The planet is always going through cycles of warmer and cooler weather, they argue, and eventually temperatures will swing back down.
But new research indicates that what’s happening on Earth right now is unlike anything the planet has experienced in the past 2,000 years — potentially putting an end to the “business as usual” argument once and for all.
On Wednesday, researchers published two new papers in the journals Nature and Nature Geoscience.
In the Nature paper, they detail how they used 700 proxy records of temperature changes to recreate Earth’s climate conditions over the past 2,000 years. Meanwhile, in the Nature Geoscience paper, they focused on charting the planet’s average temperature.
This allowed them to analyze several extended periods of warming and cooling often cited as examples of Earth’s penchant for cycling through temperatures, including the Roman Warm Period from 250 to 400 and the Little Ice Age from 1300 to 1870.
The Nature paper found that no historic period of warming or cooling affected more than half the Earth at any one time — a stark contrast to 20th century warming, which affected more than 98 percent of the planet.
“This paper should finally stop climate change deniers claiming that the recent observed coherent global warming is part of a natural climate cycle,” University College London climatology professor Mark Maslin, who wasn’t involved in the studies, told the BBC.
The Nature Geoscience article, meanwhile, revealed that this warming has never happened so quickly — meaning we literally don’t have time to argue about it anymore.
READ MORE: Climate change: Current warming ‘unparalleled’ in 2,000 years [BBC]
More on climate change: Scientists Are 99.9999 Percent Sure Humans Caused Climate Change