With temperatures exceeding past norms by wide margins, experts believe the pressure on world leaders to reduce planet-warming greenhouse gas emissions has never been greater as they prepare to convene in Dubai this month for the UNCOP28 climate summit.
Drought scorched sections of the United States and Mexico in October, while vast swaths of the globe saw wetter-than-normal weather, typically connected to storms and cyclones, according to the EU's Copernicus Climate Change Service (C3S).
The month's sea surface temperatures were the highest ever recorded, a phenomenon caused by global warming that experts think plays a significant role in making storms more powerful and devastating.
"October 2023 has seen exceptional temperature anomalies, following on from four months of global temperature records being obliterated," stated Samantha Burgess, C3S Deputy Director.
"We can almost certainly predict that 2023 will be the warmest year on record, with temperatures currently 1.43 degrees Celsius above the preindustrial average." The need for bold climate action as we approach COP28 has never been greater."
The historic Paris Agreement saw over 200 countries promise to keep global warming far below two degrees Celsius since the pre-industrial period, preferably 1.5 degrees Celsius.
Rather than a single year, these temperature thresholds will be calculated as an average over several decades.
This year has also seen the start of a rising El Nino weather phenomenon, which heats seas in the southern Pacific and fuels hotter weather elsewhere; however, experts predict that the worst consequences will be noticed by the end of 2023 and into next year.
Copernicus reported that October was 1.7 degrees Celsius warmer than an estimate of the preindustrial era's October average.
The monitor said that global average temperatures since January had been the highest in data dating back to 1940, measuring 1.43 degrees Celsius above the 1850–1900 pre-industrial norm.
Beyond these official records, experts believe proxy evidence for climate dating back farther in time, such as tree rings or ice cores, shows this year's temperatures may be unparalleled in human history, maybe the warmest in more than 100,000 years.