Global heating in recent decades is of a pace and magnitude that's unique in at least the past two millennia, with human-caused climate change now "overwhelming" natural variability, new research has found.

According to three papers published in Nature and Nature Geoscience on Thursday, international teams of scientists used seven different statistical techniques to reconstruct global temperature during the so-called Common Era starting 2000 years ago.

The scientists studied variability over decades and centuries, including well-known periods of shifting temperatures such as the Medieval Warming Period and the Little Ice Age. They found no era had the spatial extent or intensity of the heating over recent decades.

"Periods of warming and cooling have happened in the past but they were nowhere near the magnitude or the speed of the current warming," said Benjamin Henley, a University of Melbourne researcher and co-author of one of the papers. "The main, overwhelming impact on the climate has been in the recent decades, since about 1950."