Alert in Nunavut, Canada sits at 81°30′ N, 62°17′W, well within the Arctic Circle. Figure 1 shows the location.

Figure 1, Alert, Nunavut

As noted in recent posts here and elsewhere, much has been made of the rapid warming of the Arctic and melting of sea ice. Data from Environment Canada provides the following overview of temperature trends at Alert, the northernmost weather station available on the download. Figure 2 shows the raw mean maximum temperature on a year by year basis.

Fig 2: Mean Maximum temperatures for Alert. Blue line shows temperature. Black line shows 10 year rolling average.

A perusal of the graph shows that temperatures were higher in 1957 than the early part of this century. The trend is fairly flat, though one could claim a cooling trend from 1957. Figure 3, below, shows the average annual temperature from 1951 to 2007. Again, the trend is basically flat, with a peak in 1981 and 2007.

Fig 3: Average annual temperature, Alert, Nunavut 1951 to 2007. Blue line shows temperature, black line shows 10 year rolling average.

I will admit that one station does not make for a comprehensive study. However, Alert is a real, physical station, right on the frontline of the sea ice melting crisis. The charts above show that it has been warmer and cooler in the past. Have summers become drastically warmer in the last 10 years? In the last 20? In both cases, not substantially.

Alert experienced monthly mean maximum temperatures exceeding 8.0 degrees C in 9* of the past 58 years. In this case, seven of the nine hottest years in Alert were not in the last 12 or 15 years. Seven of the nine occurred between 1953 and 1967. Only two 1993 and 2003 occurred during our current warming period.

Hadley Centre has produced a chart showing ice extent for the period 1953 to 2007 (Fig 4). There does appear to be a drop off since 1970. Mean maximum Arctic temperatures, recorded at Alert, in 1970 through 1987 do not show warming. So is there another factor, more important than surface temperatures that governs sea ice extent and thickness?

Fig 4: Mean sea ice anomalies, 1953-2007: Passive microwave-derived (SMMR / SSM/I) sea ice extent departures from monthly means for the Northern Hemisphere, January 1953 to September 2007. Image by Walt Meier and Julienne Stroeve, National Snow and Ice Data Center, University of Colorado, Boulder.

Note: the chart above shows sea ice extent for the Northern Hemisphere, which includes areas outside the Arctic.

Figure 5, below, shows the ice extent for the last year.

Fig 5: Recent Sea Ice Area (last 365 days) from The Cryosphere Today

The black line, showing actual variation looks alarming, but we must remember that ice increases in winter and melts in summer. The more important record is the red line showing departure from the average which shows that ice extent has not dropped significantly as it did in 2007.

A chart showing ice extent from 1979 to present can be found here: http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/sea.ice.anomaly.timeseries.jpg

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* 1953, 1954, 1956, 1960, 1961, 1962, 1967