1 Introduction

We are aware of the various challenges caused by global warming, looking at changes in climate, unusual weather patterns, melting ice, and rising sea levels [1]. Human activities, especially those linked to the industrial revolution, have played a big role in increasing the release of greenhouse gases (GHGs) [2, 3]. To address this growing problem, countries worldwide came together in 2015 and created the Paris Agreement under the United Nations Framework Convention on Climate Change (UNFCCC) [4, 5]. The goal is to collaborate to slow global temperature increases and become better prepared for the consequences of climate change. The Paris Agreement sets ambitious, challenging goals, including ensuring that the worldwide temperature rise remains significantly below 2 °C compared to pre-industrial levels and striving for an even lower increase of 1.5 °C [6, 7]. Countries pledge to specific actions and measures, like reporting emissions [8,9,10,11,12] and helping each other financially and with technology. The agreement signifies a substantial shift in how the world addresses climate change, with a focus on both reducing the release of greenhouse gases (mitigation) and adapting to the changes that are already happening (adaptation) [13, 14]. The strategies detailed in the Paris Agreement have a long-term vision to regulate extreme temperatures, minimize emissions, and find a state of balance between what is released and removed from the atmosphere in the second half of this twenty-first century [15, 16].

The initiatives specified in the Global Climate Strategies are essential in advancing different Sustainable Development Goals (SDGs), highlighting the interconnected nature of worldwide sustainability goals or objectives and climate action [17, 18]. These specifically contribute a lot to SDG 13 [19], focussing on climate action by actively working towards reducing the risks of climate change. In addition, they match with SDG 2 [20], fostering sustainable food processes and agriculture systems while promoting environmentally conscious practices [21, 22]. The strategy contributes to SDG 6 by supporting sustainable water supply initiatives and ensuring clean and safe water access [23,24,25]. Gender equality (SDG 5) is also a core consideration, considering inclusivity and equal participation in climate-focused initiatives [26]. SDG 9, which focuses on infrastructure developmental works and related innovative ideas, is integral to the strategy [27, 28]. Promoting the availability and accessibility to sustainable energy (SDG 7) and fostering sustainable and inclusive economic growth with better job opportunities (SDG 8) are also contained within the strategy [29, 30]. SDG 10 (Reduced inequalities), SDG 12 (responsible consumption and production), and SDG 15 (preservation of life on land) are the rest of the Global Climate Strategy, reflecting a holistic commitment and approach to a sustainable and equitable future across several dimensions of developmental works [27, 31,32,33].

The complexities of the interchange between adaptation and mitigation strategies are better described by the decision-making processes. When the mitigation steps are taken, they are visible over the long term due to the extended residence time of greenhouse gases in the atmosphere. However, when the adaptation steps are implemented, they yield immediate returns [34]. A balance between both mitigation and adaptation approaches arises where local solutions are recognized as crucial to alleviate or avoid a global tragedy of the commons. Cites are concentrating on climate change policies as they are the ones responsible for a significant portion of emissions [35, 36]. Extreme heat waves and urban flooding situations are arising as urban areas face environmental risks, which necessitate mitigation measures for reduction in emissions and adaptation efforts to improve climate resilience [37]. Mitigation efforts target both present and future emissions due to urban mobility, changes in land use, and housing, as they are the ones with significant emission sources [38, 39]. However, adaptation efforts are needed to minimize those negative impacts. The connection between worldwide climate policies and management steps at the local level is complex. Cities are driven by international agreements and facilitated through a chain of networks and engagement or knowledge sharing between cities. As these help drive local adaptation efforts, cities are seen managing climate actions independently [40, 41].

This paper is structured into six sections, from the introduction as Sect. 1 to the conclusion. Section 2 discusses the critical approaches of mitigation and adaptation to comprehend their distinctions, whereas Sect. 3 discusses the methodological approach. Sections 4, 5 discuss the best practices in mitigation and adaptation strategies city-wise to provide a comprehensive analysis. Lastly, Sect. 6 provides the conclusions derived from synthesizing the results acquired through the cross-case analysis. In our effort, we examined case studies across different global cities as they lead to a valuable perspective emerging and can help tackle the growing challenges of global warming. These studies might serve as a tool to provide a detailed and concentrated analysis of intricate issues in relation. As there exists a wide scope within climate change, studying individual cities will provide a practical approach to evaluate how well mitigation and adaptation strategies work.

