Tracking net-zero carbon debt: who is responsible for overshoot of the 1.5°C climate limit?

International Institute for Applied Systems Analysis

Facebook

XLinkedInWeChatBlueskyMessageWhatsAppEmail

What is a fair way forward after the 1.5°C warming limit of the Paris Agreement has been breached?  In a new study, IIASA researchers explore the concept of ‘net-zero carbon debt’ — a measure for assessing who bears greater responsibility for minimizing the climate overshoot. 

Research shows that we are on course to exceed the Paris Agreement’s 1.5°C limit within a decade, exacerbating already heated international climate negotiations – some countries have achieved their wealth by polluting for decades and others argue for the same space to escape poverty and develop. Navigating this new context demands a transparent system that accounts for both historical and future emissions, ensuring each region shoulders its fair share of responsibility for climate action.

To inform efforts toward minimizing the magnitude and duration of the overshoot, in a new study, IIASA researchers explored the concept of a net-zero carbon debt. Using this measure, researchers can track which regions bear greater responsibility for the climate overshoot as it progresses, while explicitly accounting for past inaction. If a region is expected to accumulate net-zero carbon debt, it will need to compensate — either by supporting emissions reductions elsewhere in the world or by removing additional carbon from the atmosphere.

“As we near the Paris Agreement’s 1.5°C limit, the question is not just about when we will exceed it, but also how we collectively deal with the consequences in the subsequent period,” says Setu Pelz, lead author of the study and a researcher in the Transformative Institutional and Social Solutions Research Group of the IIASA Energy, Climate, and Environment Program. “To guide efforts that minimize overshoot and establish who should pay for harms caused during this period, we measure who is responsible and to what extent under a range of scenarios and approaches.”

Calculating a region’s net-zero carbon debt involves comparing historical and projected CO2 emissions in a region to its fair share of the remaining carbon budget for staying below 1.5°C. Any excess emissions by the time it reaches net-zero CO2 count as its carbon debt.

Applying this approach to deep mitigation scenarios assessed in the IPCC’s Sixth Assessment Report reveals distinct regional patterns. Some regions consistently accumulate debt due to past inaction, others accumulate debt depending on the timing of their net-zero CO2 targets this century, and some only if they delay net-zero CO2 beyond 2100.

To highlight the implications of carbon debt accumulation, authors of the study assessed carbon drawdown obligations and changes in lifetime exposure to extreme heatwaves under current global climate ambitions. Results show that every ton of net-zero carbon debt will not only increase the burden of emission reduction (and removal) on younger generations, but also worsen the climate impacts they will have to endure due to their region’s excess emissions.

Researchers argue that using the net-zero carbon debt measure alongside considerations of domestic feasibility, can help coordinate collective cost-effective efforts. They stress that regions expected to accumulate large carbon debts should strengthen sectoral mitigation plans, establish international support mechanisms to fund sustainable mitigation activities, and set clear targets for permanent carbon removal. Meanwhile, other regions should distinguish between cost-neutral domestic measures and those requiring international cooperation and climate finance.

This study is the result of cooperation between the scientists from IIASA, Climate Analytics, Humboldt University of Berlin, Imperial College London, Potsdam Institute for Climate Impact Research, and Vrije Universiteit Brussel.

 

Reference:

Pelz, S., Ganti, G., Lamboll, R., Grant, L., Smith, C., Pachauri, S., Rogelj, J., Riahi, K., Thiery, W., Gidden, M., (2025). Using net-zero carbon debt to track climate overshoot responsibility. PNAS. Vol. 122, No. 13. 10.1073/pnas.2409316122.

---

Journal

Proceedings of the National Academy of Sciences

DOI

10.1073/pnas.2409316122 

Method of Research

Computational simulation/modeling

Subject of Research

People

Article Title

Using net-zero carbon debt to track climate overshoot responsibility

Article Publication Date

24-Mar-2025

Delaying the net zero transition could impose significant economic costs, new research reveals

Delayed and disorderly energy transitions will threaten economic and financial stability whilst also increasing the economic risks from climate change, according to a new study from the University of Surrey

University of Surrey

LinkedInWeChatBlueskyMessageWhatsAppEmail

Delayed and disorderly energy transitions will threaten economic and financial stability whilst also increasing the economic risks from climate change, according to a new study from the University of Surrey. Conversely, transitions that are started sooner are likely to be more orderly and economically beneficial.  

