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Heat waves in cities getting worse under climate change

Heat waves in cities getting worse under climate change

The effects of climate change are being felt all over the world but towns and cities are feeling most hot-under-the collar, a new study finds.

Cities are usually warmer than their surroundings due to the urban heat island effect where artificial surfaces absorb more heat than their natural counterparts. Coupled with the loss of the shady effects of trees, urban areas regularly record the hottest temperatures around.

However a study by Dr Hendrik Wouters and colleagues from KU Leuven in Belgium has found that cities are getting even hotter from the effects of climate change with an increase in heat-waves.

Heat-waves are periods of time where temperatures exceed the ‘normal’ high levels. These events are already problematic in urban areas causing power surges, excessive hospitalisations and even deaths.

Wouters and colleagues have investigated how much worse this problem is likely to get as extreme weather events become more common.

Speaking at a press conference at the EGU 2017 General Assembly on 25th April, Wouters said ‘we look at how much temperature levels are exceeding during heat waves‘. Using the expected average temperatures, the climatologists can calculate a threshold of ‘normal’ temperatures and then quantify how often these values are exceeded.

This information was gathered for the whole of Belgium over the 34 years prior to 2015. In rural areas this ‘alarm’ threshold was exceeded at least twice. In urban areas the heat-stress was considerably higher- up to 16 exceedances. Overall, heat-stress was twice as large in cities for the mid 21st century.

Cities (red) show much higher annual degree exceedances than rural areas (green). These exceedances are set increase into the future. (Wouters et al., EGU 2017).

In order to anticipate how much worse this problem might get, the group have modelled heat-stress events for the next 58 years. Wouters was keen to highlight that the severity and frequency of the events is dependent on many factors: ‘There is not only one scenario for the future, it depends on how many greenhouse gases we emit and how much land change will evolve in the future.’

In an extreme scenario, where greenhouse gas emissions and urban growth increase, as many as 25 days in a year could exceed alarm levels by up to 10 degrees celsius. However, if we start to reduce our emissions, the heat-stress problem is likely to stay at current levels.

By Keri McNamara, EGU 2017 General Assembly Press Assistant

April GeoRoundUp: the best of the Earth sciences from the 2017 General Assembly

April GeoRoundUp: the best of the Earth sciences from the 2017 General Assembly

This month’s GeoRoundUp is a slight deviation from the norm. Instead of drawing inspiration from popular stories on our social media channels and unique or quirky research featured in the news, we’ve rounded up some of the stories which came out of researcher presented at our General Assembly (which took place last week in Vienna). The traditional format for the column will return in May!

Major story

Artists often draw inspiration from the world around them when composing the scene for a major work of art. Retrospectively trying to understanding the meaning behind the imagery can be tricky.

This is poignantly true for Edvard Munch’s iconic ‘The Scream’. The psychedelic clouds depicted in the 18th Century painting have been attributed to Munch’s inner turmoil and a trouble mental state. Others argue that ash particles strewn in the atmosphere following the 1883 Krakatoa volcanic eruption are the reason for the swirly nature of the clouds represented in the painting.

At last week’s General Assembly, a team of Norwegian researchers presented findings which provide a new explanation for the origin of Munch’s colourful sky (original news item from AFP [Agence France-Presse): mother-of-pearl clouds. These clouds “appear irregularly in the winter stratosphere at high northern latitudes, about 20-30 km above the surface of the Earth,” explains Svein Fikke, lead author of the study, in the conference abstract.

“So far observed mostly in the Scandinavian countries, these clouds are formed of microscopic and uniform particles of ice, orientated into thin clouds. When the sun is below the horizon (before sunrise or after sunset), these clouds are illuminated in a surprisingly vibrant way blazing across the sky in swathes of red, green, blue and silver. They have a distinctive wavy structure as the clouds are formed in the lee-waves behind mountains”, writes Hazel Gibson (EGU General Assembly Press Assistant) in a post published on GeoLog following a press conference at the meeting in Vienna (which you can watch here).

With coverage in just over 200 news items, this story was certainly one of the most popular of the meeting. Read more about the study in the full research paper, out now.

What you might have missed

Also (typically) formed in the downside of mountains and in the conference spotlight were föhn winds. The warm and dry winds have been found to be a contributing factor that weakens ice shelves before a collapse.

Ice shelf collapse has been in the news recently on account of fears of a large crack in the Larsen C Ice Shelf generating a huge iceberg.  Though the exact causes for crack generation on ice shelves remain unclear, new research presented by British Antarctic Survey scientists at the conference in Vienna highlighted that föhn winds accelerate melting at the ice shelf surface.  They also supply water which, as it drains into the cracks, deepens and widens them.

