Natural Forcing Of Arctic Climate
Increasingly Affirmed By Scientists
Three years ago a cogent paper was published in the prestigious scientific journal Nature that was surprisingly candid in its rejection of the position that the substantial warming and sea ice reduction in the Arctic occurring since the late 1970s should be predominantly attributed to anthropogenic forcing.
Dr. Quinhua Ding and 6 co-authors indicated in their paper that internal processes — natural variability associated with planetary waves and the North Atlantic Oscillation — are drivers of the recent Arctic warming and sea ice reduction, concluding that “a substantial portion of recent warming in the northeastern Canada and Greenland sector of the Arctic arises from unforced natural variability.”
“Rapid Arctic warming and sea-ice reduction in the Arctic Ocean are widely attributed to anthropogenic climate change. The Arctic warming exceeds the global average warming because of feedbacks that include sea-ice reduction and other dynamical and radiative feedbacks. We find that the most prominent annual mean surface and tropospheric warming in the Arctic since 1979 has occurred in northeastern Canada and Greenland. In this region, much of the year-to-year temperature variability is associated with the leading mode of large-scale circulation variability in the North Atlantic, namely, the North Atlantic Oscillation.”
“Here we show that the recent warming in this region is strongly associated with a negative trend in the North Atlantic Oscillation, which is a response to anomalous Rossby wave-train activity [planetary waves related to the Earth’s rotation] originating in the tropical Pacific. Atmospheric model experiments forced by prescribed tropical sea surface temperatures simulate the observed circulation changes and associated tropospheric and surface warming over northeastern Canada and Greenland. Experiments from the Coupled Model Intercomparison Project Phase 5 models with prescribed anthropogenic forcing show no similar circulation changes related to the North Atlantic Oscillation or associated tropospheric warming. This suggests that a substantial portion of recent warming in the northeastern Canada and Greenland sector of the Arctic arises from unforced natural variability.”
Since 2014, there have been several more scientific papers that have been published documenting the significance of natural forcing processes in the Arctic and how they may override a clear detection of an anthropogenic influence.
But 2017 already seems to be an exception. Papers that document the dominance of natural forcing — or that don’t even mention anthropogenic forcing as a factor in the Arctic climate processes — keep on rolling in.
As a case example, in a paper discussing the mechanisms involved in “Arctic amplification” and sea ice loss, Kim et al. (2017) never once mention anthropogenic forcing, or carbon dioxide, as mechanisms affecting the Arctic climate. In fact, in citing several other authors, they acknowledge that the physical processes involved in the forcing of Arctic climate are “subject to debate” and remain “an open question.” In other words, not only is the position that humans exert a dominant influence on the Arctic climate not “settled science”, the anthropogenic influence may be so muted a factor that it is not even worth mentioning in a paper discussing forcing mechanisms.
Understanding the Mechanism of Arctic Amplification and Sea Ice Loss
“Sea ice reduction is accelerating in the Barents and Kara Seas. Several mechanisms are proposed to explain the accelerated loss of polar sea ice, which remains an open question. … Previous studies have proposed the physical mechanisms of Arctic amplification, which involve the effect of atmospheric heat transport (Graversen et al., 2008), oceanic heat transport (Årthun et al., 2012; Chylek et al., 2009; 10 Spielhagen et al., 2011; Onarheim et al., 2015), cloud and water vapor changes (Francis and Hunter, 2007; Schweiger et al., 2008; Park et al., 2015a; Park et al., 2015b), and/or diminishing sea ice cover (Serreze et al., 2009; Screen and Simonds, 2010a; Kim et al., 2016). The accurate physical process of the Arctic amplification, however, is subject to debate.”
“Despite the general consensus that heat transfer between the ocean and atmosphere is a crucial element in the physical mechanism of Arctic amplification and sea ice reduction, a quantitative understanding of individual contributions of heat flux components is still controversial. Further, the role of upward and downward longwave radiations in Arctic amplification is vague and not fully understood. Accurately quantifying the contribution of these different mechanisms, therefore, is required for a complete understanding of the Arctic amplification.”
[CO2 is not mentioned as a mechanism responsible for Arctic amplification or sea ice loss.]
Two months ago, Dr. Ding delivered another Nature paper — this time with 10 co-authors — that once again emphasized the Arctic’s natural variability, specifically the internal processes involved in the substantial reduction in Arctic sea ice since 1979. The scientists concluded that as much as 50% of the Arctic sea ice decline in the satellite era has been natural, and that anthropogenic forcing may play a much smaller role than has previously been assumed in climate models.
Many other newly-published papers advance the position that natural, non-anthropogenic processes are significant or even dominant factors in shaping the Arctic climate. A total of 15 are cited here categorically.