The meticulous selection of these case studies aims to extract important messages and priorities for action, offering key insights to steer practical efforts in mitigating and adapting to global warming. By delving into these real-world scenarios, this work significantly contributes to and improves our understanding of the intricate challenges of addressing climate change globally. These investigations reflect the local aspects of environmental challenges and provide valuable insights that are helpful in guiding successful and best approaches on a city-wide scale.

2 Combating climate change through mitigation and adaptation

The complexities or obstacles arising due to climate change risks can be tackled through mitigation and adaptation strategies. The rate and magnitude of increases in greenhouse gases can be minimized through mitigation attempts by employing several approaches and helping slow down the progression of climate change and extreme events [42,43,44]. Cost-effectiveness measures are one of the main hurdles to mitigation efforts, which require comprehensive economic and societal effect assessments [34, 45]. The scientific and technological advancements are aimed at lowering greenhouse gas (GHG) emissions, improving carbon sinks, and developing innovative ideas for capturing and storing carbon [46,47,48].

Adaptation methods alter the natural or human processes as a response to climate-related stimuli by minimizing the adverse impacts and maximizing favourable situations [49, 50]. Adaptation has started gaining attention very recently, and that too only in developing countries, whereas mitigation has been a long-standing focus. The adaptation strategies exist in different forms, such as anticipatory, reactive, private, public, autonomous, and planned adaptation [13, 51]. Also, adaptation is categorized into two types: incremental adaptation, which involves making additional investments in existing facilities to respond to growing climate hazards, and developmental adaptation, which addresses conventional and novel climate threats in developing nations due to low capacity and investment [52]. Consequently, adaptive issues become intertwined with developmental challenges.

Mitigation focuses on reducing the rate of climate change, while adaptation involves minimizing the negative consequences. Despite sharing the common goal of sustainable development, there are substantial differences in practice, including the scales of departments and research. Mitigation predominantly concerns energy consumption and carbon emissions, while adaptation focuses on responding to climate change risks [53]. Disparities among regions and countries highlight varying attitudes toward combating climate change, particularly between developed and developing nations [54, 55]. This also results in significant disparities in funding, with mitigation focused on energy, transport, and heat in housing, gaining easier access to funding as traditional accounting focuses on bricks and mortar [56,57,58]. Adaption, particularly NBS adaption, is seen as a nice add-on, a luxury, and a financially negative liability. Developed countries prioritize mitigation, whereas vulnerable countries, especially in the Global South, urgently require adaptation actions due to high climate risks and limited emission reduction capabilities [49, 59, 60].

Mitigation actions occur predominantly at the country and regional scale, with net benefits being larger on a global scale, contributing to global benefits that are, however, postponed [34]. In contrast, adaptation actions have immediate effects, with net benefits being larger at regional scales, making them more attractive [61, 62]. Despite their importance, adaptation has been considered the ‘‘poor relation’’ of mitigation, as financial investment and institutional research remain insufficient [63, 64]. For instance, funds allocated for combating climate change were more directed toward mitigation measures than adaptation efforts. This can also be understood from Fig. 5.

Scholars offer diverse perspectives on the mutual relationship between mitigation and adaptation [4, 65, 66]. The relationship can be classified as neutral, positive, or negative, with complementarity, contradiction, or mutual reinforcement in different situations [67,68,69]. Case studies suggest complementary rather than synergetic relationships between mitigation and adaptation, with adaptation proving more financially efficient than mitigation [70]. Some scholars describe the relationship between mitigation and adaptation as resource competition [71, 72]. To summarize, effectively addressing climate change requires a comprehensive understanding of both mitigation and adaptation strategies. Achieving sustainable development necessitates a balanced approach considering the specific requirements, vulnerabilities, and financial support needed for both mitigation and adaptation, recognizing their complementary responsibilities in effectively and successfully combating climate change.

3 Methodological approach

This exploratory, multiple-case studies and qualitative research data was taken from books, relevant planning journal articles, planning and policy documents, and reports. The selection of these sources was meticulous and deliberate, ensuring that the data collected was comprehensive and representative of the diverse urban strategies being implemented globally to combat climate change. The selection criteria, scope, and analysis method are further explained below.

3.1 Selection criteria and scope

This review captures the diversity of global practices in mitigating and adapting to global warming in urban contexts. The primary considerations for selecting the case examples were relevance, geographical diversity, urban characteristics, data availability, noteworthy practices, and temporal range. This includes focusing on cities with significant or innovative climate strategies, including cities from different continents and climates, covering both developed and developing countries, and a mix of cities in size, economy, and governance. Ensuring sufficient data on the city's climate actions with pioneering innovative strategies was essential. The focus was on recent initiatives to assess the evolution of practices.

