The amount of carbon humans have put into the atmosphere might have already set the planet on a course to 3 to 7 degrees Celsius (5.4 to 12.6 degrees Fahrenheit) of global warming.
According to commentators, this was big amount of warming and the Paris climate accord, adopted less than a year ago by nearly 200 nations, had resolved to cut global carbon emissions so as not exceed 2 degrees Celsius (3.6 degrees Fahrenheit) of warming overall.
But experts dismiss the study's conclusion as ''simply wrong.''
''This is simply wrong,'' Gavin Schmidt, director of NASA's Goddard Institute for Space Studies, told Gizmodo. ''The actual committed warming is only 0.5 to perhaps 1 [degree Celsius] - and nothing in the study changes that.''
The new study, which appeared yesterday in Nature, is a reconstruction of earth's average surface temperature over the past 2 million years. Stanford's Carolyn Snyder collected dozens of sea surface temperature records developed by researchers around the world from ocean sediment cores, which was not an easy feat: ''The communities that produce these data are notoriously cagey about releasing it,'' Schmidt said, adding that Snyder ''did a big amount of work putting together disparate data'' in what will no doubt prove a valuable resource for the climate science community, Gizmodo reported.
Meanwhile, according to commentators, when it came to understanding the earth's past climates, one had to understand what the global temperatures were. Instrument readings only went back to 1800s, so researchers had had to rely on proxies - things that could be measured, like tree ring-width or oxygen isotopes, that reflected the weather conditions at the time.
This has been used for tracking as far back as the end of the last glacial period.
Beyond that, records were sparse and local and ice cores, for instance, went back over 800,000 years, but these only captured polar conditions.