Dr White thinks there may be an unknown one that varies on roughly the same timescale as the more regular solar cycle, and thus tends to fall into step with it, amplifying the solarvariation.
The research indicated that influences in solar changes and intermittent volcanic activity have accounted for at least 80% of observed climate variation over the past half century.
In an interesting variation on this theme, last year construction giant KB Home struck a deal with a Chinese solar company, BYD, to build new, moderately-priced homes with solar panels already installed in Lancaster, California.