Why are cities so much hotter than the surrounding areas?

Scorchio! London. Image: pic fix/Flickr/creative commons.

In cities, the air, surface and soil temperatures are almost always warmer than in rural areas. This effect is known as the Urban Heat Island – a term which first came into use in the mid-20th century. Until the 1980s, this effect was considered to have relatively little practical significance. In fact, given that most studies were done in cities with cold winter climates, a warmer temperature was seen as a potential benefit, because it reduced the need for heating. But since then, we’ve found a number of reasons to be concerned.

For one thing, it became clear that the Urban Heat Island (UHI) effect of cities was influencing air temperature records, which are used to assess climate change. In other words, it became important to remove urban “contamination” from weather station records to ensure their accuracy.

What’s more, as populations in warm and hot cities have increased, so too has the demand for indoor cooling – typically met by air conditioning. This even applies in colder climates, where changing building uses has increased the demand for cooling; for example, in office buildings, to offset the heat generated by computers.

In these situations, the UHI adds to the heating burden: ironically, cooling buildings with air conditioners increases outdoor air temperatures.

Heatwaves have the power to kill; for example, during the 2003 heatwave in Europe, 70,000 additional deaths were recorded, making it one of the region’s deadliest natural disasters of the last 100 years. The UHI makes city dwellers more vulnerable to the dangerous effects of extreme weather events like this.


The potential medical impact is perhaps the most significant issue related to UHI, especially against the backdrop of continued climate change and global warming. For all these reasons, it’s crucial to understand how the UHI works, so that we can find ways to mitigate and adapt to its effects.

Understanding the UHI

The UHI is strongest during dry periods, when the weather is calm and skies are clear. These conditions accentuate the differences between urban and rural landscapes. Cities are distinguished from natural landscapes by their form: that is, the extent of the urban land cover, the construction materials used, and the geometry of buildings and streets. All of these factors affect the exchanges of natural energy at ground level.

Much of the urban landscape is paved and devoid of vegetation. This means that there is usually little water available for evaporation, so most available natural energy is used to warm surfaces. Construction materials are dense, and many – particularly dark-coloured surfaces like asphalt – are good at absorbing and storing solar radiation.

Urban jungle. Image: Mdalmul/Flickr/creative commons.

Meanwhile, the shape and positioning of buildings in the city slows the movement of air near the ground, creates complex patterns of shade and sunlight and limits natural energy exchanges. Urbanisation is also associated with the emission of waste heat from industry, transport and buildings, which contributes directly to the UHI.

There are, however, different types of UHIs, with different dominant causes.

Keeping our cool

“Surface UHI” refers, unsurprisingly, to warmer urban temperatures at the Earth’s surface. Typically, this type of UHI is measured using satellites with a plan view of the city, so that the temperature of roofs and roads (but not walls) can be measured. From this perspective, the surface UHI is highest during the daytime, when hard urban surfaces receive solar radiation and warm quickly.

Another type of UHI is based on observations of air temperature, which are made close to the ground; in the city, this means placing the instruments below roof height. This UHI is usually strongest at night, as street surfaces and the adjacent air cool slowly. Above the roof level, the contributions of streets and building roofs together warm the overlying urban atmosphere. In some conditions, this warming can be detected up to 1km to 2km above the surface.

The geography of the Urban Heat Island. Image: Jamie Voogt/University of Western Ontari/author provided.

The geography of the UHI is relatively simple – it’s magnitude generally increases from the urban outskirts towards the city centre. However, it also contains many micro-climates – for example, parks and green spaces appear as cool spaces.

The UHI is an inevitable outcome of the landscape changes that accompany urbanisation. But its magnitude and impacts can be managed by modifying some physical aspects of our cities. This can include increasing vegetative cover and reducing impermeable cover; using lighter coloured materials, designing urban layouts to allow for better ventilation through the streets and buildings, and managing urban energy use.

Laying a cool roof. Image: NNSANews/Flickr/creative commons.

Of course, these solutions need to be tailored to the type of UHI. For example, a focus on building cool or green roofs will have an impact on the overlying air and the top floor of buildings, but may have little impact on the UHI at street level. Similarly, trees may be an effective means of providing street shade, but if the canopy encloses the street, then it can trap traffic emissions, resulting in poor air quality.

