During the 27th Conference of the Parties (COP) in Egypt, the Secretary-General of the United Nations António Guterres appealed to the world community to work together or face “climate hell”1. In his speech, Guterres hinted at conflicts posing barriers to cooperation on climate issues: “The war in Ukraine, other conflicts, […] have had dramatic impacts all over the world. But we cannot accept that our attention is not focused on climate change”1. Indeed, contrary to the hopes for a world society and for the end of history2 after the end of the Cold War, geopolitical fragmentation and conflicts have been spreading, and have rendered international consensus on how to escape Guterres’ climate hell more challenging and—as time passes—more unlikely.The developments leading to the current geopolitical fragmentation have not occurred overnight, but were foreseeable for some time. Nevertheless, Guterres’ concern about how conflicts and socio-economic disruptions in the fabric of global relations are significantly decelerating climate change mitigation has so far not been heeded, neither in the Assessment Reports by the Intergovernmental Panel on Climate Change (IPCC) nor in the wider peer-reviewed literature.
There is ample debate and publication on climate change causing conflict. Research on environmental conflicts increased since the 1990s3 and cumulated in a scientific discourse concerning conflict as a consequence of climate change, in other words, a Climate=>Conflict-nexus4 (Fig. 1, blue arrow and boxes). The question of a possible impact of climate change on conflict is discussed for direct and indirect conflictual outcomes such as wars, communal violence and the individual acceptance of and participation in political violence, but also via climate-affected conflict drivers such as resource scarcity, agricultural damages and climate-induced migration5,6,7,8 (see also Appendix 1 – The Climate=>Conflict-Nexus). While critics emphasize a lack of evidential validity for the existence of this nexus9,10, there is evidence that climate change impacts conflicts indirectly by aggravating other drivers of conflict11,12. As a result of being criticized for lacking research on a nexus between climate and conflict13, the IPCC in its 5th Assessment Report (AR5) included a chapter on Human Security14, in which, again, research on conflict as a consequence of climate change is summarized. In AR5 climate change is perceived as a threat for human security13, not just in forms of direct effects but also as unintended side effects15. The discussion on climate change causing conflict is continued in the 6th Assessment Report16. It also appears as one component in a set of global polycrises17.
Whilst the former has been in the public discourse since the IPCC’s 5th Assessment Report, the latter is the subject of this work.
On the contrary, a Conflict→Climate-nexus, i.e. the detrimental impact of conflict on mitigation (Fig. 1, red arrow and boxes), has not been systematically charted anywhere. Only in the Shared Socio-Economic Pathway (SSP) 3, which represents the worst case of projected SSPs in AR6, a conflict-prone geo-political situation is vaguely defined as a “Rocky Road”18: “A resurgent nationalism, concerns about competitiveness and security, and regional conflicts push countries to increasingly focus on domestic or, at most, regional issues. Policies shift over time to become increasingly oriented toward national and regional security issues. […] A low international priority for addressing environmental concerns leads to strong environmental degradation in some regions.”19,20. Although implicitly indicated, geopolitical conflicts play no explicit role in the future projection of the Rocky Road in Integrated Assessment Models (see also Appendix 2—The role of conflict in the SSPs). Conflicts also do not feature in the examination by Fujimori et al.20 of whether the SSP narratives are coherent. SSPs were developed to describe socio-economic trends at the level of the world or large world regions21. SSP3 recognises that more regional rivalries lead to less international cooperation and de-globalisation. However, it cannot recognise that geopolitical rivalries such as conflicts lead to shifts in the geopolitical balance of power, e.g. between the global North and South, and shift international cooperation patterns in terms of re-globalisation, e.g. the expansion of the BRICS-alliance, which has an impact on global mitigation policy. The consideration of such ‘surprise scenarios’22 is discussed, as is the extension and enhancement23 of SSPs. Geopolitical conflicts, such as those we outline, continue to play a subordinate role. Thus, the Conflict=>Climate-nexus constitutes an under-theorised research direction.
Not considering the Conflict=>Climate-nexus in IPCC ARs is significant and consequential: For more than 30 years, the Intergovernmental Panel on Climate Change (IPCC) has provided scenarios that depict options for mitigating climate change. The IPCC’s focus is primarily on the technological pathways required to achieve reductions of greenhouse gas emissions. In their omission of conflicts impeding mitigation, IPCC scenarios are likely overly optimistic. Moreover, increasing global fragmentation and conflict, exemplified by the Ukraine and Gaza wars and struggles for global political and economic hegemony, mean that mitigation will likely be even more obstructed in the future. Therefore, the speed of planned mitigation may need to be even faster than reflected in today’s mitigation targets, because we need to consider that global conflicts cause significant disruptions that will lead to delays in the transition to net zero.
