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The big heatwave: From Algeria to the Arctic. But what’s the cause?
By Robin McKie
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But why is so much of our world currently being afflicted with blisteringly hot weather? What is driving the wildfires, the soaring temperatures and those melting rooftops? These are tricky questions to answer, such is the complex nature of the planet’s weather systems. Most scientists point to a number of factors with global warming being the most obvious candidate. Others warn that it would be wrong to overstate its role in the current heatwaves, however.
“Yes, it is hard not to believe that climate change has to be playing a part in what is going on round the globe at present,” said Dann Mitchell of Bristol University. “There have been some remarkable extremes recorded in the past few weeks, after all. However, we should take care about overstating climate change’s influence for it is equally clear there are also other influences at work.”
One of those other factors is the jet stream – a core of strong winds around five to seven miles above the Earth’s surface that blow from west to east and which steer weather around the globe. Sometimes, when they are intense, they bring storms. On other occasions, when they are weak, they bring very calm and settled days. And that is what is occurring at present.
“The jet stream we are currently experiencing is extremely weak and, as a result, areas of atmospheric high pressure are lingering for long periods over the same place,” added Mitchell.
Other factors involved in creating the meteorological conditions that have brought such heat to the northern hemisphere include substantial changes to sea surface temperatures in the North Atlantic. “These are part of a phenomenon known as the Atlantic multidecadal oscillation,” said Professor Adam Scaife, of the Met Office.
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