Never Assume The Obvious Is Inevitably Correct – Especially With Climate

Map of the Eurasian Arctic (Inset: Severnaya Zemlya (SZ) with the drilling point at Akademii Nauk (AN) ice cap) including schematic positions of Icelandic Low and Siberian High as well as the major air-mass transport pathway (dashed arrow) for SZ. Courtesy: Climate Of The Past and Opel et al.

Click to enlarge. Map of the Eurasian Arctic (Inset: Severnaya Zemlya (SZ) with the drilling point at Akademii Nauk (AN) ice cap) including schematic positions of Icelandic Low and Siberian High as well as the major air-mass transport pathway (dashed arrow) for SZ. Courtesy: Climate Of The Past and Opel et al.

Nothing is quite what it seems in life and the fact that something sounds right does not necessarily make it so, as new research out this month reminds us.

At first glance it would seem so obvious that the significant reduction in the amount of Arctic ice that we have witnessed in recent years must be due to man made climate change that few people, apart from climate change sceptics, would even think to question the connection.

Well publicised research from the University of Colorado seemed to confirm our preconceptions last week, telling us that the Arctic is now warmer than it has been at any time in the last 44,000 years with the clear implication that global warming due to human greenhouse gas emissions is the most likely culprit. Indeed, images of melting sea ice and concerns over the fate of polar bears make a convenient and visually attractive journalistic short-hand for stories about human-induced climate change. The clear implication is that the ice in the Arctic is melting because the Earth is getting warmer – obviously!

New research questions this simple picture

Except that the connection between average surface air temperatures and conditions in the north polar region may not be quite as simple as this view of the world would suggest. A new research paper from scientists at the Alfred Wegener Institute for Polar and Marine Research in Germany reports evidence from an ice core drilled in the Russian high Arctic of significant climate regional climate variability in the polar region over the last 1,000 years.

An ice core is like a time machine. The deeper you drill, the further back in time that you look. Analysing the ratio of oxygen isotopes in the water that makes up the ice along the length of an ice core can help researchers to build up a picture of how temperatures have changed over time as the ice that makes up the core built up. This is because the ratio of different oxygen isotopes found in rain and snow is related to the air temperature at the time that the rain and snow fell.

The analysis of oxygen isotope levels in the Akademii Nauk ice core from Severnaya Zemlya shows that the Arctic has gone through a number of spells of rapid warming and cooling. The researchers detected evidence that there were higher temperatures around 900AD and in the 13th century than were found during the 17th century. They report that the oxygen isotope record exhibits “several abrupt cooling and warming events” in the 15th, 16th, 18th and 20th centuries. Moreover, this variability seems to have been highly regionalised and separate from climate changes taking place elsewhere as the researchers found little evidence of “distinct longer-lasting climate epochs” such as the Medieval warm period and the Little Ice Age which have been recorded at lower latitudes.

Internal variability has been significant in the past in the Arctic

They suggest that these abrupt changes in the Arctic and the resulting cooling and warming periods may be due to what climate scientists call “internal climate variability”; that is, Nature, to you and me. This internal variability relates to regional changes in prevailing winds and air-mass transport caused by shifts in atmospheric circulation and also to changes taking place in the Barents Sea and Kara Sea.

The implication of this is that it is possible that what is happening in the Arctic today is another example of such regional internal variability in the Arctic climate which may be only partly related to what is happening in the wider global climate.

Now we need to be clear about what this research does and does not say. It does not say that the world is not getting warmer. Nor does it say that Arctic sea ice and ice sheets have not been in long-term decline. And it does not say that there is no link between the warming seen in the second half of the 20th century and the observed reduction in Arctic sea ice and ice sheets in recent decades.

The real lesson

What it does say is that the climate in the Arctic is far more complicated that we might have thought and that even if the world is getting warmer due to human greenhouse gas emissions then that is not necessarily the sole or even the main cause of the decline in Arctic ice.

But what this new research really emphasises more than anything else is the importance, for scientists and for journalists alike, of taking nothing for granted. Not even the simplest and apparently most obvious explanation is necessarily correct.

To assume otherwise makes for sloppy science and even sloppier journalism.

Spare a moment…

If you found this article thought provoking or informative then please take a second to Like it and share it with friends and colleagues via social networking using the buttons below.  And if you enjoy reading this kind of article then press the follow button!

Data:

Click to enlarge. Akademii Nauk (AN) ice core isotope record (including linear trends for 900–1760 and 1800–1998) compared to (from top to bottom) ice cores from Austfonna, Lomonosovfonna and the Vetreniy ice-cap, as well as Arctic summer surface atmosphere temperature (SAT) anomalies, Arctic annual SAT anomalies, AN sodium concentrations, and Arctic sea-ice extent records. Abrupt warming and cooling events exceeding the dominant variability of the AN record are marked by a red asterisk. Note the different scale for the Lomonosovfonna record. Courtesy: Climate Of The Past and Opel et al.

Click to enlarge. AN ice core isotope record (including linear trends for 900–1760 and 1800–1998) compared to (from top to bottom) ice cores from Austfonna, Lomonosovfonna and the Vetreniy ice-cap, as well as Arctic summer surface atmosphere temperature (SAT) anomalies, Arctic annual SAT anomalies, AN sodium concentrations, and Arctic sea-ice extent records. Abrupt warming and cooling events exceeding the dominant variability of the AN record are marked by a red asterisk. Note the different scale for the Lomonosovfonna record. Courtesy: Climate Of The Past and Opel et al.

Citations:

Here is the paper that talks about the ice core oxygen isotope analysis published in Climate Of The Past: “Eurasian Arctic Climate Over The Past Millennium As Recorded In The Akademii Nauk Ice Core (Severnaya Zemlya)” by T.Opel, D. Fritzsche and H. Meyer

doi: 10.5194/cp-2379-2013

Clim.Past. 9-2379-2389, 2013

Read the  paper.

And here is the in press paper that reports that the Arctic is warmer now than at any time in the last 44,000 years published in Geophysical Research Letters: “Unprecedented recent summer warmth in Arctic Canada” by Gifford H. Miller, Scott J. Lehman,Kurt A. Refsnider, John R. Southon and Yafang Zhong.

DOI: 10.1002/2013GL057188

Abstract here.

Advertisements

Comments are closed.

  • Copyright © 2014. iExpon Limited
  • Enter your email address to follow this blog and receive notifications of new posts by email.

    Join 81,676 other followers

%d bloggers like this: