Weathering the storm: How Japan is factoring climate change into defense policy

Storm surges, flooding, more powerful typhoons and scorching temperatures — climate change will bring more of all to Japan, endangering military sites, personnel and gear, but also putting Tokyo and the Indo-Pacific at greater risk of geopolitical shocks.

The intensifying effects of climate change will likely aggravate security issues in the region in the coming years and decades, as growing ocean levels affect disputed low-lying maritime features, warming oceans shift waning fish stocks’ distribution and transboundary water management becomes more fraught.

At the same time, extreme weather threatens the Self-Defense Forces’ plans and operations, including the use of assets such as helicopters, planes and ships, while also impeding the performance of communication systems and remote-sensing capabilities.

Extreme weather events will also increase demand for humanitarian assistance and disaster relief (HADR) missions, with the SDF already making frequent deployments across Japan and the region in response to floods, landslides, storms and other natural disasters.

“Recurrent flooding and storm surge could force the SDF to conduct more frequent HADR activities,” said Kazumine Akimoto, a senior research fellow at the Ocean Policy Research Institute of the Sasakawa Peace Foundation.

However, the more the SDF is required to respond to natural disasters, whether in Japan or abroad, the greater the toll this will take on personnel and resources that would otherwise be needed for national defense, added Akimito, who warns of overburdening the already strained force and jeopardizing operational readiness.

The key issue, he said, is that a drop in SDF readiness could impact Japan’s deterrence strategy as well as its new, more proactive defense posture at a time when the country is grappling with a rapidly deteriorating regional security environment.

Just how much each military facility in Japan would be affected by climate change over the coming decades is unclear, with the Defense Ministry saying in a written statement that it is not yet possible to determine this with certainty.

The impact will depend on several factors, including the facilities’ locations, the scale of sea level rise, the occurrence of additional hazards such as storm surges and the facilities’ capacity to increase their resilience against those hazards.

Moreover, each facility's degree of exposure to extreme weather is projected to change at different times in the future depending on greenhouse gas emission scenarios.

The U.S. Defense Department, which operates about 5,000 sites around the world, including numerous facilities in Japan, has identified climate change as a critical national security threat.

To project the effects of climate change for almost 1,400 of these installations and understand each location's exposure to climate-related hazards, the Pentagon launched the Defense Climate Assessment Tool in 2021.

But DCAT information, which could potentially provide the Pentagon’s risk assessment on U.S. facilities in Japan, remains a tightly guarded secret.

Neither the Defense Ministry nor the Pentagon offered details in response to questions about specific bases that would be most affected.

Greater frequency and intensity

What is publicly known is that sea levels along the Japanese coastline have been rising since the 1980s and are predicted to increase by up to 1 meter by the end of this century, according to the Japan Meteorological Agency.

This suggests that military facilities near the ocean, including those at Sasebo, Nagasaki Prefecture; Yokosuka, Kanagawa Prefecture; and in Okinawa Prefecture, would be at even greater risk from storm surges, flooding and coastal erosion.

“The SDF and U.S. bases on the Okinawa islands are among the most vulnerable, as scientific estimates reveal that the sea level around those locations will rise about 30 centimeters or more by the end of 2100, compared with the year 2000,” said Akimoto, who is also a retired rear admiral with the Maritime Self-Defense Force.

In addition, Japan expects more severe typhoons and as much as 1.5 times more rainfall, both of which will increase the risk of flooding. This could further hamper operational capabilities in the country’s southwestern islands, which would play a key strategic role in any emergency over Taiwan.

Okinawa itself is located in what is called “Typhoon Alley,” with the U.S. military saying that its Kadena Air Base, perhaps more than any other facility, “needs to treat these natural storms as a part of the scheduled daily mission.”

Just how powerful these events can be was shown during Typhoon May-Li in July 2007, which brought sustained winds of up 109 knots (202 kilometers per hour), nearly 12-meter waves and almost 38 cm of rain.

“If the bases and installations in Okinawa suffer severe damage from recurrent flooding and/or storm surges, the SDF and U.S. forces won’t be able to carry out effective military operations in a conflict in the South China Sea and/or the Western Pacific,” Akimoto warned.

This is because the effects of climate change would not be limited to military infrastructure and equipment. Frequent flooding, landslides or wildfires could also impact training, with observers saying that the number of training days for SDF personnel could plummet due to damaged facilities and disrupted access to them, while also making disaster relief deployments longer and more complex.

There could also be logistical problems due to disruptions to the transportation network, or even issues with the power and water supply at military bases, rendering them largely ineffective.

And last but not least, SDF and U.S. personnel could face increased health risks due to extremely high temperatures.

This matters because the varying impacts of climate change — ranging from food, water and energy insecurity to resource competition and a decrease in national land area — could undermine the stability of politically and economically vulnerable nations in Asia, dramatically affecting regional politics.

