Thursday, June 27, 2024

Chinese cities outsourced on others’ efforts to cut carbon emissions

UNIVERSITY OF BIRMINGHAM

Experts have identified 240 Chinese cities whose emission reduction are mainly benefiting from the carbon mitigation actions of other cities, whilst putting in less effort themselves.

Researchers studied the phenomenon across 309 Chinese cities using data from 2012 to 2017 – a period when China underwent economic reform and industrial transformation.

Constructing a city-level input-output model to assess carbon footprints, the researchers identified 78% of the cities as ‘outsourced beneficiaries’, depending on carbon mitigation from the supply chain. They further divided the cities into ‘strong’ and ‘weak’ outsourced beneficiaries, reflecting their development stages and industrial structures.

Publishing their findings today (27 June) in Nature Cities, researchers from the University of Birmingham, University College London, and Tsinghua University, in Beijing, China reveal 65 cities as strong outsourced beneficiaries where their local carbon emissions still grew. In contrast, they define 175 cities as weak beneficiaries with larger outsourced mitigation efforts than local mitigation efforts.

Corresponding author Dr Heran Zheng, from University College London, commented: “We discovered a widespread trend among Chinese cities leveraging supply chain networks for carbon mitigation, indicating ‘outsourced beneficiaries’ behaviour when cities benefit from the mitigation efforts of upstream cities without comparable local efforts.

“Cities downstream of supply chains, such as high-tech cities, can effectively reduce emissions through technology and supply chain management. Our findings highlight the importance of nuanced government policies to address these differences between cities – this will help to promote a fairer distribution of mitigation responsibilities.”

The distinction between ‘strong’ and ‘weak’ is associated with a city’s development stage and industrial structure. Strong outsourced beneficiaries were often industrializing cities with more agriculture and light manufacturing, focusing for local economic growth.

In contrast, weak outsourced beneficiaries were mainly at the downstream of supply chains with services and high-tech manufacturing, which have stronger connections with upstream heavy industry cities and so as their mitigation efforts

Co-author Dr Yuli Shan, from the University of Birmingham added: “With China's focus on clean energy, central and western cities rich in wind and solar resources are emerging as clean energy supplier - compounded by growing demand for electricity from eastern high-tech cities due to the rise of the digital economy. This can lead to an outsourced mitigation situation where cities benefit from other cities' clean energy efforts without making a commensurate contribution.”

The researchers note that outsourced beneficiaries is a classic problem wherein a group providing itself with common goods, each member will have a strong tendency to contribute little or nothing toward the cost of the good, while grabbing its benefits.

Strong outsourced beneficiaries are found in energy cities and heavy industry cities, with agriculture and power as the dominant industries. Such cities should receive financial and technical support to transform outdated production capacity and turn them into weak free riders.

Conversely, weak outsourced beneficiaries with high-tech and service-oriented industries should ramp up investment in technological innovation and research to enhance industrial efficiency -transform theming into role models.

The experts add that effectively reducing emissions and acknowledging cities' role in climate change mitigation require policies that are specifically designed to address the distinct challenges and opportunities of each city.

ENDS

For more information, interviews or an embargoed copy of the research paper, please contact Tony Moran, International Communications Manager, University of Birmingham on +44 (0)782 783 2312 or t.moran@bham.ac.uk. For out-of-hours enquiries, please call +44 (0) 121 414 2772.

Notes to Editors

The University of Birmingham is ranked amongst the world’s top 100 institutions, its work brings people from across the world to Birmingham, including researchers and teachers and more than 8,000 international students from over 150 countries.

‘Outsourced Efforts in Carbon Mitigation of Chinese Cities from 2012 to 2017’ - Chengqi Xia, Heran Zheng, Jing Meng, Yuli Shan, Xi Liang, Jin Li, Zihua Yin, Minggu Chen, Pengfei Du, Can Wang is published in Nature Cities.
Participating institutions are University of Birmingham, UK; University College London, UK; and Tsinghua University, Beijing, China.
The new study is a ‘sister’ paper to research published in 2022 - https://www.birmingham.ac.uk/news/2022/carbon-reduction-study

JOURNAL

Nature Cities

METHOD OF RESEARCH

Data/statistical analysis

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Outsourced Efforts in Carbon Mitigation of Chinese Cities from 2012 to 2017

ARTICLE PUBLICATION DATE

27-Jun-2024

GOOD NEWS

Antarctic ice shelves hold twice as much meltwater as previously thought

WAIT.WHAT IF IT MELTS?!

