It’s June in January
7.12.06
D. Burfitt-Dons,GWA Aviation Correspondent

The words from the Bing Crosby classic It’s June in January from the 1934 movie “Here is my Heart” weren’t referring to the weather. It was all about love of course, but by the time the old crooner rerecorded it just a month before his death in 1977, world climate was responding to global warming. Ironically, Bing entitled the album “Seasons”.

By 1977 a few oceanographers and meteorologists had begun to ponder about the evidence coming in and wondered why temperate zone winters were becoming milder, and why indeed January was getting more like June.

As the surface layers of the oceans become hotter, more moisture is picked up by the atmosphere. Moister air makes it feel a warmer to us. And as the land warms too we get situations more in common with the tropics. Conditional instability occurs when a parcel of air becomes less dense than the air around it. As it is less dense than the surrounding atmosphere, it continues to rise of its own accord at sometimes a phenomenal rate. These conditions cause the development of towering cumuli or thunderstorms. Aircraft have experienced updrafts in thunderstorms of over 4000ft per minute. In a ‘normal’ world such instabilities would only occur in the tropics and milder versions during the summer months in the mid latitudes of Europe, America and northern Asia.

By the seventies global warming had not just increased the intensity of our depressions See GWA article High Seas Set to Become Higher, but also keen eyed observers noticed that thunderstorms were cropping up when they weren’t supposed to, such as in the depths of winter.

November in Northern Europe or equivalently May in South Africa, South America or Australia is normally dominated by essentially stable air masses. Summer is over, the land cools, the atmosphere with it and it is the month for slow moving anticyclones with clear skies, fog and frost. Not any longer.

Although there are exceptions, with increasing frequency we are seeing thermal instability in November and December in the Northern hemisphere. The forecast today 6th December 2006 covering the South East of the UK included the phrase “rumbles of thunder”. This is no longer uncommon. In December 2005, west of London a snow storm was accompanied by thunder and lightning. Although not unheard of, and known as a phenomenon called C.S.I or Convective Symmetric Instability it is extremely rare in the UK. One of the basic requirements for CSI to occur is to have thermal instability and with large land masses such as the US this is more likely to occur. That it should happen in geographically small countries such as the UK implies a change in the heat energy equation, and likely a further small clue to climate change ahead.

It looks like it really could become June in January.