Earth warmed more in the last three decades of the 20th century than it has during any 30 year period in the last 1,400 years, according to a study published Sunday.

Over the past 1,400 years, the Earth experienced a gradual cooling, according to the study, published in the journal Nature Geoscience. Between 1971 and 2000, all of the cooling was entirely reversed. More than 80 scientists in 24 countries collaborated on the report, and the findings were made using a series of climate data from ice cores, lake and ocean sediments, historical records, cave formations and tree rings.

2003's European heat wave and drought was the continent's warmest summer in at least 2,000 years, according to the study.

The study suggests that the so-called "Medieval Warm Period," a period of increased temperatures between 950 and 1250 in Europe and North America, may have been limited to just those regions – new data suggests South America stayed cool during those years.

Edward Cook, of Columbia University's Lamont-Doherty Earth Observatory and leader of the study, says the finding suggests Earth's most recent warming, which can be seen worldwide, can be attributed to humans and not normal Earth patterns.

"If we went into another Medieval Warm Period again, that extra warmth would be added on top of warming from greenhouse gases," Cook said in a statement. "This paper tells us what we already knew, except in a better, more comprehensive fashion."