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The Change In Arctic Ice – for Apr. 26, 2010

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Daniel Bezte has a special interest in farm weather, which he follows from a small farm near Winnipeg, where he has his own computerized weather station. He has been a regular contributor to other farm publications including the Farmers’ Independent Weekly and the Manitoba Co-operator. Daniel has a degree in geography, specializing in climatology, from the University of Winnipeg.

He welcomes questions and comments at[email protected]

With some interesting storm systems so far this spring, I thought I would get an early start on a discussion of severe summer weather, but I’ll have to wait for the next issue, as I’ve been getting a fair bit of email about a couple of weather topics I think I need to address. So instead of discussing thunderstorms, the first issue that needs to be looked at is the increase in Arctic sea ice over the last month. Emails on the topic range from those simply asking for an explanation of what’s going on, to those saying, “I told you so,” taking it as more proof global warming is a crock.

The amount of ice in the Arctic has increased dramatically over the last month. In fact, it has come close to climbing back to the long-term average by early April. This increase in ice was largely due to a cold snap in the western Arctic that allowed a large amount of first-year ice to grow during this period. While this increase is of interest, most Arctic ice scientists do not see this having much impact on this summer’s Arctic ice minimum.

What’s much more interesting is that the Arctic winds this winter did not push out as much second-and third-year ice as usual – so we also saw an increase in second-and third-year ice this winter (while fourth-year and older ice continued its decrease). This will probably have a bigger impact on summer ice melt than the late-season increase in first-year ice.

That said, it’s important to note yearly changes in Arctic sea ice have not been that dramatic in the winter. The Arctic has been having much warmer winters, but it’s still darn cold. When the usual temperature is supposed to be around -35 C for a high and it’s a balmy -20 C, the region is way above average – but even at -20 C, ice will form, and darn quick at that! That’s why, in the winter, the average amount of ice in the Arctic only fluctuates between 15 million and 16 million square kilometres. Summer ice coverage has been fluctuating between four million and eight million square km.

Since there’s a much smaller change during the winter peak Arctic ice season compared to the summer, a relatively small change in ice cover will result in what appears to be a large increase overall. We’ll have to wait to see what happens this summer and over the next couple of years before any conclusions can be made.

Models aren’t forecasts

This leads me to another point that’s been on my mind over the last couple of months: the idea that climate models are really long-term forecasts. At least that’s the way they’re being treated. Take this latest growth in Arctic ice, for example. The climate models say that Arctic ice should be decreasing, but wait a minute – didn’t it grow over and above what the model thought it should over the last couple of months? Well, the models are now wrong, aren’t they? And since the models are now wrong, shouldn’t we also throw out everything they predicted?

Well, I don’t know about you, but from what I’ve learned over the years, models are not forecasts, they never have been and were never intended to be. Why they have become to be interpreted in this way is beyond me. A model is supposed to predict long-term trends in the weather, not day-to-day, month-to-month, or even year-to-year weather. This type of variability is known as “weather,” and these are climate models, not weather models.

Finally, the last point of interest this issue: global temperature data have been crunched for March and according to the U. S. National Oceanic and Atmospheric Administration (NOAA), the planet had the warmest March ever recorded, eclipsing the previous record set in 2002 by 0.03 C. NASA recorded March a little cooler than NOAA, coming in 0.01 C behind the 2002 record. Interestingly, NASA had the period of January to March as the warmest ever recorded, while NOAA had that period the fourth warmest. Also, if you didn’t already guess it, Canada saw the warmest temperature anomalies during March – nowhere on Earth was it as much above average as it was in Canada this March. Only in Canada, eh?



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