The Earthly impact of the Sun's 11-year solar cycle has always seemed like one of the more reliable and straightforward elements in the vast array of climate variables. On the rise, solar radiation increases and so warms the planet a little -- the thinking goes -- and on the way down a subtle cooling takes place.
Now, a new piece of research argues that's not necessarily so. Looking inside at the individual wavelengths of solar radiance as measured by a satellite-borne device called the Spectral Irradiance Monitor, scientists report that in their study of these measurements during the declining phase of the solar cycle between 2004 and 2007, the opposite pattern emerges.
Reporting in the journal Nature, scientists from the University of Colorado and Imperial College London say that the amount of visible radiation reaching Earth actually increased rather than decreased during this period of solar cycle decline, slightly warming rather than cooling the planet.
With these findings in hand, the researchers observe that the overall increase in solar activity during the past century may have led to a small cooling effect from the Sun, rather than a warming effect as previously thought.
Physicist Joanna Haigh of Imperial College, lead author of the study, cautioned:
"We cannot jump to any conclusions based on what we have found during this comparatively short period and we need to carry out further studies to explore the Sun's activity, and the patterns that we have uncovered, on longer timescales. However, if further studies find the same pattern over a longer period of time, this could suggest that we may have overestimated the Sun's role in warming the planet, rather than underestimating it."
by "environment clean generations"