Study 'finds that the natural Pacific Decadal Oscillation [PDO] and Atlantic Multidecadal Oscillation [AMO] are responsible for about 50% of the warming observed over the past 30 years. According to the author, "In the past 30 years, the two multi-decadal oscillations contribute about half of the global mean surface temperature warming." Prior research has shown that solar activity changes were responsible for at least 50% of the observed warming over the past century. In addition, solar activity has been shown to influence ocean oscillations. Thus, most or all of the observed warming in recent decades can be attributed to natural causes.'