Tag: Climate Modelling

A major study led by Dartmouth College researchers, involving over 50 climate scientists, has revealed alarming long-term projections about Antarctica’s ice sheet and its potential collapse due to carbon emissions.

The research highlights the risk of significant sea-level rise caused by Antarctic ice melt beyond 2100 if current emission levels continue.

The findings provide a crucial long-term perspective, predicting a rapid retreat of Antarctica’s glaciers after the 21st century.

Gradual Antarctic ice loss through 2100, then rapid acceleration

The research shows that Antarctica’s ice sheet will lose mass gradually throughout the 21st century. The study used data from 16 ice-sheet models, which collectively show a slow but steady increase in Antarctic ice loss through 2100. However, the models diverge significantly when projecting ice loss after 2100.

Beyond this point, the situation worsens dramatically. If current carbon emissions continue unchecked, glaciers in western Antarctica could retreat rapidly by 2200, raising global sea levels by as much as 5.5 feet. By 2300, the study even suggests the near-total collapse of Antarctica’s ice sheet is possible.

Hélène Seroussi, the study’s lead author and associate professor at Dartmouth’s Thayer School of Engineering, emphasised the lack of focus on long-term sea-level rise in climate discussions.

“When you talk to policymakers, they mostly focus on what will happen up to 2100,” Seroussi explained. “Our study provides longer-term projections that have been lacking. Beyond 2100, the long-term impact for the regions most susceptible to sea-level rise become amplified.”

The role of carbon emissions in ice sheet melting

The study compared Antarctica’s ice sheet under both high- and low-emission scenarios. The difference in sea-level rise between these two scenarios becomes far more pronounced after 2100.

Under high-emission scenarios, ice-sheet models predict irreversible ice loss in several basins in western Antarctica. These regions are particularly vulnerable to collapse, which would cause rapid and unstoppable melting.

Mathieu Morlighem, a Dartmouth professor and co-author of the study, stressed the importance of cutting carbon emissions now to prevent a disastrous future.

“While current carbon emissions have a modest impact on projections for this century, the difference between high- and low-emission scenarios becomes critical after 2100,” Morlighem said. ” These results confirm that it is critical to cut carbon emissions now to protect future generations.”

While the exact timing of these glacier retreats varied between models, the rapid pace of ice loss once initiated was consistent. Seroussi warned that once the retreat begins, “nothing can stop or slow it down,” signalling that immediate action is required to prevent irreversible damage.

Cutting emissions to save Antarctica

The study serves as a powerful call to action, highlighting the need for global efforts to reduce carbon emissions.

Although the most severe impacts of Antarctic ice melt are projected beyond 2100, the groundwork for these outcomes is being laid today. The researchers urge policymakers and global leaders to act swiftly to prevent the worst-case scenarios.

This research highlights the importance of global scientific collaboration. By combining multiple ice-sheet models, the study provides a clearer picture of Antarctica’s ice sheet future and where uncertainties still exist.

Seroussi hopes this collaboration will continue, allowing scientists to refine their models and focus on areas with the greatest uncertainties, including Greenland’s ice sheet.

As Antarctica’s ice sheet continues to melt, its effects will ripple across the globe, making immediate action essential.

New research reveals that cities in the Global South are increasingly vulnerable to extreme heat due to a significant lack of cooling green spaces.

This disparity, when compared to cities in the Global North, highlights a pressing need for urban greening strategies to combat the escalating threat of heat-related illnesses and deaths.

Cooling disparities between Global North and South

The study, conducted by an international team including researchers from Nanjing, Exeter, Aarhus, and North Carolina State universities, found that cities in the Global South have only 70% of the ‘cooling capacity’ provided by urban green spaces compared to their counterparts in the Global North.

This difference is starkly evident as temperatures rise globally and urban heat island effects intensify, making cities significantly hotter than surrounding rural areas.

Professor Tim Lenton of the Global Systems Institute at the University of Exeter emphasises the importance of urban green spaces, noting: “Urban greenery is a really effective way of tackling what can be fatal effects of extreme heat and humidity.

“Our analysis suggests green spaces can cool the surface temperature in the average city by about 3°C during warm seasons – a vital difference during extreme heat.”

