IPCC Research Articles

Imputation of missing land carbon sequestration data in the AR6 Scenarios Database

Abstract. The AR6 Scenarios Database is a vital repository of climate change mitigation pathways used in the latest Intergovernmental Panel on Climate Change (IPCC) assessment cycle. In its current version, many scenarios in the database lack information about the level of anthropogenic carbon dioxide (CO2) removal via land sinks, as net-negative CO2 emissions and gross removals on land are not always separated and are not consistently reported across models. This makes scenario analyses focusing on CO2 removal challenging. We test and compare the performance of different regression models to impute missing data on land carbon sequestration for the global level and for several sub-global macro-regions from available data on net CO2 emissions from agriculture, forestry, and other land uses. We find that a k-nearest neighbors regression performs best among the tested regression models and use it to impute and provide two publicly available imputation datasets (https://doi.org/10.5281/zenodo.13373539, Prütz et al., 2024) on CO2 removal via land sinks for incomplete global scenarios (n=404) and incomplete regional R10 scenario variants (n=2358) of the AR6 Scenarios Database. We discuss the limitations of our approach, the use of our datasets for secondary assessments of AR6 scenario ensembles, and how this approach compares to other recent AR6 data reanalyses.

Evaluation of the effect of the water-energy nexus on the performance of the water-energy supply system.

In this study, the water-energy nexus is investigated throughout coupling the Water Evaluation and Planning (WEAP) and Low Emission Analysis Platform (LEAP) models under the climate change effects in the Marun basin, Iran. For this purpose, first, the climate change effects on water resources and consumption nodes are calculated under representative concentration pathway (RCP) scenarios from the fifth report of the International Panel on Climate Change (IPCC). Artificial neural network (ANN) is used to model river inflow and Cropwat model is used for agricultural water demand in future time (2015-2040). In the next step, water system is modeled in WEAP and energy system is modeled in LEAP. Then, three water-energy nexus scenarios include (1) calculating the actual hydropower generation capacity in LEAP model (W-E-N1), (2) water-energy nexus evaluation indexes in the WEAP model (W-E-N2), and (3) changes in the electricity consumption intensity in the LEAP model (W-E-N3) are modeled under RCP 2.6, RCP 4.5 and RCP 8.5 climate scenarios. The results of W-E-N1 scenario show that the actual hydropower generation capacity with water-energy nexus is reduced by 78%, 89%, and 91%, respectively, compared to no water-energy nexus under RCP 2.6, RCP 4.5, and RCP 8.5 scenarios. The results of W-E-N2 show that the hydropower generation reliability index will be reduced by 19%, 31%, and 13%, respectively under RCP 2.6, RCP 4.5, and RCP 8.5 compared no water-energy nexus. The results of W-E-N3 scenario show that the electricity consumption intensity will increase considering the electricity required for water transferring to demand sites. The results of the present study show that the water-energy nexus will lead to more accurate results and, as a result, more realistic planning for water and energy resources.

Insights into the ecological and climate crisis: Emerging infections threatening human health.

The Anthropocene era is marked by unprecedented human-induced alterations to the environment, resulting in a climate emergency and widespread ecological deterioration. A staggering number of up to one million species of plants and animals are in danger of becoming extinct, which includes over 10 % of insect species and 40 % of plant species. Unrestrained release of greenhouse gases, widespread deforestation, intense agricultural practices, excessive fishing, and alterations in land use have exceeded the ecological boundaries that were once responsible for humanity's wellbeing. As per the Intergovernmental Panel on Climate Change (IPCC), existing policies are expected to result in a minimum rise in global temperature of +2 °C, with more recent assessments indicating a potential increase of up to +2.9 °C. The effects of climate change and ecological degradation on the formation of diseases are complex and have multiple aspects. Deforestation diminishes biodiversity and compels wildlife to come into greater proximity with humans, hence promoting the transmission of zoonotic diseases. Climate change intensifies these impacts by modifying the habitats of disease carrying organisms, resulting in the expansion of vector-borne diseases such as malaria, dengue, and Zika virus into previously unaffected areas. Furthermore, climate change amplifies the occurrence and severity of extreme weather phenomena, which undermines water, sanitation, and hygiene (WASH) practices. This creates an environment conducive to the transmission of waterborne diseases such as cholera in densely populated resettlement camps. Climate-induced disasters contribute to the complexity of epidemiological landscapes, exacerbating antimicrobial resistance and posing a threat to modern medical advancements. This narrative review investigates the complex connections between the ecological-climatic crises and emerging illnesses, offering an overview on how environmental changes contribute to outbreaks that pose a substantial threat to public health.