The paper, published in Ecological Economics, simulates different energy transition scenarios and finds that earlier transitions are more economically beneficial than delayed, rapid shifts. By analysing the interactions between industries, investment patterns, and financial markets, the researchers show that disorderly transitions—where changes happen too quickly—can lead to economic instability and financial risks. 

Dr Andrew Jackson, Senior Research Fellow at the Centre for the Understanding of Sustainable Prosperity and lead author of the study at the University of Surrey said:  

“Transitioning to a low-carbon economy is critical. Our work shows how delayed and disorderly transitions could ultimately lead to a combination of increased inflation, higher interest rates, economic stagnation and financial instability. Avoiding these transition risks, as well as the physical risks from climate change, requires that governments take concerted action now’ and do not delay action on the transition any further.”   

The research also suggests that targeted investments in green technologies, a robust financial framework to support these investments, and a clear and credible transition pathway can enable a smoother transition while safeguarding economic stability.  

Dr Jackson continued:  

“By prioritising an orderly transition that is well signposted, governments can mitigate the risks associated with delayed and disorderly transitions. We need a re-evaluation of current transition strategies to advocate for an approach that considers the economic and financial costs from delaying the transition as well as the upfront costs of the transition itself. Only by taking a holistic view of all these costs can we pave the way for a sustainable future without jeopardising economic and financial stability.”  

  

[ENDS]   

• The full paper is available in Ecological Economics  

---

Journal

Ecological Economics

DOI

10.1016/j.ecolecon.2024.108507 

Method of Research

Observational study

Subject of Research

Not applicable

Article Title

Macroeconomic, sectoral and financial dynamics in energy transitions: A stock-flow consistent, input-output approach

 

Climate cost of global trawling still uncertain

University of Exeter

LinkedInWeChatBlueskyMessageWhatsAppmail

The amount of carbon released by seabed fishing worldwide is uncertain and must be urgently investigated, researchers say.

Convex Seascape Survey scientists are studying the impact of fishing methods that use towed nets which are dragged along the seafloor, such as trawling and dredging.

These methods are the main way that humans disturb ocean sediments – the world’s largest reservoir of organic carbon – but there is disagreement about the amount of carbon these methods release.

The new study, led by researchers at the University of Exeter, begins to untangle this mystery.

“To find out how much carbon is being released by these fishing methods, we need to know how much of the seabed is actually being disturbed,” said Mollie Rickwood, from the Centre for Ecology and Conservation on Exeter’s Penryn Campus in Cornwall.

“The best data available is from European fishing vessels, and previous research has used European fishing gear metrics to estimate the area of seafloor disturbed globally.

“Our main finding is that vessel and gear sizes vary a lot from country to country – so using European data to make global estimates is likely to lead to large inaccuracies in the amount of the seafloor trawled, and therefore how much carbon could be released to the atmosphere.”

The new paper demonstrates the need for good regional data on the size of fishing vessels and gear, to allow accurate estimates of seafloor disturbance.

“At present, this is almost impossible due to the big European bias in existing data, as well as a lack of standardised reporting of fishing gear,” Rickwood continued.

“Our paper is a ‘call to arms’ to address these knowledge gaps and encourage global collaboration between science and industry to make this data available.”

The paper, published in the journal Fish and Fisheries, is entitled: “Regional variation in active bottom-contacting gear footprints.”

The Convex Seascape Survey, an ambitious five-year global research programme, is the largest attempt yet to build a greater understanding of the properties and capabilities of the ocean and its continental shelves in the earth’s carbon cycle, in the urgent effort to slow climate change.

“Ocean carbon stores could be more secure than those on land, where forests, bogs and tundra are increasingly impacted by wildfire, flood and drought. So it is critical we understand how safe carbon is once it is locked away in the seabed,” said Professor Callum Roberts of Exeter University, who leads the Convex Seascape Survey.