3.2 Method of analysis

Considering the case examples selected, each city was treated as a detailed case study to analyse the specific practices, policies, and outcomes in depth. This method allowed for a comprehensive understanding of each city's approach to climate action. Then, a comparative analysis is performed, which involves comparing cities with similar climates but different governance structures or cities with varying levels of economic development. Then, the key themes were also identified across the selected cities: common strategies (e.g., renewable energy adoption, blue-green infrastructure), challenges faced, and outcomes achieved. It helped to analyse how these themes manifest in different urban contexts. To obtain a detailed and multifaceted perspective on the review process, covering aspects such as stakeholder involvement, technology, policy frameworks, social equity, and financial mechanisms was also included in this review as outlined below:

  1. a.

    The review also considered the role of various stakeholders, including government agencies, non-governmental organizations, private sector entities, and community groups, in implementing climate action strategies in urban areas.

  2. b.

    Including cities that have integrated advanced technologies, such as smart grids, urban data analytics, and Internet of Things (IoT) solutions, into their climate action plans was also a consideration.

  3. c.

    The analysis also considered the broader policy frameworks within which these cities operate, including national and international climate agreements, regional policies, and local ordinances.

  4. d.

    The review also explored innovative financing models cities have employed to fund their climate actions, such as green bonds, public–private partnerships, and international funding mechanisms.

  5. e.

    The effectiveness of monitoring and evaluation mechanisms used by the cities was another area of focus.

The contents of the policy documents, city plans, and academic articles were read in depth to identify the frequency and context of specific mitigation and adaptation strategies. This helped to quantify the emphasis placed on different approaches. This critical analysis helped evaluate the effectiveness, sustainability, and equity of the practices implemented in each city and discuss the potential trade-offs, unintended consequences, and challenges encountered. Throughout this study, it has been acknowledged that the approach used in the selection criteria mentioned above for selecting the cities in this review plays a crucial role in the overall conclusions.

4 Best practices in mitigation and adaptation strategies

4.1 Amsterdam in Netherlands

The New Amsterdam Climate Report 2022 serves as a comprehensive guide, outlining 20 pivotal pillars that support the city's ambitious efforts towards sustainable energy [8, 73]. These pillars consist of a spectrum of initiatives, including the gradual elimination of natural gas (Pillar 1), the creation of an eco-friendly heat distribution grid (Pillar 2), and the installation of a city-wide heating infrastructure (Pillar 3). The report highlights the significance of improving energy efficiency in several domains, such as business, housing, and social buildings, while promoting energy-neutral construction practices (Pillar 7). From minimizing polluting traffic (Pillar 8) to maximizing solar and wind energy utilization (Pillar 10 and 11), the pillars address critical aspects of reducing greenhouse gas emissions and fostering renewable energy. The transformation of the harbour into a sustainable battery (Pillar 13), the establishment of the green hydrogen economy (Pillar 14), and initiatives like carbon capture, storage, and usage (Pillar 15) show the city's commitment to innovative solutions. Furthermore, the report emphasizes the interconnected relationships of these pillars, stating that a coordinated, unified approach is essential for a successful and impactful energy transition in Amsterdam.

The Netherlands addresses climate challenges nationally and internationally under its Global Climate Strategy [74]. The first is a whole-of-government approach to support global climate action across all ministries, working with Foreign Affairs, Economic Affairs and Climate Policy, Agriculture, Nature and Food Quality, Infrastructure and Water Management, and Finance. This coordinated effort covers Paris Agreement-compliant safety, humanitarian aid, and health measures. The administration is also increasing ties with like-minded countries, prioritizing European Union and international influence, expanding public–private partnerships in key industries, and supporting financial services sustainability and innovation. For COP26 (Conference of the Parties), the policy commits to phase out support for unabated fossil fuel energy activities overseas, diverting investments to green export potential and supporting organizations dedicated to greening and fulfilling the Sustainable Development Goals [74, 75]. The Dutch government is proactive about climate change and developing a sustainable and resilient world with these policies.

Along with the COP26 'Statement on global public backing for the transition to clean energy' and the coalition agreement, the government is dedicated to discontinuing support for international unabated fossil fuel generation projects [75]. Financial investments focusing on the promotion of green exports and providing support to organizations that contribute to advancing greening and SDGs follow the guidelines laid out by COP26. These significant actions demonstrate the Dutch government's commitment to climate finance, green investment, and withdrawal assistance for fossil fuel energy activities overseas in alignment with international accords and climate goals.

