Doyle Rice

USA TODAY

Humanity just sweltered through its hottest summer ever recorded, beating the previous mark set only last year.

From June to August, average temperatures across global land and ocean surfaces soared 1.6 degrees Fahrenheit above the average of 60.1 degrees (F), according to a federal climate report released Tuesday.

The warmth was fueled by a combination of the fading El Niño and the long-term trend of human-caused global warming, according to climate scientist Ahira Sánchez-Lugo of NOAA's National Center for Environmental Information.

Climatologists define summer as the three warmest months of June, July and August. Global climate records go back to 1880.

Before 1880, scientists rely on paleoclimatic records such as ice cores, tree rings and lake sediments that provide an ever further look back in time: "It is plausible that this summer was the warmest in thousands of years, perhaps even longer," said meteorologist Michael Mann of Penn State University.

"There is now very robust paleoclimate evidence that the past decade was likely Earth’s warmest in more than a thousand years, and there is somewhat more tentative but nonetheless compelling evidence that we have moved into territory unseen in more than a hundred thousand years," he added.

Another climate scientist, Gavin Schmidt of NASA, agrees that while individual seasons may be hard to quantify in terms of record warmth, the unusual warmth over the past few decades "seems exceptional in many hundreds and perhaps thousands of years.

"Glacier retreat is indicative of this, since they are unearthing soil, debris, and trees that were buried 1,000, to 4,000, years ago," he said.

Western Alaska, northern South America, central and southern Africa, the Middle East, northwestern and Far East Russia, China, Indonesia and New Zealand all tallied record warmth this summer, NOAA said.

Last month also marked the hottest ever for August, which was also the 16th straight month to set a global heat record, according to Sánchez-Lugo.

The last time the Earth had a cooler-than-average month was December 1984, Sánchez-Lugo said. The "average" in this case is the average 20th-century temperature.

The first eight months of the year were also record warm, putting 2016 on track to be the warmest year on record.