The environmental benefits of green spaces

Urban green spaces, such as parks, urban forests, and rooftop gardens, play a crucial role in cooling cities through shading and transpirational cooling—the process of water evaporation from plants.

These spaces not only lower surface temperatures but also contribute to better air quality, reduced energy consumption, and enhanced biodiversity. In the face of climate change, the environmental benefits of green spaces extend beyond temperature regulation.

They serve as carbon sinks, sequestering CO2 and helping to mitigate urban pollution. Green spaces also foster resilience against flooding by absorbing rainfall, thus reducing the strain on urban drainage systems.

A global need for urban greening

The study’s findings, based on satellite data from the world’s 500 largest cities, underscore a vast potential to enhance urban cooling in the Global South and address growing inequality.

All of the top ten cities for cooling capacity are in the United States, with Charlotte and Raleigh-Durham leading the list. In contrast, Mogadishu in Somalia ranks lowest, followed closely by Sana’a in Yemen and Rosario in Argentina.

The analysis also revealed that the average resident in the Global South experiences a cooling benefit of just 2.2°C from urban greenery, compared to 3.4°C for residents in the Global North.

This disparity is largely due to the quantity and management of vegetation, as well as differences in tree species.

Professor Jens-Christian Svenning of Aarhus University added: “The good news is that this nature-based solution to cooling can be substantially improved across the Global South, helping to tackle future heat stress for billions of people.”

Future targets

Re-greening cities, particularly in the Global South, will be challenging and costly in the short term, but it is essential for making urban areas liveable in the face of climate change.

Potential solutions include expanding ground-level green spaces, implementing vertical and rooftop gardens, and protecting existing greenery from further loss.

As cities grapple with rising temperatures, green spaces emerge as a critical tool for not only reducing heat but also enhancing the overall environmental health and sustainability of urban areas.

Investing in these natural cooling systems is imperative for safeguarding the well-being of millions in the Global South.

A comprehensive analysis of thousands of climate policy measures worldwide has revealed that only a fraction are effective in reducing emissions.

The study, led by researchers from the Potsdam Institute for Climate Impact Research (PIK) and the Mercator Research Institute on Global Commons and Climate Change (MCC), offers critical insights into which climate policies effectively reduce carbon emissions.

In collaboration with experts from the University of Oxford, the University of Victoria, and the Organisation for Economic Co-operation and Development (OECD), the study evaluates a broad range of policy measures, going beyond the limited scope of previous evaluations.

The importance of policy mixes in climate action

Over the past two decades, thousands of climate policies have been implemented worldwide, yet there is little consensus on which are most effective.

This new study fills that gap by analysing a wide variety of climate policies across different sectors, including building, electricity, industry, and transportation, in both industrialised and developing countries.

Lead author Nicolas Koch from PIK and MCC emphasises that simply increasing the number of policies does not necessarily lead to better outcomes.

Instead, the study reveals that the right mix of complementary climate policy instruments is crucial. For example, while subsidies or regulations alone may not be sufficient to drive significant emission reductions, their effectiveness can be greatly enhanced when combined with price-based instruments such as carbon and energy taxes.

Comprehensive analysis of global climate policies

The study embarked on a detailed analysis of 1,500 climate policy interventions implemented between 1998 and 2022.

This analysis leverages the most comprehensive global inventory of climate policies available, alongside advanced statistical techniques, to assess the real-world impact of these policies on emissions.

Among the 1,500 policies examined, only 63 were found to have significantly reduced emissions, with reductions ranging from 0.6 billion to 1.8 billion tonnes of CO2.

These findings underscore the importance of using a mix of climate policy instruments to achieve substantial emission reductions.

Contrary to some claims, the study demonstrates that effective policy combinations are not redundant but are essential in addressing different market failures.

Pricing mechanisms, for instance, have proven particularly effective in the industry and electricity sectors, while a combination of incentives and regulations works better in the building and transportation sectors.

Sector-specific insights and challenges in developing countries

The study also highlights the varying effectiveness of policy instruments across different sectors and regions.

In industrialised countries, pricing mechanisms have been highly successful in reducing emissions. However, in developing nations, regulatory and subsidy measures often need to precede or complement pricing mechanisms to be effective.

