Multi-decadal climate changes have significant ecological and societal impacts. Even small changes in temperature and rainfall, when they persist for decades, can affect many sectors, from water resource management to agriculture to coastal-zone planning. Multi-decadal fluctuations have long been assumed to be driven by the ocean circulation. Focusing on the Atlantic, we discuss challenges to diagnosing the drivers of climate changes at these timescales, and question this longstanding assumption.
In particular, most previous explanations identify the driver of the Atlantic multi-decadal variability (AMV) as natural changes in the ocean circulation. Applying a novel experimental design to climate models, we argue that this is not the case. Instead, we show that common diagnostic frameworks often fail to identify the main drivers, and we propose a more complete attribution of the causes of AMV, including multi-decadal changes in anthropogenic forcing. We discuss the implications of these results for predicting climate changes of the coming decades.