4.1.1 Mitigation strategies

The Dutch government has identified specific mitigation strategies to address climate challenges, emphasizing a multifaceted approach as detailed below [76, 77]:

  1. a.

    Investing in education, skills development, and employment opportunities:

    • A significant focus on making sustainable climate decisions.

    • Initiatives encompass the closure of mines and coal-fired power stations, as well as efforts to combat deforestation.

    • Introduction of projects centred on renewable energy and circular solutions.

    1. b.

      Transition to Circular Economy:

      • A key mitigation strategy.

      • It aims to reduce reliance on virgin raw materials.

      • Promotes maximum reuse and minimizes waste.

      • Addresses issues across production, consumption, and waste processing

      1. c.

        Prioritization of Nature-Based Solutions (NBS) and Building with Nature (BWN):

      • Actively prioritizes NBS and BWN.

      • Contribution to biodiversity protection and restoration.

      • It involves sharing knowledge and expertise internationally.

      • Follows the precautionary principle of avoiding harm.

Collectively, these mitigation measures reflect the Dutch government's commitment to a comprehensive and sustainable response to climate challenges.

4.1.2 Adaptation strategies

  1. (a)

    Development of sustainable and resilient energy settings:

Through the above-outlined holistic strategy, the city seeks to address climate change and develop sustainable, resilient, and equitable energy settings for its residents, which is crucial for adapting to the impacts of climate change on energy infrastructure.

  1. (b)

    Quality, availability, and accessibility of climate action funds:

Initiatives include improving the quality, availability, and accessibility of climate action and green investment funds to maximize benefits for small and medium-sized Dutch enterprises involved in green international activities.

  1. (c)

    Public Infrastructure Projects in Underdeveloped Nations:

Last but not least, the government is investing in green public-private market development strategies and greening public infrastructure projects in underdeveloped nations to improve climate action and green investment finance.

  1. (d)

    Greening Public Infrastructure Projects:

Future investments in green public-private market development techniques and public infrastructure projects are also planned and designed to make infrastructure more resilient to future climate impacts, ensuring that critical systems can withstand extreme weather and other climate-related events.

4.2 Boston in USA

A range of adaptation and mitigation techniques have been put into practice in Boston to deal with the effects of climate change. These tactics aim to mitigate greenhouse gas emissions while also preparing for and adapting to the impacts of climate change. Several particular instances of these tactics are as follows [77,78,79,80]:

4.2.1 Mitigation strategies

  1. a.

    The Department of Neighbourhood Development supported the implementation of a standard for City-funded affordable housing that ensures zero emissions from buildings. This standard encourages the adoption of electric heating and cooling systems as well as high-efficiency insulation.

  2. b.

    The Building Emissions Reduction and Disclosure Ordinance mandates that sizable structures disclose their yearly energy and water consumption and implement measures to enhance energy efficiency, thus diminishing carbon emissions.

  3. c.

    The Boston Transportation Department and Environment Department have published a roadmap to expedite the shift towards electric vehicles and other vehicles that produce no emissions.

  4. d.

    The Community Clean Air Grants programme provides funding for projects initiated by communities to decrease air pollution and promote public health in local areas, so contributing to broader efforts to mitigate environmental harm.

4.2.2 Adaptation strategies

  1. a.

    Local climate resilience plans have been established in susceptible regions to facilitate district-level climate adaptation, aiding communities in their preparedness for and response to climate-related consequences.

  2. b.

    The city has established a designated flood elevation for planning purposes. This elevation will be used to enforce zoning restrictions in areas that are prone to flooding and at risk of rising sea levels. This proactive approach aims to increase the city's ability to withstand and recover from flood events.

  3. c.

    There are ongoing initiatives to create programming for green jobs and establish a worker-owned cooperative focused on green infrastructure. These efforts aim to support low-income immigrant groups and utilize climate adaptation to promote economic development.

  4. d.

    The city is dedicated to guaranteeing that individuals belonging to racial and ethnic minorities and those from low-income groups do not bear a disproportionate burden from climate dangers. Likewise, the city strives to ensure that the positive outcomes of climate mitigation and preparedness initiatives are distributed fairly among all individuals to ensure equitability.

These strategies demonstrate an integrated approach to tackling climate change, incorporating both attempts to mitigate its impact and adapt to its effects to create a more environmentally friendly city better equipped to withstand future challenges. Figure 1 depicts the summary of Boston’s climate goals.

