Earth just had the hottest September on record – and by a record-breaking margin, according to the leading international datasets which are used by the World Meteorological Organization (WMO) for its State of the Global Climate monitoring. This continues an extended streak of extraordinary land and sea-surface temperatures and is an ominous signal about the speed with which greenhouse gases are changing our climate. The year 2023 is now on track to be the warmest year on record, with June, July, August and September all breaking monthly temperature records.