Studies show rapid rise
Recent warming events have been unmatched in the past 2,000 years, according to international and Australian researchers.
A suite of new studies have used seven different statistical methods to look at 2,000-year-long global data on average temperatures.
It finds the largest warming trends have happened in the second half of the 20th century. The data highlights the unusual character of warming in recent decades, the experts say.
Another paper has looked at the rates of surface warming and driving forces, and also found that all rates of warming were fastest in the later 20th century.
The assessment of the global patterns of climate variability finds that before the 20th century, climate epochs did not occur simultaneously across the globe.
For example, the coldest temperatures over the Common Era occurred in central and eastern Pacific regions in the 15th century, in northwestern Europe and southeastern North America in the 17th century, and elsewhere during the 19th century.
Similarly, no pre-industrial period experienced globally coherent, long-term warmth.
By contrast, the warmest period during the Common Era occurred in its final decades for more than 98 per cent of the globe.
The analyses reveal that rates of warming over periods of at least 20 years were fastest during the later 20th century. Pre-industrial fluctuations were primarily driven by volcanic activity. Agreement between reconstructions and simulations suggests that climate forecasts for the next few decades may be realistic, the authors say.
“The findings give us the clearest picture yet of the speed and global extent of modern climate change relative to the pre-industrial climate of the last 2000 years,” says one of the study’s authors, University of Melbourne researcher Ben Henley.
“Our study shows that the most rapid warming of the past 2000 years has occurred during, and since, the second half of the 20th century, highlighting the extraordinary character of current climate change, due mostly to human emissions of heat-trapping gases.
“We humans are responsible for immense changes to the global climate. It is up to the global community to determine if this is what we want to be doing to our planet. Australia has an important part to play in that global community.”