PLEA Network

26 July 2018, The Conversation, It’s a savage summer in the Northern Hemisphere – and climate change is slashing the odds of more heatwaves. In Australia we know about sweltering summer heat. We all remember the images of burned koala paws, collapsing tennis players and, far more seriously, the tragic events of Black Saturday. Aussies may scoff at Britain’s idea of a heatwave, but this time it’s the real deal and it’s no laughing matter. Extreme heat has hit locations throughout the Northern Hemisphere, in places as far apart as Montreal, Glasgow, Tokyo and Lapland. In the past few weeks heat records have tumbled in a wide range of places, most notably: a new record high temperature for Africa of 51.3℃ in Algeria; a record high temperature in Japan of 41.1℃ near Tokyo; a world record hottest overnight minimum of 42.6℃ in Oman. Heat has not been the only problem. Much of northern Europe is experiencing a very persistent drought, with little to no measurable rainfall in months. This has caused the normally lush green fields of England and other European countries to turn brown and even reveal previously hidden archaeological monuments. There have also been major wildfires in northern England, Sweden and, most recently and devastatingly, Greece. The Greek wildfires came off the back of a very dry winter and spring. What’s behind the widespread extreme heat? The jet stream, a high-altitude band of air that pushes weather systems around at lower altitudes, has been weaker than normal. It has also been positioned unusually far to the north, particularly over Europe. This has kept the low-pressure systems that often drive wind and rain over northern Europe at bay. The jet stream has remained locked in roughly the same position over the Atlantic Ocean and northern Europe for the past couple of months. This has meant that the same weather types have remained over the same locations most of the time. Weather is typically more transient than it has been recently. Even when we do have blocking high-pressure systems associated with high temperatures in northern Europe, they don’t normally linger as long as this. Read more here