Why are Spain and Portugal so unbelievably hot right now?

Wildfires in the Algarve, Portugal, last weekend. Image: Getty.

Wildfires, drought and extreme heat have been the talk of the town and country across Europe this summer. Attention has now turned to Portugal and Spain, where temperatures at the weekend reached more than 46℃ in some parts of both countries – close to the all-time European record of 48℃, set in Greece in 1977. Records aside, the obvious question is what is causing the current Iberian heatwave and whether this might be a harbinger of the future.

A number of factors can be identified. These include unusually warm sea surface temperatures in the North Atlantic, a wandering jet stream and associated “blocking” pattern of high pressure, a very dry land surface, and climate change.

The anomalous size and position of warm water areas in the North Atlantic this summer have shifted the so-called “polar front” northwards. This is the point where warm air from the south meets cold polar air, and any movement in the front will affect the distribution of high and low atmospheric pressure right across the Atlantic. This in turn influences the flow of westerly winds across the Atlantic and over Western and Southern Europe, especially the thin and fast “jet stream” in the upper atmosphere.

This summer, an area of persistent high pressure or “blocking” has become established over Western Europe and the eastern parts of the Atlantic. Such blocking causes the jet stream to appear “lazy” and wander much further north and south than its average position.

Maximum temperatures for 6 August, with large areas well into the 40s. Image: Agencia Estatal de Meteorología (AEMET).

The upshot of all of this is that atmospheric blocking and a very snake-like jet stream prevents low pressure systems, and the “bad” weather they bring, from heading eastwards across Western and Southern Europe. In such a situation, the usual fluctuations between good, and not so good, summer weather are largely put on hold. Instead, as Portugal, Spain and much of Europe have experienced, clear skies, lots of heat, and very dry surface conditions become the norm.

In certain circumstances, persistent blocking can even draw in very warm air from elsewhere. This is what happened in Portugal and Spain, after intense heat caused an area of low pressure to form over Iberia. This “heat low” created the conditions for the flow of hot dry air from the Saraha Desert. Currently life in Portugal and Spain is not just in an oven, but more like a convection oven.


A warmer baseline means hotter extremes

Heatwaves in Portugal and Spain are not uncommon because this type of extreme weather is characteristic of the hot and dry summers in the Mediterranean climate region. Yet there is convincing observational evidence that heatwaves are happening more frequently across the Iberian Peninsula. Logically the question arises as to what extent the current heat is associated with climate change.

Although answering this question thoroughly would involve undertaking some well-designed climate modelling experiments, it’s safe to say that there is indeed a fair chance the current heatwave is associated with climate change. That is because heatwaves are now happening on a background of rising global temperatures so the base level of background temperature on which extremes are occurring has lifted somewhat compared to pre-industrial levels.

And what of the question on everyone’s parched lips: are the current extremes the “new norm”? The short answer is no, not right now, as extremes of over 46℃ still constitute rare events. However, analyses of the pronounced 2003 European heat wave, which affected both Portugal and Spain, indicate that the very similar extremes of August 2003 could be fairly normal by the 2040s.

The ConversationThis of course raises questions as to the habitability of places that already possess harsh summer climates. Most likely their sustainability will depend on the extent to which traditional climate adaptation strategies related to building and lifestyles can be pushed to the limit to cope with a new climate future typified by summers with temperatures in and over the mid 40s - and how flexible people and businesses might be to the idea of going elsewhere or literally underground during summer.

Glenn McGregor, Professor of Climatology, Durham University.

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

 
 
 
 

Never mind Brexit: TfL just released new tube map showing an interchange at Camden Town!!!

Mmmmm tube-y goodness. Image: TfL.

Crossrail has just been given a £1bn bail out. This, according to the Financial TImes’s Jim Pickard, is on top of the £600m bailout in July and £300m loan in October.

That, even with the pound crashing as it is right now, is quite a lot of money. It’s bad, especially at a time when there is still seemingly not a penny available to make sure trains can actually run in the north.

But the world is quite depressing enough today, so let’s focus on something happier. On Saturday night – obviously peak time for cartographic news – Transport for London emailed me to let me know it would be updating the tube map, to show more street-level interchanges:

Connections between several pairs of stations that are near to each other, but have traditionally not been shown as interchanges, now appear on the map for the first time. These include:

  • Camden Road and Camden Town
  • Euston and Euston Square
  • Finchley Road and Finchley Road & Frognal
  • Kenton and Northwick Park
  • New Cross and New Cross Gate
  • Seven Sisters and South Tottenham
  • Swiss Cottage and South Hampstead

The stations shown meet a set of criteria that has been used to help determine which should be included. This criteria includes stations less than a 700m or a 10 minute walk apart, where there is an easy, well-lit, signposted walking route and where making the change opens up additional travel options.

The results are, well, this:

In addition, interchanges between stations have traditionally appeared on the Tube map as two solid lines, irrespective of whether they are internal or external (which means customers need to leave the station and then re-enter for the station or stop they need). This approach has now been updated and shows a clear distinction between the two types, with external interchanges now being depicted by a dashed line, linking the two stations or stops.

And lo, it came to pass:

I have slightly mixed feelings about this, in all honesty. On the positive side: I think generally showing useful street-level interchanges as A Good Thing. I’ve thought for years that Camden Road/Camden Town in particular was one worth highlighting, as it opens up a huge number of north-east travel options (Finchley to Hackney, say), and apps like CityMapper tell you to use it already.


And yet, now they’ve actually done it, I’m suddenly not sure. That interchange is pretty useful if you’re an able bodied person who doesn’t mind navigating crowds or crossing roads – but the map gives you no indication that it’s a harder interchange than, say, Wanstead Park to Forest Gate.

The new map also doesn’t tell you how far you’re going to be walking at street level. I can see the argument that a 400m walk shouldn’t disqualify something as an interchange – you can end up walking that far inside certain stations (Green Park, Bank/Monument), and the map shows them as interchanges. But the new version makes no effort to distinguish between 100m walks (West Hampstead) and 700m ones (Northwick Park-Kenton), which it probably should.

I’m also slightly baffled by some of the specific choices. Is Finchley Road-Finchley Road & Frognal really a useful interchange, when there’s an easier and more direct version, one stop up the line? No hang on West Hampstead isn’t on the Metropolitan line isn’t it? So that’s what it’s about.

Okay, a better one: if you’re switching from District to Central lines in the City, you’re generally better off alighting at Cannon Street, rather than Monument, for Bank – honestly, it’s a 90 second walk to the new entrance on Walbrook. Yet that one isn’t there. What gives?

The complete new tube map. The full version is on TfL’s website, here.

On balance, showing more possible interchanges on the map is a positive change. But it doesn’t negate the need for a fundamental rethink of how the tube map looks and what it is for. And it’s not, I fear, enough to distract from the Crossrail problem.

Jonn Elledge is the editor of CityMetric. He is on Twitter as @jonnelledge and on Facebook as JonnElledgeWrites.