Fig. 1
figure 1

Summary of Boston’s climate goals [79]

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4.3 Singapore

Singapore unveiled an enhanced national climate target on October 25, 2022, committing to achieve net-zero emissions by 2050 as part of its Long-Term Low-Emissions Development Strategy (LEDS) [81]. The nation aims to reduce emissions to around 60 MtCO2e (metric tons of carbon dioxide-equivalent) in 2030 after peaking earlier, following a revised 2030 Nationally Determined Contribution (NDC). Despite resource constraints, Singapore exceeded its 2009 commitment, achieving a remarkable 32% reduction below Business-As-Usual (BAU) levels in 2020 [82, 83]. The country, grappling with alternative energy challenges, emphasizes its dedication as a responsible international community member. Successful realization of these ambitious targets hinges on global commitment to the Paris Agreement, climate pledges, and advancements in decarbonization technologies, necessitating effective international cooperation.

As a vulnerable, low-lying city-state with an open economy, Singapore actively champions multilateral approaches and collaborates with other nations to address climate challenges. Since ratifying the UN Framework Convention on Climate Change (UNFCCC) in 1997, Singapore has played a pivotal role in international climate efforts, engaging in climate negotiations, ratifying key agreements, and shaping global climate agreements. The city-state's involvement in international forums, environmental cooperation through bilateral and regional platforms, and active participation in key initiatives like COP-26 and COP-27 underscore Singapore's commitment to global collaboration and its significant role in advancing sustainable practices.

4.3.1 Singapore mitigation efforts

Despite its geographical difficulties, Singapore has pledged to attain net zero emissions by 2050. Four main initiatives are being actively pursued by the commitment to accelerate the low-carbon transition in industry, economy, and society: business transformation, low-carbon technology investment, international cooperation, and adoption of low-carbon practices. The imposition of a carbon tax serves as the foundation for these strategic initiatives and is an essential facilitator of the overall shift. The mitigation efforts by Singapore are listed in Table 1 [84].

Table 1 Singapore mitigation efforts
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4.3.2 Singapore adaptation approach

Singapore is proactively taking early measures to adapt to the evolving impact of climate change. Recognizing the dynamic nature of our understanding of climate change, the government has implemented a resilience framework to guide long-term efforts in preparing for the projected effects over the next 50 to 100 years. Singapore’s Adaptation Approach is illustrated in Fig. 2.

Fig. 2
figure 2

Singapore's approach to adaptability [85]

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4.4 Ahmedabad in India

The Ahmedabad Heat Action Plan (HAP) was released in 2013 jointly by the Ahmedabad Municipal Corporation (AMC) and its stakeholders/collaborators following the response to the severe heatwave that occurred in 2010 and resulted in an additional 1,344 deaths. The primary objective of this HAP was to establish a structured framework for executing, coordinating, and assessing activities in response to extreme heat occurrences in Ahmedabad. The HAP encompasses a set of comprehensive mitigation/adaptation measures or strategies at the city scale aimed at addressing the adverse impacts of extreme heat events, as stated below [86].

4.4.1 Mitigation efforts through HAP

  1. (a)

    Under this plan, an important initiative is the implementation of the cool roofs program, which intends to mitigate elevated ambient temperatures in vulnerable neighbourhoods and communities. Cool roof program encourages the usage of reflective surfaces on rooftops, effectively countering the urban heat and optimizing thermal comfort for residents to provide a better thermal environment [87, 88].

  2. (b)

    Training programs and workforce development are designed to equip individuals with the knowledge and skills required to install cool roofs and identify heat-related illnesses. Investment in the capacity-building of the workforce is an important part of this HAP, which aims to create a team of individuals capable of effectively implementing and upkeep heat mitigation strategies.

4.4.2 Adaptation efforts through HAP

  1. (a)

    The HAP focuses on greater outreach, public awareness, and community engagement. It recommends informing the general public about the high risks associated with heat waves, mainly in summer. The plan attempts to widen the circulation of information on practices that can prevent heat-related illnesses and fatalities through several media outlets, advertisements, etc., fostering a proactive approach to excessive heat.

  2. (b)

    The idea is to set up an early warning system and facilitate inter-agency coordination. This approach guarantees that inhabitants are promptly informed regarding anticipated excessive temperatures. The corporation has developed official communication channels involving government agencies, healthcare facilities, medical personnel, emergency personnel, media sources, and local civic organizations to minimize the impact of extreme heat events through coordinated actions.

  3. (c)

    Another aspect of HAP is heat-resilience urban planning. It assesses vulnerable populations and areas within the city region prone to heat waves to create targeted interventions that enhance heat prevention measures, ensuring an even more resilient urban thermal environment [89].

