“Polar amplification” usually refers to greater climate change near the pole compared to the rest of the hemisphere or globe in response to a change in global climate forcing, such as the concentration of greenhouse gases (GHGs)… RealClimate [emphasis added]
It’s fall. The Arctic is trying to cool down, but what would typically be a steady decline into frigid temperatures is being held back by the increasingly strong hand of human-forced climate change.
(Over recent weeks, temperature departures above the 1958-to-2002 average line [green line above] have grown in the region north of the 80th parallel. In general, the Arctic has experienced much warmer than normal temperatures. Failure of the Arctic to rapidly cool down during fall has been a feature of recent years that is related to human-forced climate change. Image source: DMI.)
Over the past month, temperature anomalies for the entire Arctic have ranged near 3 degrees Celsius or more above average. These temperatures appear to have represented the highest departures from average for any world region for the past month. Overall, they’ve greatly contributed to what is likely to be another record hot month globally.
Into the first week of October, this trend is expected to intensify. By Friday, according to GFS model runs, temperatures above the 66° North Latitude line are expected to range near 4.5 C (8 degrees Fahrenheit) above average for the entire region. Meanwhile, areas of Greenland, the Arctic Ocean and Northeastern Siberia are expected to see 10-18 C (18 to 32 F) above-average temperature departures for the day.
(Extreme Arctic heat is likely to lead record-high global temperatures for the month of September. Such heat is also likely to help push October into top 3 record-hot month ranges. Image source: Climate Reanalyzer.)
It doesn’t need to be said that these are extraordinary warm temperature departures from normal, which represent near-record or record warm ranges for many locations, but this is what we would expect with human-forced climate change. As the sun falls in the Arctic sky and night lengthens, energy transfer in the form of heat coming in from the warming ocean and atmosphere intensifies. This effect is driven by what is now a great overburden of greenhouse gasses in the Earth’s atmosphere.
Early Indicators Point Toward a Record-Hot September
Powerful heat transfers slowing down the rate of fall cooling in the Arctic came amid what is likely to be the hottest September in the global climate record. Australian scientist Nick Stokes found that September temperature departures were about 0.05 C higher than August’s record temperature departures. Translated to NASA GISS figures, if they were to match this increase, September values would fall around 1.03 C hotter than NASA’s 20th-century baseline and about 1.25 C hotter than 1880s averages.
(August 2016 was the hottest month on Earth in all of the past 136 years. Though the Earth is cooling into fall, September 2016 looks like it will be the hottest September ever recorded. Overall, 2016 is on track to be the hottest year on record by a significant margin. Image source: Earth Observatory.)
Temperatures in these ranges would represent the hottest September on record by a pretty big margin (about 0.13 C globally). Meanwhile, the annual averages for the first nine months of the year would hit near 1.27 C above 1880s averages if the NASA measure saw a warming similar to that showing up in Stokes’s early NCEP/NCAR reanalysis figures — a measure disturbingly close to the 1.5 C departure levels that represent the first major global climate threshold, a level that many scientists have advised us we’d be wise to avoid.