Making cities cooler is a no brainer – so why aren’t we doing it?

Record temperatures hit New York City in 2008. Image: Getty.

You walk through a park in a city on a warm day, then cross out to a narrow street lined with tall buildings. Suddenly, it feels much hotter. Many people will have experienced this, and climate scientists have a name for it: the urban heat island effect.

Heavily urbanised areas within cities are 1-3 degrees hotter than other areas. They are contributing to global warming and damaging people’s health, and it’s set to get worse as urbanisation intensifies.

Numerous cities around the world are trying to do something about this problem. But there is a very long way to go. So what is holding us back, and what needs to happen?

Urban heat relates to how most cities have been designed. Many rows of tall buildings are organised into blocks which resist any natural breeze. Streets and roofs are clad in dark materials like asphalt and bitumen, which retain more heat than lighter materials and natural surfaces like soil.

Natural ground absorbs rain, which is evaporated by the sun’s rays on a warm day and released into the air, cooling everything down. In a city, the rain just runs into the sewer system instead.

Urban areas tend to lack trees. Trees help reduce the air temperature by blocking the sun’s rays, while cutting the levels of pollution by absorbing harmful particles.

Cities are also warmer because they are full of human activity. Everything from transport to industry to energy output makes them hotter than they otherwise would be.

Cause and effect

Urban heat has various consequences. Combined with heatwaves and global warming, both of which are also on the rise, these hotspots are producing conditions that kill and hospitalise growing numbers of people. The worst affected are the elderly and other vulnerable groups like the homeless.

The World Health Organisation (WHO) has warned that increased city temperatures lead to more pollutants in the air. These can aggravate respiratory diseases, particularly among children. As cities get bigger, more and more people will be affected by these threats to their health.

Higher city temperatures are one reason why we are using more and more air conditioning. One US study found that the urban heat island effect in Florida was responsible for over $400m (£287m) of extra aircon, for example.

Aircon feeds climate change by producing more carbon emissions through the extra electricity demand, creating a vicious circle where it gets hotter because more aircon is required. The increased energy demand means a greater risk of summer blackouts, causing both human discomfort and economic damage.

Hotter city roads and pavements also raise the temperature of storm-water runoff in sewers. This in turn makes rivers and lakes warmer, which can affect fish and other aquatic species in relation to things like feeding and reproduction.

Finally, there are major economic consequences to hotter cities. One paper from last year predicts that all the extra wear and tear caused by the excess heat would amount to between 1 per cent and 10 per cent of lost GDP in thousands of cities around the world.


How we’re reacting

The solutions to the problem are clear enough: they include using paler more reflective building materials, and wiser urban planning that incentivises more parks, tree planting and other natural open spaces.

When it comes to taking these steps, however, it’s a very mixed picture. Countries and municipal authorities have typically become very good at adopting plans to cut emissions of carbon dioxide and other greenhouse gases. They are not so good at taking steps to adapt to climate change. A study from 2014 found that most European cities had failed to introduce urban heat plans, and the situation looks little better today.

This being the case, city administrations that have gone the extra mile look particularly enlightened – even though they tend to be somewhat sporadic. Melbourne, for instance, has substituted its trademark bluestone pavements in several areas with a permeable version that absorbs rainwater, thereby increasing the amount of evaporation.

New York City’s Cool Roof Initiative has seen thousands of volunteers painting some of the city’s flat bituminous roofs with a reflective polymer material. Lately, Los Angeles has launched an initiative to paint roads white, part of a pledge by city hall to lower the temperature by 3 degrees in the next 20 years. Beijing, meanwhile, has been introducing zoning measures to reduce smog.

Other administrations have been encouraging green roofs – rooftops covered in vegetation: they are a legal requirement for big new developments in Toronto; there are floor area bonuses for developers who include them in Portland, Oregon; and Chicago had a funding scheme for a while. In Swiss cities and regions, green roofs have been a legal requirement for many buildings for years.

These are all just pockets of activity, however. Many other mayors and city administrations need to start implementing the kinds of bylaws and incentives to adapt to the reality of hotter cities.

The ConversationThe cities of the future can still be green and cool, but only if they move up the agendas of many city halls. The laggards need to follow the example of those that have been leading the way. The reality is that the social, environmental and economic costs of urban heat islands add up to a bill that is too high for humanity to pay.

