Worldwide, last month was the warmest September on record, topping a record set just a year before, European scientists announced Wednesday.
It was also the hottest September on record for Europe. Northern Siberia, Western Australia, the Middle East and parts of South America similarly recorded above-average temperatures.
The announcement, by the Copernicus Climate Change Service, an intergovernmental agency supported by the European Union, capped nine months of devastating wildfires and followed the most active Atlantic hurricane season since 2005.
It also came as Arctic sea ice plunged to its second-lowest levels on record, driven by record temperatures in late June. Many experts predict that by 2050, Arctic sea ice could melt completely during the summer.
According to Copernicus, last month was 0.63 degrees Celsius warmer than average and topped the average for September 2019 by 0.05 degrees Celsius. The agency’s satellite observations date to 1979, and averages are calculated using data spanning 1981 through 2010.
The National Oceanic and Atmospheric Administration also publishes monthly assessments of global temperature data, which are generally issued about a week after the Copernicus measurements.
The two organizations calculate averages differently, but the results are generally similar. NOAA relies on surface temperature measurements from land stations, ships and buoys. Copernicus relies heavily on computer modeling.
“Even though the details of the report are different, they all come to the same conclusion that the global temperatures are increasing,” said Ahira Sánchez-Lugo, a physical scientist for NOAA’s National Centers for Environmental Information.
According to NOAA’s predictions, this year is 99.9 percent certain to be one of the top five hottest years on record. Whether that prediction holds true will partly rely on the impact of La Niña, which NOAA scientists declared last month.
La Niña is the opposite phase of the climate pattern that also brings El Niño and affects weather across the globe. Its strongest influence is usually felt in winter. And while the precise effects are unpredictable, La Niña can result in warmer and drier conditions across the Southern United States and cooler conditions in southeastern Alaska, the Northern Plains and Western and Central Canada.