This winter the UK weather news was snow, storms and cold. This spring the news was cold, rain and flooding. Now, the news is deadly record heatwave.
Over the past week, the UK has baked under record high temperatures ranging from the high 80’s and into the low 90’s (Fahrenheit). These record temperatures, the highest since 2006 (which was the hottest in 350 years), are implicated in the deaths of nearly 800 persons, have buckled roads and tennis courts alike, set off dozens of wildfires that have taken hundreds of firefighters to contain, and threatened thousands of square miles of UK croplands.
The heat is expected to continue for portions of England, Scotland and Ireland this week with some forecasters calling for the potential of 100 degree (F) temperatures across the region. Forecasts also show the potential for severe thunderstorms with an increased threat of lightning and localized flash floods emerging.
Though other regions of the world often experience temperatures hotter than those seen over the UK throughout the past week, the UK has very few buildings equipped with air conditioning, as daytime temperatures only rarely rise into the 80s. So the young, the elderly and this sick are more vulnerable when high temperatures do arrive as they are both not acclimated to heat and lack access to indoor cooling systems that, in cases like these, can be life-savers.
Mangled Jet Stream Delivers Extremes Yet Again
(Image source: California Regional Weather Service)
A deep Rossy-Wave type dip in the Jet Stream that had extended from Greenland, across the North Atlantic and into the UK and Western Europe this winter and spring, bringing cold weather, record snow and rainfall, and extraordinarily stormy conditions, slowly collapsed over late June and early July. Then, last week, a large bulge and related heat dome high pressure system began to form. As the bulge extended far north toward Greenland, Iceland and Svalbard, temperatures over the UK built until a record heatwave began to scorch the region.
So, in this area, the cold and wet winter extremes that caused the UK Met Office to call an emergency meeting on climate change has been replaced by deadly heat, dryness and wildfires.
The underlying causes of these extremes is likely a great weakening of the Jet Stream’s flow over the Northern Hemisphere. According to researchers, the Jet Stream has slowed down by at least 14% since the 1990s. This slowing down has caused the Jet Stream to act like a lazily flowing river creating great north-to -outh and south-to-north loops and meanders. These large meanders bring cold, wet and stormy conditions when they flow from north to south, as happened over Europe for much of this winter and spring. The south-to-north flows, conversely, bring hot, dry conditions that increase the risk of droughts, wildfires and heatwaves.
Driving these new extremes, according to the research of climatologists like Dr. Jennifer Francis at Rutgers, is a massive, global warming driven erosion of snow cover and sea ice in the Arctic. Since 1979 sea ice volume has dropped 80% while sea ice extent has fallen 50%. Over past years, summer snow cover has also hit new record lows. The loss of ice creates Arctic weather conditions that are many degrees warmer than average. This response, is a result of the elimination of cold, reflective snow and ice cover that turns back the sun’s heating rays. Areas devoid of ice and snow cover instead absorb more of the sun’s light and heat. The result is that the difference in temperature between high lattitudes and lower lattitudes is much lower.
Since large differences between hot and cold temperatures are the primary driver for Earth’s Jet Stream, the speed of air flow is now slowing down as the north pole warms faster than the temperate and tropical regions. And these changes help to drive increasing instances of extreme weather. In the UK, it resulted in an extreme winter and spring (cold rain and snow) followed by an extreme July (heatwaves, hot temperatures, dryness, fires).
Dr. Jennifer Francis provides an excellent explanation of these conditions in the following video:
Sadly, the UK is not the only location to have experienced deadly and extreme weather this year. Weather Underground provides a long and growing list of damaging weather events for 2013. And this list includes many events such as floods, extreme winter conditions, and heat waves that can all be tied to new extreme patterns of the Northern Hemisphere Jet Stream.
1) Flooding, Central Europe, 5/30 – 6/6, $22 billion
2) Drought, Brazil, 1/1 – 5/31, $8.3 billion
3) Tornado, Moore, OK, and associated U.S. severe weather, 5/18 – 5/22, $4.5 billion
4) Drought, Central and Eastern China, 1/1 – 4/30, $4.2 billion
5) Flooding, Calgary, Alberta Canada, 6/19 – 6/24, $3.8 billion
6) Flooding, Indonesia, 1/20 – 1/27, $3.31 billion
7) Flooding, Australia, 1/21 – 1/30, $2.5 billion
8) Tornadoes and severe weather, U.S., 5/26 – 6/2, $2 billion
9) Severe weather, Midwest U.S., 3/18 – 3/20, $2 billion
10) Winter weather, Europe, 3/12 – 3/31, $1.8 billion
11) Drought, New Zealand, 1/1 – 5/10, $1.6 billion
12) Flooding, Sichuan Province, China, 7/7 – 7/11, $1.6 billion
13) Flooding, China, 6/29 – 7/3, $1.4 billion
14) Flooding, Argentina, 4/2 – 4/4, $1.3 billion
15) Flooding, India and Nepal, 6/14 – 6/18, $1.1 billion
16) Winter weather, Plains, Midwest, Northeast U.S., 2/24 – 2/27, $1.0 billion
And now we can tentatively add:
17) Heatwave, drought UK 7/13-?, $xxxx?
The UK swing from extreme cold, snow, rain and flooding to extreme heat and dryness over the course of about 7 months is a perfect example of the new types of weather extremes human caused climate change is driving. We are just at the beginning of these changes so, unfortunately, conditions should continue to worsen, especially if we fail to provide proper mitigation rapidly cutting human greenhouse gas emissions.