For instance, a comparatively high economic impact of climate change on India could slow or reverse the widening economic gap with neighboring Pakistan, which has weakened Islamabad both diplomatically and militarily in relation to New Delhi, wrote Jeffrey Mazo, an associate fellow at the International Institute for Strategic Studies (IISS) specializing in conflict, security and development.

This could similarly reduce India’s burgeoning role in regional security as part of “the Quad” it belongs to — alongside Australia, Japan and the United States — and leave it at a considerable disadvantage compared with China.

Also, a comparatively high climate change impact on Taiwan could weaken its capacity to resist Chinese threats, while acute climate-related issues in North Korea, which already suffers from perennial food insecurity, could spark a major crisis or outbreak of armed conflict, Mazo added.

Enhancing resilience

Until recently, there was only limited interest in climate security within Japan’s defense circles, despite the growing frequency and severity of extreme weather events, wrote IISS security experts Shiloh Fetzek and Yuka Koshino.

However, this changed in May 2021, when then-Defense Minister Nobuo Kishi unveiled a high-level Climate Change Task Force, signaling Tokyo’s acknowledgement of the issue’s severity.

This was followed two months later by Japan’s Defense White Paper, which described climate change for the first time as a security issue facing the country.

An important factor behind this move was Tokyo’s commitment in October 2020 to become a carbon-neutral economy by 2050, the IISS experts noted. The strategy sets an emissions reduction target for the Defense Ministry and SDF of 50% from the level in the fiscal year that began April 2013 by fiscal 2030, excluding those emissions produced by defense equipment.

But arguably the biggest step forward in its approach was the ministry’s launch last August of its first Response Strategy on Climate Change, which outlines Japan’s commitment to integrate climate-related risks into defense policy and planning.

The strategy, Fetzek and Koshino wrote, places a heavy emphasis on innovation and Japanese energy development, mentioning hydrogen and ammonia and setting a target to “research, develop, manufacture and procure” alternative fuels in Japan — an initiative to be applied to the defense sector.

Part of this is promoting the defense energy transition, which will increasingly be needed for interoperability among allies — assets running on different energy sources have different logistical requirements, for example — as Washington makes a major push to develop military technologies for a post-fossil fuel world.

The strategy also prioritizes capacity-building and expertise-sharing with Southeast Asian and Pacific island countries to reduce HADR demand overseas, as well as using reservists, retired SDF personnel, volunteers and private companies in domestic disaster response, the experts added.

“There is a concern to not overburden the SDF with disaster response commitments that might affect operational readiness,” Fetzek said in an interview, noting that demand for disaster response has increased so significantly that the Defense Ministry is also thinking about turning to the private sector for help there in order to preserve military capabilities for national defense needs.

Another important step to mitigate the effects of climate change was Tokyo’s pledge in its recently revised National Defense Strategy to improve the sustainability and resilience of the country’s defense facilities within a 10-year period.

The government said it plans to construct underground command headquarters and relocate and consolidate facilities in major bases and camps, starting with those considered important for operations that could face significant damage from disasters such as typhoons and tsunamis.

More broadly, Tokyo also aims to systematically draft a roadmap for strengthening all of the country’s military facilities amid climate concerns.

Besides reinforcing the bases, there is a goal to make them more energy independent by using renewables.

The idea is to adapt military facilities to withstand increasingly challenging climate conditions and strengthen their ability to rapidly recover from disruptions to public infrastructure.

The government is also considering modifications to existing and planned equipment, including climate change-resilient functions such as the ability to withstand extreme heat.

What more can be done?

It’s difficult to predict just how much climate change will aggravate international security issues, given the shortfall in adaptation funding, slow progress on decarbonizing economies and economic upheaval inherent in shifting away from petrostates. But it is likely to be a significant disruptor, at a time when international cooperation is becoming ever more fragmented.

One positive aspect is that the global security and defense sectors — which are often the largest single energy users within governments, contributing considerably to global warming — have taken notice of the issue and started taking steps to alleviate concerns over certain aspects of military and security operations as part of a “green defense” approach.

In this regard, experts believe Tokyo could do more.

Making physical infrastructure and installations more resilient to climate change is the more straightforward part of preparing militaries for a future impacted by global warming, because for the most part the technologies exist and are ready to be implemented, Fetzek said.

The defense energy transition, she noted, will be much more complicated because many of the technologies, such as carbon-neutral fuels and propulsion systems for land, sea and air platforms, do not yet exist or cannot yet be implemented at scale.

“This transition will also require a range of updates to installations such as building energy infrastructure (generation and storage) to power future military needs,” Fetzek added.

While dealing with Japan's increasingly severe security environment remains the SDF's main task, the force is being pulled in several directions at once — making the energy transition, improving resilience, increasing HADR missions and all the while trying to upgrade its overall capabilities as Japan changes its defense strategy. And as the impact of climate change increases, this threatens to push the SDF to the limit.