---

Journal

Fish and Fisheries

DOI

10.1111/faf.12893 

Article Title

Regional Variation in Active Bottom-Contacting Gear Footprints

Article Publication Date

25-Mar-2025

 

Refining Siberia’s land cover data: A leap forward for climate science

Machine learning techniques reveal a high-precision land cover map for Siberia, enhancing climatic predictions

Chiba University

Facebook

XLinkedInWeChatBlueskyMessageWhatsAppEmail

 

image: 

Researchers use advanced machine learning techniques and multiple global land cover datasets to develop a high-precision land cover map of Siberia.

view more 

Credit: Professor Kazuhito Ichii from Chiba University, Japan

Siberia, a province located in Russia, is a significant geographical region playing a crucial role in the world’s carbon cycle. With its vast forests, wetlands, and permafrost regions (permanently frozen grounds), Siberia stores a considerable amount of carbon on a global scale. But climate change is rapidly altering Siberia’s landscape, shifting its vegetative distribution and accelerating the permafrost thaw. Classifying land cover is essential to predict future climatic changes, but accumulating land cover data in regions like Siberia is challenging due to the limited availability of ground observation data.

In a step towards advancing climatic studies, a recent study led by Professor Kazuhito Ichii from the Center for Environmental Remote Sensing and Graduate School of Science and Engineering, Chiba University, Japan, unveils a refined land cover map for Siberia. By leveraging multiple sources and applying a random forest classifier (a machine learning algorithm), the team addresses the inconsistencies between existing land cover datasets with a remarkable accuracy of 85.04%. The study was conducted in collaboration with Nagoya University, Japan, and was published in Volume 12, Issue 3 of the Progress in Earth and Planetary Science on January 6, 2025.

Prof. Ichii discusses the motivation for this study by saying, “While working for the Pan-Arctic Water-Carbon Cycles project, we were surprised to find major differences among existing land cover datasets, even in the widely used data sets. It was then clear that a more reliable dataset was needed, which led us to carry out this research.”

The researchers started by comparing various global datasets and then used various data points to ensure an accurate land classification. The newly developed map gave a clearer picture of the forests, wetlands, and permafrost areas, which are key elements in climate studies. When compared with the previous datasets, the researchers observed major errors in the previous sets, especially in the high-latitude regions, which could potentially lead to incorrect climate predictions.

Addressing the discrepancies in land classification, the new dataset enabled more accurate assessments of carbon flux and ecosystem changes. “By focusing on land cover, something previously thought to be well understood, we have created better data for an area that was not well characterized, opening doors for improved climatic predictions,” says Ms. Munseon Beak from the Graduate School of Science and Engineering and Center for Environmental Remote Sensing at Chiba University.

The implications of this study are extensive. By providing a more accurate land cover dataset, the research can enhance climate models with better predictions of environmental changes.

Assistant Professor Yuhei Yamamoto from the Institute of Advanced Academic Research and Center for Environmental Remote Sensing, Chiba University, emphasizes, “By integrating multiple data sources and enhancing classification accuracy, we aim to provide essential insights for climate scientists. This is particularly crucial given the rapid climatic changes occurring in Siberia.”

Siberia is greatly affected by climate change, such as global warming, resulting in major changes such as the Siberian Taiga moving northwards and the surface of the earth changing due to the thawing of permafrost. The refined land cover data would, therefore, help scientists monitor these major changes, serving as a foundational tool for predicting and managing these changes in the coming decades. These datasets also support carbon cycle assessments, which are crucial for understanding greenhouse gas dynamics and environmental studies.

Additionally, the study determined the factors that can affect the distribution of vegetation in a particular region. Professor Tetsuya Hiyama from the Institute for Space-Earth Environmental Research, Nagoya University, notes: “We have used geographical distribution analysis across different climates to understand how the distribution of vegetation gets affected. This led us to the fact that precipitation plays a major role in vegetation patterns, especially during warm summer climates."

Therefore, these datasets could also offer valuable guidance for policymakers. Aiding in sustainable land management and conservation efforts, the findings can contribute to disaster risk management, helping mitigate the impacts of permafrost thaw, wildfires, and habitat loss in the coming years.

About Professor Kazuhito Ichii from Chiba University, Japan
Professor Kazuhito Ichii is a distinguished professor and a skilled researcher specializing in terrestrial biosphere monitoring and modeling. He has more than 90 publications to his credit contributing to the fields of Bio-geoscience, Earth Systems, and ‪Terrestrial Remote Sensing. Throughout his career, he has held notable positions, including Research Scientist at NASA Ames Research Center, Senior Researcher at the Japan Agency for Marine-Earth Science and Technology, and the Chair of AsiaFlux. Currently, he is working as a Professor at Chiba University's Center for Environmental Remote Sensing (CEReS).