The highlighted measures or strategies are designed considering the extreme heat-related illness and events in Ahmedabad, but they can be replicated in similar city regions facing similar issues. Implementation and adoption of such measures strengthen heat preparedness and help improve the overall well-being and health of the vulnerable population.

4.5 Copenhagen and Portland climate plan

Copenhagen and Portland employ comparable strategies to mitigate and adapt to climate change, focusing on reducing GHG emissions and building resilience to its impacts [90]. However, disparities exist in the extent of detail and integration between the mitigation and adaptation methods. Copenhagen has enacted policies that offer benefits in mitigation and adaptation, whereas Portland is currently concentrating on formulating its adaptation strategy.

4.5.1 Mitigation strategies of Copenhagen and Portland

Implementing a range of techniques to mitigate GHG emissions is the foremost objective in both of the city climate plans. This comprises the improvement of energy efficiency, growth of renewable energy sources, reduction of waste generation, and promotion of sustainable mobility [91, 92]. The plan includes strategies to mitigate the urban heat island phenomenon, such as expanding vegetated cover and encouraging the implementation of green facades and roofs.

4.5.2 Copenhagen's adaptation strategies vs. Portland's developing adaptation approaches

In the case of adaptation methods for the Copenhagen climate plan, the necessity of establishing protective zones is highlighted, adjusting to growing intensified storms and floods and substantial rise in sea levels. Copenhagen has implemented comprehensive plans and strategies to address the anticipated challenges of rising sea levels and more frequent and intense rainfall. The city's approach includes:

  1. 1.

    Rising Sea Levels:

    • Evaluation of potential impacts on storm surges, identifying high-risk zones exempted from building and designated for flood-tolerant uses.

    • Municipal planning incorporating flood-proofing requirements for construction on flood-prone properties.

    • Allocation of areas for essential technical facilities like dikes and locks to safeguard against flooding, ensuring their readiness.

    • Implementation of the storm surge law, governing compensation, providing incentives for damage prevention, and addressing floods from rivers and lakes.

  2. 2.

    More Frequent and Heavier Rain:

    • Zoning for urban development while safeguarding at-risk regions from new construction to address higher rainfall and building flooding.

    • Designation of sites for technical facilities such as rainwater collection and retention basins through municipal planning.

    • Regulation of the use of watercourses, lakes, and seas to manage water-related challenges.

    • Specification of areas for local stormwater infiltration permissions in the municipal plan to enhance adaptability to changing conditions.

  3. 3.

    Groundwater inundation:

    • Preservation of at-risk regions from building growth to prevent groundwater inundation.

    • New construction on elevated land is mandatory to protect against entering water.

    • Implementation of building codes requiring structures to mitigate upward moisture and adapt existing buildings to changing groundwater levels, ensuring both damage prevention and health safety

Copenhagen's proactive stance on climate adaptation is evident in these efforts, which include municipal planning and building laws aimed at mitigating the effects of rising sea levels and increasingly frequent and intense rainfall in the future.

On the other hand, Portland is now developing an independent adaptation strategy that will specifically target the consequences of climate change, including intense heat waves, heightened flooding, and wildfires. In addition, both the Copenhagen and Portland Climate plans include initiatives to expand green spaces, increase the extent of permeable surfaces, and strengthen the resilience of natural systems. Table 2 depicts some of the common objectives and actions in Portland and Copenhagen [90, 93, 94].

Table 2 Objectives and actions in Portland and Copenhagen
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4.6 Hamburg's green roof strategy in Germany

Hamburg's Green Roof Strategy is anchored in four key pillars [95]: financial incentive, dialogue, regulation, and science, which are discussed below.

4.6.1 Green roof as a mitigation approach

  1. (a)

    The city aims to install 100 hectares of green roof surface, supported by a €3 million financial commitment until 2024 from the Ministry for Environment and Energy. In the face of climate change projections, green roofs contribute to mitigating increased temperatures and extreme rainfall events.

  2. (b)

    Green roofs contribute to the city's climate resilience by reducing the urban heat island effect, improving building insulation, lowering maintenance costs, and managing rainwater.

  3. (c)

    Building owners are eligible to receive subsidies that can cover up to 60% of the costs associated with installing green roofs, so encouraging its implementation.

  4. (d)

    Funds include green roofing measures and green facades at subsidized rates; the strategy highlights energy saving, extended green roof lifespan, and rainwater fee reductions as long-term benefits.

