The notion that man-made global warming causes Arctic ice to melt took a major hit with a recent publication. The article is Influence of high-latitude atmospheric circulation changes on summertime Arctic sea ice by Qinghua Ding, Axel Schweiger, Michelle L’Heureux, David S. Battisti, Stephen Po-Chedley, Nathaniel C. Johnson, Eduardo Blanchard-Wrigglesworth, Kirstin Harnos, Qin Zhang, Ryan Eastman & Eric J. Steig. (Warning: Reliability of published papers diminishes as numbers of co-authors increases.)
The paper was published online by Nature Climate Change on 13 March 2017. It is behind a paywall, but the reactions to it are revealing. The abstract says:
The Arctic has seen rapid sea-ice decline in the past three decades, whilst warming at about twice the global average rate. Yet the relationship between Arctic warming and sea-ice loss is not well understood. Here, we present evidence that trends in summertime atmospheric circulation may have contributed as much as 60% to the September sea-ice extent decline since 1979. A tendency towards a stronger anticyclonic circulation over Greenland and the Arctic Ocean with a barotropic structure in the troposphere increased the downwelling longwave radiation above the ice by warming and moistening the lower troposphere. Model experiments, with reanalysis data constraining atmospheric circulation, replicate the observed thermodynamic response and indicate that the near-surface changes are dominated by circulation changes rather than feedbacks from the changing sea-ice cover. Internal variability dominates the Arctic summer circulation trend and may be responsible for about 30–50% of the overall decline in September sea ice since 1979. (my bolds)
Announcements of the finding were welcomed by skeptics and lukewarmists as an indication that climatologists were taking off their CO2 blinders and at last admitting to natural forces internal to the climate system. Some responses were:
Arctic Ice Loss Driven by Natural Swings
Arctic ice loss driven by natural swings, not just mankind
Study in journal Nature: HALF of Arctic ice loss driven by natural swings — not ‘global warming’
Arctic Ice Alarmists are finding themselves skating on thin ice, as evidenced by their articles attempting to control the damage. Some of these titles are:
We Deserve Half the Blame for Declining Arctic Sea Ice (Discover)
Humans to blame for bulk of Arctic sea ice loss: study (Phys.org)
Human activity is driving retreat of Arctic sea ice (from the misnamed Skeptical Science blog)
Why Alarmists are Twisting in the Wind
The full paper is behind a paywall, but we have description of the method and content by the lead author in an article at Popular Science Up to half of the Arctic’s melt might be totally natural–But climate change is still responsible for the rest. He begins with his profession of faith:
“Anthropogenic forcing is still dominant — it’s still the key player,” said first author Qinghua Ding, a climate scientist at the University of California Santa Barbara. . .”But we found that natural variability has helped to accelerate this melting, especially over the past 20 years.” A colleague adds: “The results of Ding et al. do not call into question whether human-induced warming has led to Arctic sea-ice decline – a wide range of evidence shows that it has”.
This is the shibboleth demanded from any and all scientists who do not wish to be called “deniers” and cast into the outer darkness.
Note: A shibboleth is an old belief or saying that is repetitively cited but untrue. This meaning evolved from its earlier significance as a word or custom whose variations in pronunciation or style are used to distinguish members of ingroups from those of outgroups, with an implicit value judgment based on familiarity with the shibboleth.(Wikipedia)
“The tribe has spoken. Time for you to go!”
What Ding et al. Studied
Ding goes on to describe the nature of their analysis. (From Popular Science)
“There is a mismatch between the model’s output and the observation,” said lead author Qinghua Ding, a professor in the Geography Department at the University of California Santa Barbara. “Observation shows very fast, very abrupt sea ice melting, whereas the climate model cannot capture the fast melting.”
To understand why, Ding and his team focused on the connection between September sea-ice extent (or how much of the Arctic sea had at least 15 percent sea ice) and the preceding summer’s (June-August) atmospheric circulation. Ding knew from earlier work that tropical circulation can affect seasonal variability of sea ice in the Arctic.
“In the model we turned off all CO2 forcing,” said Ding, or all climate changes that were “forced” by the addition of carbon dioxide into the atmosphere. “And we still got some sea ice melting, that was very similar to the observation.”
“If the circulation changes are caused by anthropogenic greenhouse warming (or other human or natural external forcings such as ozone depletion, aerosol emissions, or solar activity) this pattern of atmospheric change should emerge as a clear signature when averaging together many climate model simulations of this period,” Neil Swart, a Research Scientist with Environment and Climate Change Canada who wasn’t involved in the new study, wrote in an accompanying article.
But when Ding averaged the climate models together, the air circulation changes cancelled each other out—like a balanced equation. They only data that remained in the models was responding to external forcings, like greenhouse gas emissions. In other words, Ding found that between 30-50 percent of the arctic melting is due to these unforced, or non-climate change caused variations—and that with this factored in, the climate models were generally accurate. The increased rapidity of Arctic melting was due to natural variations outside of the scope of the climate change models.
What Can Be Learned from Ding et al.
First note that they are climate modelers studying the behavior of models when parameters are manipulated. It is encouraging that they notice the incompleteness of their models leads to discrepancies from reality. This is a step in the right direction.
Second, note that the CO2 forcing is actually their term for all external forcings, including solar, aerosols etc. They seem to be blind to oceanic multi-decadal and multi-centennial oscillations. They make a leap of faith when they attribute every factor outside of atmospheric circulation to CO2.
Others more comprehensive in their research have concluded that fluctuations in the ocean water structure drive both ice extent changes and atmospheric circulations. See Arctic Sea Ice: Self-Oscillating System featuring the work of V. F. Zakharov and others at the Arctic and Antarctic Research Institute in St. Petersburg.
Some climate modelers are undermining core beliefs even while using a flawed methodology based on studying models rather than nature itself. Alarmists are forced into scrambling to continue blaming humans for declining Arctic Sea Ice. When the effects of oceanic circulations are added to atmospheric effects, there is little influence left for CO2.
The abstract mentions downwelling longwave radiation, a theoretical effect that in practice is overwhelmed by massive heat transfers upward into space.
In the Arctic (and also at the South Pole), the air is in direct contact with an infinite heat sink: outer space. The tropopause (where radiative loss upward is optimized) is only 7 km above the surface at the poles in winter, compared to 20 km at the equator. There is no door to open or close; the air is constantly convecting any and all energy away from the surface for radiation into space.
Instead of an open door, Arctic ice melts when the sun climbs over the horizon. Both the water and air are warmed, and the ice cover retreats until sundown in Autumn.
Most people fail to appreciate the huge heat losses at the Arctic pole. Mark Brandon has an excellent post on this at his wonderful blog, Mallemaroking.
By his calculations the sensible heat loss in Arctic winter ranges 200-400 Wm2.
As the diagram clearly shows, except for a short time in high summer, the energy flow is from the water heating the air.
“Then the heat loss over the 2×109 m2 of open water in that image is a massive 600 GW – yes that is Giga Watts – 600 x 10^9 Watts.
If you want to be really inappropriate then in 2 hours, that part of the ocean lost more energy than it takes to run the London Underground for one year.
Remember that is just one component and not the full heat budget – which is partially why it is inappropriate. For the full budget we have to include latent heat flux, long wave radiation, short wave radiation, energy changes through state changes when ice grows and decays, and so on. Also large heat fluxes lead to rapid sea ice growth which then insulates the ocean from further heat loss.”