July sees extreme weather with impacts

Extreme weather, including record temperatures and heatwaves, drought and disastrous precipitation, has marked the first half of summer in the northern hemisphere. This has had widespread impacts on human health, agriculture, ecosystems and infrastructure and led to devastating wildfires.

“2018 is shaping up to be one of the hottest years on record, with new temperature records in many countries. This is no surprise. The heatwaves and extreme heat we are experiencing are consistent with what we expect as a result of climate change caused by greenhouse gas emissions. This is not a future scenario. It is happening now,” said WMO Deputy Secretary-General Elena Manaenkova.

The persistency of high temperatures in some regions – including northern Europe – has been due to a stationary high pressure system. This is common in summer in both Northern and Southern Hemispheres. The jet stream, a core of strong winds around 10 kilometers above the Earth’s surface that blow from west to east and which steer weather around the globe – is generally slower in summer and occasionally become weaker than usual, then very settled weather occurs on the surface.

Another possible player in creating summer atmospheric blocking situations is the interaction between the atmosphere and the Atlantic ocean, which modulates sea surface temperature patterns on decadal time scales. These surface temperature patterns can influence the occurrence probability of summer blocking.

There is much scientific research into whether climate change and substantial changes to sea surface temperature are contributing to more profound effect in altering the atmospheric circulation and so leading to more “blocking patterns.”