There are new warnings changing global climate patterns are creating growing challenges for densely populated metropolitan areas where environmental risks are often interconnected and amplify one another.

Research from HDI Risk Consulting (HRC), which conducted a physical climate risk assessment of Ueno Park in Tokyo looked to visualise physical climate risks and evaluate their potential impacts.

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 examined 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.”

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 showed 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 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.

HDI added 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, (above pic) 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.

“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.”

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 showed 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.