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Cosmoclimatology: A New Perspective on Global Warming
Volume 10, Number 8: 21 February 2007

Has recent global warming primarily been caused by increases in the air's CO2 content? Or has it been caused by reductions in low-level cloudiness that have caused less solar radiation to be reflected back to space, thereby permitting more solar energy to warm the earth? Henrik Svensmark, Director of the Center for Sun-Climate Research of the Danish National Space Center in Copenhagen, thinks the latter; and in an enlightening article published in the February issue of Astronomy & Geophysics (Svensmark, 2007) he tells us why.

Svensmark begins by describing how he and his colleagues experimentally determined that electrons released in the air by galactic cosmic rays act as catalysts that significantly accelerate the formation of ultra-small clusters of sulphuric acid and water molecules that are the building blocks of cloud condensation nuclei. He then discusses how the flux of cosmic rays through the atmosphere is affected by variations in solar magnetic activity. During periods of greater activity, greater shielding of the earth occurs, less cosmic rays penetrate to the lower atmosphere, less cloud condensation nuclei are produced, fewer and less reflective low-level clouds occur, and more solar radiation is absorbed by the surface of the earth, increasing near-surface air temperatures.

Support for key elements of this scenario is provided by graphs illustrating the close correspondence between global low-cloud amount and cosmic-ray counts over the period 1984-2004, as well as by the history of changes in the flux of galactic cosmic rays since 1700, which correlates well with earth's temperature history over the same time period, starting from the latter portion of the Maunder Minimum (1645-1715), when Svensmark says "sunspots were extremely scarce and the solar magnetic field was exceptionally weak," and continuing on through the 20th century, over which last hundred-year interval, as noted by Svensmark, "the sun's coronal magnetic field doubled in strength."

Continuing to expand the timescale of interest, Svensmark next cites the superlative work of Bond et al. (2001), who in studying ice-rafted debris in the North Atlantic Ocean determined, in the words of Svensmark, that "over the past 12,000 years, there were many icy intervals like the Little Ice Age" that "alternated with warm phases, of which the most recent were the Medieval Warm Period (roughly AD 900-1300) and the Modern Warm Period (since 1900)." And as we note in our review of Bond et al.'s work, the ten-member team clearly states that "over the last 12,000 years virtually every [our italics] centennial time-scale increase in drift ice documented in our North Atlantic records was tied to a solar minimum."

In another expansion of timescale - this one highlighting the work of Shaviv (2002, 2003) and Shaviv and Veizer (2003) - Svensmark presents plots of reconstructed sea surface temperature anomalies and relative cosmic ray flux over the last 550 million years, during which time the solar system experienced four passages through the spiral arms of the Milky Way galaxy, with the climatic data showing "rhythmic cooling of the earth whenever the sun crossed the galactic midplane, where cosmic rays are locally most intense." In addition, he notes that the "Snowball Earth" period of some 2.3 billion years ago "coincided with the highest star-formation rate in the Milky Way since the earth was formed, in a mini-starburst 2400-2000 million years ago," when, of course, the cosmic ray flux would have been especially intense.

In light of these many diverse observations, Svensmark concludes "it now seems clear that stellar winds and magnetism are crucial factors in the origin and viability of life on wet earth-like planets," as are "ever-changing galactic environments and star-formation rates." And within this expansive context of both space and time, humanity's emissions of CO2 literally fade away into climatic insignificance.

Sherwood, Keith and Craig Idso

Bond, G., Kromer, B., Beer, J., Muscheler, R., Evans, M.N., Showers, W., Hoffmann, S., Lotti-Bond, R., Hajdas, I. and Bonani, G. 2001. Persistent solar influence on North Atlantic climate during the Holocene. Science 294: 2130-2136.

Shaviv, N. 2002. Cosmic ray diffusion from the galactic spiral arms, iron meteorites, and a possible climatic connection. Physics Review Letters 89: 051102.

Shaviv, N. 2003. The spiral structure of the Milky Way, cosmic rays, and ice age epochs on Earth. New Astronomy 8: 39-77.

Shaviv, N. and Veizer, J. 2003. Celestial driver of Phanerozoic climate? GSA Today 13 (7): 4-10.

Svensmark, H. 2007. Cosmoclimatology: a new theory emerges. Astronomy & Geophysics 48: 1.18-1.24.