What's the most effective way of keeping a hot city cool?

Nantes during last summer's heat wave. Image: Getty.

The recent spate of heatwaves through eastern Australia has reminded us we’re in an Australian summer. On top of another record hot year globally, and as heatwaves become more frequent and intense, our cities are making us even hotter.

This is the urban heat island, where city temperatures can be significantly warmer than the surrounding rural regions. The question, then, is what we can do to keep our cities cooler.

Why are cities hotter?

The temperature difference is caused by a range of factors, including dense building materials absorbing more of the sun’s energy, fewer trees to provide shade, and less soil to cool by evaporation.

Buildings can also act like the hairs on a husky, reducing wind speeds and blocking thermal radiation up to the night sky. On top of that, waste heat from car engines, air-conditioners and other energy use adds to overall air temperatures.

Why does this matter? Even a small increase in air temperature pushes up overall energy demand, and about 25 per cent of our energy bills are for only 40 hours per year when the grid is most heavily used.

The most extreme heat events can buckle train lines, cause rolling blackouts and cost billions in lost productivity. And it’s not just bad for our wallets.

Heat stress can damage organs or exacerbate existing illnesses. Since 1900, extreme heat events have killed more Australians than bushfires, cyclones, earthquakes, floods and severe storms combined.

So, what can we do?

There are a number of things individuals can do to reduce the impact of heat in their homes, such as installing light coloured roofing material, insulation or an air-conditioner.

But it gets more complicated when considering the city as a whole, and how these small actions interact with each other and with the climate.

Air-conditioners

In heatwaves, air-conditioners save lives, allowing stressed bodies time to cool. But our homes can only be made cooler by blowing heat outside, along with the extra energy to run the system.

As well as increasing outside air temperatures in the short term, the fossil fuels burned add to global warming. A world cooled by air-conditioning probably isn’t the answer.

Trees and parks

Trees provide shade, but also cool the air, because evaporating water from leaves takes energy, reducing peak temperatures by 1-5° C.

Most city planners agree on the broad benefits of urban vegetation, with some metropolitan councils developing urban greening strategies.

However, urban trees can be a vexed issue for some councils; they use water, can be costly to maintain, can damage utilities and property, and can worsen air quality instead of improving it. Larger cities are often made up of dozens of councils; getting them to agree is a major challenge.

White roofs

We know that black surfaces get hotter in the sun, but demand for dark roof tiles still far outweighs demand for light colours. More reflective roofs can reduce a household’s energy bill, as well as the overall temperature of a city.

White roofs are most effective in warmer climates, because in cold climates, the cost savings in summer must be balanced with additional heating costs in winter.

Green roofs and walls

Green roofs and walls are building structures with integrated vegetation. They provide cooling benefits by shading buildings and through evaporation from leaves. They generally show less cooling benefit than white roofs, cost more to install and maintain, and use additional water and energy.

But they do look nice, improve biodiversity and make people happier.


Pavement watering

Prior to an extreme heatwave, it may be possible to reduce temperatures by wetting down building and road surfaces. It’s a traditional practice in Japan, and is now being considered in major cities like Paris.

But temperature and humidity are important factors in heat stress, so pavement watering should only be undertaken if the extra humidity does not increase heat stress.

Large scale rooftop solar

Solar panels convert energy from the sun into electricity, so less energy is required from the network overall. If enough roofs were covered with solar panels, could that lower air temperatures?

Probably a little. Other benefits include a reduction in the energy required for cooling (because the roofs are shaded by panels), and a stable, lower cost, decentralised renewable energy system.

Building density

A building with lots of thermal mass (think sturdy, double-brick home) can be an effective way to keep inside temperatures more stable. Heat is absorbed during the day and released at night. The same idea can work for an entire city.

An urban cool island can form in high-density cities like Hong Kong because tall buildings provide extra heat capacity and shade.

For similar reasons, the tight street layout of traditional Arabian and Mediterranean cities keep those streets cooler.

Shading structures

Installing light shading structures over streets, pavements and roofs can reduce the surface temperature of materials, and reduce the heat absorbed and radiated back into streets. Shading structures need to be designed so that they do not limit airflow, trapping heat and air pollution in streets.

Which is best?