Evidence for the Conflict→Climate link
Here we aim to elucidate the adverse effects of conflict on climate change. Our understanding of conflict follows the Heidelberg Institute for International Conflict Research, which defines conflict as “… the clashing of interests (positional differences) on national values of some duration and magnitude between at least two parties (organized groups, states, groups of states, organizations) that are determined to pursue their interests and win their cases.”24 This definition shows “conflict” understood in a general sense as covering armed, economic, trade and political clashes. Our distinction lies less in whether a conflict is armed or not, but rather in whether its effects on mitigation are direct or indirect.
Through a comprehensive survey of the (mostly grey) literature, we identify seven primary channels within the Conflict→Climate nexus (Table 1): 1) direct impacts of conflict such as military vehicle emissions, asset destruction and other impacts stemming from war (such as damage to fuel infrastructure and reconstruction activities), 2) diverted attention, such as funds or media coverage, 3) energy security measures such as shifting trade relations, increased self-sufficiency, and reduced technology transfer, and 4) reduced international cooperation. We arrived at this typology by considering the causal mechanisms underlying the various channels. First, we made a clear distinction between direct and indirect effects, that is channels involving actual greenhouse gas emissions, such as military vehicle emissions and direct war-related impact, and channels where effects are not caused by the actual warfare. Diverted attention includes the reassignment of budget allocations from climate change mitigation to military purposes, or the shifting of media attention from climate change to war. Shifting trade relations, increased self-sufficiency, and reduced technology transfers affect emissions in as much as they arise out of energy security needs and alter energy markets. Reduced international cooperation focuses on the global governance aspect of climate change mitigation, distinct from trade relations or technology investment. We excluded channels that primarily affect adaptation rather than mitigation, since these do not directly cause climate change. The following paragraphs offer a summary substantiation of each of the seven channels; a more detailed version can be found in Appendix 3 – The Conflict→Climate-Nexus.
Direct impacts of conflict
Military vehicle emissions
Assessing emissions from military activities is crucial25 due to their substantial carbon footprint contribution, amounting to approximately 5.5% of global emissions26. It is therefore not surprising that, in 1997, the US successfully secured an exemption for military emissions from the Kyoto Protocol27. Direct emissions from military sites constitute about 1% of national emissions, primarily from combat aircraft and naval operations28. For instance, a B-2 stealth bomber emits around 1t of CO2 per 45 kilometers of flight29, while a destroyer ship emits about 9t of CO2 per hour30. The IPCC guidelines do not explicitly address wartime greenhouse gas emission reporting. During 18 months of the war in Ukraine, estimated wartime activities generated emissions of 77 Mt CO2-e31, exceeding the annual emissions of countries such as Austria, Portugal, or Hungary. NATO members’ military carbon footprints notably increased since 2021, with 15 member states surpassing 1 Mt CO2-e by 2023. In 2021, NATO’s total military carbon footprint was 196 Mt, rising to 226 Mt by 2023. Direct emissions from military infrastructure and hardware contribute an additional 1%32. Direct warfare emissions caused by the Russia-Ukraine war over its first two years have been estimated at 51.6 Mt CO2-e33. A database tracking military-related emissions is maintained by the Conflict and Environment Observatory (https://ceobs.org). These emissions hinder global decarbonization goals, delay climate targets, exacerbate global warming, and thus undermine mitigation efforts.
Asset destruction
The UNFCCC briefly acknowledges the environmental impacts of war, citing the Kuwaiti oil field fires and resulting pollution during the Gulf War, alongside issues such as mass displacement and shelling34. However, it primarily focuses on how climate change contributes to conflict rather than the reverse. In Ukraine, the Ministry of Environmental Protection and Natural Resources has documented damages35,36 exceeding €56bn as of February 202437. The ongoing conflict in Ukraine generates around 15 Mt CO2-e emissions monthly38, stemming from troop movements, refugee migration and munitions usage33. Elsewhere, the sabotage of the NordStream gas pipeline led to a significant methane leak39, releasing approximately 300 kt CH440.
