If carbon didn’t warm us, what did?

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 right, an active field means a warming earth with fewer clouds. A quiet sun though, means a cooler earth with more clouds.

AGW replies: Lochwood and Frohlich showed the theory doesn’t fit rising temperatures after 1980.

Skeptics say: They used surface temperatures, not atmospheric ones (see the graph above). Cosmic rays correlate well with temperatures from weather-balloons. But thermometers on the surface are affected by things like car-parks, and air conditioners which are close to the sensors. All that Lockwood and Frohlich prove is that there’s no link between cosmic rays and air conditioners.

Skeptics say: That’s only true if you look at the wrong kind of rays and the wrong kind of clouds. There’s a good correlation between high energy rays and low clouds.

The correlation between cosmic rays and temperature is much better over all time spans than that with carbon and temperature.

Sources: Reply to Lockwood and Frohlich Svensmark 2007. Falls in cosmic rays affect low clouds Svensmark 2009, see also Linkages between solar activity, climate predictability and water resource development, Alexander.

Looks like your article covers it well enough. I'll just add this...

The Center for Sun-Climate Research at the DNSC (Danish National Space Center) investigates the connection between variations in the intensity of cosmic rays and climatic changes on Earth. This field of research has been given the name 'cosmoclimatology'"..."Cosmic ray intensities – and therefore cloudiness – keep changing because the Sun's magnetic field varies in its ability to repel cosmic rays coming from the Galaxy, before they can reach the Earth." :
http://www.spacecenter.dk/research/sun-climate
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Climate debate and FAQ:

What is climate research at the DNSC? [Danish National Space Center]

The Earth’s climate is always changing. This has been the case in the geological and historical time and even during the last 150 years, where systematic climate measurements have been made, we have seen clear climate changes.

Climate changes have both a scientific and a social perspective. The social perspective is associated with the range of climate change that can be attributed to the increasing human induced contribution. The scientific perspective is an endeavour to understand the full complex system of the various sources of climate change and their mutual interactions.

The Danish National Space Center, DNSC, comprises the country's largest collected expertise in the scientific disciplines that play a major and documented role in the understanding of climate change both in geological and historical time, namely variations in solar activity. DNSC regards it essential that this collected expertise is being used in an attempt to understand the natural causes of climate change in order to evaluate the contribution of natural causes to global change. Taking into account the large uncertainty associated with the estimated human contribution, a good research based estimate of the range of natural climate variations is an essential information.

DNSC is basing its effort in this area on own scientific results – observational, experimental, and theoretical. The scientific results have been published internationally and indicate that the varying activity of the Sun is indeed the largest and most systematic contributor to natural climate variations. The effect goes through solar modulation of the cosmic radiation, which affects the formation of aerosols and thereby also the formation of clouds. Even though a physical mechanism connecting cosmic rays to aerosol formation has been found experimentally, no climate model has yet made an attempt to include such an effect.

That there exists a significant contribution from solar activity variations to global temperature increase does not, however, exclude other contributions to the rising global temperature, natural as well as human. DNSC, however, is focused on establishing the best possible and scientifically based evaluation of the size of solar induced effects on climate.

Why is the climate changing?

Climate is subject to influences by both natural and human forces, including greenhouse gases, aerosols, solar activity, and land use change. The climate system is extremely complex and any estimate of the human contribution to climate change is very uncertain.

What are the natural causes to climate change?

Changes in the Sun contribute to climate change. Solar activity has been exceptionally high in the 20th century compared to the last 400 years and possibly compared to the past 8,000 years. When solar activity is high, the flux of galactic cosmic rays is reduced due to increased magnetic shielding by the Sun. The cosmic rays may influence Earths climate through formation of low lying clouds.

How can cosmic rays influence cloud formation?

Cosmic rays ionize the atmosphere and an experiment performed at the Danish National Space Center has found that the production of aerosols in a sample atmosphere with condensable gases (such as sulphuric acid and water vapor) depends on the amount of ionization. Since aerosols work as precursors for formation of cloud droplets, this is an indication that cosmic rays affect climate.

Climate models only include the effects of the small variations in the direct solar radiation (infrared, visible and UV). The effects of cosmic rays on clouds are not included in models and the models do a rather poor job of simulating clouds in the present climate. Since cloud feedbacks are a large source of uncertainty, this is a reason for concern when viewing climate model predictions.

http://www.spacecenter.dk/research/sun-climate/climate-debate-and-faq
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Here's an excellent ~new book out on the subject titled "The Chilling Stars, 2nd Edition: A Cosmic View of Climate Change". It's written by one of the top scientists advancing the theory (Henrik Svensmark, of the above mentioned Danish National Space Center/DNSC).

"The authors explain their theory that sub-atomic particles from exploded stars have more effect on the climate than manmade CO2."
http://www.sciencedaily.com/books/t/1840468157-the_chilling_stars_the_new_theory_of_climate_change.htm

Amazon Books: "The Chilling Stars, 2nd Edition: A Cosmic View of Climate Change"
http://www.amazon.com/Chilling-Stars-2nd-Cosmic-Climate/dp/1840468661 zs90]

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