Climate change adaptation and dealing with heatwaves

Madrid and Miami often rank among the world’s most desirable cities to live in.

Reflecting such demand, house prices in the Spanish capital have risen more than 60 per cent since 2015, while the average price of single-family homes in the second-most populous city in Florida more than doubled in the three years to 2021.Institute of National Statistics in Spain as of 31.03.2022; in Miami-Dade, Broward and Palm Beach counties, ISG World Miami report Q4 2021

Yet, thanks to global warming, both cities could become uninhabitable in a matter of decades.

This year, for example, Madrid, suffered its earliest heatwave in more than 40 years, with the mercury having risen above 40°C in early May.

Scientists warn possible increases in maximum temperatures of as much as 5°C in the Spanish capital by 2050 will lead to more frequent and intense episodes of wildfires, droughts and floods; at the same time, loss of biodiversity and changes in ecosystems could boost risks to public health by hastening the spread of infectious disease.City of Madrid

Miami’s existential threat, meanwhile, comes in the form of rising sea levels. It is, by common consent, one of the most vulnerable coastal metropolises in the world.

A recent report by the Urban Land Institute warned that by 2040, more than USD3 billion worth of the city’s property could be lost to daily tidal flooding. By 2070, that figure is projected to increase to a staggering USD23.5 billion.https://knowledge.uli.org/reports/research-reports/2020/the-business-case-for-resilience-in-southeast-florida

Madrid and Miami are isolated cases. Today, around 30 per cent of the world's population, many living in cities, is exposed to lethal heat events for at least 20 days a year.Mora et al. Global risk of deadly heat. Nature Clim Change 7, 501–506 (2017). https://doi.org/10.1038/nclimate3322 Meanwhile, the total urban population at risk from sea level rise could reach over 800 million people, living in 570 cities, by mid-century, with global economic costs amounting to USD1 trillion.C40

And this problem is about to get worse. Even if we stop carbon emissions today, global temperatures will take a long time to fall.

This is because about half of the CO2 that we have emitted in the past will remain in the atmosphere for a long time and will continue to warm the planet even though no new CO2 is being added.

The influential Intergovernmental Panel on Climate Change (IPCC) estimates global warming will stay for at least another 100 years at about the level reached when emissions are completely stopped.

This explains why adaptation to climate change – efforts to adapt and live with the effects of warming already in the pipeline – is just as important as measures to mitigate global temperature rises.

Adaptation examples include improved cropland management, sustainable urban planning, improved water and resource efficiency and resilient power systems.

The problem, as COP26 President Alok Sharma has observed, is that adaptation has long been the “poor cousin” of mitigation.

A huge gap in finance also reinforces his point. The OECD estimates that adaptation captures only about 25 per cent of climate finance, compared with 64 per cent for mitigation.

Dr Nicolas Gruber, Professor of Environmental Physics at ETH Zurich, says adaptation and mitigation can overlap.

“There are a number of areas, especially in the areas of buildings and infrastructure, where the two have strong synergies. Those should be fully exploited,” he says.

The IPCC, of whose reports Dr Gruber has been an author, defines climate change adaptation as efforts to reduce risk and vulnerability to climate change, strengthen resilience, enhance well-being and the capacity to anticipate, and respond successfully to change.IPCC AR6 WGII, SPM (2022)

A report by the Global Centre on Adaptation (GCA) shows that without adaptation, climate change may depress growth in global agriculture yields up to 30 per cent, affecting 500 million small farms the most.

What is more, the number of people who may lack sufficient water at least one month per year will exceed 5 billion by the middle of the century from today’s 3.6 billion.https://gca.org/wp-content/uploads/2019/09/GlobalCommission_Report_FINAL.pdf

But the benefits of investing adaptation often outweigh the costs.

The GCA estimates investing in USD1.8 trillion globally from 2020-2030 could generate USD7.1 trillion in total net benefits targeting five areas: early warning systems, climate resilient infrastructure, improved dryland agriculture crop production, global mangrove protection and investments in efficient and resilient water sources.

Urban cooling

Some countries like Singapore are already taking action and investing in adaptive projects. Among them is Cooling Singapore, where researchers led by Dr Gruber’s colleagues at the ETH-Singapore centre are addressing ways to mitigate urban heat challenges.https://sec.ethz.ch/research/cs/About.html

Currently in phase three, the project has already come up with 80 measures to reduce urban heat. Just as importantly, the research team has also developed metrics to assess heat island effects – the phenomenon through which urban temperatures climb as much as 7°C higher than in rural ones – and has proposed climate-responsive urban design guidelines.

In tackling urban heat, it’s important to know that heat stress is generated by not just high temperatures but also humidity.

High temperatures alone are seldom fatal; it’s the combination of high temperatures and humidity that is deadly, since at high humidity, the body’s ability to cool itself by sweating is greatly diminished.

This is why scientists monitor the wet bulb temperature, which measures precisely both heat and humidity.

Not commonly known except among meteorologists until recently, the wet bulb temperature represents the minimum temperature a water saturated body can attain by evaporative cooling. If this is too high, the human body cannot cool itself down and die of hyperthermia.

Humans are unable to survive for more than a few hours in the shade, even with unlimited water, at a wet bulb temperature of around 35°C.

Fortunately, such conditions are currently very seldom reached in the current climate. But unmitigated climate change could push a number of regions, among those places with high populations, into this range.

To effectively cool a building, therefore, it is important to not only reduce heat but also lower humidity.

Typically, conventional building air conditioning units do both at the same time with a single temperature setting. However, the centralised system tends to be bulky, energy intensive and take up floor space.

The ETH-Singapore centre project has come up with an innovative building design which tackles one thing at a time: removing heat from the building interior; and removing moisture from outside air.

In its “3for2” design, the cooling and dehumidifying functions are split, because it is more efficient to cool a building at a temperature that is higher than what is required for dehumidifying.https://systems.arch.ethz.ch/demonstrators/3for2-at-uwc

It also uses several small and decentralised ventilation units instead of a single one.

This way, air distribution through the entire building becomes unnecessary and compact units can be integrated into the façade or the floor.

Compared with a standard “green building” in Singapore, this concept provides 20 per cent more office space, reduces energy consumption by 40 per cent and requires 16 per cent less construction materials.https://www.researchgate.net/project/3for2-Buildings-Achieving-Material-Energy-Space-Efficiency

"The 3for2 building concept is a great example of how adaptation and mitigation goes hand in hand. This is unfortunately not always the case, since adaptation is complex and comes with substantial risks for maladaptation. An adaptive and forward thinking strategy is key to success,” Dr Gruber says.

Maladaptation occurs when adaptation projects provide wrong incentives, such as when the construction of seawalls to protect against sea-level rises leads to developers putting even more assets at risk. Such projects waste time and money and make the world more, rather than less, vulnerable to climate change.

“Yet, adaptation is not rocket science. Many solutions are already developed and in the market. What is missing is a better understanding of the risks and benefits, and then the implementation of these solutions,” he says.