Other impacts
Western sanctions compelled Russia to burn off excess natural gas41, further adding to emissions. Total emissions caused by the Russia-Ukraine war over its first two years have been estimated at 175 Mt CO2-e, with most of this (57%) fitting into the asset destruction category33, and increased by 30% in its third year, reaching 230 MtCO2e—equivalent to the annual emissions of Austria, Hungary, the Czech Republic, and Slovakia combined [ref. 42]. Historical events such as the deforestation caused by the US’s use of Agent Orange in Vietnam (300 Mt CO2) and Iraqi sabotage of Kuwaiti oil wells during the Gulf War (320 Mt CO2) contributed a combined 600 Mt CO232. Conflict-related activities such as settlement burning and post-war reconstruction significantly contribute to emissions32,33,43. Moreover, conflicts disrupt infrastructure vital for emission reduction, as seen in Ukraine’s wind and solar capacity reductions due to the war44. Environmental compliance45 suffers during conflicts, leading to further damage like land degradation and resource exploitation. For instance, the aftermath of a coup in Niger has exacerbated environmental crises, hindering climate mitigation efforts46.
Finally, conflicts such as the Red Sea dispute have forced ships to avoid the Suez Canal, leading to longer routes and increased carbon emissions47. Similarly, airspace closures over Ukraine and Russia divert aircraft47, increasing fuel consumption47, and causing 24 Mt CO2-e over the first two years of the war33. Environmental destruction from conflict obstructs mitigation and adaptation, delaying progress on clean energy and further entrenching fossil fuel dependencies.
Diverted attention
Funds diverted for military purposes
Following Russia’s invasion of Ukraine, Ukraine’s ability to invest in climate change mitigation suffered due to the diversion of funds towards war and reconstruction efforts48,49. In response, the UK government announced reallocating unused funds from its climate finance budget to partially support a £1 billion military aid package for Ukraine50. These funds could potentially finance 1.4 GW of solar PV, capable of avoiding over 15 Mt of CO2-e emissions, comparable to the UK’s annual energy sector emissions in 2023. International donors, such as the World Bank and the European Commission, also face pressure to redirect climate finances towards Ukraine’s reconstruction48. Additionally, NATO’s objective51,52,53 of allocating 2% of GDP towards military expenditure is poised to worsen climate change by diverting billions of dollars away from climate finance, leading to increased greenhouse gas emissions. In 2023, NATO members collectively spent US$1.26 trillion on military endeavours, equivalent to 12 years’ worth of pledged climate finance for low-income nations. If NATO continues to meet its 2% GDP spending target, an estimated US$2.5754 trillion could be redirected from climate funding by 2028. Applying the same logic as in the UK case above, ie assuming that these funds were used to deploy solar PV to replace fossil-fuelled power, this amount would avoid more than 40 Gt CO2-e over 25 years, and suffice to finance climate adaptation initiatives for all low- and middle-income countries for a span of seven years54. On a global scale, military expenditure sits at about US$ 2 trillion (peaking in 2023 at US$2.4tr55), which amounts to half of the cost estimated to reach net zero emissions by 205056, avoiding 80.8 Gt CO2-e over a technology lifetime of 25 years. Since 2013, military expenditure has reached $16.8 trillion, far exceeding the estimated US$243.9b allocated for climate finance57. Egypt, for example, receives more military imports than climate adaptation assistance58. The top global military spenders coincide with the highest carbon emitters, indicating a concerning trend where wealthier nations prioritize military dominance over addressing climate change. This exacerbates conflict and instability, particularly in regions already vulnerable to climate catastrophes, hindering their ability to tackle climate challenges independently57. Diverted funds slow the transition to renewables, reduce climate adaptation support for vulnerable nations, and deepen inequalities in global climate action.
Diverted media coverage
Media and governments can effectively distract from the climate agenda. With view of Russia’s war in Ukraine, UN Secretary Guterres warned that conflict was putting the climate change agenda “on the backburner”59,60. Between November 2021 and March 2022, the daily mentions of climate change in Russian media fell from 1400 to less than 30061. In many developing countries, journalists report difficulties to report effectively on climate change due to a lack of training, unsupportive editors and weak outreach from domestic policymakers62,63. They frequently express the need for the media to cover the climate crisis as seriously as it covered Covid64.
Energy security measures
Shifting trade relations
Trade disputes have historically undermined climate change negotiations38. Furthermore, conflicts disrupt trade balances, influencing fossil fuel usage. For example, Russia’s reliance on fossil fuel exports to fund the Ukraine conflict benefited India by being able to purchase oil at discounted prices. Indian oil consumption rose by 9–14% in 2022–2023 and 2023–2024 compared to 2021–2022, with associated emissions accounting for 1.5–2.3% (51–91 Mt) of national emissions (3.7–3.9 Gt) respectively65. Similar shifts may occur for African nations courted by Russia66. The Israel-Hamas war currently tempts importers of Middle Eastern oil to secure their supplies, thus diverting attention from transitioning to renewable energy. Higher oil prices can under certain circumstances eg lack of alternative fuels such as for aviation) make investment in oil production more profitable temporarily, reminiscent of the 1973 Arab-Israeli war’s impact on oil markets. Even a transition from fossil to renewable energy sources can entail conflict. Whilst arguably a decentralised renewable energy system reduces the opportunities for weaponising energy, endowment concentration, trade competition and supply chain disruptions surrounding critical materials and components as well as potentially unjust transitions can lead to increased geopolitical tension, and ultimately to a slow-down in decarbonisation67.