Indonesia's country-specific CO2 emission factor based on gas fuels for greenhouse gas inventory in the energy sector.

Indonesia currently calculates CO2 emissions from gas fuels using Tier 1 emission factors adopted from the Intergovernmental Panel on Climate Change (IPCC). However, this method may not accurately capture the country's specific emission characteristics. To address this, this study aims to derive country-specific CO2 emission factors for gas fuels, including liquefied petroleum gas (LPG), liquefied gas for vehicles (LGV), natural gas (NG), and liquefied natural gas (LNG), by analyzing fuel samples collected nationwide. A total of 128 LPG samples from 25 regions, 5 LGV samples from 2 regions, 23 NG samples from 11 regions, and 2 LNG samples from 2 regions were analyzed. Emission factors were determined based on gas composition, carbon content, and net calorific value. The uncertainties were calculated to reflect the contributions of all key parameters in the emission factor calculation. The results show that LPG has the highest EF Tier 2, while LNG has the lowest. The average country-specific CO2 emission factors for Indonesia are 65.41 ± 0.67 tCO2/TJ for LPG, 64.89 ± 0.07 tCO2/TJ for LGV, 57.64 ± 10.18 tCO2/TJ for NG, and 57.27 ± 9.50 tCO2/TJ for LNG. We expect stakeholders to incorporate these EF Tier 2 values into greenhouse gas reporting, enabling more accurate assessments of carbon footprints, supporting evidence-based policymaking, and strengthening Indonesia's climate action efforts.

Carbon sequestration potential of green corridor to reduce transportation greenhouse gas emissions: a case study in Malang City

The increasing rate of population growth and urbanization will lead to an increase in escalating greenhouse gas (GHG) emissions from the transportation sector, which brings various negative impacts of climate change to people's lives. In this study, an inventory and projection of GHG emissions in the transportation sector in Malang City for 10 years were carried out using the Intergovernmental Panel on Climate Change (IPCC) tier 1 method. The potential of carbon sequestration from trees along urban roads or in green corridors was measured as a mitigation measure to reduce GHG emissions in the transportation sector. It was estimated with i-Tree canopy, along with determining the baseline GHG emission target to be reduced. The results showed that GHG emissions in the transportation sector in Malang City amounted to 511,011.24 tons CO2-eq and are projected to reach 6.043.940 tons CO2-eq in 2034. The highest potential is observed in the green corridor in Klojen District, totaling 12,816 trees and dominated by Swietenia mahagoni. Street trees in Malang City’s green corridors in the 2024 - 2034 interval have the potential to reduce GHG emissions by 10.195,90 tons CO2-eq in Malang City. The green corridor is projected to contribute 1,69 % to Malang's regional target in GHG mitigation.