This nuance is crucial for designing climate policies that are tailored to the specific economic and developmental contexts of different countries.

Lead author Annika Stechemesser from PIK acknowledges the complexity of disentangling the effects of individual measures within a policy mix.

Nevertheless, the study’s 63 success stories provide valuable insights into how well-designed climate policy combinations can be tailored to specific sectors and development levels. This knowledge is essential for supporting policymakers in their efforts to transition toward climate neutrality.

Climate Policy Explorer: A tool for policymakers

To make these findings accessible and actionable, the study’s results are available through an interactive online tool called the ‘Climate Policy Explorer.’

This platform offers detailed insights into specific countries, sectors, and policy measures, allowing users to explore successful climate policy combinations in different contexts.

For example, the UK’s success in reducing emissions in the electricity sector, driven by a minimum carbon price and a coal phase-out plan, serves as a notable example of effective policy design.

Similarly, the US transportation sector’s emission reductions, achieved through a mix of tax incentives for low-emission vehicles and CO2 efficiency standards, demonstrate the importance of coordinated policy efforts.

These insights are crucial for policymakers worldwide as they design and implement strategies to meet the Paris Agreement’s climate targets.

The Climate Policy Explorer provides a comprehensive overview of the study’s findings, offering a valuable resource for those seeking to understand and apply effective climate policy combinations.

A recent Dartmouth College-led study offers a more optimistic perspective on one of the most alarming predictions about sea level rise due to polar ice melt.

While the research confirms the significant risks posed by melting ice sheets in Greenland and Antarctica, it challenges an extreme scenario forecasted in the latest United Nations’ Intergovernmental Panel on Climate Change (IPCC) report.

Re-examining sea level rise scenarios

The IPCC’s sixth assessment report introduced a worst-case scenario involving the Marine Ice Cliff Instability (MICI) mechanism.

According to this model, the collapse of Antarctica’s ice sheets could lead to a sea level rise of up to 50 feet by 2300, potentially submerging vast coastal regions.

However, the Dartmouth study finds this scenario highly unlikely, using more accurate high-resolution models.

Methodology: Testing the ‘Doomsday Glacier’

To assess the validity of the MICI hypothesis, researchers focused on Antarctica’s Thwaites Glacier, often dubbed the ‘Doomsday Glacier’ due to its rapid melting and potential contribution to sea level rise.

They used three high-resolution models to simulate two scenarios:

1. Sudden ice shelf collapse: A 100-year simulation of Thwaites Glacier retreat following a hypothetical sudden collapse of its ice shelf. The ice shelf acts as a barrier, and its loss could theoretically accelerate glacier movement toward the ocean.
2. Ongoing retreat: A 50-year simulation under current conditions, where the ice shelf is gradually thinning rather than collapsing suddenly.

The high-resolution models allowed the researchers to simulate the physical processes of ice flow, fracture, and interaction with ocean and bedrock more accurately than previous studies.

These models showed that even in a worst-case scenario, the glacier’s retreat was much slower than the MICI hypothesis predicted.

Key findings and implications

The simulations revealed that Thwaites Glacier’s ice cliffs would not reach the critical height necessary to trigger a rapid, domino-like collapse.

Instead, the glacier’s accelerated movement would cause thinning at the edges, reducing the likelihood of catastrophic failure. The study concluded that MICI is unlikely to occur within this century.

However, the study emphasised that other processes, such as Marine Ice Sheet Instability (MISI), could still drive significant ice loss and contribute to sea level rise over the coming centuries.

MISI occurs when glaciers resting on a bed that slopes toward the continent’s interior retreat unstably once ice shelves collapse.

Importance for coastal planning

While the study offers some reassurance by downplaying the extreme MICI scenario, it underscores the ongoing threat of rising sea levels driven by other mechanisms.

Accurate projections are crucial for policymakers and planners, especially in designing infrastructure like sea walls or considering the relocation of communities from low-lying areas.

The study provides a critical re-evaluation of extreme sea level rise predictions, suggesting that while the most alarming scenarios may be less likely, significant risks remain.

Continued research and monitoring are essential to understand and mitigate the impacts of polar ice melt on global sea levels, ensuring that coastal communities can prepare for future challenges.