October 29, 2025
KATHMANDU – The global construction sector's carbon footprint is on track to double by 2050, potentially undermining global efforts to meet the Paris Agreement's climate targets, a new international study warns, as the world on Friday marks UN World Cities Day, a call to make cities more sustainable.
The study finds that in 2022, over 55 percent of construction emissions came from cementitious materials, bricks and metals, while glass, plastics and chemicals contributed the rest. Bio-based materials accounted for only 6 percent, with the remaining 37 percent coming from transportation, machinery and on-site activities.
In 2022, the construction industry was responsible for 33 percent of global carbon emissions – up from 20 percent three decades ago. This steady increase is largely due to material-related inputs such as cement, steel and glass, which exceeded reductions from other sources.
In 1995, emissions from tangible and intangible sources – such as on-site activities and services – were approximately equal. But over time, the material-related carbon footprint has skyrocketed, showing that the industry has become increasingly dependent on carbon-rich materials.
The paper highlights the need for low-carbon, circular and bio-based building materials such as engineered wood, bamboo and recycled composites. For fast-growing cities like those in Nepal, such materials could be crucial to balancing urbanization with climate goals.
“The study shows that the construction sector is now responsible for a third of global CO₂ emissions, up from around 20 percent in 1995. If current trends continue, the sector could exceed the 2°C carbon budget by 2040,” said Chaohui Li of Peking University, the lead author.
Based on historical data, researchers projected several future emissions scenarios. Under a business-as-usual path, the construction sector alone will exceed the annual carbon budget for the 1.5°C and 2°C targets within the next two decades.
“Between 2023 and 2050, cumulative construction-related emissions could reach 440 gigatons of CO₂ – enough to use up the entire remaining global carbon budget for 1.5°C,” said Prajal Pradhan, co-author and professor at the University of Groningen.
The study shows a significant shift in emissions from developed to developing regions. In 1995, high-income countries produced half of the world's construction emissions. By 2022, emissions in these economies had stabilized, while developing regions had seen rapid increases due to heavy reliance on steel and cement.
Meanwhile, the use of bio-based materials such as wood has declined, missing an opportunity to promote low-carbon building alternatives.
The authors call for a global “materials revolution” – a fundamental shift away from carbon-intensive building materials towards circular, low-carbon and renewable options. Their analysis shows that cement, bricks and metals now account for more than half of the sector's total emissions, highlighting the urgency of transforming the way buildings are designed and constructed.
“The challenges and solutions for decarbonizing construction are not the same everywhere,” said Jürgen Kropp from the Potsdam Institute for Climate Impact Research. “Real change requires systemic changes along the supply chain that reduce reliance on traditional materials like cement and steel while encouraging innovation and alternatives.”
The authors argue that high-income regions need to lead the way by investing in innovation, circular design and stricter regulation, while developing regions – where most new construction will take place – need financial and technological support to transition to sustainable building practices.
Without such transformations, the report warns, the construction sector alone could consume the entire remaining carbon budget for the 1.5°C target within two decades. The study calls for a coordinated global push to spread low-carbon materials and redesign building systems to keep climate goals within reach.
As the world continues to rapidly urbanize, reducing the impact of the construction sector is key to creating sustainable, climate-resilient cities. The study, covering 49 countries and regions and 163 economic sectors between 1995 and 2022, provides the most comprehensive analysis of global construction emissions to date.
“Humanity has cornered itself with steel and cement,” said Hans Joachim (John) Schellnhuber, director general of the International Institute for Applied Systems Analysis (IIASA).
“To achieve the Paris Goals, we must reinvent the materials that shape our cities. A global materials revolution based on circularity, innovation and collaboration can transform the construction sector from a climate problem into a cornerstone of sustainability.”
Asia-Pacific forestry leaders explore carbon markets ahead of COP 30
Senior forestry officials from Indonesia, Vietnam and Nepal, as well as private sector and climate finance experts met in Seoul this week to plan next steps to expand highly integrated forest carbon transactions across the Asia-Pacific region.
Hosted by the Global Green Growth Institute (GGGI) during Global Green Growth Week, the roundtable was co-organized by UN-REDD to help countries transition from REDD+ readiness to results-based financing and the implementation of Article 6 under the Paris Agreement.
“Countries in the Asia-Pacific region show that forest protection and credible carbon markets go hand in hand,” said Gabriel Labbate, head of UNEP’s Climate Action Unit. “They are moving from readiness to results – building systems that not only store carbon, but also support livelihoods, restore ecosystems and build trust in markets.”
In Indonesia, Vietnam and Nepal, more than 230 million tonnes of CO₂ equivalent (tCO₂e) worth of potential reduction results are being prepared for review or exhibition.
Indonesia is leading the region with a jurisdictional REDD+ pipeline that could deliver up to 200 million tonnes of CO₂e per year between 2022 and 2026, alongside verified provincial programs in East Kalimantan and Jambi.
Vietnam is advancing the validation of emissions reductions of approximately 25 million tonnes of CO₂e in 11 provinces, combining jurisdictional ART-TREES readiness with new private sector initiatives.
Nepal is preparing to verify and spend around 20 million tonnes of CO₂e under its subnational ART-TREES and FCPF programs, marking a transition from donor-funded REDD+ payments to market-linked carbon financing. The country is also developing a larger jurisdiction program that could cover about 3 million hectares of forest.