Some scientists question the reliability of the observations, whereas others, who accept them as reliable, suggest that the correlation may be caused by other physical phenomena with decadal periods or by a response to volcanic activity or El Niño. (science.sciencemag.org)
Some explain the origins of fire, heavenly bodies and other physical phenomena. (scientificamerican.com)
Perhaps most importantly, the approach used can be applied to other physical phenomena that are described by wave equations, such as acoustics. (sciencedaily.com)