Arctic sea ice [image credit: cbc.ca]
The researchers find ‘a significantly declining AA effect on the millennial time scale’ — but then attempt to link that to anthropogenic forcing in recent times, according to the article at least. That seems illogical if the argument is that humans are playing a part. In any case if the effect has been shown to occur over at least a millennium, that in itself casts doubt on claims that humans must be the prime (or any) cause of the most recent observed changes.
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The recent amplified warming in the Arctic during the last decades has received much attention, says Phys.org.
But how Arctic amplification (AA) has varied on longer time scales and what drives these variations remain unclear.
Recently, a study has provided a new perspective on the AA effect during the past millennium based on the best available paleoclimate data and novel data assimilation methods.
The study was published in Nature Communications on April 6.
It was conducted by researchers from the Northwest Institute of Eco-Environment and Resources of the Chinese Academy of Sciences (CAS), the Institute of Tibetan Plateau Research of CAS, the Lund University and the University of Gothenburg.
The researchers produced a new millennium-long temperature reconstruction over the Northern Hemisphere by combining climate model simulations with newly available paleoclimate proxy records from the Past Global Changes 2k Network (PAGES2k) consortium, resulting in physically consistent and spatiotemporally continuous temperature fields.
Additionally, to quantify the variations in the strength of the AA, the researchers reconstructed a millennial AA index series, which revealed a significantly declining AA effect on the millennial time scale.
The millennial AA index series revealed that AA exhibited strong variations over a broad range of time scales, which can be explained, to a large part, by the phase of the Atlantic Multi-decadal Oscillation (AMO) and recent anthropogenic greenhouse gas forcing.
Full article here.
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AA is an emergent property of the physics of circulation. By definition it has an impact on the polar regions. That the AA, like nearly all other climate related manifestations, is dynamic, should surprise no one. What is predictable is the sciencey version of “then a miracle occurred” when “man made climate change” is trotted out for the faithful.
Reading the paper, the obvious conclusion is that the variability in the AA declines as the probable accuracy of measuring it increases! The rest is just statistics on models with some pretty dubious methods, such as averaging model runs to “remove variability”. Even then, they can’t explain more than 60% of what is going on.
And they say this: “Much uncertainty remains about the mechanisms behind and their relative importance to AA, as evidenced by the disagreement about future AA by model projections and the general overestimation of AA by models.” But then they assume all the models are somehow right! So they admit the models overestimate AA but can’t see that the higher AAs they get when they rely largely on models might be due to the models.
When you are locked in to a dogma, you end up being very stupid.
AA exhibited strong variations over a broad range of time scales
In which case attributing such variations to humans is just an agenda-driven personal choice, not a scientific result.
The first question should be ‘what actual real evidence do they have?’. If it is all based on computer models then there is no real evidence and so the standard computer warning applies, Garbage In = Garbage Out and no amount of wishful thinking or desire will change the outcome.
When they have a validated model it might be worth listening to them but until such time it is all so much hot air.
‘the AA effect during the past millennium based on the best available paleoclimate data’
‘Best’ doesn’t mean accurate. The thermometer wasn’t invented until the 17th century. In fact, I don’t accept that it is ‘data.’
‘and novel data assimilation methods’
I think they are trying to be funny.
I think the resolution of their analysis will yield “it was warmer, over a 50-year period.” That’s about all the detail you’ll get from ‘best paleoclimate data (sic)’ and ‘novel assimilation.’