The world has experienced record-breaking warmth every month so far in 2015, making this year virtually guaranteed to be the hottest on record, according to a US science agency.

The National Oceanic and Atmospheric Administration (Noaa) said that 2015 was 97% likely to be the hottest year so far, eclipsing 2014, the current warmest year.

Last month was the warmest ever August globally since records began in 1880, at 1.58F above the 20th century average. Every month this year has been the hottest on record, with the period of January to August 1.51F above the long-term average.