Saturday, May 19, 2007

Solar Variability And Earth's Climate

This review of an article studying the relationship between variations in the amount of energy received by the Earth, from the sun, varies regularly with time. Remember, the sun is what provides warmth to the Earth's atmosphere, not man. The energy from the sun penetrates the atmosphere on the way down, heats the surface of the Earth, where some of this heat is then trapped in the atmosphere by greenhouse gases. Also note that of the greenhouse gases, 99.9% is water vapor.

What is terribly important here is that the measurable variations in the sun's energy reaching the Earth is cyclical. This means it varies in a predictable pattern, and most significantly this pattern MATCHES the changes in the Earth's climate, from major changes like ice ages, to more minor warming and cooling. This has been happening as far back in time as scientists can measure. The inescapable conclusion is that man is not causing our present global warming and climate change.


Solar Variability and Earth's Climate
ReferenceBeer, J., Vonmoos, M. and Muscheler, R. 2006. Solar variability over the past several millennia. Space Science Reviews 125: 67-79.
What was done: The authors review the current state of knowledge relative to solar variability and its possible effects on earth's climate.

What was learnedThere are two types of variability related to the flux of solar radiation incident on the earth. The first type, according to Beer et al., "is due to changes in the orbital parameters of the earth's position relative to the sun induced by the other planets," which arises from gravitational perturbations that "induce changes with characteristic time scales in the eccentricity (~100,000 years), the obliquity (angle between the equator and the orbital plane, ~40,000 years) and the precession of the earth's axis (~20,000 years)." The second type of variability in earth-incident solar radiation is due to variability within the sun itself; and it is this subject that occupies the bulk of their review.

Direct observations of total solar irradiance above the earth's atmosphere have only been made over the past quarter century, while observations of sunspots have been made and recorded for approximately four centuries. In between the time scales of these two types of measurements fall neutron count rates and aurora counts. Therefore, 10Be and other cosmogenic radionuclides (such as 14C) stored in ice and sediment cores and tree rings currently provide our only means of inferring solar irradiance variability on a millennial time scale; and as reported by Beer et al., who have studied the subject in depth, these cosmogenic nuclides "clearly reveal that the sun varies significantly on millennial time scales and most likely plays an important role in climate change," especially within this particular time domain.

What it means: In reference to their 10Be-based derivation of a 9,000-year record of solar modulation, Beer et al. note that its "comparison with paleoclimatic data provides strong evidence [our italics] for a causal relationship between solar variability and climate change." And so it does, as may be verified by perusing the many items we have archived under the headings of Solar Effects (Millennial-Scale Cycles and Centennial-Scale Cycles) in our Subject Index.Reviewed 16 May 2007

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