The ‘Beast from the East’ and the freakishly warm Arctic temperatures are no coincidence

Frozen: the Kennet & Avon canal, Bath. Image: Getty.

During the past few weeks, bitterly cold weather has engulfed the UK and most of Northern Europe. At the same time, temperatures in the high Arctic have been 10 to 20°C above normal – although still generally below freezing.

The co-occurence of these two opposite extremes is no random coincidence. A quick climate rewind reveals how an unusual disturbance in the tropics more than a month ago sent out shock-waves thousands of kilometres in all directions, causing extreme weather events – not only in Europe and the Arctic, but in the southern hemisphere too.

The outbreak of cold weather across the UK was publicly forecast at least two weeks in advance. In early February, meteorologists noticed a large-scale weather event developing 30km high in the Arctic stratosphere, whose effects on our less lofty weather systems are well understood.

The strong westerly winds, known as the Polar Vortex, that normally circle the Arctic at this altitude had begun to weaken and change direction. Extremely cold arctic air – usually entrapped by this 360° barrier – was able to spill out to lower latitudes, flooding across Siberia.

Meteorologists refer to this type of event as a Sudden Stratospheric Warming (SSW) because the air in the stratosphere above the North Pole appears to warm rapidly. In fact, the cold air isn’t itself warming up so much as flooding south and being replaced by warmer air from further south.

Current air temperatures in the Arctic are much higher than recent historical averages. Image: Zachary Labe.

Changes to wind directions and temperatures 30km above the ground initially went unnoticed to those on the ground – both in Europe and in the Arctic. But over a period of several weeks, the influence of this weather event moved gradually downwards through the lower region of the atmosphere, eventually changing weather patterns near the surface.

One such change was the development of high pressure across Scandinavia, which generated easterly winds across the whole of Northern Europe, pulling cold air from Siberia directly over the UK. Out over the Atlantic Ocean the same area of high pressure resulted in southerly winds allowing warm air from the Atlantic to move northwards into the Arctic basin. Research shows that these weather shifts tend to be fairly persistent once they do occur – hence the unusual length of the cold spell we’re experiencing, and the warmth in the Arctic.

But what caused the stratospheric Arctic warming event to happen in the first place? For this we need to look thousands of kilometres away to the atmosphere above the tropical West Pacific Ocean. In late January, a vast area of thunderstorms, as large and strong as have ever been recorded, were disturbing the atmosphere across this region. The effect of these storms was equivalent to the dropping of a large boulder into a pond – they caused waves of alternating high and low pressure to spread through the atmosphere, particularly into the northern hemisphere. It was these waves bumping into the vortex of winds around the North Pole that caused the Sudden Stratospheric Warming event in early February.

The very same area of thunderstorms across the tropical Pacific acted as the birthplace for the less-reported Cyclone Gita, which tracked through the South Pacific, causing damage in Tonga and Samoa and even leading to unseasonably stormy weather across New Zealand at the end of their summer.


The near simultaneous occurrence of all of these extreme weather events is a perfect meteorological illustration of the butterfly effect. While we usually talk about weather in local and regional terms, the atmosphere is one continuous fluid expanse. Disturbances in one region are bound to have consequences to the weather in other parts of the world – and when they are severe the shock-waves can be immense.

Many have linked the severity of these events with climate change. But, particularly for this event, its important for us meteorologists to exercise caution. The occurrence of this particular stratospheric warming event is not itself a consequence of climate change, as one extreme weather event on its own does not tell us anything about long-term trends in the Earth’s climate.

What’s important is to look at how often these events occur – and how severe they are when they do. However, the series of events that lead to cold weather over Europe are complex and have only been well understood for the past 20 years or so. Without a few more decades of data, it is difficult to say whether either the stratospheric warming or the intense tropical storms are part of a pattern that falls outside of what we would normally expect – though limited research does already suggest that Stratospheric Sudden Warming events are becoming more frequent.

The ConversationFor other extreme weather events, the story is clearer – evidence increasingly suggests that hurricanes, storms and wildfires are becoming both more frequent and more severe than they once were. Time will tell if its the same story for Stratospheric Sudden Warming and tropical disturbances.

Evidence from these recent temperature extremes will certainly help researchers to understand this question. But if we do what we can to minimise the damaging impacts of climate change, we may never need to find out.

Peter Inness, Lecturer in Meteorology, University of Reading.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

What other British cities can learn from the Tyne & Wear Metro

A Metro train at Monument. Image: Callum Cape/Wikipedia.

Ask any person on the street what they know about Newcastle, and they’ll list a few things. They’ll mention the accent; they’ll mention the football; they’ll mention brown ale and Sting and Greggs. They might even mention coal or shipbuilding, and then the conversation will inevitably turn political, and you’ll wish you hadn’t stopped to ask someone about Newcastle at all.

They won’t, however, mention the Tyne and Wear Metro, because they haven’t probably heard of it – which is a shame, because the Metro is one of the best things the north-east has to offer.

Two main issues plague suburban trains. One is frequency. Suburban rail networks often run on poor frequency; to take Birmingham for an example, most of its trains operate at 30-minute intervals.

The other is simplicity. Using Birmingham again, the entire system is built around New Street, leading to a very simple network. Actually, that’s not quite true: if you’re coming from Leamington Spa, Warwick, Stourbridge, Solihull or a host of other major minor (minor major?) towns, you don’t actually connect to New Street – no, you don’t even connect to the ENTIRE SYSTEM BUILT AROUND NEW STREET except at Smethwick Galton Bridge, miles away in the western suburbs, where the physical tracks don’t even connect – they pass over each other. Plus, what on earth is the blue line to Walsall doing?

