A new study has drawn the clearest picture yet of the Southern Hemisphere’s climatic history, showing about a thousand years of detailed variations.

The international study has put together an extremely comprehensive reconstruction of past Southern Hemisphere climate records, for a clearer climate picture of the globe’s temperature history.

The study revealed that over the past 1000 years temperature variations have differed greatly between the two hemispheres, however, they appear to have shared a single warm period beginning after the 1970s.

“Our findings showed there were considerable decade-to-decade regional temperature variations in the Southern Hemisphere, that were different to the Northern Hemisphere,” says Dr Joelle Gergis, ARC Fellow from the University of Melbourne.

“But despite the two hemispheres behaving differently over the past 1000 years, what is consistent is the recent warming in the last 40 years.”

The study involved the coordination of an international scientific team with data from past climate information from tree-rings, lake sediments, corals, ice cores and climate modelling.

Scientists compiled climate data from hundreds of different locations and used a range of methods to estimate Southern Hemisphere temperatures over the past 1000 years.

In 99.7 percent of the results, the warmest decade of the millennium occurred after 1970.

Surprisingly, only twice over the entire past millennium have both hemispheres simultaneously shown extreme temperatures.

One of these occasions was a global cold period in the 17th century; the other was the current warming phase.

Lead author Dr Raphael Neukom from Switzerland said the study showed the ‘Medieval Warm Period’, as identified in some European chronicles, was a regional phenomenon.

“During the same period, temperatures in the Southern Hemisphere were only average. Our study revealed it was not a common climate event that many people have previously assumed,” he said.

The investigations showed that regional differences such as these were larger than previously thought.

“This study provided an opportunity to refine regional climate model predictions in the Southern Hemisphere for countries like Australia and South America by extending our understanding of natural temperature variations recorded since 1850 back over the past 1000 years,” Dr Gergis said.

Led by the Oeschger Centre at the University of Bern, the Swiss Federal Research Institute WSL and the University of Melbourne, the study has been published in the journal Nature Climate Change.