For the first decade of the twenty-first century, global warming seemed to take a vacation. The early 2000’s saw a much slower rate of warming at Earth’s surface than previous years, fueling skepticism about climate change. But recent studies show that global warming has neither slowed nor disappeared—it’s just very complex.

Scientists at both the National Center for Atmospheric Research (NCAR) and the University of Tokyo have concluded that natural variation likely caused the apparent “hiatus” in global warming. Random shifts in the atmosphere can alter wind patterns, which then change ocean currents. This affects how ocean water mixes, and can cause heat to be pushed into the deep ocean and trapped there. Scientists have determined that this is what occurred during the hiatus period. The excess heat was still there, but hidden from surface measurements. This process “has happened before, and will happen again,” according to Gerald Meehl, the lead author of the NCAR paper. Scientists also believe other factors, including particles from volcanic eruptions, may have helped cool the Earth during the hiatus period—adding to the apparent pause in warming.

Erwan Monier, a research scientist at MIT’s Center for Global Change Science who was not involved in these studies, says these new findings help scientists understand why the hiatus occurred, and show that the theory behind global warming is “not disputable.”

Meehl writes that new methods for climate analysis, which incorporate natural variability over time, could have predicted the hiatus in advance. He stresses that climate fluctuations are normal, and “global warming is not a relentless upward trend.” Still, such variability can make predicting climate change difficult. Haiyan Teng, Meehl’s co-author at NCAR, puts it this way: “We’re like blind people trying to feel an elephant—we’re only seeing a small part of the picture.”