© Greenpeace/ Nick Cobbing

Pancake ice in the Arctic Ocean

It cannot be said too often that climate and weather are not the same thing. The first regulates the temperature and weather patterns on a long term basis, the other one is guilty for blocking the traffic with snow this morning, or making the heat today unbearable. NASA puts it better than I could:

Weather is what conditions of the atmosphere are over a short period of time, and climate is how the atmosphere "behaves" over relatively long periods of time.

This is why we most often talk to climatologists, not meteorologists, to understand climate change. This is why no single weather event can be linked directly to climate change: whether or not CO2 levels continue to rise, we will always have extreme weather events. Winters will always be colder than summer, and the possibility of snow will always be there.

What climate change will likely influence is the frequency and severityof extreme weather events: droughts that would have been called "once in a century" might become "once in a decade", or worse, "once a year".

Why do I bring this up today? Well, if you live in the Northern Hemisphere, you'll have noticed it's colder than usual. Some countries have been turned white for several weeks with snow falling, but not melting at all. In the Netherlands, where I live, the entire country seemingly stopped moving for a few days before Christmas, both enchanted by the winter wonderland, and having roads and train tracks completely blocked by the snow.

This has been going on for about a month, which is an unusually long time for us to bear the inconvenience and disruption which results, but an extremely short period on the time scale with which climate is analysed - one point on the charts, which, against a perpetual background of natural variation, are nonetheless showing an ongoing upward trend over time-scales of years to decades. The current cold snap is part of that natural short-term fluctuation which we will always face, even in a future world which, on the basis of global, long-term averages, may be much warmer than present. And while it might seem that the entire globe is caught in its icy grip, it is actually a far more regional phenomenon than might immediately be apparent.

The extreme cold weather has been caused by an extremely interesting (yet not so well understood) weather pattern called the Arctic Oscillation. Simply put, a pattern of high atmospheric pressure over Greenland and parts of the Arctic has been blocking the usual pattern of much milder south westerly winds from the Atlantic and instead sending cold northerly and easterly winds to lower latitudes from the Arctic and the northern European land masses. At the same time, however, this same high pressure system has been causing much higher temperatures than usual in parts of the Arctic, but since population density is obviously much lower there, we haven't heard as much about these. Furthermore, during the last week of December when the cold weather across Europe began to take hold, many parts of the North East USA and Canada, as well as North Africa, the Mediterranean and large areas of South West Asia were a good few degrees warmer than usual, up to 10 degrees Celsius warmer in parts of Northern Canada.

Despite the Arctic Oscillation being a known (if unpredictable) weather pattern, this hasn't stopped would-be witty headlines all over the world, wondering what happened to global warming, worrying we are now entering global cooling etc. - all more designed to attract readership and page views than to reflect scientific knowledge. The old adage - never let the truth get in the way of a good story - is hard at work.

So, to contradict these attention-grabbing headlines, let's remind everyone of what's been happening so far:

- The 2000s have been the hottest decade on record.

- Arctic sea-ice is dramatically decreasing.

- Sea level is rising.

- Global average temperature are rising.

- Atmospheric CO2 concentration is at its highest since at least 650,000 years.

A dot on a chart does not change that, and neither does wishful thinking. We are emitting too much greenhouse gases, much more than this planet's climate - the climate that allowed the human civilisation to thrive for thousands of years - can handle. Enjoy making that snowman, but don't think we fixed the climate - we still have a long way to go for that.