Paper: ‘no clear increase in blocking’

US-blockingA paper, accepted for publication in Geophysical Research Letters just two days ago, challenges the warmist hypothesis that reducing ice in the Arctic is causing more blocking events resulting in more frequent instances of extreme weather. The paper, by Elizabeth Barnes, is available in PDF here.

Given the weather in the US at the moment (see previous post here), which the headbangers are using as evidence of extreme weather arising from Arctic warming, the paper shows how difficult it is to make such a link. From the abstract (my emphasis):

Observed blocking trends are diagnosed to test the hypothesis that recent Arctic warming and sea ice loss has increased the likelihood of blocking over the Northern Hemisphere. To ensure robust results, we diagnose blocking using three unique blocking identification methods from the literature, each applied to four different reanalyses. No clear hemispheric increase in blocking is found for any blocking index, and while seasonal increases and decreases are found for specific isolated regions and time periods, there is no instance where all three methods agree on a significant trend. Blocking is shown to exhibit large interannual and decadal variability, highlighting the difficulty in separating any potentially forced response from natural variability.

Of course, the paper has provoked the ire of the true believers, in particular a certain Jennifer Francis, for whom this appears to be her pet theory. She gave an interview back in August last year, when the paper was first made public, in which she questions the ‘motivation’ of the author, and labels Barnes’ approach “less than objective” and “a direct attempt to disprove [Francis’] work”.

Judith Curry expresses the views of the majority reading such comments:

So why on earth would Elizabeth Barnes be out to ‘get’ Jennifer Francis and discredit her work?  Its very hard to imagine a reason, beyond the obligation of a scientist to challenge existing findings and push forward at the knowledge frontier.

JC message to Jennifer Francis:  I’ve found that your credibility is reduced and your own motivations are questioned when you attack the motives of another scientist, particularly a young scientist without any apparent agenda beyond doing good science and advancing her academic career.  The high ground is a much better place to be, and not just in a hurricane.

Warning: Arctic alarmism ahead

Warning! Alarmism ahead…

UPDATE [1.45pm AEST]: And, right on cue, the ABC (Alarmist Broadcasting Corporation) comes up trumps:

The sea ice in the Arctic Ocean has melted to its smallest point ever in a milestone that may show that worst-case forecasts on climate change are being realised, say US scientists.

They say the extent of ice observed on Sunday broke a record set in 2007 and there will likely be further melting with several weeks of northern hemisphere summer still to come. (source)

Batten down the hatches for an avalanche of alarmism relating to the impending Arctic sea ice minimum. It looks to be heading for a record low (although some measures are showing otherwise, see here), and whatever the cause, we will be swamped with links to AGW from the climate science consensus and the media.

And whilst it is at least possible that a proportion of the ice loss is attributable to warming from human emissions, the question, as always, is one of degree: how large are those effects relative to other, natural, forces?

Climate Depot details some of the other factors that may worthy of consideration, before we all leap to conclusions about the role of AGW:

  • satellite measurement began just over 30 years ago, and is too short a period to draw such confident conclusions about attribution
  • at the time satellite measurement began, Arctic ice had been growing for many years after a period of global cooling, and so a subsequent decline during a period of warming is to be expected
  • Arctic likely to have had less ice in 1930s and 40s
  • recent ice loss may be attributable to changes in ocean currents, wind or other weather-related phenomena
  • this year, a particularly severe storm caused the disintegration of a considerable area of sea ice
  • cyclical fluctuations of Arctic ice are known to have existed for millennia

I am not making any claim about the significance of any of the above, other than to say they may play a role.

But unfortunately, the AGW believers invariably insist on using Arctic sea ice levels as a crude “gotcha” to “prove” that they are right (canaries, coal mines etc), claiming absolute certainty of attribution, when in fact, as is almost always the case in these matters, it is a subtle combination of factors that lead to the present conditions.

Just another example of the extreme polarisation of the issues when the middle ground is where everyone should be focussing.

Arctic warm periods 'inexplicable' by greenhouse gases alone

Drilling on Lake Unpronounceable

Quick, throw another heretic on the fire. The ABC momentarily abandons its trademark groupthink on climate to report on a paper which shows warm periods in the Arctic over the past 2.8 million years, and which cannot be explained by greenhouse warming alone.

Funny, because usually they can’t explain things but for greenhouse gases…

The Arctic went through ice-free periods of extreme warmth over the past 2.8 million years, based on a new analysis of deep sediment in Russia.

The team led by Martin Melles of the University of Cologne, Germany, drilled into an iced-over lake formed by a meteorite impact on the Chukchi Peninsula in Siberia for the longest sediment core ever collected in the terrestrial Arctic.

Since the meteorite struck an area of Lake El’gygytgyn that was not eroded by glaciers, the sediment record reaches back nearly 30 times further in time than ice cores from Greenland that cover the past 110,000 years.

The sediment reveals periods of extreme warmth that show the polar regions are much more vulnerable to change than previously thought, and are difficult to explain by greenhouse gases alone, according to the study in the journal Science.

Scientists have long known that the Arctic went through climate cycles, but the latest research shows some of these warm phases were “exceptional”, with temperatures 4°C to 5°C warmer and 30 centimetres wetter than during normal interglacials, the study’s authors write. (source)

More evidence of natural climate change perhaps? You can be sure this paper won’t make it into IPCC AR5…

Paper is here.

%d bloggers like this: