Systemic Risk: what Ueno Park reveals about climate stress in Asian cities

Tokyo - Changing global climate patterns are creating growing challenges for densely populated metropolitan areas where environmental risks are often interconnected and amplify one another. HDI Risk Consulting (HRC), a wholly owned subsidiary of Corporate & Specialty insurer HDI Global, conducted a physical climate risk assessment of Ueno Park in Tokyo. Using advanced analytical tools, the study visualises physical climate risks, evaluates their potential impacts, and identifies appropriate response measures.

As one of Japan's five oldest public parks and a major tourism destination attracting around two million visitors each year during cherry blossom season, Ueno Park provides a useful lens through which HDI Global examines the potential impacts of climate change on tourism, infrastructure, and public spaces, as well as their insurance-related implications.

"Our goal is to identify climate risks with precise spatial accuracy," said Lars Regner, Head of Resilience Services at HDI Risk Consulting. "Ueno Park shows that local changes are part of broader climatic developments affecting entire cities. As a result, adaptations related to cooling, storm water management, and vegetation stability are required."

Analysis Identifies Climate Risks Facing Ueno Park

Temperatures in Japan, including urban areas such as Tokyo, have risen significantly. By 2016, temperatures were already around 0.88°C above the average for 1981-2010, exceeding the global trend. Under a business-as-usual scenario, HRC's analysis based on EarthScan™ datasets shows that heatwaves in Tokyo could lengthen by more than two weeks on average by 2050. Instead of lasting 6.94 days annually as they did in 1970, they are projected to last approximately 21.28 days.

At the same time, risks from heavy rainfall are increasing. Studies have identified new precipitation patterns across the Greater Tokyo Area. For instance, "guerrilla rainstorms" – which refer to localised, sudden, torrential downpours that occur primarily during the summer months – push urban drainage systems to their limits and trigger cascading effects. Local flooding can disrupt underground and road transport, interrupt supply chains, and cause temporary business closures that extend far beyond the area directly affected by the rainfall.

Prolonged heat, drought, or excessive rainfall can have significant consequences for Ueno Park's tourism appeal by impacting the flowering periods of climate-sensitive cherry blossoms. This may reduce the park's attractiveness during peak viewing seasons. As one of Japan's key tourism events, generating billions in revenue each year, changes to the season can have immediate economic consequences.

The overall visitor experience may also deteriorate, as heat-related health risks increase and visitors spend less time outdoors. Studies from other countries indicate shorter dwell times and engagement of up to 20% on extreme heat days. Nearby restaurants and service providers may experience economic losses as well.

Measures to Strengthen Urban Resilience

The vulnerabilities identified in Ueno Park reflect wider climate risks across Tokyo, highlighting the need to strengthen urban resilience. "In densely populated areas like Tokyo, the urban heat island effect acts as a systemic risk factor. Sealed surfaces, waste heat, and limited air circulation intensify heat stress," explained Johanna Rohrer, Risk Analyst for Natural Hazards at HDI Risk Consulting.

"This has economic consequences: extreme heat reduces worker productivity in logistics, construction, and transport, increases energy demand for cooling, and poses a serious public health risk. At the same time, business interruption risks and threats to infrastructure and supply chains are rising, putting pressure on companies and insurers. Our location-specific analyses and preventive measures help identify risks early and minimise losses."

To address these challenges, Tokyo has long pursued a range of climate adaptation initiatives. Major projects such as the G-Cans underground flood protection system, designed to divert typhoon and heavy rainfall runoff, have set global benchmarks. Likewise, the citywide installation of approximately 190 kilometres of heat-reducing road surfaces ("Cool Pavements") by the end of 2023 has significantly reduced urban heat island effects. The insurance sector has also adapted, with climate-related risks being modelled in greater detail and considered in risk analyses and pricing.

HRC's analysis further identifies opportunities for optimisation that should be considered in modern urban and economic planning:

• Micro-Heat Zoning: High-resolution urban models can precisely identify heat hotspots. This enables targeted prioritisation of cooling measures in particularly sensitive residential or transport clusters and enhances the effectiveness of cool pavements and green spaces.
• Cooling Corridors: Parks such as Ueno Park contribute to urban cooling through evapotranspiration. Interconnected green spaces create ventilation corridors that improve night-time cooling across the city. Preserving and expanding these areas becomes a key adaptation measure against overheating.
• Sponge City Elements: Green roofs, infiltration zones, and urban retention areas absorb water like a sponge, release it through evaporation during hot periods to provide cooling, and reduce pressure on drainage systems during heavy rainfall.
  Protection of Underground Infrastructure: Protection of metro entrances, technical facilities, and substations through mobile barriers and backflow prevention systems can prevent widespread infrastructure failures and economic disruptions.
• Heat as Economic Risk: Heat-related factors should be systematically embedded in risk assessments and decision-making processes to enable prioritisation of measures such as adapted working hours, cooling technologies, and resilience strategies.

"Through forward-looking analytics, we translate cutting-edge climate risk models into practical, action-oriented solutions for our clients and stakeholders," added Hiro Yamasaki, Managing Director of HDI Global Japan.

"The example of Ueno Park demonstrates the far-reaching economic and environmental consequences of local extreme weather events. As a trusted partner, we help businesses and public authorities safeguard investments, ensure business continuity, and protect culturally significant events such as the cherry blossom season over the long term."

As part of its Iconic Landmarks series, HDI Global applies advanced analytical tools, including HDI ARGOS 4.0. By combining precise data analysis with progressive risk assessment, HDI Global supports clients in identifying climate‑related risks at an early stage, strengthening local economic resilience, and preparing locations for future challenges.