Earth Today | ‘In pursuit of cool’

AS THE sweltering summer heat hit hard this week, so did the need to revisit the raft of measures to cool cities that are detailed in a 2021 publication of the United Nations Environment Programme (UNEP).

Beating the Heat: A Sustainable Handbook for Cities was launched at the 26th sitting of the international climate talks, held annually to work through a common approach to tackling global climate change that is projected to continue to bring the heat.

The document calls, among other things, for cities to develop a city-wide cooling action plan that includes a framework for prioritising and organising interventions towards sustainable urban cooling, as well as the strategic assessment of recommendations.

The plan, according to the publication, should include strategies to address urban cooling needs, neutralise the emissions impact of current and future cooling needs, and enable access to cooling where needed, without worsening local warming.

“Such an approach – referred to as a whole-system approach – would bring integrative benefits and accelerate the shift towards sustainable urban cooling,” the publication said.

STRATEGIES

Some specific actions under that approach include:

• Reducing heat at the urban scale through the use of thermally favourable materials, and nature-based cooling practices designed to reduce the urban heat island effect, while also reducing cooling loads in buildings;

• Reducing cooling needs in buildings through energy-efficient and thermally efficient buildings, with a focus on “enhancing the thermal performance of buildings and minimising the mechanical cooling requirements, as well as the overall energy and emissions footprint of buildings using passive building design practices”; and

• Serving cooling needs in buildings efficiently through efficient and best-fit cooling technologies and operations.

The urgency to act, according to the UNEP report – launched in collaboration with the Cool Coalition, RMI, the Global Covenant of Mayors for Climate & Energy, Mission Innovation, and the Clean Cooling Collaborative – is obvious.

“We are living in an increasingly warming world … 2020 was the hottest year on record, with the average global surface temperature around 1.3 degrees Celsius higher than the late 19th-century average. The seven-year period from 2014 to 2020 was the hottest in 140 years of record-keeping. This, researchers say, is a clear indicator of the ever-increasing impact of greenhouse gas emissions,” it said.

“With growing populations – predominantly in the tropics – and rapid urbanisation, the impact of global warming is felt most acutely in cities,” the publication added.

This comes against the background of research, which shows that cities globally are warming at twice the global average due to urban heat island effect, “a phenomenon where urban areas experience higher temperatures than outlying areas due to a combination of diminishing green cover, heat gain and thermal properties of the materials commonly used in urban surfaces, as well as waste heat from human activities, such as industrial processes, transport and air conditioning”.

The implications are varied and many, and include ‘the catastrophic impact on public health.

“The urban population exposed to high temperatures – that is, average summertime temperature highs above 35 degrees Celsius – is expected to increase by 800 per cent to reach 1.6 billion by mid-century,” the publication said.

“The latest Intergovernmental Panel on Climate Change report alerts of a faster warming trend and finds that unless there are immediate, rapid and large-scale reductions in greenhouse gas emissions, limiting warming to close to 1.5 degrees Celsius or even two degrees Celsius could be beyond reach, leading us to heat extremes that more often reach critical tolerance thresholds for health,” the document noted.

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