Over the past two decades, Japan has emerged as both a victim of and a laboratory for climate change impacts. Rising temperatures, increasingly erratic weather patterns, and more frequent extreme events are no longer abstract forecasts but are in fact realities across the archipelago for 125mn people. Tokyo, the country’s capital, is not immune and in many ways is more vulnerable than many realise.

Japan’s geography makes it particularly susceptible to the effects of climate change. The country sits on the Pacific Ring of Fire and spans multiple climate zones — from subarctic Hokkaido in the north to subtropical Okinawa in the south. It is also subject to frequent natural hazards: typhoons, floods, landslides and earthquakes, the most (in)famous perhaps being the earthquake of March 11, 2011 following which the city of Tokyo ground to a halt as trains above and below ground stopped running for days and people had to walk for hours to get home. But while seismic risk has long been part of Japan’s national psyche, the new, compounding pressures of a warming planet are stretching systems already designed to handle the extreme.

Two decades of intensifying heat

Since the early 2000s, Japan has recorded a steady rise in average temperatures. According to the Japan Meteorological Agency (JMA), the country’s mean annual temperature has increased by approximately 1.3°C over the past century, with much of that rise accelerating in recent decades. Summers have become markedly hotter, with record-breaking heatwaves now a near-annual occurrence.

At the turn of the century this was marked by a period of 30 straight days on which the mercury topped 30°C by 7am.

But the signs were there a decade earlier that something was changing. Throughout the mid and late 90s then on into the early 2000s, Tokyo was becoming hotter and hotter, its winters colder and colder. The extremes were noticeable to all. Snowfall of levels previously unseen in Tokyo hit the capital hard in 1997 and 1998, then for years, nothing. No snow fell for many years, and only every few years since has the Japanese capital seen snowfall of note. At times too, in the warmer months, purple sunsets were not uncommon over Tokyo. Different experts put this down to air pollution and/or the excessive heat of the day in the summer months still dissipating.

In the immediate aftermath of the devastating March 2011 megaquake which left thousands dead, and with summer still a few months away, Japan's government then ruled that air conditioners could not be set below 28°C in public buildings "to save electricity".

At the same time the majority of lifts and escalators in train stations, government offices and the like were switched off — for months on end in some places. Large corporations followed suit, which led to more than a few frayed tempers in crowded train stations and other public areas with tens of millions of commuters having to push past each other on a daily basis on their way to and from work in the city.  

More recently the heatwave of July 2018 was a wake-up call. Temperatures in Kumagaya, just northwest of Tokyo in Saitama Prefecture, reached 41.1°C — the highest official temperature ever recorded in Japan at the time. Although higher temperatures have been recorded, they were not recorded on government maintained apparatus so don’t count.

That year, more than 1,000 people died from heat-related causes, and over 35,000 were hospitalised. Tokyo bore the brunt of the crisis, with its dense urban landscape amplifying the heat through the so-called "urban heat island" effect.

This pattern has continued. In 2022 and 2023, Tokyo experienced extended stretches of 35°C-plus days. The elderly, who make up a significant portion of the city’s population and increasingly Japan’s as a whole, are particularly vulnerable. Cooling centres run by local communities have become a necessity during the summer months, and electricity demand has soared due to air conditioning use, which raises further questions about energy resilience in the context of climate and energy policy shifts.

Rising seas and sinking land

While heatwaves dominate headlines, Tokyo also faces a quieter, creeping threat: sea level rise. It is one often ignored at the governmental level, however, given the lack of relative wealth in areas closer to the waters of Tokyo Bay.

Much of Tokyo lies in low-lying areas of the Kanto Plain, particularly in northern and eastern wards such as Adachi, Kōtō, Edogawa and Sumida. These districts were historically marshland, reclaimed during the city’s industrial expansion and in some regions, even the names of neighbourhoods are based on the character for 'reed' or in other ways water related. As a result, parts of Tokyo sit below sea level — a situation worsened by subsidence, where the ground sinks due to groundwater extraction and other human activities.

Estimates from Japan’s Ministry of Land, Infrastructure, Transport and Tourism (MLIT) suggest that nearly 10% of Tokyo’s 23 wards are technically below sea level. Add to this the projected global sea level rise, and there is an ever increasing flood risk. 

During Typhoon Hagibis in 2019, this risk became very real. The storm brought record rainfall and river overflows across Greater Tokyo, testing the capital’s elaborate flood defences. The underground Metropolitan Area Outer Discharge Channel north of the city, played a crucial role in protecting the capital from catastrophic flooding. But climate experts warn that infrastructure designed and based on 20th-century models may soon be outpaced by 21st-century weather patterns.

Typhoons and rainfall extremes

Japan has always lived with typhoons, but their intensity has grown in recent years. Warmer ocean temperatures east of the Philippines are fuelling stronger and wetter storms that strike with greater ferocity. These storms are closely watched across the archipelago after forming, with hourly news updates informing people if they have carried on west of the Philippines towards Taiwan and Hong Kong or have veered north to skirt the Japanese Pacific coast. From around 2010 onwards, more and more have been turning north, but then more than ever have been forming off the Philippines, thanks to warming seas near the equator south of Japan.

Between 2010 and 2020, Japan experienced multiple once-in-a-decade storms in rapid succession. Typhoon Jebi in 2018 shut down Kansai International Airport in Osaka, after storm surges flooded its runways. Typhoon Faxai in 2019 caused blackouts in Chiba Prefecture, just east of Tokyo, leaving nearly 1mn households without power for days. That same year, Hagibis, described as the most powerful typhoon to hit the Kanto region in decades, caused widespread flooding and killed over 90 people.

Tokyo’s river systems, including the Sumida, Arakawa and Tama Rivers, all man-made in parts, are now closely monitored for overflow. The city has also upgraded levees and invested in early-warning systems, but experts caution that these defences must continue to evolve to keep up with changing precipitation patterns.

Tokyo's climate dilemma

Despite its vulnerabilities, Tokyo has also become a focal point of climate adaptation and mitigation efforts. The city government, under its Zero Emission Tokyo Strategy, aims to achieve net-zero carbon emissions by 2050. Measures to reach this goal include expanded use of renewable energy, stricter building efficiency standards, green roofs and incentives for electric vehicles.

However, critics argue that adaptation is outpacing mitigation. Tokyo has made strides in managing the symptoms of climate change — better heat alerts, improved flood management and public education campaigns. But Japan as a whole remains heavily dependent on fossil fuels, particularly since the 2011 Fukushima nuclear disaster led to the shutdown of most nuclear reactors. Nuclear is making a comeback, however, but will take time to reach full capacity. In the meantime, fossil fuels reign, which only compounds the issues at hand.

In 2020, renewables accounted for only about 20% of Japan’s total energy mix. While that share is growing, progress has been slow. And as climate impacts accelerate, the pressure to decarbonise grows more acute.

Lessons from a global city

What Tokyo represents, perhaps more than anything else, is a test case. It is a global megacity grappling with the overlapping stresses of urbanisation, ageing demographics and climate risk. It is both highly exposed and highly prepared in what is a paradox of modern resilience.

But this also raises tough questions about sustainability, equity, and political will. After all, how do you protect a city of around 37mn people from something as abstract and global as atmospheric carbon?