To figure out what works best, we need to be able to model the physics of different strategies, in different types of cities and in different climates. We can then assess the economic and health impacts and decide on appropriate and plans that give us the biggest bang for our buck.

Here we have focused on heat in cities, but there are other important concerns like air quality or flooding.

In colder cities, an urban heat island could actually be a good thing. Each city is different; each requires a tailored and integrated plan developed over the entire metropolitan region, and then implemented locally by councils, businesses and households.The Conversation

Mathew Lipson is a PhD Candidate, and Melissa Hart the graduate director of the ARC Centre of Excellence for Climate System Science, at UNSW Australia.

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

 
 
 
 

British television once sounded like Britain. But then, the ITV mergers happened

The Granada Studios, Quay Street, Manchester. Image: Wikimedia Commons.

This summer, several ITV franchises celebrated half a century of continuous operation. There was a Yorkshire Television themed cake, and a flag bearing the company’s logo was flown over ITV’s Yorkshire base for a time. It was all very jolly – but while a few people beyond Britain’s small community of television historians and old telly nerds engaged with the idea, any excitement was brief.

The main reason for is not, as you might assume, that, in the era of streaming and so forth, ITV is no longer a dominant presence in many people’s cultural lives: even the quickest of glances at the relevant figures would tell you otherwise. No, it’s because the mere existence of ITV’s franchises is now passing out of common memory. They are the trademarks, literally rather than figuratively, of a version of ITV that today exists only nominally.

For most of its history, ITV operated on a federal model. ITV wasn’t a company, it was a concept: ‘Independent Television’, that is, television which was not the BBC.

It was also a network, rather than a channel – a network of multiple regional channels, each of which served a specific area of the UK. Each had their own name and onscreen identity; and each made programmes within their own region. They were ITV – but they were also Yorkshire, Granada, Grampian, Thames, and so on.

So when I was a child growing up the in Midlands in the ‘80s, no one at school ever said “ITV”: they said “Central”, because that’s what the channel called itself on air, or “Channel Three” because that’s where it was on the dial. To visit friends who lived in other regions was to go abroad – to visit strange lands where the third channel was called Anglia, and its logo was a bafflingly long film sequence of a model knight rotating on a record turntable, where all the newsreaders were different and where they didn’t show old horror films on Friday nights.

The ITV regions as of 1982, plus Ireland. Image: Wikimedia Commons.

Of course, there were programmes that were shown across the whole network. Any station, no matter in what part of the country, would be foolish not to transmit Coronation Street during the period where it could persuade nearly half the population to tune in. But even The Street wasn’t networked from the beginning: it started in six of the then eight ITV regions, and rolled out to the other two after a few months when it became clear the series was here to stay.

This was a common occurrence: The Avengers, one of the few ITV series to genuinely break America, began in an even more limited number of regions in the same year, with other areas scrambling to catch up when the programme became a hit.

The idea behind ITV’s structure was that the regions would compete with each other to put programmes on the network, opting in and out of others’ productions as worked best for them. ITV was, after all, an invention of a 1950s Conservative government that was developing a taste for the idea of ‘healthy competition’ even as it accepted the moral and practical case for a mixed economy. The system worked well for decades: in 1971, for example, the success of London Weekend Television’s Upstairs, Downstairs, creatively and commercially, and domestically and internationally, prompted other regions to invest in high end period dramas so as to not look like a poor relation.


Even away from prestige productions there was, inexplicable as it now seems, a genuine sense of local pride when a hit programme came from your region. That Bullseye was made on Broad Street in Birmingham was something that people knew. That 17.6m people watched the 1984 Xmas special, making it one of the ten most watched programmes of the year, made Bully a sort of local hero. In more concrete terms, Bullseye and other Birmingham based programmes provided jobs, and kept that part of the country visible from all others. This was true of all areas, and from all areas.

ITV franchises would often make programmes that were distinctive to, or set in, their region. Another of Central’s late eighties hits was Boon. It might have starred the cockney-sounding Michael Elphick, but it was filmed and set in Birmingham, just as Central’s predecessor ATV’s Public Eye had been at the end of the sixties. In Tales of the Unexpected, one of the poorest and smallest ITV regions, the aforementioned Anglia, made a bona fide international hit, largely filmed in transmission area, too. HTV produced a string of children’s series set in its south west catchment area, including some, such as The Georgian House, that examined the way the area had profited from the slave trade.

