Three Reasons the Climate Crisis Is Redefining War

The Interwoven Realities of War and Climate Change

The Earth's average temperature has crossed a significant threshold, rising more than 1.5°C above pre-industrial levels in 2024—a milestone that underscores the urgency of the climate crisis. At the same time, major armed conflicts continue to unfold in regions such as Ukraine, Gaza, and Sudan. This convergence highlights an increasingly clear reality: war must now be understood within the context of climate breakdown.

The relationship between war and climate change is complex, but three key factors reveal how the climate crisis must reshape our understanding of warfare.

War Exacerbates Climate Change

War has long had devastating environmental consequences, but its climatic impact is only now gaining widespread attention. Researchers and civil society organizations have begun to track greenhouse gas emissions from military activities, particularly in conflict zones like Ukraine and Gaza. These efforts also include assessing emissions from post-war reconstruction and all military operations globally.

A study by Scientists for Global Responsibility and the Conflict and Environment Observatory estimates that the total carbon footprint of global militaries exceeds that of Russia, which currently ranks fourth in emissions. The United States is believed to have the highest military emissions. According to UK-based researchers Benjamin Neimark, Oliver Belcher, and Patrick Bigger, if the U.S. military were a country, it would rank as the 47th-largest emitter, placing it between Peru and Portugal.

However, these findings are based on limited data. Military agencies often provide partial emissions reports, requiring researchers to rely on government and industry figures. Data on countries like China and Russia remains particularly scarce. Additionally, wars can disrupt international climate cooperation, as seen in the breakdown of scientific collaboration between the West and Russia in the Arctic since the start of the Ukraine war.

Critics argue that acknowledging the climate costs of war should prompt a reevaluation of military spending. Some advocate for demilitarization as a path to preventing climate catastrophe, while others emphasize the need for strategic restraint and reducing the environmental impact of warfare.

Climate Change Demands Military Responses

Before the climate crisis gained prominence, researchers debated whether it could act as a "threat multiplier," potentially intensifying existing conflicts in regions already facing food and water insecurity, poor governance, and territorial disputes. Some conflicts in the Middle East and Sahel have been labeled "climate wars," suggesting they might not have occurred without the pressures of climate change.

While this idea remains contentious, there is growing recognition that the climate crisis is leading to increased military involvement in civilian emergencies. This includes combating wildfires, reinforcing flood defenses, conducting evacuations, search-and-rescue missions, and delivering humanitarian aid. As climate-related disasters become more frequent and severe, the demand for military assistance is likely to rise.

Governments will face difficult decisions about prioritizing tasks and balancing military budgets with other societal needs. The question remains whether the climate crisis will lead to more violence or whether military force will be needed more frequently to respond to disasters.

Armed Forces Will Need to Adapt

With geopolitical tensions rising and conflicts increasing, calls for demilitarization seem unlikely to gain traction soon. This means militaries must adapt to operate in a world grappling with both climate change and the transition to low-carbon energy.

Preparing military personnel and infrastructure for extreme weather conditions is becoming a pressing concern. For example, two major hurricanes in the U.S. in 2018 caused over $8 billion in damage to military facilities. Research indicates that some defense officials in the UK are increasingly aware of the need to address the implications of the energy transition on military operations.

Militaries face a critical choice: remain heavy users of fossil fuels or embrace the energy transition that will reshape how military force is generated and sustained. Operational effectiveness will depend on how well militaries understand and adapt to the impacts of climate change.

As Prussian general Carl von Clausewitz famously noted, while war’s nature remains constant, its character evolves. Recognizing the scale of the climate crisis is essential to understanding future conflicts and finding ways to prevent or reduce their destructiveness.