Vertical land motion is underestimated in sea-level projections from the Oka estuary, northern Spain

Coastal populations are susceptible to relative sea-level (RSL) rise and accurate local projections are necessary for coastal adaptation. Local RSL rise may deviate from global mean sea-level rise because of processes such as geoid change, glacial isostatic adjustment (GIA), and vertical land motion (VLM). Amongst all factors, the VLM is often inadequately estimated. Here, we estimated the VLM for the Oka estuary, northern Spain and compared it to the VLM component of sea-level projections in the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (AR6) and the Spanish National Climate Change Adaptation Plan (NCCAP). To estimate VLM, we updated Holocene RSL data from the Atlantic coast of Europe and compared it with two 3D GIA models. Both models fit well with RSL data except in the Oka estuary. We derived a VLM rate of − 0.88 ± 0.03 mm/yr for the Oka estuary using the residuals of GIA misfits. Comparable VLM rates of − 0.85 ± 0.14 mm/yr and − 0.80 ± 0.32 mm/yr are estimated based on a nearby Global Navigation Satellite Systems station and differenced altimetry-tide gauge technique, respectively. Incorporating the updated late Holocene estimate of VLM in IPCC AR6 RSL projections under a moderate emissions scenario increased the rate of RSL rise by 15% by 2030, 11% by 2050, and 9% by 2150 compared to the original IPCC AR6 projections, and also increased the magnitude of RSL rise by over 40% by 2035 and 2090 compared with projections from the Spanish NCCAP. Our study demonstrates the importance of accurate VLM estimates for local sea-level projections.

Recent advances in the study of mercury biogeochemistry in Arctic permafrost ecosystems.

Permafrost predominates in polar and high mountain regions, encompassing nearly 15% of the exposed land in the Northern Hemisphere. It denotes soil or rock that remains at or below 0°C for the duration of at least two consecutive years. These frozen soils serve as a barrier to contaminants that are stored and accumulated in permafrost over extended periods of time. One of these chemical compounds is mercury (Hg), a heavy metal well recognized for its severe toxic effects. Mercury presents a major risk worldwide to ecosystems, biota and human health and is strengthened by the Minamata Convention on Mercury. The International Panel on Climate Change (IPCC) scientific group monitors and assesses the science related to climate change and highlights the significant impacts of global warming. The phenomenon known as Arctic amplification has accentuated warming of the Arctic in recent years and has led to the degradation and rapid thawing of permafrost. This process has significant implications in hydrology of the ecosystems and for the mobility of previously sequestered carbon and trace metals, such as Hg, with possible adverse environmental and human health impacts. In this article, we provide a comprehensive review of the current understanding of the Hg cycle in permafrost regions, exploring the effects of global warming on these intricate processes. Additionally, we highlight existing research gaps and propose directions for future investigations.

Sensemaking and Media Logic of Filipino Environmental Activist Groups in Communicating Climate Science and Action

Climate change is a reality felt across all sectors of society and in many countries. The Philippines, a developing country, has been cited as one of the most vulnerable countries to climate change even though several reports point to developed countries as major contributors of historical greenhouse gas (GHG) emissions. With the release of the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), it was concluded that the global surface temperature will continue to increase and may exceed the 1.5-degree Celsius threshold. This makes climate change the most serious issue among other environmental problems and requires concerted effort from all levels of government, public and private sectors, and civil society. One of the crucial voices in the climate change discussions is the environmental activist groups. Multiple case studies of three mainstream and three grassroots environmental activist groups based in the National Capital Region (NCR) and provinces showed that they consult science and use media to communicate climate action in their online and on-the-ground campaigns. Their understanding of climate science allows them to perform their roles and functions and communicate effectively with other change agents such as the government, scientific community, industry, media, and ordinary citizens. They likewise use social media accounts to meet where their audiences mostly are and produce creative multimedia materials imbued with specific climate action messages. This study proves that environmental activist groups are critical sources of climate change-related messages. They demonstrate high value for research and social media as foundations for their communication strategies. Keywords : climate change, communication strategies, environmental problems, media logic, science communication

Estimating soil carbon sequestration with woody and bamboo biochar using the Japanese Industrial Standard (JIS) M 8812

