The global construction sector’s carbon footprint is on track to double by 2050, threatening to derail global efforts to meet the Paris Agreement climate targets, a new international study warns as the world marks UN World Cities Day on Friday, 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 made up just 6 percent, and the remaining 37 percent arose from transport, machinery, and on-site activities.

In 2022, the construction industry accounted for 33 percent of global carbon emissions—up from 20 percent three decades ago. This steady rise is largely driven by material-related inputs, such as cement, steel, and glass, which have outpaced reductions from other sources.

In 1995, emissions from materials and non-material sources—such as on-site activities and services—were roughly equal. But over time, material-related carbon footprints have surged, showing that the industry has become increasingly dependent on high-carbon materials.

The paper emphasises the need for low-carbon, circular, and bio-based building materials, such as engineered timber, bamboo, and recycled composites. For rapidly growing cities like those in Nepal, such materials could be critical in balancing urbanisation with climate goals.

“The study shows that the construction sector now drives 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, the researchers projected several future emission scenarios. Under a business-as-usual pathway, the construction sector alone will exceed the per-annum 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 consume the entire remaining global carbon budget for 1.5°C,” said Prajal Pradhan, co-author and professor at the University of Groningen.

The study reveals a major shift in emissions from developed to developing regions. In 1995, high-income countries generated half of global construction emissions. By 2022, emissions in these economies had stabilised, while developing regions saw rapid increases due to heavy reliance on steel and cement.

Meanwhile, the use of bio-based materials such as timber has declined, missing an opportunity to promote low-carbon construction alternatives.

The authors call for a global “material revolution”—a fundamental shift away from carbon-intensive building materials toward 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, underlining the urgency of transforming how buildings are designed and constructed.

“The challenges and solutions for decarbonising construction are not the same everywhere,” said Jürgen Kropp from the Potsdam Institute for Climate Impact Research. “True change requires systemic shifts across the supply chain, reducing dependence on traditional materials like cement and steel while scaling up innovation and alternatives.”

The authors argue that high-income regions must lead by investing in innovation, circular design, and stricter regulation, while developing regions—where most new construction will occur—need financial and technological support to leapfrog 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 scale up low-carbon materials and redesign construction systems to keep climate goals within reach.

As the world continues to urbanise rapidly, reducing the construction sector’s impact is key to achieving sustainable, climate-resilient cities. The study, covering 49 countries and regions and 163 economic sectors between 1995 and 2022, offers the most comprehensive analysis of global construction emissions to date.

“Humanity has built itself into a corner with steel and cement,” said Hans Joachim (John) Schellnhuber, director general of the International Institute for Applied Systems Analysis (IIASA).

“To meet the Paris goals, we must reinvent the materials that shape our cities. A global material revolution rooted in circularity, innovation, and cooperation can transform the construction sector from a climate problem into a cornerstone of sustainability.”

Asia-Pacific forest leaders explore carbon markets ahead of COP 30

Senior forestry officials from Indonesia, Vietnam, and Nepal, along with private-sector and climate finance experts, met in Seoul this week to plan the next steps for scaling up high-integrity forest carbon transactions across the Asia-Pacific.

The roundtable, hosted by the Global Green Growth Institute (GGGI) during Global Green Growth Week, was co-organised by UN-REDD to help countries transition from REDD+ readiness to results-based finance and Article 6 implementation under the Paris Agreement.

“Countries in the Asia Pacific are showing that forest protection and credible carbon markets go hand in hand,” said Gabriel Labbate, Head of UNEP’s Climate Mitigation Unit. “They are moving from readiness to results—building systems that not only store carbon but also sustain livelihoods, restore ecosystems, and build trust in markets.”

Across Indonesia, Vietnam, and Nepal, more than 230 million tonnes of CO₂ equivalent (tCO₂e) in potential mitigation outcomes are being prepared for verification or issuance, marking a major pipeline of forest-based climate results linked to community resilience and green investment.

Indonesia leads the region with a jurisdictional REDD+ pipeline that could deliver up to 200 MtCO₂e per year between 2022 and 2026, alongside verified provincial programmes in East Kalimantan and Jambi.

Vietnam is advancing validation for around 25 million tCO₂e in emission reductions across 11 provinces, combining jurisdictional ART-TREES readiness with emerging private-sector initiatives.

Nepal is preparing to verify and issue around 20 million tCO₂e under its subnational ART-TREES and FCPF programmes, marking a shift from donor-funded REDD+ payments to market-linked carbon finance. The country is also developing a larger jurisdictional programme that could cover about 3 million hectares of forest.