Nature. Among the coauthors is Tom Wigley of the National Center for Atmospheric Research. NCARs primary sponsor is the National Science Foundation.
Our results imply that, over the past century, climate change due to human influences must far outweigh the effects of changes in the Sun's brightness, says Wigley.
SourceFrom the original paper:
Variations in solar luminosity and their effect on the Earths climate (P. Foukal, C. Frohlich, H. Spruit & T. M. L. Wigley, Nature, Vol 443|14 September 2006)
Variations in the Suns total energy output (luminosity) are caused by changing dark (sunspot) and bright structures on the solar disk during the 11-year sunspot cycle. The variations measured from spacecraft since 1978 are too small to have contributed appreciably to accelerated global warming over the past 30 years. In this Review, we show that detailed analysis of these small output variations has greatly advanced our understanding of solar luminosity change, and this new understanding indicates that
brightening of the Sun is unlikely to have had a significant influence on global warming since the seventeenth century. Additional climate forcing by changes in the Suns output of ultraviolet light, and of magnetized plasmas, cannot be ruled out. The suggested mechanisms are, however, too complex to evaluate meaningfully at present. SourceFrom:
Studies at the Max Planck Institute for Solar System Research reveal: solar activity affects the climate but plays only a minor role in the current global warming (2004)
Since the middle of the last century, the Sun is in a phase of unusually high activity, as indicated by frequent occurrences of sunspots, gas eruptions, and radiation storms. Researchers at the Max Planck Institute for Solar System Research (MPS) in Katlenburg-Lindau (Germany) and at the University of Oulu (Finland) have come to this conclusion after they have succeeded in reconstructing the solar activity based on the sunspot frequency since 850 AD. To this end, they have combined historical sunspot records with measurements of the frequency of radioactive isotopes in ice cores from Greenland and the Antarctic. As the scientists have reported in the renowned scientific journal, Physical Review Letters, since 1940 the mean sunspot number is higher than it has ever been in the last thousand years and two and a half times higher than the long term average. The temporal variation in the solar activity displays a similarity to that of the mean temperature of the Earth. These scientific results therefore bring the influence of the Sun on the terrestrial climate, and in particular its contribution to the global warming of the 20th century, into the forefront of current interest.
However, researchers at the MPS have shown that the Sun can be responsible for, at most, only a small part of the warming over the last 20-30 years. They took the measured and calculated variations in the solar brightness over the last 150 years and compared them to the temperature of the Earth. Although the changes in the two values tend to follow each other for roughly the first 120 years, the Earths temperature has risen dramatically in the last 30 years while the solar brightness has not appreciably increased in this time. SourceFrom:
Do Models Underestimate the Solar Contribution to Recent Climate Change?PETER A. STOTT, GARETH S. JONES, AND JOHN F. B. MITCHELL, Hadley Centre for Climate Prediction and Research, Met Office, Bracknell, Berkshire, United Kingdom
(Manuscript received 2 September 2002, in final form 10 June 2003)
Current attribution analyses that seek to determine the relative contributions of different forcing agents to observed near-surface temperature changes underestimate the importance of weak signals, such as that due to changes in solar irradiance. Here a new attribution method is applied that does not have a systematic bias against weak signals. It is found that current climate models underestimate the observed climate response to solar forcing over the twentieth century as a whole, indicating that the climate system has a greater sensitivity to solar forcing than do models. The results from this research show that increases in solar irradiance are likely to have had a greater influence on global-mean temperatures in the first half of the twentieth century than the combined effects of changes in anthropogenic forcings.
Nevertheless the results confirm previous analyses showing that greenhouse gas increases explain most of the global warming observed in the second half of the twentieth century. SourceFrom:
The effect of increasing solar activity on the Sun's total and open magnetic flux during multiple cycles: Implications for solar forcing of climate( J. L. Lean, E. OY.-M. Wang. E. O. N. R. Sheeley Jr.,E. O., Hulburt Center for Space Research, Naval Research Laboratory, Washington DC, USA, GEOPHYSICAL RESEARCH LETTERS, VOL. 29, NO. 24, 2224, 2002 , )
We investigate the relationship between solar irradiance and cosmogenic isotope variations by simulating with a flux transport model the effect of solar activity on the Sun's total and open magnetic flux. As the total amount of magnetic flux deposited in successive cycles increases, the polar fields build up, producing a secular increase in the open flux that controls the interplanetary magnetic field which modulates the cosmic ray flux that produces cosmogenic isotopes. Non-axisymmetric fields at lower latitudes decay on time scales of less than a year; as a result the total magnetic flux at the solar surface, which controls the Sun's irradiance, lacks an upward trend during cycle minima.
This suggests that secular increases in cosmogenic and geomagnetic proxies of solar activity may not necessarily imply equivalent secular trends in solar irradiance. Questions therefore arise about the interpretation of Sun-climate relationships, which typically assume that the proxies imply radiative forcing. SourceFrom NASA Earth observatory website:
Is the Sun Brighter or Not? (2003)
Unfortunately, total solar irradiance measurements made by different instruments dont agree with one another. The magnitude of change from one moment to the next is nearly equal, but the absolute measurement of solar irradiance differs by up to 0.7 percent. This doesnt sound like much, but the change in solar irradiance from solar maximum to solar minimum is only about 0.2 percent. The situation is even more complicated because the datasets from different instruments dont always overlap, making comparisons difficult. (Graph courtesy Richard Willson, Columbia University)
Integrating the conflicting satellite measurements into one consistent data set is as much art as it is sciencethe data sets of two research groups disagree. The data compiled by Richard Willson and Alexander Mordvinov (blue line) show an increase in solar irradiance between the past two solar minima (in 1986 and 1996), while Claus Frlich and Judith Leans data (red line) show no difference in solar irradiance over the same time period. Source