The Intergovernmental Panel on Climate Change (IPCC) established a methodology to estimate carbon sequestered from biochar additions to mineral soils in the 2019 Refinement Guideline, requiring a pyrolysis temperature exceeding 350 °C and three variables: organic carbon content in fraction (F c), fraction of biochar carbon remaining after 100 years (F perm), and biochar mass. Japan has reported biochar amendments in its national greenhouse gas inventory since 2020 using default IPCC values. However, Japan has traditionally evaluated biochar properties based on Japanese Industrial Standard (JIS) M 8812, which measures fixed carbon (FC), volatile matter (VM), and ash content. This study developed a protocol to convert the JIS parameters to the IPCC variables F c and F perm for woody and bamboo biochar. We established a VM/FC-based power approximation expression to estimate pyrolysis temperature, and derived a conversion equation from the liner relationship between JIS values, organic carbon content (Corg, %) and F perm. Inventory country-specific values for woody and bamboo biochar were proposed, with F c (F c = Corg/100) and F perm reflecting three pyrolysis temperature levels. This conversion protocol enables practical, cost-effective application to diverse biochar feedstocks, supporting country-specific variable development and broader biochar use for carbon dioxide removal.

Urban–Rural Disparities in Greenhouse Gas Emissions: Fuel Consumption in Moldovan Households and Implications for Energy Policies

Climate change, driven by greenhouse gas (GHG) emissions, poses a critical global challenge, with household energy use as a significant contributor. In the Republic of Moldova, stark urban–rural disparities in fuel consumption and emissions necessitate targeted research to inform effective energy policies. This study analyzes GHG emissions from household fuel consumption, focusing on the differences between urban and rural areas, using a quantitative approach guided by the Intergovernmental Panel on Climate Change (IPCC) methodologies. The findings reveal that rural areas, heavily reliant on traditional fuels like firewood, contribute disproportionately to emissions compared to urban areas, where modern energy sources such as natural gas dominate. Nationally, the research provides critical data to shape energy transition strategies, promoting renewable energy adoption and energy efficiency in rural areas. Internationally, it offers a valuable case study on household emission dynamics in developing countries, contributing to the global understanding of energy use patterns and their environmental impacts. Recommendations include enhancing access to cleaner energy, modernizing infrastructure, and encouraging sustainable practices to align with Moldova’s commitment to GHG reduction goals and serve as a model for similar contexts worldwide.

Comparative Life Cycle Assessment (LCA) in the Agri-Food Industry, Focusing on Organic and Conventional Coffee

This study evaluates the environmental burden of organic and conventional coffee systems with a functional unit (FU) of 1 kg for market-ready, dried coffee. The ISO 14040 and ISO 14044 framework and guidelines are applied to organic and conventional coffee systems, using a cradle-to-grave approach and the methodology of ReCiPe Endpoint 2008, cumulative energy demand (CED), and the Intergovernmental Panel for Climate Change (IPCC). Superior sustainability was achieved for organic coffee compared to the performance of conventional coffee, with values of 218.50 mPt (conventional) and 146.10 mPt (organic), and a global warming potential (GWP) of 2.12 kg CO2 eq FU−1 (organic) and 1.44 kg CO2 eq FU−1 (conventional). CED fossil-based consumption totalled 25 MJ and 35 MJ for organic and conventional coffee systems, respectively. Conventional and organic coffee system hotspots stemmed from the planting (chemical fertilizer), drying, and packaging processes. This study emphasizes the environmental benefits of organic practices and their relatively lower impact than conventional methods. Within a growing sector, best management practices in the form of actionable insights from a life cycle assessment must be sought to ensure environmental sustainability in parallel with the UN’s goals.

