August was the sixth month in 2015 that has broken its monthly temperature record since records began in 1880 – following February, March, May, June, July, and August.
Temperatures during the period of January to August were o.84C (1.51F) above the 20th century average, with August temperatures clocking in at 0.88C (1.58F) above the long-term average.
In the summary published on Thursday, scientists said that manmade global warming as well as climate phenomenon El Niño were the cause.
Deke Arndt, chief of the monitoring branch at NOAA’s national centres for environmental information said:
Longterm climate change is like climbing a flight of stairs: over time you get higher and higher. El Niño is like standing on your tippy toes when you’re on one of those stairs. Both of those together work to create the warmest temperature on record. We would not be threatening records repeatedly if we had not climbed the stairs for decades.
The agency also said that there was “high confidence” that El Niño – a phenomenon occurring when a vast pool of water in the western tropical Pacific Ocean becomes abnormally warm – would last through winter and the high level of heat in the oceans made it extremely likely that 2015 would be the warmest on record.
We would have to see some really unusual cooling behaviour and the reason that the probabilities are so high are not just that we have such a big lead just now but because much of that is being driven by the oceans, and the ocean tends to have a strong persistence, meaning one month is very, very related to the next month. The oceans don’t turn quickly.
Arndt described the jump in the record broken for August as “relatively large” compared to previous new records. According to an NOAA blog post, 2015 temperatures during the January – July period were 0.13C higher than during the same period in 2014.
Temperature records have been broken 30 times since the beginning of the 21st century.
31.5% of the contiguous US was in drought during August, up 6 percentage points from July, with droughts intensifying in parts of the south-eastern US.
Oregon and Washington registered their warmest summers on record, while California and Nevada are among the four US states on track to experience their hottest year yet. Alaska is having its secondest warmest year to date.
UN climate chief Christiana Figueres, in charge of forging a binding agreement with global leaders at the Paris climate summit in December, tweeted the NOAA findings demonstrated the need for climate action.
The NOAA data follows a report by the UK Met Office earlier this week which predicted that 2015 and 2016 will be the warmest or near-warmest on record.