WASHINGTON — It sounds like a broken record: Last month again set a new mark for global heat. And meteorologists say Earth is on pace to tie the hottest year ever recorded, or more likely, to break it.

The National Oceanic and Atmospheric Administration announced today that last month the globe averaged 60.3 degrees Fahrenheit. That was the hottest September in 135 years of record keeping.

It was the fourth monthly record set this year, along with May, June and August.

NASA, which measures temperatures slightly differently, had already determined that September was record-warm.

The first nine months of 2014 have a global average temperature of 58.72 degrees, tying with 1998 for the warmest first nine months on record, according to NOAA’s National Climatic Data Center in Asheville, N.C.

“It’s pretty likely” that 2014 will break the record for hottest year, said NOAA climate scientist Jessica Blunden.

The reason involves El Niño, a warming of the tropical Pacific Ocean that affects weather worldwide. In 1998, the year started off super-hot because of an El Niño. But then that El Niño disappeared and temperatures moderated slightly toward the end of the year.

This year has no El Niño yet, but forecasts for the rest of the year show a strong chance that one will show up, and that weather will be warmer than normal, Blunden said.

If 2014 breaks the record for hottest year, that also should sound familiar: 1995, 1997, 1998, 2005 and 2010 all broke NOAA records for the hottest years since records started being kept in 1880.