Implementing FAIR data principles in the IPCC seventh assessment cycle: Lessons learned and future prospects

Every five to seven years, the Intergovernmental Panel on Climate Change (IPCC) convenes the climate science community to assess the latest knowledge on climate change relevant to policy-makers. This generally takes the form of Assessment Reports (AR) covering the scientific basis of climate change, its impacts and future risks, and options for adaptation and mitigation. With each cycle, these reports have grown in scope, length, number of referenced papers, and underpinning datasets. During the sixth assessment cycle, a large-scale collective effort went into archiving digital products assessed and generated through the IPCC process. The main objectives driving this initiative are making IPCC’s work more transparent, improving the reproducibility and reusability of the assessment outcomes, better utilization of the services of the IPCC Data Distribution Centre (DDC), and, more generally, compliance with best practices in open science. This paper expands on the motivations for the curation and preservation of digital objects in the IPCC. It gives an overview of how FAIR (Findable, Accessible, Interoperable, Reusable) and open data principles have been implemented in practice and explores some of the successes and setbacks of the AR6 experience. It concludes with recommendations for consolidation and expansion of the approach for AR7. These include a tighter integration of digital curation activities in the IPCC timeline and workflows, better support of IPCC authors and contributors through early training and use of suitable software, improved standardization and harmonization of data and software handling across Working Groups (WGs), and close collaboration with key external data providers and research organizations.

Assessment of Greenhouse Gas Emissions and Carbon Sequestration in Dairy Goat Farming Systems in Northern Extremadura, Spain.

Livestock farming is an activity closely linked to the environment, directly affecting its surrounding ecosystem while utilizing the natural resources it provides. Accordingly, it is essential to study these production systems in order to implement more sustainable models that allow for a balance between socioeconomic and environmental factors. The main objective of this study was to analyze the environmental impact of nine different dairy goat production systems located in northern Extremadura, Spain. The selected farms ranged from extensive and organic production models to more intensive ones. The methodology used was a life cycle assessment (LCA) to calculate the carbon footprint, following the IPCC (Intergovernmental Panel on Climate Change) guidelines. A comprehensive evaluation of emissions was conducted, considering the different global warming potentials (GWPs) established by the IPCC for the main gases associated with livestock farming. In addition, carbon sequestration (Cseq) was incorporated into the analysis to assess the contribution of goat farming to climate change mitigation based on its production management. CH4 emissions were the main source (44-67%) of GHGs, followed by CO2 from inputs (20-48%), and finally N2O (7-13%). A trend was observed linking increased CH4 emissions to more extensive and less productive livestock systems. However, the significant role of soil as a carbon sink was highlighted, as it greatly offsets the emissions produced, demonstrating its potential mitigation due to Cseq, particularly in more extensive models. The importance of this factor suggests that it should be taken into account in such studies to provide a realistic view of the final impact of each production system.

Más allá del Derecho Internacional y la sostenibilidad: reseña del libro Blue Planet Law. The Ecology of our Economic and Technological World (2020)

The Intergovernmental Panel on Climate Change (IPCC), has revealed in its latest report, entitled Synthesis Report Summary for Policymakers, published in 2023 that, as part of these repercussions, rainfall will intensify and with it, local flooding, as well as the inevitable rise in sea level will increase vulnerability and risks to coastal ecosystems, people and infrastructure. The book Blue Planet Law, The Ecology of our Economic and Technological World, edited by Maria Da Glória Garcia and António Cortês (2023), brings together more than thirty authors and is part of the “Sustainable Development Goal Series”. Its main objective is to commemorate half a century since the Stockholm Conference and to generate a reflection on the path to build the Global Law on Ecosystems. the way to build a Global Law on the Earth's ecosystems.

