The other large force at work, the Pacific decadal oscillation, is a long period — sometimes, as the name implies, spanning decades — of relatively cooler or warmer water. Since about the year 2000, the oscillation has been in a cool state, which many climate scientists say has allowed the ocean to soak up a great deal of the heat generated by greenhouse gases as part of climate change.

This, in turn, may have kept global average surface temperatures from rising. Climate scientists have called that condition the warming hiatus, and those who deny the overwhelming scientific consensus on warming have used the hiatus to raise doubts about whether climate change exists.

Now, however, the oscillation appears to be entering a warming phase, said Gerald A. Meehl, a senior scientist at the National Center for Atmospheric Research, and strong El Niños tend to nudge the cycle into a new phase. So the oscillation and El Niño “can all add together to give you a really big shift” toward warming over all.

“That’s going to provide a bigger boost to a global warming system,” he said. “These things will add together.” Already, 2015 is on track to be the hottest year in the historical record.

Climate change could nudge all of the interacting cycles of ocean heat and cold. Scientists are still trying to determine its effect on hurricanes, though it is widely believed that because warm ocean water provides the energy for hurricanes, the more powerful storms will grow even more potent over time.

Whether there is a clear and detectable human-caused component to today’s cyclone activity is harder to prove, said Thomas R. Knutson, a research meteorologist with NOAA’s geophysical fluid dynamics laboratory at Princeton. “We don’t expect to necessarily be able to detect these changes at this time,” he said.