There was another element of ‘competition’ in the structure of ITV as originally conceived: the franchises were not for life. Every few years, a franchise round would come along, forcing the incumbent stations to bid to continue its own existence against other local offerings.

The process was no simple auction. Ministers were empowered to reject higher financial bids if they felt a lower bid offered other things that mattered: local employment or investment, programming plans that reflected the identity of the region they were bidding to serve, or simply higher quality programmes.

Yorkshire Television itself owes its existence to just such a franchise round: the one that followed a 1967 decision by regulator IBA that Granada, until then the holder of a pan-northern England licence, was insufficiently local to Yorkshire. For a decade, commissioning and production had been concentrated in Manchester, with little representation of, or benefit for, the other side of the Pennines. IBA’s decision was intended to correct this.

Yorkshire existed in practical terms for almost exactly 40 years. Its achievements included Rising Damp, the only truly great sitcom ever made for ITV.

But in 1997 it was, ironically, bought out by Granada, the company who had had to move aside in order for it to be created. What had changed? The law.

In 1990, another Conservative government, one even keener on competition and rather less convinced of the moral and practical case for a mixed economy, had changed the rules concerning ITV regions. There was still a ‘quality threshold’ of a sort – but there was less discretion for those awarding the franchises. Crucially, the rules had been liberalised, and the various ITV franchises that existed as of 1992 started buying out, merging with and swallowing one another until, in 2004, the last two merged to form ITV plc: a single company and a single channel.

The Yorkshire Television birthday cake. Image: ITV.

Yorkshire Television – or rather ITV Yorkshire as it was renamed in 2006 – is listed at Companies House as a dormant company, although it is still the nominal holder of the ITV licence for much of Northern England. Its distinctive onscreen identity, including the logo, visible on the cake above, disappeared early this century, replaced by generic ITV branding, sometimes with the word Yorkshire hidden underneath it, but often without it. Having once been created because Manchester was too far away, Yorkshire TV is now largely indistinguishable from that offered in London. (It is more by accident of history than anything else that ITV retains any non-London focus at all; one of the last two regions standing was Granada.)

The onscreen identities of the all the other franchises disappeared at roughly the same time. What remained of local production and commissioning followed. Regional variations now only really exist for news and advertising. TV is proud that is can offer advertisers a variety of levels of engagement, from micro regional to national: it just doesn’t bother doing so with programming or workforce any more.

Except for viewers in Scotland. Curiously, STV is an ITV franchise which, for reasons too complicated to go into here, doesn’t suffer from the restrictions/opportunities imposed by upon its English brethren in 1990. It also – like UTV in Northern Ireland, another complex, special case – Its own onscreen identity. Nationalism, as it so often does, is trumping regionalism – although it was not all that long ago that Scotland had multiple ITV regions, in recognising its own lack homogeneity and distinct regions, while respecting its status as a country.


As is often observed by anyone who has thought about it for more than four seconds, the UK is an almost hilariously over-centralised country, with its political, financial, administrative, artistic and political centres all in the same place. Regionalised television helped form a bulwark against the consequences of that centralisation. Regional commissioning and production guaranteed that the UK of ITV looked and sounded like the whole of the UK. The regions could talk about themselves, to themselves and others, via the medium of national television.

The idea of a federal UK crops up with increasing frequency these days; it is almost inconceivable that considerable constitutional tinkering will not be required after the good ship UK hits the iceberg that is Brexit, and that’s assuming that Northern Ireland and Scotland remain within that country at all. If the UK is to become a federation, and many think it will have to, then why shouldn’t its most popular and influential medium?

A new Broadcasting Act is needed. One that breaks up ITV plc and offers its constituent licences out to tender again; one that offers them only on the guarantee that certain conditions, to do with regional employment and production, regional commissioning and investment, are met.

Our current national conversation is undeniably toxic. Maybe increasing the variety of accents in that conversation will help.

Thanks to Dr David Rolinson at the University of Stirling and britishtelevisiondrama.org.uk.