 Short-term hiatus periods of global warming are compatible with long-term climate change patterns.The North Atlantic Oscillation (NAO) leads to multidecadal variability in Northern Hemispheric mean surface temperature by 15–20 years through a delayed effect on the North Atlantic Ocean, and can be a useful predictor of multidecadal periods of warming and cooling in both AMO and Northern Hemispheric mean surface temperature.A study published in January 2015 proposed that the hiatus resulted from a 60-year oscillatory pattern of natural variability ssociated with the AMO and PDO, interacting with a secular warming trend due mainly to human caused increases in greenhouse gas levels.