Tiziana Susca, Research Fellow, Edinburgh Napier University and Francesco Pomponi, Vice Chancellor's Research Fellow, Edinburgh Napier University.

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

 
 
 
 

It’s time to rethink how the British railway network works

Nothing doing: commuters await a long-delayed train. Image: Getty.

The recent meltdowns on Northern and Thameslink not only left many passengers besides themselves with frustration about not being able to get to work on time, if at all. It also led to a firestorm of criticism and condemnation from politicians and media alike.

With the immediate shock of that first Monday morning of the meltdown passed, there’s a now a bigger debate about whether the way that rail services are provided for cities needs some far reaching reform. But before coming to that, the first thing to say – and as we set out in our Rail Cities UK report, launched today – is that the fundamentals for urban rail remain very strong.

Here’s why. All cities want to become denser, more dynamic places which attract the best people to the growth sectors of the economy (including the ‘flat white economy’ of media, communications and information). In order to achieve this, as well as to improve air quality, cities are also reducing space for motorised traffic in favour of space for people.

It’s very difficult to see how this can be achieved without expanding rail networks and their capacity. What’s more, if housing need is to be met without creating more sprawl and traffic congestion, then again its rail that will be key – because it opens up former rail-connected brownfield industrial sites, it extends commuting range, plus housing can be built above or around new or existing rail stations and interchanges.

In some ways there’s nothing new here. From Metroland to Docklands, successful cities have always grown with their rail networks. And to be fair, there is significant investment going into urban rail at present. Northern will get a lot better (the pacers are doomed) and both Merseyside and Tyne & Wear are getting a whole new fleet of trains for their urban rail networks.

However, much (but not all) of this investment is incremental, or replacing rolling stock on its last legs. It stops short of the wider vision for the rail cities that we need.


What would that look like in practice? There comes a point when the biggest cities need more cross-city routes, because running trains in and out of edge-of-centre termini can’t cope with the numbers. That explains the push for Crossrail 2 in London, but also the need for more cross-city capacity in cities like Birmingham (on the Snow Hill route) as well as in Manchester (on the Oxford Road to Manchester Piccadilly corridor, as well as a potential new underground route).

Tram-train technology can also help – allowing the lucky commuter that benefits to get on board at their local station and get off right outside their city centre office on main street in the city centre, rather than piling out at a Victorian railway terminal on the edge of that city centre.

Tram-trains aren’t the only tech fix available. Battery packs can extend the range of existing electric trains deeper into the “look ma, no wires” hinterlands, as well as allow trams to glide through city centres without the expensive clutter of overhead wires.

More mundane but equally useful work to increase capacity through signalling, station, track and junction work offers the opportunity to move to turn-up-and-go frequency networks with greater capacity and more reliability – networks that start to emulate the best of what comparable German rail cities already enjoy. Interlocking networks of long distance, regional express, regional, S-bahn, U-bahn, trams and buses, all under common ticketing.

But in talking about Germany and common ticketing I am now getting back to where I started around the debate on whether some fundamental change is needed on how urban rail networks are provided. Obviously there is a bigger national discussion going on about whether the current structure is just too layered, with too many costly interfaces and too fractured a chain of command. And in addition another, on whether the railway should be publicly or privately owned and operated.

But it’s been heartening to see the growing recognition that – regardless of how these debates are resolved – more devolution for urban and regional services should be part of any solution. That’s not only because fully devolved services have been out-performing comparators both operationally and in passenger satisfaction; it’s because local control rather than remote control from Whitehall will mean that the dots can be joined between rail and housing, between rail and the wider re-fashioning of city centres, and between rail and local communities (for example through repurposing stations as wider hubs for local community use, enterprises and housing). It will also allow for rail and the rest of local urban public transport networks to be part of one system, rather than be just on nodding terms as is all too often the case at present.

The crisis on Northern and Thameslink has been a miserable experience for rail users, affected cities and the rail industry. If any good has come out of it, it is that it shows how important rail is to cities, and opens up a space for some bigger thinking about what kind of rail cities we will need for the future – and how best we can make that happen.

Jonathan Bray is the Director of the Urban Transport Group which represents the transport authorities for the largest city regions. You can read the group’s full report here.