I think the scientific consensus will be that February probably should not have been so darn hot. But it was. And that’s pretty amazingly weird.
Clocking in at 1.32 C above 1880s averages, the month was oddly and disturbingly warm. The strong equatorial Pacific Ocean surface warming that was the El Nino of 2015-2016 had long since passed. The effects of a weak La Nina cooling of the same waters during late 2016 still lingered. And the Pacific Decadal Oscillation (PDO) — a measure of ocean surface temperature oscillation in the Pacific that tends to help drive natural variability based warming and cooling cycles — showed a meager warming bias value of 0.08 (or barely positive).
All these factors pointed toward a climate system that should have been pulling the world into a cyclical short term cooling during 2017 and 2018 (relative to 2016 record warmth). Global temperatures under such conditions would have been expected to recede about 0.1 to 0.2 C off highs hit during 2016 of 1.2 C hotter than 1880s temperatures. Averaging in a still disturbingly warm range near 1 C above 1880s values but waiting for the next El Nino cycle for a run at new global record warmth.
Heat Heads Toward the Poles
But, so far, the expected cyclical cooling isn’t happening. Instead, January of 2017 showed up as 1.14 C hotter than 1880s while February was 1.32 C hotter. The combined average of these two months was 1.23 C warmer than the preindustrial baseline — or a hair warmer that the 2016 average. This shouldn’t have happened. But it did. And now there is some risk that 2017 may be yet another record hot year. The fourth in a row consecutively.
So what was the cause?
(February saw highest above average temperature readings centered near the poles — a signal that polar warming was the primary factor driving near record heat for the month. Image source: NASA.)
According to NASA, both polar zones experienced considerable above average temperatures during the month of February. Lower latitude temperatures were also well above average, but the highest temperature spikes appeared in the far north and the far south. At the 80 to 90 north and south latitude zones, temperatures were 4.5 and 2 C above average respectively. And the heat was particularly intense in the Northern Hemisphere Arctic and near Arctic between 60 and 90 north latitude with temperatures ranging from 3 to 4.5 C above average.
Polar Amplification Appears to Drive Weird 2017 Warmth
Such strong warming at the poles is indicative of a global warming related condition called polar amplification. The causes of polar amplification include increasing water vapor at the poles, high greenhouse gas overburdens in the Arctic, a darkening of the polar ice from particulates (wildfire and human-produced smoke), intensification of transport of heat from the lower and middle latitudes toward the poles, warming oceans and changes in ocean circulation, and loss of snow and ice cover at the poles. To this final point, sea ice coverage has been consistently at or near record lows for both the northern and southern polar regions.
(Global sea ice extent at record lows likely helped to contribute to extremely warm conditions at the poles during February of 2017. Less sea ice means more water vapor evaporating from oceans in the polar regions. Water vapor is a powerful greenhouse gas. In addition, warmth from the ocean can more readily ventilate into local atmospheres which aids in heat transport to the polar regions as the skein of sea ice retracts. Image source: Wipneus. Data Source: NSIDC.)
Polar amplification is not typically cited as a climate event that can overcome the transient cooling signal of a post El Nino period. However, given a first look at the evidence, this appears to be exactly what happened during early 2017. If this is the case, it is cause for serious concern. It is an indicator that a global tipping point has been reached in that warming at the poles (which is an upshot of the ridiculously high greenhouse gas levels we now see globally) is strong enough to drown out some of the traditional ENSO and PDO signals.
Hat tip to Colorado Bob