The ConversationAs a first step, many cities have completed UHI studies to identify the “hot-spots”, where design interventions could have greatest effect. But what most cities need is a coherent climate plan, which addresses interrelated environmental issues including flooding and air quality, as well as surface and air temperatures.

Gerald Mills, Senior Lecturer in Geography, University College Dublin.

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

 
 
 
 

Canada’s gay neighbourhoods are struggling. Can queer pop-ups plug the gap?

Vancouver. Image: Getty.

Queer life was highly visible in Western Canada last year. In May, Vancouver declared 2018 the “Year of the Queer,” celebrating decades of service that the city’s cultural organisations have provided for lesbian, bisexual, gay, transgender, queer and two-spirit (LGBTQ/2S) people across the region.

Yet 2018 also saw the loss of multiple queer venues and gay bars. While economic forces, such as rapacious gentrification are part of the story and struggle, our research shows that something creative and generative is happening in the city as well.

In the face of changing urban landscapes, economic hardships, and more straights moving into historically gay neighbourhoods, queer pop-ups — ephemeral gathering spaces whose impact lingers among revellers long after the night is over — now play a large role in the fight for LGBTQ/2S equality.

Scattered gay places became neighbourhoods

Queer life germinated in “scattered gay places” across cities in North America from the late 1800s to the Second World War. Inside cabarets, bars, theatres or outside in public parks, washrooms and city streets, queers found spaces which could hold and celebrate transgressive sexual connections while also providing respite from daily experiences of discrimination and social exclusion.

After the Second World War, scattered gay places congealed into permanent gay bars and residential “gaybourhoods” in a period anthropologist Kath Weston calls “the great gay migration.” Queer people flocked to urban centres and sexual subcultures flourished in cities like New York, Chicago, San Francisco, Los Angeles and Toronto.

The formation of queer community spaces has always been controversial. Cultural and legal backlashes marred early developments. A host of laws and regulations tried to suppress and contain homosexuality in North America by limiting its presence in the public sphere.

These measures resulted in frequent hostilities, police raids and violence. Queers congregated together not just to find love or community, but to protect themselves, to protect one another and to find refuge. Pride parades, now celebrated worldwide, commemorate these early turf wars.

Pop-ups revitalise queer spaces

Researchers have written a great deal on the cultural and political importance of gay districts in urban centres, and they have grappled with concerns that these areas, along with the establishments they house, are fading.

But innovative urban forms challenge arguments about the death and demise of queer spaces in the city. Our research suggests that queer pop-ups, or temporary cultural gathering spaces, cater to diverse and often marginalised queers.

Some gaybourhoods are dwindling in their residential concentration and gay bars are dropping like flies. But new queer place-making efforts are emerging.

Two of the authors at the queer pop-up in 2018 at East Side Studios in Vancouver. Ryan is on the far left, back row, Adriana is on the far right of the back row. Image: author provided.

Unlike gaybourhoods and gay bars, pop-ups are intentional in how they address persistent, intersectional forms of inequality. Queer pop-ups offer patrons a space to explore non-binary forms of gender and sexual identities, and especially a place to experience collective effervescence among queer people of colour, and femme lesbians.

Some pop-ups create environments that are explicitly trans-inclusive, consent-focused, and sex-positive. Pop-ups are not panaceas for queer life. Pop-ups can also be places where issues around socioeconomic status, gender identity and expression, and racial inequality are called out.

Yet these spaces directly and indirectly encourage dialogue on inequalities within the queer community, conversations that help produce safer spaces for marginalised queers to find each other and forge enduring queer consciousnesses.

Turf wars

Queer pop-ups show similar trajectories of infighting and compromise that the LGBT social movement encountered from the late 1970s through the early 2000s when trying to forge a collective consciousness, gain social visibility and win legal rights.

These turf wars, expressed as contests over space and inclusion, are generally sparked over three perennial concerns: privilege, race and gender. One interviewee, a 20-year-old self-identified queer, trans person of colour (QTPoC), who spoke about Vancouver’s gay district told us:

“I tend to avoid the gay bars on Davie [because] a lot of the gay bars there have now been taken over by cis-gender, heterosexual people. I’ve [also] heard from a lot of QTPoC friends that they are often uncomfortable going to gay bars on Davie, because it’s usually very dominated by cis-gender, white gay men.”