---

Journal

Progress in Earth and Planetary Science

DOI

10.1186/s40645-024-00672-5 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Land cover classification for Siberia leveraging diverse global land cover datasets

 

Maternal deaths from cardiovascular causes on the rise in U.S.

Black women and women in Southern states face amplified risk as death rates have increased in the U.S. over two decades

American College of Cardiology

Facebook

XLinkedInWeChatBlueskyMessageWhatsAppEmail

The rate of maternal mortality related to cardiovascular causes more than doubled between 1999 and 2022 in the United States, according to a study being presented at the American College of Cardiology’s Annual Scientific Session (ACC.25).

The finding is concerning, especially as the U.S. has the highest overall rate of maternal mortality among all developed countries, researchers said. Since cardiovascular problems are a leading cause of death around the time of pregnancy and childbirth, the new findings shed light on the drivers behind recent trends and draw attention to particularly high rates of mortality seen among Black women and those living in Southern states.  

“We’re heading in the wrong direction. The United States is supposed to be a global leader in advancing health and medicine, and the fact that we still have pregnant women who are dying—often because of preventable causes—should sound alarm bells,” said Mohammad Ahabab Hossain, MD, the study’s lead author and a resident physician at Rutgers New Jersey Medical School in Newark, New Jersey. “The fact that there are disparities based on race means we need to pay better attention to more vulnerable populations, specifically Black women.”

Maternal mortality refers primarily to deaths that occur when a person is pregnant or has recently given birth. It can also include deaths that occur up to a year after giving birth, if the cause of death is linked to having been pregnant.

For the study, researchers used data from the U.S. Centers for Disease Control and Prevention WONDER database collected between 1999-2022 to analyze rates of maternal mortality attributed to conditions such as high blood pressure, conditions related to dangerous blood clots and conditions that weaken the heart’s pumping ability. They divided the number of cardiovascular-related maternal deaths by the total number of women of reproductive age to calculate the rate of cardiovascular-related maternal mortality for each year, adjusted by age.

The results showed that the rate of maternal mortality from cardiovascular disease rose from 3.6 per 1 million individuals in 1999 to a peak of 10.5 per million in 2021 and then decreased slightly to just under 9.1 per million in 2022. In terms of absolute numbers, those rates translate to hundreds of deaths per year. For example, in 2022, it is estimated that about 600 U.S. women died from cardiovascular causes, such as peripartum cardiomyopathy, hypertensive disorders of pregnancy and heart attack, around the time of pregnancy.

The data showed especially high rates of maternal mortality in 2020 and 2021, which researchers said may have been due to limited access to prenatal care or a hesitancy to visit medical clinics during the peak of the COVID-19 pandemic. Researchers noted that the greatest year-over-year increase was seen in 2018, which they attributed to the nationwide adoption of standardized reporting of pregnancy status on death certificates, which began in 2003 and expanded to all 50 states by 2018.

“While the addition of the pregnancy checkbox on death certificates complicates the comparison of maternal mortality pre- and post-2018, what remains certain is that maternal deaths due to cardiovascular causes remain unacceptably high,” Hossain said.

Researchers also compared rates of cardiovascular-related maternal mortality during more recent years (2018-2022) by race and geographic region. During this period, Black women had about triple the rate of maternal mortality as White women, with a mortality rate of 21.9 per million among Black women versus 7.1 per million among White women. Those living in the South saw the highest mortality rate of any U.S. region, with a mortality rate of 12.1 per million compared with 5.4 per million in Western states.

Factors such as socioeconomic disadvantages, limited access to health care, higher prevalence of risk factors and issues with trust in the health care system, especially among Black people, likely play a role in creating disparities, researchers said. Increasing rates of health conditions related to cardiovascular problems may have also contributed to the rise in rates of cardiovascular-related maternal mortality in the U.S. population as a whole over time.

“Part of the reason this is happening is because heart disease and hypertension are becoming more and more prevalent, as are the conditions that are connected to heart disease, like diabetes and obesity. As a result, we wind up with more high-risk pregnancies,” Hossain said. “However, a lot of this is preventable. If a patient has a history of hypertension or other preexisting cardiovascular disease, that patient should be connected with a high-risk obstetrics clinic to receive the care they need.”