4.6.2 Climate resilience as an adaptation effort

  1. (a)

    These roofs help enhance the city's resilience to climate change, offering multiple benefits with a 50% reduction in rainwater fees due to improved rainwater retention.

  2. (b)

    The strategy aligns with the city's Rain Infrastructure Adaptation 2030 (RISA) plan, addressing the challenges of increased heavy rains and flooding. Scientific support from the HafenCity University evaluates water retention and management effectiveness, contributing to climate change adaptation. Hamburg's ambition is to create a sustainable urban landscape that adapts and responds to climate change challenges while fostering community engagement and green spaces through promotion, exchanges, policy integration, and scientific investigation.

  3. (c)

    Hamburg’s objective is to balance urban expansion with green quality spaces. The Green Roof Strategy targets greening at least 70% of new and suitable roofs, totalling 100 hectares, with a focus on enhancing recreational spaces and biodiversity.

  4. (d)

    This program started in 2014 and was supported until 2024. The development of green roofs is projected to last 40 years while contributing to Hamburg's sustainable practice.

Hamburg's ongoing collaboration with other cities on climate action and utilization of shared experiences help to customize its approach to climate change. The city's unique incentive program for green roofs, developed with input from other cities, focuses on surface area and thickness rather than water retention. Internal stakeholder groups, united in the goal of greening 100 hectares in a decade, include housing estate companies, constructors, architects, and urban planners. Despite challenges, Hamburg's Green Roof Strategy aligns with its vision of growth, climate-friendliness, and resilience. This strategy is financially supported by the Ministry for the Environment to take initiatives and prioritize communication channels and research to address the barriers. It also includes legally related efforts to make green roof installation compulsory while balancing housing and environmental goals. Figure 3 depicts an overview of Hamburg's Green Roof Strategy.

Fig. 3
figure 3

Hamburg's Green Roof Strategy: Overview [96]

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4.7 Rain city strategy (RCS) in Vancouver

The desire for equitable and sustainable urban water management, the need for urban resilience, and climate change risks played key roles in transitioning Vancouver to become a water-sensitive city [97]. Also, due to a concern that conventional urban water management techniques are unsustainable and inequitable, this call arose for new approaches to safeguard, preserve, and improve the health of natural systems and waterbodies, mitigate risks associated with floods, and foster physical activity and well-being. An overview of the Rain City strategy, Vancouver, is illustrated in Fig. 4.

Fig. 4
figure 4

Rain city strategy, Vancouver: Overview [98]

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4.7.1 Mitigation strategies

  1. 1.

    Green rainwater infrastructure (GRI)

    1. (a)

      GRI consists of different elements such as permeable pavement, bioswales, rain gardens, green roofs, etc., which capture, store, and treat rainwater, reducing the strain on drainage/sewer systems while preserving water quality.

    2. (b)

      This involves using GRI to manage rainwater at its origin, shifting away from depending solely on conventional grey infrastructures like pumps and pipes. The strategy aims to optimize blue resource usage, taking into account the entire water cycle from source to tap to treatment to discharge.

    3. (c)

      The strategy aims to control rainwater volume and enhance water quality for 40% of impermeable areas in the city of Vancouver by 2050, achieved through infrastructure projects, new development, and strategic retrofits.

  2. 2.

    Sustainable urban water management

    1. (a)

      The transition into a water-sensitive city is done by incorporating perspectives (complete, holistic, and inter-generational) in the design, planning, and provision of water resources.

    2. (b)

      Achieving integrated water utility servicing with a focus on economic viability and sustainability ensures efficiency.

  3. 3.

    Promoting water equity

    1. (a)

      Elevating the standard of life and promoting water equity for all inhabitants to ensure that water management practices are equitable and sustainable.

4.7.2 Adaptation strategies

  1. 1.

    Building climate resilience

    1. (a)

      The climate change effects mainly include water quality issues and sewer and drainage systems issues, marked by an increase in extreme weather events and rising sea levels. Because of these issues and the urgent necessity to build resilience against these impacts, the transformation into a water-sensitive city is seen as a strategic response.

    2. (b)

      Expediting initiatives to protect the overall health and vitality of surrounding water ecosystems to address climate change risks promptly and building resilience against its impacts.

  2. 2.

    GRI implementation for adaptation

    1. (a)

      The RCS attempts to transition urban water management using green rainwater infrastructure (GRI), recognizing rainwater as a valuable blue resource and aiming for equity, sustainability, and resilience. The RCS advances this groundwork by outlining an ambitious blueprint for GRI implementation alongside a roadmap to achieve this vision and subsequent plan.