Increased self-sufficiency
International tension and conflict shift domestic political priorities from decarbonisation towards energy security, with the consequence of high-carbon domestic energy sources not being phased out as rapidly as planned68, or even being brought into the market69. Russia’s invasion of Ukraine has triggered national governments to rethink their energy security strategies, leading to the development of new fossil fuel reserves70. An exemplary reflection of such thinking is a tweet by Elon Musk from 4 March 2022: “Hate to say it, but we need to increase oil & gas output immediately. Extraordinary times demand extraordinary measures.” Musk’s tweet was exploited by the global fossil fuel industry in painting Russia’s invasion as an opportunity to ramp up domestic coal, oil, and gas production56.
Reduced technology transfer
Sanctions on the Russian economy following its invasion of Ukraine meant that inputs critical for clean energy investments were not available anymore and environmental legislation such as emissions targets and standards were relaxed56, according to Western61 and Russian71,72 media. For example, in March 2022 the Finnish company Fortum withdrew all its operations from Russia73, throwing into doubt wind and solar energy projects. A more subtle case in point are international power grid initiatives that are highly dependent on mutual trust, and that are hence jeopardised by conflict. For example, the French energy regulator cancelled a 1.4 GW electricity interconnector project between Britain and France, following Brexit74. Eight days prior, the UK had itself rejected a “politically controversial” cross-Channel 2 GW power cable75. A further side-effect of conflicts is the rising of oil prices and inflation, which in turn leads to increased interest rates, thus slowing investment in renewable energy sources66,76. Without the unrestricted global flow of capital and cross-national research and development, renewable technologies such as photovoltaics, are less likely to achieve projected levels of widespread uptake77.
Geopolitical disruptions, such as shifting trade relations, increased self-sufficiency and reduced technology transfer, may impede global clean energy adoption, lead to increased reliance on fossil fuels, potentially slowing the transition to renewable energy and exacerbating emissions.
Reduced international cooperation
Climate change is a global challenge affecting all nations regardless of emission responsibilities. International cooperation is vital to address it, but political factors often hinder multilateral efforts, making it hard for countries to meet climate targets. John Kerry, the US climate envoy, stressed at the American University in Cairo that conflicts should not divert attention from climate action78. However, ongoing conflicts threaten cooperation and undermine environmental peacebuilding79. Notably, China-US climate cooperation was suspended due to political tensions after Nancy Pelosi’s visit to Taiwan, cancelling crucial China–US Climate Working Group meetings on methane, forestry, and clean energy80,81,82,83. In 2023, Russia blocked the EU from hosting COP 29, accusing it of a “politicized” approach, leading to Azerbaijan hosting instead of Bulgaria84. The Israel-Hamas war exacerbated tensions, with oil-producing nations supporting Palestine, distracting from climate discussions during events like the 28th Conference of the Parties66,76.
Further, the current lack of financial support undermines the Global South’s goodwill for cooperation on climate issues. The reluctance by affluent countries to provide sufficient financial assistance for low-income countries to adapt to climate hazards causes the latter significant resentment, resulting in an erosion of trust and good-will, hardening negotiation positions and ultimately hampering progress66. For example, the failure of the wealthiest nations to fulfill their 2009 pledge of US$100bn in climate finance to poor and climate-vulnerable countries has bred longstanding mistrust and impeded climate negotiations. This breach of promise has become even more problematic when considering that the US’s funding earmarked for aiding Israel’s military in their conflict in Gaza, and to aid Ukraine against Russia, exceeds the US$100bn pledge. This is because it provides low-income countries with the impression that whilst financial assistance for climate adaptation is grossly inadequate, it seems to be easily available when it comes to supporting allies in wars60. The beneficiaries of the repercussions resulting from failed climate commitments are arms and security firms. These companies—predominantly situated in NATO nations—then supply weaponry to countries deemed susceptible to global climate impacts60. Political tensions disrupt critical negotiations on climate finance and emissions reductions, delaying essential actions and eroding trust among key emitters. This not only undermines the efficacy of multilateral climate efforts but also exacerbates fragmentation, as countries prioritize national interests over the pursuit of shared global objectives.