Expanded Bioclimatic Variables Extracted from Monthly Climate Predictions under the SSP Climate Scenarios over South Korea

Numerous studies, including the Intergovernmental Panel on Climate Change (IPCC) sixth assessment report, have documented species habitat shifts caused by climate change. These shifts lead to transformations in ecosystem structure, components, and functions. Exploring the connections between species and climate change is essential for developing adaptation strategies. Many studies use species distribution models (SDMs), which are based on the correlation between species habitats and climatic surroundings, to predict ecological shifts under climate change. The primary climate variables for these models are the only 19 variables whose concepts are based on monthly average temperature and precipitation from the BIOCLIM package developed in 1984. These 19 bioclimatic variables usually are obtained from WorldClim data set and other datasets. However, they have limitations in reflecting local climate characteristics and their association with ecology. Firstly, future projection data from global dataset including WorldClim dataset is derived directly from global climate models rather than regional climate models. Secondly, the 19 variables based on monthly temperature and precipitation do not adequately express hydrological characteristics of terrestrial ecosystem which are crucial for species habitats. Lastly, although there are various biogeographical indices excepts the 19 bioclimatic variables, there have been just a few cases that they were applied to SDMs for Korea. To overcome these limitations, this study expands the various bioclimatic variables, using regionally specialized climate data from Korea Meteorology Administration (KMA). The newly extended indices, which can reflect water availability, are expected to improve the prediction of SDMs, enabling more precise assessment of ecological risks due to climate change and effective adaptation strategies to mitigate the impacts of climate change on ecosystems.

The IPCC in the hybrid public sphere: divergent responses to climate mitigation solutions in mainstream and social media

In April 2022 the Intergovernmental Panel on Climate Change (IPCC) published its report on the mitigation of climate change, which included detailed discussion of the wide range of solutions at the personal, societal and governmental level needed to reduce emissions. The report generated extensive societal debate and interest in mainstream and social media. Using manual text analysis, we examined 66 articles on more than 20 popular English-language online news sites in the UK and USA and the 56 most shared posts or tweets on Facebook and Twitter about the report. First, we found that the mainstream media faithfully reported the IPCC’s priority messages, and often included the IPCC’s own critique of some solutions, such as Carbon Dioxide Removal, as compared to critiques from other sources. The coverage represented a sharp break with the historical tradition of focusing on the negative, disaster-focused impacts of climate change in favor of more positive, solutions-based reporting. Secondly, in sharp contrast, many of the most widely-shared social media posts did not closely follow the IPCC’s main messages. Less than a quarter of the posts contained the summary message of the report, and about half mentioned no solutions at all. Instead they focused on the direness of the situation and the urgency with which action needs to be taken. Finally, there was a very low presence of voices from the organized climate countermovement, who often question the need to take far-reaching and rapid mitigation action. We discuss the significance of our results for future research and for practical action.

Fusion of Probabilistic Projections of Sea‐Level Rise

AbstractA probabilistic projection of sea‐level rise uses a probability distribution to represent scientific uncertainty. However, alternative probabilistic projections of sea‐level rise differ markedly, revealing ambiguity, which poses a challenge to scientific assessment and decision‐making. To address the challenge of ambiguity, we propose a new approach to quantify a best estimate of the scientific uncertainty associated with sea‐level rise. Our proposed fusion combines the complementary strengths of the ice sheet models and expert elicitations that were used in the Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC). Under a low‐emissions scenario, the fusion's very likely range (5th–95th percentiles) of global mean sea‐level rise is 0.3–1.0 m by 2100. Under a high‐emissions scenario, the very likely range is 0.5–1.9 m. The 95th percentile projection of 1.9 m can inform a high‐end storyline, supporting decision‐making for activities with low uncertainty tolerance. By quantifying a best estimate of scientific uncertainty, the fusion caters to diverse users.

