Earth is having its second-warmest year to date, and it's not over yet.

Global temperature departures from average during Sept. 2017.

Image: nasa giss.

Planet Earth has had its second-warmest year so far, and in the end, 2017 may wind up being the third-warmest year on record, ranking just behind behind 2016 and 2015. This year is also headed for the warmest year to occur without any El Niño or La Niña event in the tropical Pacific Ocean.

El Niño and La Niña events influence global average surface temperatures. El Niño in particular is well-known to boost global average temperatures on top of the long-term warming due to human emissions of greenhouse gases. This is what helped vault 2015 and 2016 to the top of the record warm years list, and this year’s lack of an El Niño event could keep 2017 at number three. 

New data released on Wednesday shows that the first nine months of the year ranked just 0.23 degrees Fahrenheit behind the record warmth seen in 2016. However, the same period only exceeded 2015 by 0.02 degrees Fahrenheit, and 1998 by 0.34 degrees Fahrenheit, according to the National Oceanic and Atmospheric Administration (NOAA).

The month of September was the fourth-warmest such month for the globe on record, according to both NOAA and NASA. 

January to September average temperatures between 1880 and 2017, showing the increasing trend.

January to September average temperatures between 1880 and 2017, showing the increasing trend.

Image: noaa/ncei

The warmth in 2017 continues the trend of increasing global average surface temperatures that has accelerated in recent years, due to a combination of the emissions of greenhouse gases, such as carbon dioxide and methane, along with natural climate variability. 

The 10 warmest Septembers have occurred since 2003, according to the National Centers for Environmental Information (NCEI) in Asheville, North Carolina. In a report, NCEI scientists found that September 2017 marked the 41st straight September, and 393rd straight month with temperatures “at least nominally above the 20th century average.”

The last cooler-than-average month on Earth occurred in December of 1984, the same year that Steve Jobs introduced the first Macintosh computer.

Further driving home the point that the climate is headed further into record territory, the report found that nine of the 10 warmest January through September periods have occurred since 2005, with just one of the 10 warmest such periods occurring during the 20th century.

A weak La Niña event that may develop in the next three months could cause slightly lower global average temperatures toward the end of the year. This should help 2017 slide into the number three slot on the list of warmest years since modern record-keeping began in 1880.

Year-to-date global average temperatures compared to other warmest years.

Year-to-date global average temperatures compared to other warmest years.

Image: noaa/ncei

In the Arctic, cooler and cloudier than average weather patterns during the summer melt season helped keep loss of sea ice to a relatively insignificant level. 

On Sept. 13, Arctic sea ice reached its annual minimum extent, at 1.79 million square miles, which was the eighth-smallest minimum extent in the satellite data record. This was the largest amount of sea ice remaining at the end of the summer melt season since 2014, but was still more than 400,000 square miles below the long-term average. 

Arctic sea ice is rapidly declining because of increasing temperatures in the Arctic, and feedback loops inherent in the climate of the Far North that ensure the region is experiencing about twice the rate of global warming as the rest of the world. 

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