A popular climate sceptic theory - that the Earth's recent warming is simply a return to the norm after an unusually cool period - has now been busted, scientists say.
The 'Little Ice Age' lasted from the Renaissance period until about 1850, and saw parts of Europe and North America suffer chilling winters, with rivers frequently frozen over and crops failing.
The Earth has warmed considerably since then as we all know, with climate scientists blaming the rapid rise in emissions of greenhouse gases since the mid-1800s. Sceptics have long argued that if climate change is happening it's a natural process - and to be expected after centuries of cooler temperatures.
But two new studies, published Thursday in journals Nature and Nature Geoscience, have found the recent upswing in temperatures worldwide is unprecedented. They looked at not just recorded temperature data, but other evidence closely linked with temperature, such as tree rings, ice cores, lake sediments and corals.
"It's true that during the Little Ice Age it was generally colder across the whole world," said lead author of one of the studies Raphael Neukom, "but not everywhere at the same time. The peak periods of pre-industrial warm and cold periods occurred at different times in different places."
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With a lack of data from other parts of the world, previous research only looked at North America and Europe.
"In the absence of data from other parts of the Earth, this notion was applied to the whole planet, raising expectations that relatively cold or warm periods throughout the last 2000 years were globally synchronous phenomena. But it has now been shown that this was not the case," the researchers said in a statement.
It got cold in different places at different times largely due to local phenomena - usually volcanic eruptions - and random fluctuations, the new research found.
"The coldest temperatures... 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," the researchers said.
Even the Medieval Warm Period - which preceded the Little Ice Age - affected less than half the planet.
In contrast, the recent change in temperatures - a constant, fast rise - has affected 98 percent of the world.
"This shows - once again - that modern climate change cannot be explained by random fluctuations, but by anthropogenic emissions of CO2 and other greenhouse gases," the researchers said.
"What we didn't know until now is that not only average global temperatures in the 20th century are higher than ever before in at least 2000 years, but also that a warming period is now affecting the whole planet at the same time for the first time. And the speed of global warming has never been as high as it is today."
"There is no doubt left - as has been shown extensively in many other studies addressing many different aspects of the climate system using different methods and data sets," Stefan Brönniman, who led the second study, told the Guardian.
Paleoclimatologist Jennifer Hertzberg told NBC News the studies were "very important" and should spark action.
"The global temperatures that we're seeing now are higher than they have been in the last 2000 years," she told the broadcaster. "What we're seeing now is uncharted territory. It's time for everybody to wake up and make changes now."