I would like to make a few comments about the DMI arctic temperature data. I made the numeric version of this data available yesterday by digitizing the yearly graphs available from DMI. I have had a chance to look at the data and draw some initial conclusions.
Anthony Watts, who I have the greatest respect for, presented an animation of the 52 yearly DMI Arctic temperature plots form 1958 to 2009. He said “See if you can spot the temperature spikes or the “…cooling trend reversed in the mid-1990s.” His animation appears below…
Anthony Watts' animation of DMI temperature plots.
As Anthony Watts implied, I found it difficult to detect a trend over time by viewing the animation. So I created a simpler version that shows only five frames, each consisting of an overlay of 10 years, 1958 to 1967, 1968 to 1977, …, 1998 to 2007. The problem is that when I view this simpler animation, I do see a trend, with temperatures rising in the freezing season on the the far left and right sides of the graph in the last frame (1998-2007). My animation is below (double click is the image does not appear animated)…
Moriarty's animation of 10 year composites of DMI Arctic temperature graphs.
The data that I made available yesterday gives the DMI Arctic temperature for each half day from 1958 to 2009. This set of data allows a plot of the Arctic temperature for a particular day of the year as a function of the 52 years covered. For example the following two graphs show the temperature on September 1st and October 16th. Notice how the temperature trend seems to increase after 1995 for the October 16th data but not for the September 1st data.
September 1st temperature as a function of year.
October 16th temperature as a function of year.
If we are interested in a change of trend after the mid-1990s, then the trend before up to 1995 and the trend after 1995 for every day of the year can be compared in the same way they are compared for October 16th in the above image. The following image shows the temperature trend for each day of the year for 1958 to 1995 and from 1995 to the present.
Arctic temperature trends for each day of the year.
The total trend for each day for all data from 1958 to present is shown in the following graph.
Arctic temperature trend vs. day of the year for all data from 1958 to 2009.
So, the DMI data, presented in the crude fashion that I have used, lends support to the idea that the Arctic has been heating more rapidly since the mid-1990s than before. Those of you who have read my blog in the past know where I stand
on the probability of the Arctic ice melting in the near future, and I stand by my previous posts
. But I think this data must be presented as part of the scientific pursuit of truth.
I would be very happy to hear the opinions of people smarter than me on the significance of this data.