An ageing map of the West Midlands rail network: click any of the images in this article to expand them. Image: Transport for the West Midlands/Centro.

But Newcastle has long been a hub of railway activity. Tragically, the north-east has fewer active railway lines than any other region of the UK. Less tragically, this is because Tyne and Wear has the Metro.


The Metro was formed in 1980 from a somewhat eccentric collection of railways, including freight-only lines, part of the old Tyneside Electrics route, underground tunnelling through the city centre, track-sharing on the National Rail route to Sunderland, and lines closed after the Beeching axe fell in the early 1960s.

From this random group of railway lines, the Metro has managed to produce a very simple network of two lines. Both take a somewhat circuitous route, the Yellow line especially, because it’s literally a circle for much of its route; but they get to most of the major population centres. And frequency is excellent – a basic 5 trains an hour, with 10 tph on the inner core, increasing at peak times (my local station sees 17 tph each way in the morning peak).

Fares are simple, too: there are only three zones, and they’re generally good value, whilst the Metro has been a national leader in pay-as-you-go technology (PAYG), with a tap-in, tap-out system. The Metro also shares many characteristics of European light rail systems – for example, it uses the metric system (although this will doubtless revert to miles and chains post-Brexit, whilst fares will be paid in shillings).

 

The Metro network. Image: Nexus.

Perhaps most importantly, the Metro has been the British pioneer for the Karlsruhe model, in which light rail trains share tracks with mainline services. This began in 2002 with the extension to Sunderland, and, with new bi-mode trains coming in the next ten years, the Metro could expand further around the northeast. The Sheffield Supertram also recently adopted this model with its expansion to Rotherham; other cities, like Manchester, are considering similar moves.

However, these cities aren’t considering what the Metro has done best – amalgamated local lines to allow people to get around a city easily. Most cities’ rail services are focused on those commuters who travel in from outside, instead of allowing travel within a city; there’s no coherent system of corridors allowing residents to travel within the limits of a city.

The Metro doesn’t only offer lessons to big cities. Oxford, for example, currently has dire public transport, focused on busy buses which share the same congested roads as private vehicles; the city currently has only two rail stations near the centre (red dots).

Image: Google.

But it doesn’t need to be this way. For a start, Oxford is a fairly lateral city, featuring lots of north-south movements, along broadly the same route the railway line follows. So, using some existing infrastructure and reinstating other parts, Oxford’s public transport could be drastically improved. With limited engineering work, new stations could be built on the current track (blue dots on the map below; with more extensive work, the Cowley branch could be reinstated, too (orange dots). Electrify this new six-station route and, hey presto, Oxford has a functioning metro system; the short length of the route also means that few trains would be necessary for a fequent service.

Image: Google.

Next up: Leeds. West Yorkshire is a densely populated area with a large number of railway lines. Perfect! I hear you cry. Imperfect! I cry in return. Waaaaaah! Cry the people of Leeds, who, after two cancelled rapid transit schemes, have had enough of imaginative public transport projects.

Here’s a map of West Yorkshire:

Image: Google.

Here’s a map of West Yorkshire’s railway network:

 ​

Image: West Yorkshire Metro.

The problem is that all of the lines go to major towns, places like Dewsbury, Halifax or Castleford, which need a mainline connection due to their size. Options for a metro service are limited.

But that’s not to say they’re non-existent. For example, the Leeds-Bradford Interchange line passes through densely populated areas; and anyway, Bradford Interchange is a terminus, so it’s poorly suited to service as a through station, as it’s currently being used.

Image: Google.

With several extra stops, this line could be converted to a higher frequency light rail operation. It would then enter an underground section just before Holbeck; trains from Halifax could now reach Leeds via the Dewsbury line. The underground section would pass underneath Leeds station, therefore freeing up capacity at the mainline station, potentially simplifying the track layout as well.

 

Image: Google.

Then you have the lines from Dewsbury and Wakefield, which nearly touch here:

Image: Google.

By building a chord, services from Morley northwards could run into Leeds via the Wakefield line, leaving the Dewsbury line north of Morley open for light rail operation, probably with an interchange at the aforementioned station.

Image: Google.

The Leeds-Micklefield section of the Leeds-York line could also be put into metro service, by building a chord west of Woodlesford over the River Aire and connecting at Neville Hill Depot (this would involve running services from York and Selby via Castleford instead):

The path of the proposed chord, in white. Image: Google.

With a section of underground track in Leeds city centre, and an underground line into the north-east of Leeds – an area completely unserved by rail transport at present – the overall map could look like this, with the pink and yellow dots representing different lines:

Et voila! Image: Google.

Leeds would then have a light-rail based public transport system, with potential for expansion using the Karlsruhe model. It wouldn’t even be too expensive, as it mainly uses existing infrastructure. (Okay, the northeastern tunnel would be pricey, but would deliver huge benefits for the area.)

Why aren’t more cities doing this? Local council leaders often talk about introducing “metro-style services” – but they avoid committing to real metro projects because they’re more expensive than piecemeal improvements to the local rail system, and they’re often more complex to deliver (with the lack of space in modern-day city centres, real metro systems need tunnels).

But metro systems can provide huge benefits to cities, with more stops, a joined-up network, and simpler fares. More cities should follow the example of the Tyne and Wear Metro.