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Study finds global warming over past 400 years was due to increased Solar activity

TODAY June 7th 2011: Phenomenal eruption on the sun (see the bottom of the post for more info).

Apparently previous studies of the sun-climate connection looked at the equatorial polar magnetic field which produces sun spots, but they did not consider the polar magnetic component of the solar dynamo. The polar fields are less strong than the equatorial fields, but it is claimed that the total magnetic fluxes of both fields are comparable. With proxy data they derive an empirical relation between tropospherical temperatures and solar equatorial and polar magnetic fields. The polar field could contribute about 30% as much as the equatorial field.

The paper, published in the Journal of Atmospheric and Solar-Terrestrial Physics focused on the period 1844-1960 (but extended at least one graph back to 1600) and finds our current warming period is not that different from earlier episodes and that the increase in solar activity in the last 400 years explains the warming, without any need to invoke a man-made enhanced greenhouse hypothesis.

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If carbon didn’t warm us, what did?

Svensmarks Cosmic Ray Theory. TOP: If the sun's magnetic field is weak it allows more cosmic rays, which may seed more clouds on Earth. BOTTOM: A strong solar magnetic field blocks the same rays and could mean less clouds and clearer skies.

People have known for 200 years that there’s some link between sunspots and our climate.  In 1800, the astronomer William Herschel didn’t need a climate model, he didn’t even have a calculator — yet he could see that wheat prices rose and fell in time with the sunspot cycle. Since then, people have noticed that rainfall patterns are also linked to sunspots.

Sunspots themselves don’t make much difference to us, but they are a sign of how weak or strong the sun’s magnetic field is. This massive solar magnetic field reaches out around the Earth, and it shields us from cosmic rays. Dr Henrik Svensmark has suggested that if more cosmic rays reach further down into our atmosphere, they might ionize molecules and help “seed” more clouds. As it happens, this year, the sun has almost no sunspots, but for much of the late 20th Century, the solar magnetic field was extremely active. If the theory is [...]