To help prevent maternal deaths, Hossain said it is important for both clinicians and patients to recognize that having cardiovascular risk factors can lead to serious problems during and after pregnancy. Being aware of these factors and taking steps to control them—for example, by getting blood pressure under control and managing diabetes—can help to prevent complications. Awareness of these risk factors can also inform preconception counseling.

Increasing access to prenatal care at clinics that are equipped to handle high-risk pregnancies is key to reducing disparities, Hossain said, noting that this requires a team effort bringing together obstetricians, cardiologists, nursing staff and social workers. Better access to care is also important after childbirth, since some women experience health problems related to their pregnancy even after the baby is born, he said.

One limitation of the study was that maternal mortality was calculated as a ratio of the number of cardiovascular-related maternal deaths divided by the total number of women of childbearing age in each year, which includes all women ages 15-44 and not only those who became pregnant. The calculated rates would be higher if maternal mortality were compared against the total number of pregnancies that occurred in each year.

Hossain will present the study, “Trends and Disparities in Cardiovascular-Related Maternal Mortality in the United States: 1999-2022,” on Saturday, March 29, 2025, at 9:30 a.m. CT / 14:30 UTC in Moderated Poster Theater 9.

ACC.25 will take place March 29-31, 2025, in Chicago, bringing together cardiologists and cardiovascular specialists from around the world to share the newest discoveries in treatment and prevention. Follow @ACCinTouch, @ACCMediaCenter and #ACC25 for the latest news from the meeting.

The American College of Cardiology (ACC) is the global leader in transforming cardiovascular care and improving heart health for all. As the preeminent source of professional medical education for the entire cardiovascular care team since 1949, ACC credentials cardiovascular professionals in over 140 countries who meet stringent qualifications and leads in the formation of health policy, standards and guidelines. Through its world-renowned family of JACC Journals, NCDR registries, ACC Accreditation Services, global network of Member Sections, CardioSmart patient resources and more, the College is committed to ensuring a world where science, knowledge and innovation optimize patient care and outcomes. Learn more at ACC.org.

###

 

New study maps the life situation of transgender people in Sweden

Stockholm University

Facebook

XLinkedInWeChatBlueskyMessageWhatsAppEmail

A new study provides a unique insight into the group seeking gender-affirming care in Sweden. It shows that transgender people are a socioeconomically vulnerable group and that in 2020, 0.07% of Sweden's population had received a gender incongruence diagnosis, while 0.03% had undergone a legal gender change.

The study reveals that transgender people are socioeconomically disadvantaged — a vulnerability that spans across different generations.

“People seeking trans healthcare have significantly lower incomes on average compared to others, regardless of the time period or age group we compare. It’s a very small and economically vulnerable group,” says Emma von Essen, a researcher at the Institute for Social Research (SOFI) at Stockholm University, who leads the research team.

In the study, published in the journal Demography, researchers analyzed how gender incongruence diagnoses  and legal gender changes relate to education, geography, marital status, and income, as well as compared different ages and birth cohorts.

“This is the first comprehensive study on the socioeconomic conditions of those who have received gender-affirming care in Sweden,” says Martin Kolk, one of the authors and a lecturer at the demography unit (SUDA) at Stockholm University.

“The number of people receiving a gender incongruence diagnosis has increased, but from a very low level. In recent years, we’ve seen an increase in the number of trans men, while in the past, a majority were trans women,” Kolk continues.

The study is a collaboration between SOFI, SUDA, Uppsala University, and the University of Liverpool.

Read the full study here: Kolk, Martin, Lucas Tilley, Emma von Essen, Ylva Moberg, Ian Burn (2025) “The Demography of Sweden’s Transgender Population – A Research Note on Patterns, Changes, and Sociodemographics,” Demography.

How the Study Was Conducted
The study is based on Swedish administrative data and covers the entire population from 1973 to 2020. The researchers analyzed gender incongruence diagnoses in healthcare records and legal gender changes. The data comes from the Swedish National Board of Health and Welfare (Socialstyrelsen), the Swedish Tax Agency (Skatteverket), and Statistics Sweden (SCB). Since the study is based on administrative data, it only includes those who have sought care or undergone a legal gender change, thus not covering all transgender people in Sweden.

---

Journal

Demography

DOI

10.1215/00703370-11850105 

Method of Research

Data/statistical analysis

Subject of Research

People

Article Title

The Demography of Sweden's Transgender Population: A Research Note on Patterns, Changes, and Sociodemographics

Article Publication Date

24-Mar-2025