The earth has had warmer-than-average temperatures for 400 straight months now

The dubious milestone was reported in the April edition of NOAA's monthly global climate report. The report also states that this April had the third-highest temperatures of any April since NOAA began collecting such records in 1880.

"It's mainly due to anthropogenic (human-caused) warming," NOAA climatologst Ahira Sanchez told CNN. "Climate change is real, and we will continue to see global temperatures increase in the future."

There are natural causes for warmer years, too.

"If you were to remove the human factor, you would still see a variability, but it would be up and down," Sanchez says.

Natural factors like the warming effects of an El Niño or the cooling effects of a La Niña have an impact on global average temperatures.

2016 was the warmest year on record, and it featured a strong El Niño system.

Similarly, during significant volcano eruptions, global temperatures can go down because the ash and smog deflects solar radiation away from the earth.

When climatologists talk about temperatures and averages, they are comparing the numbers to the 20th Century averages of a given month or year. So "higher than average," in this case, means higher than the average temperatures of the 100 years between 1900 and 2000.

The bottom line is, 18 of the warmest 19 years have occurred since 2000. While natural factors can account for some of those anomalies, NOAA scientists say the overall pattern is definitely not natural.