    2. (b)

      The city started GRI implementation over two decades ago; the city initially prioritized rain gardens and bioswales in public spaces, and later expansion efforts included green roofing, permeable pavement, and other GRI components in private spaces.

  3. 3.

    Harmonious urban planning

    1. (a)

      The city showcases the harmonious management of urban water with natural systems, community planning, and diverse infrastructure on a citywide scale and actively leads in water-sensitive urban planning and design.

    2. (b)

      There are three GRI implementation action plans detailing necessary actions required in the short term for public spaces-streets, beaches-parks, and buildings-sites. Leveraging past efforts and commitment to GRI, the RCS seeks to speed up the adoption of the GRI element and establish it as a central place in the urban water management approach.

5 Discussion

The assessment of the performance and effectiveness of global warming mitigation and adaptation strategies at the city scale presented in this paper offers an insightful exploration and comprehension of best practices and initiatives in international cities. The different mitigation strategies listed in this work, by comprehending various case examples in several global cities, including sustainable energy initiatives, zero-emission buildings, and sustainable battery technologies advancement, all aim to minimize GHG emissions as well as restrict the long-term adverse effects of climate change. The adaptation strategies comprehended in the case examples included blue-green solutions, climate resilience urban planning, nature-based strategies, and integrated mechanisms for early warning signs. Adaptation highlights strengthening the resilience of communities and cities to respond to climate change's immediate and future impacts.

5.1 Climate strategies and initiatives comparison

Amsterdam, Boston, Singapore, Ahmedabad, Copenhagen, Portland, Hamburg, and Vancouver each employ distinct yet impactful climate strategies to address environmental sustainability challenges, as observed in the above sub-sections. This section provides a comparative analysis of each, as presented in Table 3.

Table 3 Comparative analysis of climate strategies and initiatives in Amsterdam, Boston, Singapore, Ahmedabad, Copenhagen, Portland, Hamburg, and Vancouver
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Amsterdam takes a comprehensive approach with a guide featuring 20 pillars for sustainable energy, emphasizing a multi-faceted approach, circular economy, nature-based solutions (NBS), and Blue-Green Networks (BWN). Boston focuses on mitigation through zero-emission buildings, an EV roadmap, and climate resilience planning with flood elevation measures. Singapore has set a net-zero emissions target by 2050, employing four primary strategies: business transformation, tech investment, international cooperation, and low-carbon practices. The cities also implement specific mitigation and adaptation measures, such as sustainable batteries, green hydrogen, and carbon capture, as well as zero-emission buildings and clean air grants. The city of Ahmedabad focuses on heat-resilient urban planning. In contrast, it was found that Copenhagen's adaptation strategies are more advanced, with detailed zoning and building regulations to address rising sea levels and intense rainfall, compared to Portland's adaptation strategies. Hamburg's aim for widespread green roof adoption is to reduce the urban heat island effect and regulate rainwater through financial incentives and regulatory support. Vancouver prioritizes a long-term vision for integrating green rainwater infrastructure into its water management system across the city.

5.2 Understanding the allocation of funds between mitigation and adaptation initiatives

Every city reflects its climate vulnerabilities and priorities, suggesting models that could be implemented in identical contexts globally. Cities demonstrate a commitment to climate finance, international climate involvement, waste, and water management through circular economy initiatives, as well as unique urban sustainability and household energy consumption efforts. Figure 5 illustrates the funding levels (low, moderate, high) for mitigation actions vs. adaption actions in each city [9, 95, 99,100,101]. The collaborative government approach in Amsterdam or Ahmedabad, the whole-of-government strategy in Boston or Hamburg, external partnerships in Vancouver, and international support in Singapore highlight their commitment to global climate initiatives.

Fig. 5
figure 5

Understanding the funding levels for mitigation actions vs. adaption actions in each city

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6 Conclusions

The case studies investigated provide critical messages for action priorities and valuable lessons in addressing the challenges of global warming at the city level. The close scrutiny of mitigation and adaptation strategies exposes the interconnected and complex nature of efforts to combat global warming. It is observed that cities play a crucial role in driving climate change-related policies as the importance of localized solutions stands out. The relationship between local management practices and global climate policies is depicted as intricate, with cities independently managing climate actions while being facilitated through cooperation and networks between cities and pushed by international agreements. The case studies of the selected cities offer critical insights into the effectiveness of city-wide climate strategies and local environmental challenges. The chosen case studies emphasize innovation, challenges, and collaboration, offering other worldwide cities crucial guidance for effective climate action and building a sustainable, resilient future.