As London swelters, adaptation to
heat extremes is now ‘urgent’
In July 2022, London experienced a temperature shock: two days of unprecedented 40 degree Celsius (104 degrees Fahrenheit) heat that buckled rail lines, put pressure on hospitals and the ambulances, overwhelmed air conditioning systems and gave the London Fire Brigade its busiest day since World War II, in part fighting home-destroying wildfires near the city’s outskirts.
“It took everybody by surprise. What we saw in two days of 40 degree heat and things grinding to a halt was how London is just not ready for an extended period of extreme heat,” said Emma Howard Boyd, the former chair of Britain’s environment agency.
London is known for its cool and rainy weather, and for its flood risks. But extreme heat is now also a top worry for the city, according to a new London Climate Resilience Review, led by Howard Boyd and published in July 2024.
It calls, among other recommendations, for swift creation of a London-wide heat action plan, and deeper preparation for potential “cascading risks”, such as extended extreme heat leading to water shortages, power failures, transport shutdowns and overwhelmed hospital emergency rooms.
With the world having seen the four hottest days in recorded history in one week in July - and London now more regularly seeing summer temperatures pass 30C - “the biggest thing we have to get right is the urgency of this. We haven’t got a second to lose,” said Howard Boyd, who is also a board member of Climate Resilience for All.
Faced with a globally rising heat death toll and surging economic losses, U.N. Secretary-General António Guterres last week called for the world’s first planet-wide extreme heat action plan, noting that “climate change is running faster than all the measures now being put in place to fight it.”
understanding heat risk
London authorities are working to better understand what fast-growing heat might mean for the city. In June, mirroring an earlier exercise in Paris, the city held Operation Helios, a simulation of a five-day 40-degree Celsius heatwave in London, to test responses and coordination among emergency services, transport and utility providers, health agencies, businesses and political leaders.
The exercise revealed not only where gaps in preparedness exist but showed how actions by some agencies and services could affect many others, and therefore require joined-up decision making, Howard Boyd said.
For instance, if extreme heat handicaps public transport systems, major sporting fixtures, concerts or other cultural events may need to be postponed, she noted.
But in a city where air conditioning remains rare in homes and on key public transport, and where many people celebrate hot and sunny weather without understanding the health risks very hot temperatures can bring, much more needs to be done, Howard Boyd said.
Many London buildings are still being constructed with large south-facing glass windows, which can make them sweltering in hot weather, and key exams in schools are scheduled for hot months. Classes for many students let out for the summer only in late July.
“Teachers that are friends of my grown-up children say the classrooms they work in are unbearable during quite moderate temperatures. That has consequences for the ability to learn, with concentration shifting dramatically during these hot periods,” Howard Boyd said.
“These are things we should be taking into account,” she said. “Are our students taking exams at the wrong time of year? Do we need to shift the timetable?”
Research by the London mayor’s office found that during the 2022 summer heatwaves, 33 days of learning were lost across 47 schools surveyed.
water scarcity
Water supplies for the growing city of more than 9.7 million people also need a rethink as heat extremes grow, the resilience review notes. When temperatures surged above 40C in 2022, London’s water use grew by half, leaving reservoirs at their lowest levels in 30 years.
With water shortages predicted to grow in the city, a new reservoir in southeast England will be needed to shore up supplies in the face of growing demand and more unpredictable rainfall, the review noted.
More efforts to save water and use it efficiently also will be needed, it said, including more rainwater capture by homes and businesses.
“We have to stop thinking about our current climate as the climate of the future. A lot of what we’ve already built is fit for an old climate and not the new one we’re moving into,” Howard Boyd said.
Measures are also needed to protect some of the city’s most vulnerable residents from increasingly extreme heat, whether they are residents of old-age homes in rooms without windows that open, the poor who often live furthest from cooling green areas or homeless populations.
Simply adding air conditioning capacity throughout the city is not the answer, she said, because it could dramatically boost demand for electricity, which puts further stress on utilities and could drive more planetary heating, especially with about a third of Britain’s electricity still coming from fossil fuels, the main driver of climate change.
Where possible, smarter passive cooling - ranging from buildings designed with shade awnings, windows that open, cool roofs and good airflow, to streets lined with shady trees - is a better choice, the review noted.
“You can absolutely feel the difference that greener environment creates,” noted Howard Boyd, who said she recently made her way across London on foot on a hot day, avoiding the sweltering subway system, by choosing a route that kept her to parks and shaded walkways as much as possible.
As extreme heat risks rapidly grow, putting in place smart cooling systems should be treated as “essential to national resilience”, noted a report released in July by the UK-based Centre for Sustainable Cooling.
political shifts
The good news is that recent political shifts in London, and in Britain, may make coordinating efforts to battle worsening heat extremes - and other climate impacts - easier.
London is governed by rules and policies created by three major levels of British government: The national UK leadership, the Greater London Authority and the leaders of the city’s 32 borough councils. Getting policies aligned across all three has long been a giant hurdle.
But British voters in July brought in a new Labour government which has included key climate change resilience measures in its manifesto. London Mayor Sadiq Khan, who has championed measures to cut climate-changing emissions and green London, just won a third term in office in May. His new deputy mayor for climate change and environment issues is a borough councillor experienced in green policy.
“There are huge challenges but also a massive opportunity now, with the new (UK) government and a chance for the mayor to reconvene on how to work with boroughs across London,” Howard Boyd said.
Acting on heat and other growing climate risks swiftly makes economic sense, she said. Climate adaptation measures are regularly criticised as expensive, but failing to prepare for risks is likely to be much more costly, not just in lives but to London’s economy, she said - though key data on the scale of the costs still needs to be collected.
But businesses, investors, homeowners and others who fail to take heat and other growing climate impacts into account in their decision-making - whether it’s failing to install enough insulation, ventilation or shade awnings, or buying homes in flood-prone areas - are setting themselves up for economic pain, Howard Boyd noted.
“Adaptation and climate resilience is non-negotiable,” she said. “If we don’t invest in it, if we don’t make our homes, hospitals, schools ready for the climate we know is locked in, if we don’t put our investment into net-zero transport and energy, all of it will be at risk because it might not function in the weather we know we’re going to be experiencing.”
London’s more uncomfortable and dangerous summer heat is “the early warning sign, the dress rehearsal” for what is coming, she said - and a chance to act early to get ahead of growing heat risk.
“We know this is solvable. We could get this right,” she said. “But it’s coming so quickly.”