Dust flux, Vostok ice core

Dust flux, Vostok ice core
Two dimensional phase space reconstruction of dust flux from the Vostok core over the period 186-4 ka using the time derivative method. Dust flux on the x-axis, rate of change is on the y-axis. From Gipp (2001).

Saturday, February 4, 2012

Temperature records from the North Atlantic show cyclicity

Let's consider this post to be an update of an earlier missive about possible climate change from Arctic records.

Change in state for Arctic sea ice?

In the article linked above we agreed that the recent change in the extent of Arctic sea ice was consistent with warming over the duration of the records (since 1979), but this warming was not conclusively anthropogenic. Below, with minimal comment I present some records presented in a recent International Council for the Exploration of the Sea (ICES) Report on Ocean Climate (2010). (Available as a pdf here).

The following graphs are all screen caps from figure 1 of the ICES report.

I have only selected a few of the records available. What I would take from this, especially from the longer records, is that ocean temperatures have varied in a cyclical fashion over multi-decadal periods. I would also note that most of the records show warming since 1979 (although many suggest cooling over the past few years).

This is to reinforce the point I raised last time--the time-frame since 1979 is not sufficient to conclude that anthropogenic warming is responsible for the reduction in sea ice extent over the past three decades. I would go further and point out that the temperature records we look at today are not sufficient to exclude anthropogenic warming--for instance, it is not clear whether the amplitude or period of the cycles is increasing, which is an important question. But we need to recognize the importance of natural variability in any discussion of recent climate change.

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