A new report has shone a light on some dramatic and urgent steps needed to protect London and Londoners from increasingly severe and frequent weather events – such as the flash floods of 2021 and the 40-degree heatwave of 2022.

The compelling 168-page document, by UN Global Ambassador and former Environment Agency Chair Emma Howard Boyd CBE, outlines a series of past, present and imminent scenarios that are likely to have real effects on life in the capital. Flooding, droughts and high temperatures will drive “cascading risks” of disrupted infrastructure, damage to property, and even loss of life.

“The new government’s plans to build more homes and better infrastructure must include updating resilience and technical standards to cope with the weather extremes London can expect in the coming decades,” says Howard Boyd.

The team suggests “climate change is likely to impact London’s GDP by 2-3% every year by the 2050s, with those costs further increasing in the second half of the century.”

Amongst other things, we need a new reservoir to supply water, while at the same time new flood defences will be needed before 2040, and the whole Thames Barrier will need to be replaced within 45 years.

The report also warns that “around 43% of London properties are likely to be affected by subsidence by 2030,” citing a Met Office report that explains: “Ground movement/subsidence, shrinkage and heave of high plasticity soils are expected to be exacerbated by projected increases in drought conditions and periods of prolonged heavy rainfall… This in turn would lead to shrink-swell effects permeating deeper into the soil.”

Solutions could include planting more trees, levying “stormwater charges” on home-owners who pave-over gardens (and offering incentives to remove paving), installing “rain gardens” on or near roads to soak up surface water, and working with landowners to create “sacrificial zones” along the River Thames to mitigate wider flooding.

But it’s not all doom-mongery. “Resilience exists in the weave of the 32 boroughs and the City of London,” note the report’s authors, and Sadiq Khan’s re-election as Mayor “after doubling down on health and climate policies” indicates strong public and legislative support for the necessary changes.

The London Climate Resilience Review flags six areas in need of “urgent attention and action”:

1. A strategic, London-wide, action plan on heat risk is needed. Management of heat risk is a gap across all sectors and organisations. This risk urgently, needs leadership, strategy and collaboration. Warmer temperatures and extreme heat pose a threat to the systems London is dependent on, from transport infrastructure to water supply and health care services. Heat related deaths are set to increase in the UK and people will be exposed to unsafe temperatures. The Grantham Institute’s Turning Up the Heat Report said England is ill-prepared for future extreme heat events and calls for a national heat risk strategy. We urge the Mayor and the new national government to act.

2. Despite greater coordination of stakeholders since the floods of 2021, London is not prepared for another major surface water flooding incident and lives and livelihoods are at risk. Flooding poses a lethal risk to Londoners. In November 2023, the Chief Executive of the Environment Agency told the Public Accounts Committee: “What genuinely keeps me awake at night is surface water flooding. In July, we saw a tragic incident with two deaths in Liverpool. We saw multiple fatalities in the west of Germany last year. We saw 25 fatalities in South Korea last year. As a society, we have to take that much more seriously. It is difficult to forecast these very intense rain cells, and often we do not have the necessary warning systems.” Once again this is a nationwide problem with London-specific considerations. In July 2021, London was hit by two extreme rainstorms; some parts of the city received more than twice the average July rainfall in two hours causing major disruption and over 2,000 properties flooded with stormwater and sewage. The voluntary London Surface Water Strategic Group is good, but is not currently moving at the pace needed.

3. London must accelerate work to understand cascading risks and system interdependencies within and beyond London’s boundaries. London has many interdependent parts: transport infrastructure is dependent on energy infrastructure which is dependent on water infrastructure and vice versa; disruption to one part of the system creates cascading risks. The heatwaves of 2022 stretched many interdependent systems beyond their limits. The IPCC has stated that concurrent, extreme events (like extreme heat followed by an extreme thunderstorm) are a ‘virtual certainty’. These interdependencies, and the potential for systemic failure, must be better understood nationally and regionally. Currently, where this knowledge exists at all, it sits with emergency response mechanisms, not wider policy teams or planners. That modus operandi is undermined by climate change, but managing it better is an opportunity. Network Rail told us: “Our reliance on other sectors, e.g., power, suppliers and other transport organisations, means we will need to work more closely with them to adapt appropriately.”

4. National, regional, and local governments must do more to enable investment in climate resilience. This means embedding climate resilience as a strategic priority across all sectors and investment decisions and improving skills provision. Responding to events and repairing damage is more costly than investing in adaptation and climate resilience. Improved understanding about the costs of climate impacts, and how the costs and benefits of adaptation are distributed is needed. The Climate Change Committee emphasises the cost-effectiveness of early action, revealing a benefit-cost ratio for adaptation ranging between 2:1 and 10:1.

5. Londoners should be engaged on climate impacts, the risks they pose and adaptation options. Adaptation to climate change needs to work for all Londoners, from individuals and households through to community groups and large organisations. Building understanding of climate impacts and supporting Londoners to make climate ready choices is critical. This includes investing in social infrastructure, community groups and London’s voluntary sector and other trusted voices who work at the community level.

6. All the above must be coordinated strategically. A shared regional vision and framework for adaptation is important. Stakeholders across London have asked for coordination and clarity to ensure that effective adaptation and climate resilience is delivered. Currently, governance is spread between many actors (including local authorities, the Mayor and government departments) and where roles and responsibilities are understood they are often siloed out to environment teams. This is a national problem, but the whole country would benefit if the Mayor took a lead. In January 2023, the Climate Change Committee report, “Investment for a well adapted UK” said: “Currently there is no agreed and well-defined vision for what a well-adapted UK looks like set out by Government, and there are no associated targets or goals for desired resilience standards at a national, local or sectoral level. Without these inherently political judgements on the level of risk tolerance desired in key systems, the full scale of investment needed to deliver increased climate resilience is impossible to assess.”

Emma Howard Boyd CBE, Chair of the London Climate Resilience Review: “We are entering a new era. In 2024, even as El Niño fades, we are set for another record-breaking year of deadly heatwaves, wildfires and storms. In the last year, floods in the UK have upended lives and battered local economies.

“The Mayor of London took a world-leading step by calling for an independent review of London’s climate resilience. The health and security of Londoners and the health of the national economy are inseparable.

“This is a reset moment for efforts to increase the UK’s stability in the face of global climate disruption. As the new government takes action to end the cost-of-living crisis, protecting the lives and livelihoods of working people from extreme weather is non-negotiable.”

Mayor of London, Sadiq Khan: “Climate change is one of the biggest dangers our capital faces, and its effects cannot be ignored.

“I welcome this review, which I commissioned after seeing first-hand during recent years how extreme weather can devastate communities, ruin businesses and end lives. It is essential that we invest in key sectors and prepare our public services so that London can continue to grow and thrive in the face of climate change, and the review provides clarity and direction on how to do this. This is also an issue of social justice as the review makes clear it is Londoners on lower incomes that are most exposed to the impacts of dangerous climate change.

“I accept the recommendations made to City Hall, and we will work to take forward the recommendations over the coming months, working with our new national Government, local councils, businesses and London’s communities We do not have a moment to waste.”