Thursday, 24 July 2014

Global connections

Photo: Clive Simpson

As temperatures across the UK soared again this week it is worth taking note of how meteorological events in one part of the world can trigger weather on the opposite side of the globe.

Last weekend the UK recorded a total of 62,277 lightning strikes as storms moved in from Spain and France.

This followed a mini heatwave which enveloped most of the country, bringing with it temperatures in the low 30s and by far the hottest day of the year so far.

And all this was because of a storm thousands of miles away - super typhoon Negouri which had been churning across the north west Pacific in the first week of July.

As well as bringing strong winds and heavy rain to Japan it also dragged a mass of tropical air northwards and gave the jet stream a kick in the process.

That set off a ripple effect along the jet stream, running across the Pacific and extending its influence out across the Atlantic, forcing the jet stream there to swing northwards across Europe.

Super typhoon Negouri photographed by astronauts on the Space Station.

This is what allowed the exceptionally warm and humid air - known as a Spanish plume - to spread up and across the UK, bringing a brief heatwave before breaking down with severe thunderstorms.

So, a storm over the north west Pacific can set off thunderstorms 10 days later some 10,000 miles away - illustrating in a very real way how the weather in one part of the globe is often directly influenced by what is happens elsewhere.

We’ve also had news this week - data released by NOAA (the National Oceanic and Atmospheric Administration) - that last month was Earth's warmest June since records began in 1880. It marked the second month in a row the world has set a warm-temperature record.

The average temperature over global surfaces for June 2014 was 1.3 degrees above the 20th century average of 59.9 degrees. In May, the Earth's temperature was 1.33 degrees above the average of 58.6 degrees.

"The warmth was fueled by record warm ocean temperatures," explained Jessica Blunden, a NOAA climate scientist.

"Large parts of the Pacific Ocean and most of the Indian Ocean hit record-high temperatures or were much warmer than average for the month."

Most of the world's land areas saw warmer-than-average monthly temperatures, with record warmth measured across part of southeastern Greenland, parts of northern South America, areas in eastern and central Africa, and sections of southern and southeastern Asia.

Every continent except Antarctica set temperature records and overall Earth's land areas in June were the seventh-warmest on record. It was also the 352nd consecutive month that the global temperature was above average.

So far, this year is tied with 2002 as the third warmest year on record, with a global temperature about 1.21 degrees above average.

According to NOAA, the last below-average global temperature for June was in 1976 and the last below-average global temperature for any month was February 1985.

It seems likely more records will be broken in the coming months as global warming combines with an emerging El Niño (see Countdown to El Niño).

NOAA currently puts the chance of El Niño forming at about 70% during the northern hemisphere summer and close to 80% during the autumn and early winter.


The Lighthouse Keeper is written by Clive Simpson - for more information, commission enquiries or to re-publish any of his articles click here for contact information

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