Does the recent cold snap in certain parts of the world mean another ice age or the climate isn’t getting warmer?  First we need to understand the difference between climate and weather.

Weather is what happens outside today, tomorrow, this winter or even over several seasons, whereas climate is what is averagely happening right around the planet over longer periods of time.  So just because the weather turns cold, and even quite cold, does not mean the climate is changing as it is long term trends that matter.  Even quite short periods of climate history show that an upward or downward climate change trend which, looking back is absolutely obvious, is at times punctuated by moves in the opposite direction.  So to understand climate movement we need to consider only multi year periods which unfortunately need to be at least decades long.

There are lots of reasons why weather should periodically go against the climate trend, one of which is El Nino which particularly alters weather patterns around the Pacific.  But weather patterns are altered by many things including polar flipping where the normal low pressure area over the Arctic – causing winds to go towards the North Pole and weather patterns in our latitude to be warmer as the winds tend to be from the south – to a high pressure area which does the opposite.  And this is what has happened this winter and why the weather across northern Europe has been unseasonally cold.  This is a change in the weather not the climate.

Climate is the sum of the global weather and when we have polar flipping it only means the weather has been moved around.  If the entire planet cooled over decades then we could question climate change, but what seems like a cold period for even several years actually means nothing by itself.

Another hugely important reason why the weather changes is the Jet Stream – a relatively constant high speed air flow going round the entire planet between 28,000 and 38,000ft up and from west to east.  But the Jet Stream (there are 2 in each hemisphere) moves around and as it does so it changes the weather but does not alter the climate. The total energy is simply redistributed.

Washington DC was recently covered in snow, less reported (as it doesn’t sell papers) is the fact that the Rockies on the other side of North America have had the warmest January on record and is extremely short of snow.  Above Vancouver (Winter Olympics) they have been so short of snow they imported it in huge lorry trains!  So should we argue the planet is getting colder because Washington has record snow, or warmer as Vancouver doesn’t have much?  Bizarre that people on the West Coast, having suffered record forest fires, record drought, water rationing and minimal snow should be racing to fight climate change when those in NY may be thinking an ice age is coming.

The weather in both is changing but that tells us nothing about the climate.

Mike (Hillard)