A 28-year-old white, cisgender, queer male found pop-ups more politically and culturally radical than gay bars. He put it this way:

“It’s very rare that we’ll ever have a conversation about politics [in gay bars]. It’s just about partying and things that we kind of see as very stereotypical portrayals of gay culture: like going out, dancing, drinking, fucking.”

Historically, gaybourhoods have served an important role in the fight for LGBT rights, but they have also developed to cater to a specific cis-gender, white, middle-class, male sensibility. One 30-year-old, white, trans DJ put it bluntly, “the mainstream scene is just not welcoming to trans people, in my experience,” adding that verbal transphobic harassment is common in the streets of Vancouver’s gaybourhood.

At Vancouver Pride this year we were reminded of this schism at a local pop-up event. “Gay men won’t come here, it’s too trashy,” shouted a white Australian lesbian playfully to friends over loud music. We were at Eastside Studios, a large warehouse turned into the newest collaborative queer venue in Vancouver.


The comment was striking because it highlights the visible bifurcation occurring in queer life and queer consumption in Vancouver. Many gay men tend to patronise businesses and events in the West End, Vancouver’s official gaybourhood; whereas, other members of the LGBTQ community are scattered across the city at events and venues that are far less permanent. Eastside Studios attempts to break through the homonormative bent some gay bars perpetuate. It is a space that generously houses some of the struggling pop up events who lost space to gentrification in Vancouver’s out of control rental market.

Historically, pop-ups arose as the first signs of urban sexual transgression. They continue to emerge as spatial innovations which nurture transgressive queer diversities that do not have space or representation in the gaybourhood. Weekly social media blasts via Facebook or Instagram and word-of-mouth dissemination play an important role in linking queers around the city to these events. Pop-ups take different tones and establish different vibes among patrons. Collectively, pop-ups highlight the many important projects local queers are undertaking to increase the plurality of what queer life looks like and how it is expressed.

Struggles for equality

Marriage is the leading story in many headlines these days, but queer struggles for equality were never only about relationship recognition or acceptance into the mainstream.

Queer struggles are also fights to resist oppressive normativity, to end racial inequality and white supremacy, to end sexualised violence, to reconcile generational traumas associated with colonialism.

Continuing these fights is perhaps what makes queer pop-ups unique. Organisers of these events are intentional and responsive to such concerns. They seek to create new worlds that soften the impact of inequalities, both in gaybourhoods and in other parts of Canadian cities as well.

Pop-ups nourish queer lives; they emerge as temporary meeting grounds where diverse, oftentimes marginalised, queers flock for community and collective, momentary release. Here an image from a Man Up pop-up event in Vancouver. Image: Shot by Steph/Facebook/The Conversation.

Many of these spaces are an opportunity for patrons to travel in a re-imagined world, even if only for the night. While not all pop-ups that appear survive, the ones that do matter, fundamentally, because they create spaces that resist heteronormative culture and homonormativity, address intersecting inequalities, assert and anchor queer cultural and political identities, and promote well-being for a wider portion of the community in ways that gaybourhoods used to and have always had the potential to.

Pop-ups nourish queer lives in ways that gaybourhoods and gay bars historically had. They emerge as temporary meeting grounds where diverse, oftentimes marginalised, queers flock for community and collective, momentary release. They allow patrons to dance and comfortably explore the implications of their gender and sexual identities around like-minded individuals. At times they are more than friendly social gatherings, becoming sites where the moral arch of the community is shaped through demonstrations on urgent issues impacting queer lives and the surrounding community.

Queer pop-ups are vibrant locations that work to push forward the unfinished projects of social justice first envisioned during gay liberation.

The Conversation

Ryan Stillwagon, Ph.D. Student, Sociology, University of British Columbia; Adriana Brodyn, Ph.D. Candidate, University of British Columbia; Amin Ghaziani, Associate Professor of Sociology and Canada Research Chair in Sexuality and Urban Studies, University of British Columbia, and D. Kyle Sutherland, PhD Student, Department of Sociology, University of British Columbia.

This article is republished from The Conversation under a Creative Commons license. Read the original article.