Meanwhile, deep under ocean waters, great gouge marks left behind on the seafloor as ancient icebergs dragged along seabed sediments have been collected into an Atlas of Submarine Glacial Landforms, published by the Geological Society of London. The collection of maps sheds light on the past behaviour of ice and can give clues as to how scientists might expect ice sheets to respond to a changing climate.

Drumlins (elongate hills aligned with the ice flow direction) from the Gulf of Bothnia in the Baltic Sea. Credit: Atlas of Submarine Glacial Landforms/BAS

Closer to the Earth’s surface, groundwater also attracted its fair share of attention throughout the meeting. It’s hardly surprising considering groundwater is one of the greatest resources on the planet, globally supplying approximately 40% of the water used for irrigation of crops and providing drinking water for billions around the world. ‘Fossil’ groundwater, which accumulated 12,000 years ago was once thought to be buried too deep below the Earth’s surface to be under threat from modern contaminants, but a new study presented during the General Assembly has discovered otherwise.

Up to 85% of the water stored in the upper 1 km of the Earth’s outermost rocky layer contains fossil groundwater. After sampling some 10,000 wells, researchers found that up to half contained tritium, a signature of much younger waters. Their presence means that present-day pollutants carried in the younger waters can infiltrate fossil groundwater. The study recommends this risk is considered when managing the use of fossil waters in the future.

Links we liked

News from elsewhere

The spectacular end to the Cassini mission has featured regularly in this month’s bulletins.

During its 13 years in orbit, Cassini has shed light on Saturn’s complex ring system, discovered new moons and taken measurements of the planet’s magnetosphere. On September 15th,  the  mission will end when the probe burns up in Saturn’s atmosphere.

On 22 April, the final close flyby of Saturn’s largest moon, Titan, propelled the Cassini spacecraft across the planet’s main rings and into its Grand Finale series of orbits. This marks the start of the final and most audacious phase of the mission as the spacecraft dives between the innermost rings of Saturn and the outer atmosphere of the planet to explore a region never before visited; the first of 22 ring plane crossings took place on 26 April.You can watch a new movie which shows the view as the spacecraft swooped over Saturn during the dive here.

For an overview of highlights from the mission and updates from the ring-grazing orbits that began in November 2016 watch this webstream from a press conference with European Space Agency scientists at the General Assembly last week.

To stay abreast of all the EGU’s events and activities, from highlighting papers published in our open access journals to providing news relating to EGU’s scientific divisions and meetings, including the General Assembly, subscribe to receive our monthly newsletter.

At the General Assembly 2017: Thursday highlights

At the General Assembly 2017: Thursday highlights

Welcome to the fourth day of General Assembly excitement! Once again the day is packed with great events for you to attend and here are just some of the sessions on offer. You can find out more about what’s on in EGU Today, the daily newsletter of the General Assembly – grab a copy on your way in or download it here.

The Union-wide session of the day focuses on making facts greats again: how can scientists stand up for science (US3)? The session aims to identify strategies to counter recent attacks on science and brainstorm ways in which scientists can stand-up for science. With a selection of high profile panellists: Christiana Figueres, Sir David King, Heike Langenberg, Christine McEntee and the EGU’s President, Jonathan Bamber as chair person, the session promises to be one of the conference highlights. Join the discussion from 10:30 to 12:00 in room E2.

Thursday also sees two interesting Great Debates taking place: Arctic environmental change: global opportunities and threats (GDB1, from 08:30–10:00 in E2, jointly organised with American Geophysical Union – AGU). While many scientist support open access publishing, is support for open access to the underlying research data as easy to achieve? Join the discussion in GDB4, from 15:30 to 17:00 in room E1. At the same time, in room D1, conference participants can take part in the third Great Debate of the day. The two-way, complex interactions between urban and geophysical systems has been recently recognised as the key question for the fate our planet and the issue of the Anthropocene. How can we transition to next generation cities and planet Earth future?  Tune into to the sessions on Twitter using the #EGU17GDB hashtag or online at http://www.egu2017.eu/webstreaming.html.

Today’s interdisciplinary highlights include sessions on…

Take the opportunity to expand your skills in one of today’s short courses and splinter meetings. Be sure to share what you learn on social media using the hashtag #EGU17SC:

There’s also a number of Medal Lectures on throughout the day – here’s a sample of what’s on offer:

What have you thought of the Assembly so far? Let us know at www.egu2017.eu/feedback, and share your views on what future EGU meetings should be like!

If you need a change of pace, stop by the Imaggeo Photo Exhibition beside the EGU Booth (Hall X2, basement, Brown Level). You can vote for your favourite finalists there and – while you’re in the area – take the opportunity to meet your Division’s representatives in today’s Meet EGU appointments. While on the subject of competitions, make sure to ‘like’ your favourite  Communicate Your Science Video Competition film on the EGU YouTube channel.

Have a lovely day!

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