Nature News | 06 Oct 2010
An influence of solar spectral variations on radiative forcing of climate - JD Haigh et alThe Sun may have caused as much warming as carbon dioxide over three years.
An analysis of satellite data challenges the intuitive idea that decreasing solar activity cools Earth, and vice versa. In fact, solar forcing of Earth's surface climate seems to work the opposite way around — at least during the current Sun cycle.
Joanna Haigh, an atmospheric physicist at Imperial College London, and her colleagues analysed daily measurements of the spectral composition of sunlight made between 2004 and 2007 by NASA's Solar Radiation and Climate Experiment (SORCE) satellite. They found that the amount of visible light reaching Earth increased as the Sun's activity declined — warming the Earth's surface. Their unexpected findings are published today in Nature.
The study period covers the declining phase of the current solar cycle. Solar activity, which in the current cycle peaked around 2001, reached a pronounced minimum in late 2009 during which no sunspots were observed for an unusually long period.
Sunspots, dark areas of reduced surface temperature on the Sun caused by intense magnetic activity, are the best-known visible manifestation of the 11-year solar cycle. They have been regularly observed and recorded since the dawn of modern astronomy in the seventeenth century. But measurements of the wavelengths of solar radiation have until now been scant.
- Nature 467 696 (07 Oct 2010) DOI: 10.1038/nature09426
PhysOrg | Earth Sciences | 06 Oct 2010
Sun's activity flies in face of climate expectations
New Scientist | Environment | 06 Oct 2010
Sun's Surprise: Even As It Relaxes, It May Heat Earth's Climate
Space.com | Science | 06 Oct 2010