Assessing carbon footprint from cattle in insemination farming, Malang Indonesia

Abstract Ruminants such as cattle and goats are significant contributors to greenhouse gas emissions, particularly methane (CH4) and nitrous oxide (N2O). Methane is produced through enteric fermentation in ruminants and their manure management practices, while nitrous oxide emissions stem from the utilization of animal manure. At the Singosari Artificial Insemination Centre (BBIB), there are around 180 male cattle and 140 goats, this study was conducted to assess methane and nitrous oxide emissions from these animals and arrange the strategies for emission reduction. The Intergovernmental Panel on Climate Change (IPCC) methodology was implemented to calculate emissions, whereas the methane levels was determined by using local factors (Tier-2) and nitrous oxide levels using default for Asian countries. TOPSIS analysis was chosen to identify the key strategies for reducing greenhouse gas emissions, considering technical, cost, and environmental criteria. Three strategies for carbon emission reduction are community-based livestock biogas initiatives (BATAMAS), organic fertilizer processing units (UPPO), improved manure storage systems, and the provision of high-quality animal feed. Findings revealed methane emissions of 286.10 tonnes CO2-eq/year or 1.59 tonnes Co2-eq/head/year, mainly from enteric fermentation, and nitrous oxide emissions totaling 2.75 tonnes CO2-eq/year or 0.015 tonnes CO2-eq/head/year from direct livestock manure management.

Drivers of soil organic carbon recovery under forest restoration: a global meta-analysis

Forest restoration by planting tree seedlings is a crucial strategy to mitigate climate change and restore forest functions. The Intergovernmental Panel on Climate Change (IPCC) targets to remove around 70 Pg carbon (C) from the atmosphere via forest restoration. However, the impact of forest restoration on the recovery of soil organic carbon (SOC) and its driving factors remains unclear. Here, we conducted a global meta-analysis, based on 348 observations from 144 studies across 150 sites, to evaluate the recovery time of SOC and the driving factors of surface SOC recovery during forest restoration. We found that soil clay content and stand age were recognized as the dominant factors regulating SOC recovery during forest restoration. Overall, SOC recovery was lower in boreal and Mediterranean forests than that in tropical, subtropical, and temperate forests, lower in burned areas and mine sites than that in other sites, and lower in soils with 0%–20% clay contents than that in those with higher clay contents, and comparable among soils with different pH values. Across studies, surface SOC in restored forests with stand ages ranging from 1 to 200 years did not fully recover to the levels of reference forests. However, the SOC recovery rate was roughly twice as fast in tree polycultures (~ 10 years to plateau) as that in monocultures (~ 20 years). This global synthesis identifies critical drivers of SOC recovery during forest restoration and provides important insights into SOC management in forests.Graphical

Impacts of Sea Level Rise on Danish Coastal Wetlands - a GIS-based Analysis.

Intergovernmental Panel on Climate Change (IPCC) scenarios run by an ensemble of models developed by the Coupled Model Intercomparison Project (CMIP) projects an average sea level rise (SLRs) of 0.6 to 1.2 m for the low and high emission scenarios (SSP1-1.9, SSP5-8.5), during the next century (IPCC 2021). The coastal zone will experience an increase in the flooding of terrestrial habitats and the depth of marine productive areas, with potential negative consequences for these ecosystems. The coast in Denmark is highly modified due to anthropogenic uses. Dikes, dams, and other coastal infrastructure are widespread, causing a coastal squeeze that prevents natural coastal development and inland migration of coastlines. We performed a national-scale analysis on the impacts of mean sea level rise (MSLR) in 2070 and 2120, and a 1 in 10-year storm surge water level (10SS) in 2120 MSLR for the Danish coast. Our study shows extensive permanent flooding of coastal habitats (~14%), whereas only 1.6% of urban areas will be flooded. Finally, very large agricultural areas (~191,000 ha) will be frequently flooded by 10SS if no extra protective measures are planned. With the present coastal protection structures, key habitats will be affected by permanent flooding or coastal squeeze while even larger extents will be subjected to intermittent marine flooding. About 45% (199 km2) of all Danish coastal wetlands will be permanently flooded by 2120, while areas occupied by forest, lakes and freshwater wetlands will be more frequently flooded by marine water. This study highlights the importance of including coastal habitats as dynamic elements in climate adaptation plans. Conservation and restoration of key habitats such as coastal wetlands should be prioritized in management plans. If Denmark does not change its current priorities, it may face the complete loss of coastal wetlands habitat in the 22nd century.