NASA and NOAA both announced today that 2017 was among the 3 warmest years on earth

NASA's analysis of global surface temperature data found that 2017 was the second warmest on record, with a global average surface temperature falling just short of the record warmth in 2016.  NOAA's analysis found that global average surface temperature was slightly cooler, resulting in 2017 ranking as the third warmest year.  Worldwide temperature records extend back 138 years, to 1880.

Why the difference in ranking?  NOAA and NASA are two independent keepers of the global temperature record.  In an email, Gavin Schmidt, director of NASA's Goddard Institute for Space Studies explained:

This reflects the fact the NASA’s calculations are extended to account for temperature changes at the poles, where there are far fewer monitoring stations, but where warming (specifically in the Arctic) has been more rapid relative to non-polar regions. NOAA NCEI does not use any extrapolation to account for sparse station density at the poles, and only reports the temperature averaged over areas with dense coverage.

This explanation was agreed upon by NOAA/NCEI.

During the announcement Schmidt also said that, while there are slight differences in the details from year-to-year, the overall warming trend is clear.

• The last four consecutive years (2014, 2015, 2016, and 2017) have all ranked in the top four warmest years on record
• The 5 hottest years on record have come since 2010
• The 10 hottest years have come since 1998
• The last 41 years in a row have been warmer than the 20th century global temperature average

What's remarkable about the extreme warmth that 2017 saw is that it occurred without the help of an El Nino pattern.  El Nino is the name given to the cyclical warming of ocean water in the equatorial Pacific Ocean, and often helps to raise global mean surface temperatures.

As this writer at Mashable said, these visualizations comparing earth's temperature to average each year since since 1850 look like disturbing modern art. They also deliver the point clearly -- the earth is warming, it's caused primarily by human activities, and it's fixable... if we act now.