Matching analyses by the Copernicus Climate Change Service and NASA, NOAA found September featured exceptional warmth worldwide, particularly in North America and the Northern Hemisphere overall.
For the first nine months of the year, the average global land and ocean surface temperature was 1.69 degrees above the 20th-century average, which was 0.22 degrees behind 2016, and just 0.02 degrees above the third-warmest year, which was set in 2017.
In keeping with human-caused global warming trends, all of the top 10 hottest years on record have occurred since 2005, with the exception of one — 1998 — when an unusually intense El Niño provided a major natural boost to global temperatures, added on top of long-term human-caused warming.
According to NOAA, there’s a 0.11 percent chance that 2019 will wind up as the warmest year on record, but a greater than 99.9 percent chance of a top 5 warmest year. The most likely range is between the second and fourth warmest year on record, the agency stated in its monthly climate report.
The NOAA analysis found 7.93 percent of the world’s land and ocean surfaces had a record warm September, but not a single land or ocean area had a record cold September.
The annual temperature rankings display a snapshot of climate change. However, global warming is not linear, meaning not every year is warmer than the year before it. Instead, scientists put far more emphasis on long-term trends of 30 years or more, and in that case, the sharp increase in global average temperatures clearly stands out.
This year has featured increasingly clear signs of global warming impacts worldwide, from a rare ice melt event in Greenland to lightning striking sea ice multiple times just 110 miles from the North Pole, deadly heat waves in Europe and tropical cyclones that have intensified at some of the fastest rates ever observed.
As another indicator of the warming climate, Arctic sea ice extent declined to its second-lowest level on record in mid-September. According to the National Snow and Ice Data Center, the 13 lowest ice extents in the satellite era have all occurred in the past 13 years. Sea ice extent bottomed out at 811,000 square miles below the 1981 to 2010 average minimum extent, meaning a chunk of ice roughly the size of Alaska and Colorado was missing from the top of the world due to unusually high air and sea temperatures.
In the midst of this near-record warm year, a youth-led social movement has sprung up to push for immediate action to reduce greenhouse gas emissions as many studies show the window to avoid the most damaging future impacts is closing quickly.