01:35 Report: 2017 One of Top 3 Warmest Years Ever Meteorologist Ari Sarsalari talks about a new report shows that last year was one of the three warmest years ever on Earth.

At a Glance Earth's average temperature in 2017 ranked among the three warmest years on record.

This continues a trend of long-term warming temperatures.

Heat released from the oceans may have played a role in boosting temperatures in recent years.

The long-term warming trend of Earth's climate continued in 2017, a year confirmed among the three hottest on record, according to separate analyses released Thursday by NASA and NOAA.

NASA's Goddard Institute for Space Studies (GISS) said 2017 was the second-hottest year in their database , which extends back to 1880. The past year ranked second to 2016 and knocked 2015 into third place in NASA's rankings.

Since 2001, the planet has recorded 17 of its 18 warmest years since record-keeping began, NASA added.

"Despite colder-than-average temperatures in any one part of the world, temperatures over the planet as a whole continue the rapid warming trend we've seen over the last 40 years," said GISS Director Gavin Schmidt.

NOAA calculated that 2017 was the third-warmest year on record in its database .

The small difference in rankings between NASA and NOAA is due to differences in how temperatures are analyzed by both agencies.

Earth's four hottest years on record have now occurred since 2014, led by 2016, which holds the top spot, according to NOAA.

<img class="styles__noscript__2rw2y" src="https://dsx.weather.com/util/image/w/noaa-temp-trend.jpg?v=at&w=485&h=273&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0" srcset="https://dsx.weather.com/util/image/w/noaa-temp-trend.jpg?v=at&w=485&h=273&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0 400w, https://dsx.weather.com/util/image/w/noaa-temp-trend.jpg?v=ap&w=980&h=551&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0 800w" > The long-term trend of warming global temperatures from the late-1800s to 2017. (NOAA)

Last year, the planet's mean surface temperature was 0.84 degrees Celsius above the 20th-century average. That's warmer than the 2014 departure from average of 0.74 degrees Celsius, but just cooler than 2016 and 2015, which were 0.94 degrees Celsius and 0.9 degrees Celsius above average, respectively.

Ultimately, what's most important is not whether a given month is a fraction of a degree warmer or colder; rather, it's the overall trend, which continues its upward climb since the late 1970s.

The globe hasn't had a cooler-than-average year since 1976 – a stretch of 41 consecutive warm years – NOAA said. All of the 20 warmest years have occurred since 1995 , and 17 of those years have come this century.

Much of the globe's recorded temperatures were near or above average in 2017, according to NOAA. Pockets of record warmth were observed in North America, South America, Africa, Europe, Asia and Australia.

<img class="styles__noscript__2rw2y" src="https://dsx.weather.com/util/image/w/noaa-analysis_0.jpg?v=at&w=485&h=273&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0" srcset="https://dsx.weather.com/util/image/w/noaa-analysis_0.jpg?v=at&w=485&h=273&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0 400w, https://dsx.weather.com/util/image/w/noaa-analysis_0.jpg?v=ap&w=980&h=551&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0 800w" > Analysis of global temperatures in 2017. No data is available for the areas shaded gray. (NOAA/NCEI)

NOAA also reported that Arctic sea ice extent in 2017 was the second-smallest for an annual average since records started in 1979. Antarctic sea ice averaged the lowest for any year in that same period of time.

Recent Record Warmth Caused By Heat Released From Oceans

A new study says the spike in global temperatures from 2014 to 2016 was caused by "unusually large" releases of oceanic heat.

"This heat had built up since the 1990s mainly due to greenhouse-gas forcing and possible remote oceanic effects ," said the scientists who authored the study from the University of Arizona, Princeton University, GFDL/NOAA and the University of Michigan.

The strong El Niño of 2015-16 helped to release a large amount of heat that built up in the western tropical Pacific Ocean. That heat release led to the boost of global temperatures in the three-year period.

Authors of the study say more record-breaking global warmth is likely in the future unless action is taken to curb emissions.

"Large record-breaking events of global surface temperature are projected to increase in the future unless greenhouse-gas forcing is reduced," the study concluded.