During late 2016, the Pacific Ocean started to cool off along its Equatorial region after experiencing one of the strongest warming events for that zone ever recorded. But despite this late cooling phase, the year ended up being the hottest ever recorded in the 137 year climate record — topping out at around 1.22 degrees Celsius above preindustrial temperatures. A longer term warming trend that has been directly driven by human burning of fossil fuels and related greenhouse gas emissions.

2017 annual mean prediction updated using Oct data. Probability of ~94% it will be the 2nd warmest yr in the GISTEMP record. pic.twitter.com/Ot7V8wGR5z — Gavin Schmidt (@ClimateOfGavin) November 16, 2017

This year, the periodic Equatorial cooling known as La Nina is again taking place in the Pacific during fall following a very mild warming during winter and spring. But despite the appearance of a second such periodic cooling event, according to NASA 2017 is 94 percent likely to be the second warmest year ever recorded (see above).

October readings have come in and at 0.9 C above NASA baseline (1.12 C above 1880s averages), temperatures are disturbingly high. The month is now the second hottest ever seen by modern humans. With only October of 2015 coming in warmer at 1.08 C above the 20th Century baseline (1.3 above 1880s).

(Heat transfer into the polar zones is increased during La Nina periods. This effect is enhanced by polar amplification related to human caused climate change. This week, very high relative temperature departures are expected for the Arctic. Image source: Climate Reanalyzer.)

Over the past two years, La Ninas (cooling Pacific) appear to have been at least partly off-set by very strong warming in the Arctic and Antarctic. Atmospheric circulation tends to transport more heat into the polar zones as the Pacific cools. This is due to the fact that temperature differential between Equator and poles during La Nina is less and the lower temperature differential causes the upper level winds to slow and meander. Coupled with polar amplification due to human-caused climate change, the result can be some pretty extreme temperature departures. This week is no exception as Arctic temperatures by Thursday through Saturday are expected to be between 4 and 5 degrees Celsius above average for the entire region above the 66 North parallel.

Such record warm temperatures do not occur in isolation. They help to drive extreme weather events such as severe droughts, rainfall, and powerful hurricanes. They are also accelerating sea level rise by melting glaciers even as both warming temperatures and related increasing ocean acidification contribute to dead zones, coral reef deaths and declining ocean health. Global temperature rise coupled with rising CO2 is therefore producing a major systemic crisis the world over.

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@ClimateOfGavin @MichaelEMann Earth at +1.12 C above 1880s (approx) despite La Nina. Strong polar amplification signal continues — though not as strong as 2016 so far. pic.twitter.com/0j3zvdizv7 — Robert Fanney (@robertscribbler) November 20, 2017