Climate science / Weather

I’m dreaming of a white Christmas…

Yes, exactly like the ones I used to know. Growing up in Poland in the nineties wasn’t worriless. Even though, contrary to the common belief, we have polar bears only in zoos, it can get quite cold here. Not the English type of cold (wet and windy minus one), but minus twenty degrees or so. Hence my biggest December worry was: will Santa Claus manage to visit me in such a weather?

But this was ages ago. I don’t recall any white Christmas over the last couple of years. In 2013 we even had the warmest Christmas in the history of temperature measurements. I remember walking my dog in a T-shirt and wondering if we shouldn’t make a barbecue instead of the traditional Christmas dinner (my family didn’t approve of this idea). The last white holidays in my country were in 2013 but… it was Easter. Well, we shouldn’t be picky.

How do we define white Christmas? I personally define it like that:

christmas-snow-wallpaper-18

However, my expectations seem to be a bit higher than the definition provided by the British Met Office. For them Christmas is white if anywhere in the whole UK on 25th of December we observe… one snowflake. I wouldn’t say that one single snowflake makes a day particularly white, but I won’t argue with experts.

They used to look out for this snowflake only in London. It doesn’t snow too often in the capital of the UK, which made the occurrences of white Christmases even more uncommon. However, now it gets more and more popular to bet on the white 25th of December, so the observations come from multiple spots all over the country.

Since Met Office uses a rather mild criterion, using the historical data they estimate the likelihood of a snowfall (or rather a snowflake) somewhere in the UK to be over 50%. This is because on 38 out of 54 last Christmas days some snow was observed.

What if one snowflake doesn’t satisfy us and we really want to walk in a winter wonderland? Luckily, Met Office provides data also for the more rigid criterion, i.e., more that 40% stations in the UK observing snow on the ground at 9 am. This happened only 4 times in the last 51 Decembers. Last time it occurred in 2010 – does anyone remember it?

Unfortunately the climate keeps getting warmer, so we can expect even fewer occurrences of a snowfall in the future. Will the future generation even understand “Do You Want to Build a Snowman?” song?

Apparently this year Christmas again will be rather grey than white. But it’s a time of miracles. I wish you all a white Christmas!

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