The past decade was the warmest on record, government science agencies announced Wednesday.
That conclusion, based on newly released data, also found that 2019 was the second-hottest year in recorded history.
The yearly analysis is a closely watched indicator of the Earth's changing climate, particularly as projections for future years anticipate the trend to continue.
“Every decade since the 1960s has been warmer than the decade previously, and not by a small amount,” Gavin Schmidt, director of the NASA Goddard Institute for Space Studies in New York City, told reporters in a news briefing Wednesday.
Average global temperatures in 2019 were 1.71 degrees Fahrenheit (0.95 degrees Celsius) warmer than the 20th century average, according to separate independent analyses by NASA and the National Oceanic and Atmospheric Administration (NOAA).
Last year fell just shy of 2016, which remains the hottest year in NOAA’s 140-year climate record. Part of 2016's record warmth is attributable to that year's strong El Niño event, a naturally occurring climate pattern that has far-ranging effects on global temperatures, rainfall, hurricanes and severe storms. But, Schmidt said that the planet's warming trend persists even if scientists ignore the effects of El Niño episodes and their opposite, La Niña.
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"It would have changed the order of the years slightly — 2017 would have been the warmest year in the absence of an El Niño effect, and 2019 would have been the third-warmest year," he said. "Whether you think the El Niño and La Niña effect is important or not, the basic results are consistent regardless of that."
The agencies also found that ocean temperatures in 2019 were the highest ever recorded, which could contribute to ocean acidification, sea-level rise and extreme weather. These findings were consistent with a study published earlier this week in the journal Advances in Atmospheric Sciences that found record-high ocean temperatures in 2019 and evidence that the world's oceans are warming at an accelerated pace.
Deke Arndt, chief of climate monitoring at NOAA's National Centers for Environmental Information, said that temperatures in the top 2,000 meters of the ocean hit "a new mark."
"It's an important measure because roughly 90 percent of the additional warming due to greenhouse gases is transferred into the upper ocean," he added.
Arctic sea ice continued to decline in 2019, with the second-smallest average yearly sea ice coverage recorded in both the Arctic and the Antarctic oceans since 1979.
The agencies found that the past five years have been the warmest since record-keeping began in 1880, and 2019 marked the 43rd consecutive year that global land and ocean temperatures were above average.
A report released by the Intergovernmental Panel on Climate Change in October 2018 stated that the planet had already warmed by 1 degree Celsius since the 19th century, and warned that further warming by 1.5 degrees could trigger melting ice, extreme heat and rising seas that may be life-threatening for tens of millions of people around the world. The trend in the newly released NASA and NOAA report could be bad news for those projections.
"The warming up until now, since the 1970s, has been quite close to linear," Schmidt said. "If you extrapolate that forward, you would imagine we would cross 1.5 [degrees Celsius] in around 2035."
But he added that there are yearly variabilities to consider, as well as potential progress that could be made by cutting greenhouse gas emissions.
"We aren't able to tell you, by looking at the past, how society will actually react to this information."