The heatwave continues...

July 22, 2018

The Met Office has issued an amber heat watch warning today, which applies from 9am today to 9am on Friday in the Midlands, south-eastern and eastern England. This means that there is a 90% chance that temperatures will reach at least 30â„ƒ during the day and 15â„ƒ at night for two or more days during the period. Their advice is to ‘Stay out of the sun. Keep your home as cool as possible. Keep drinking fluids.’

Elsewhere though, the situation is far worse. A weather station at Ouargla in Algeria has recorded a temperature of 51.3â„ƒ (124.3â„‰), which could become the highest ever reliably recorded temperature in Africa. A higher temperature of 55â„ƒ was recorded at Kebili in Tunisia in 1951, but some climate scientists suspect that it was not obtained correctly and have asked the World Meteorological Organisation to invalidate the Kebili reading.

Meanwhile in Japan, temperatures have risen to 41.1â„ƒ (105.98â„‰) in Kumagaya, the highest ever recorded in Japan, causing the deaths of at least 44 people since 9 July. And in southern California, many locations recorded temperatures 10â„‰ to 15â„‰ above previous records. On 6 July, the hottest ever temperatures were recorded at UCLA (111â„‰), Santa Ana and Burbank Airport (114â„‰), Van Nuys Airport and Ramona (117â„‰) and Riverside (118â„‰). In Burbank, California, the highest ever overnight low temperature of 82â„‰ was recorded, whilst on 7 July 79â„‰ was the overnight low in Los Angeles.

And in northern Europe, more than fifty forest fires are burning in Sweden, a dozen of them within the Arctic Circle. This has arisen after months without rain. Sweden has appealed for international assistance to help with combating the fires.

So why is this happening? Well, we know that our planet is getting warmer, as a result of emissions of carbon dioxide (CO2) caused by human activities. CO2 is a greenhouse gas, which helps to trap heat in our atmosphere, making the planet warmer. But whilst climate change is certainly a factor, it isn’t wholly the cause of our current long hot summer. The jet stream is the name we give to winds five to seven miles above the planet’s surface that blow from west to east, herding weather systems around the world. Currently, the jet stream is very weak, which means that areas of high pressure are remaining stuck in the same place for long periods. So all across the northern hemisphere, we are seeing unusually high temperatures and settled weather.

The surface temperatures in the Atlantic are higher than usual, as indicated by the Antlantic Multidecadal Oscillation (AMO). When the AMO is higher than average, it tends to lead to higher average temperatures and lower rainfall, across areas such as Europe, the Sahel in Africa, North America and North Eastern Brazil.

Conditions with the jet stream and the AMO coincided in a very similar way back in 1976, when the UK had blazing sunshine and drought conditions. At Heathrow, there were 16 consecutive days of temperatures over 30â„ƒ from 23 June to 8 July, while for 15 consecutive days from 23 June to 7 July, temperatures reached 32.2â„ƒ (90â„‰) somewhere in England. By the end of that summer, the Haweswater reservoir was only 10% full and people were able to walk on its dried out bed, some 60 feet (18.3 metres) below its normal water level.

The difference today is that we have had 40 years more climate change in the meantime, 40 years more global warming. So it could be that we see even more dramatic effects before the summer of 2018 comes to an end.

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