Across large swathes of the Northern Hemisphere bitterly cold temperatures and heavy snowfalls are causing travel chaos, disrupting work and resulting in loss of life through accidents and exposure. Even for those living in the southern hemisphere or warmer parts of the north it is hard to ignore what is going on given the near saturation media coverage. As a person involved in the climate change issue I don’t have to get too far into each day before somebody asks me how this can happen in an increasingly warming world.

I don’t really know the answer to that question, but I can at least offer an observation which seems to make some sense to me – at the risk of showing that my knowledge in this area isn’t really a strong point.

Working for a company based in the Netherlands for nearly 30 years, it is hard not to know about the Elfstedentocht. This is a 200 km, eleven city skating race which is only held in years when there is extensive freezing of the canal network and the ice is several inches thick (although a committee plans for it every year just in case). In the first half of the twentieth century it was held ten times, but in recent decades the frequency has plummeted. But some are still held and there is hope that it may happen this year – it has certainly been very cold. The last one was in 1997, prior to that in 1985 & 1986, then 1963. I remember the one in 1985 as I was living in the Netherlands and it was bitterly cold for weeks (Australians remember cold weather). There was huge excitement on the day as there hadn’t been one for 22 years and as I recall I was one of the few in the office. Everybody else was either competing or watching.

I recently came across the chart below (Frölich, C. 2006: Solar irradiance variability since 1978. Space Science Rev., 248, 672-673), which has been constructed from satellite data. It plots total solar irradiance over time and shows the cyclical nature of solar variability. What it also shows is that we are presently in the deepest most prolonged solar minimum in the period of satellite data. The 11-year solar cycle is struggling to rebound. Interestingly, if you look at the years in which the Elfstedentocht was held, they coincide with the minimums of the cycle – although there wasn’t one around 1974, but looking back further there was one in 1963 which is consistent with the pattern.

I am not going to claim that this is the cause of the current severe weather, but it is an interesting trend. It also puts solar variability into some context with regards specific weather events versus long term warming as a result of increasing CO2 levels. Equally, this could be a coincidence. The “missing Elfstedentocht” winter of 1974 was very mild, yet 1979 was one of the most spectacular cold outbreaks in Western Europe of the century. 2007 and 2008 were quite mild winters yet are also near the solar minimum. Another perspective is presented by the BBC today, showing the current cold regions of the northern hemisphere in contrast to other parts which are unseasonably warm. A similar picture emerges for December 2009 as shown below. Although there were unseasonably cold parts of the northern hemisphere, there were also significant departures on the warm side, notably in the Arctic regions.

All good food for thought.