UNIVERSITY OF CAMBRIDGE

Pooled meltwater and slush on the Tracy Tremenchus Ice Shelf — IMAGE:
POOLED MELTWATER AND SLUSH ON THE TRACY TREMENCHUS ICE SHELF, WHICH FLOWS INTO THE SOUTHERN OCEAN. CONTAINS MODIFIED COPERNICUS SENTINEL DATA [2018], PROCESSED BY REBECCA DELL
view more
CREDIT: REBECCA DELL

Slush – water-soaked snow – makes up more than half of all meltwater on the Antarctic ice shelves during the height of summer, yet is poorly accounted for in regional climate models.

Researchers led by the University of Cambridge used artificial intelligence techniques to map slush on Antarctic ice shelves, and found that 57% of all meltwater is held in the form of slush, with the remaining amount in surface ponds and lakes.

As the climate warms, more meltwater is formed on the surface of ice shelves, the floating ice surrounding Antarctica which acts as a buttress against glacier ice from inland. Increased meltwater can lead to ice shelf instability or collapse, which in turn leads to sea level rise.

The researchers also found that slush and pooled meltwater leads to 2.8 times more meltwater formation than predicted by standard climate models, since it absorbs more heat from the sun than ice or snow. The results, reported in the journal Nature Geoscience, could have profound implications for ice shelf stability and sea level rise.

Each summer as the weather warms, water pools on the surfaces of Antarctica’s floating ice shelves. Previous research has shown that surface meltwater lakes can contribute to ice shelf fracture and collapse, as the weight of the water can cause the ice to bend or break. However, the role of slush in ice shelf stability is more difficult to determine.

“We can use satellite imagery to map meltwater lakes across much of Antarctica, but it’s hard to map slush, because it looks like other things, such as shadows from clouds, when viewed from a satellite,” said lead author Dr Rebecca Dell from Cambridge’s Scott Polar Research Institute (SPRI). “But using machine learning techniques, we can go beyond what the human eye can see and get a clearer picture of how slush might be affecting ice in Antarctica.”

Using optical data from NASA’s Landsat 8 satellite, the Cambridge researchers, working with researchers from the University of Colorado Boulder and the Delft University of Technology, trained a machine learning model to obtain monthly records of slush and meltwater lakes across 57 Antarctic ice shelves between 2013 and 2021.

“Machine learning allows us to use more information from the satellite, since it can work with more wavelengths of light than the human eye can see,” said Dell. “This allows us to determine what is and isn’t slush, and then we can train the machine learning model to quickly identify it across the whole continent.”

“We’re interested in learning how much slush is present during the Antarctic summer, and how it’s changed over time,” said co-author Professor Ian Willis, also from SPRI.

Using their machine learning model, the researchers found that in the peak of the Antarctic summer in January, over half (57%) of all meltwater on Antarctica’s ice shelves is held in slush, with the remaining 43% in meltwater lakes.

“This slush has never been mapped on a large scale across all of Antarctica’s large ice shelves, so over half of all surface meltwater has been ignored until now,” said Dell. “This is potentially significant for the hydrofracture process, where the weight of meltwater can create or enlarge fractures in the ice.”

Meltwater affects the stability of the floating ice shelves that fringe the Antarctic coastline. As the climate warms and melt rates in Antarctica increase, meltwater – whether in the form of lakes or slush – can get into cracks on the ice, causing the cracks to get bigger. This can cause fractures in the ice shelf, and could cause vulnerable ice shelves to collapse, which in turn would allow inland glacier ice to spill into the ocean and contribute to sea level rise.

“Since slush is more solid than meltwater, it won’t cause hydrofracture in the same way that water from a lake does, but it’s definitely something we need to consider when attempting to predict how or whether ice shelves will collapse,” said Willis.

In addition to the potential implications of slush on hydrofracture, it also has a large effect on melt rates. Since slush and lakes are less white than snow or ice, they absorb more heat from the sun, causing more snowmelt. This extra melt is currently unaccounted for in climate models, which may lead to underestimates in projections of ice sheet melting and ice shelf stability.

“I was surprised that this meltwater was so poorly accounted for in climate models,” said Dell. “Our job as scientists is to reduce uncertainty, so we always want to improve our models so they are as accurate as possible.”

“In future, it’s likely that places in Antarctica that currently don’t have any water or slush will start to change,” said Willis. “As the climate continues to warm, more melting will occur, which could have implications for ice stability and sea level rise.”

The research was supported in part by the European Space Agency and the Natural Environment Research Council (NERC), part of UK Research and Innovation (UKRI). Rebecca Dell is a Fellow of Trinity Hall, Cambridge.