A report released by C40 Cities finds that consumption-based emissions from nearly 100 of the world’s big cities already represent 10% of global greenhouse gas emissions. Without urgent action, those emissions are projected to nearly double by 2050.

The new research, The Future of Urban Consumption in a 1.5°C World, was produced in partnership with Arup and the University of Leeds, and cautions that urban consumption-based emissions must be cut by at least 50% by 2030 in order to maintain the possibility of keeping global temperature rise below 1.5°C.

When combined with firm city efforts to reduce local emissions, this would allow cities to deliver 35% of the emission savings needed to put them on a path to 1.5 °C, according to the report.

High income areas, which generate the bulk of emissions, need to cut their emissions much faster—two-thirds by 2030. The research suggests that if nations, business, cities and citizens take ambitious climate action over the next 10 years, cities will be on track to reduce their emissions in line with a 1.5°C world.

Twenty-seven C40 cities have already peaked their production emissions—those emitted locally. However, the C40 network represents one-quarter of the global economy, and 85% of the emissions associated with goods and services consumed within their boundaries are imported from elsewhere.

The place to start is with those who consume the most, the report says. To reach the reductions needed, high-income urban areas must reduce the climate impact of consumption by two-thirds within the next decade, while rapidly developing economies must adopt sustainable consumption patterns as they continue to grow.

The report explores six sectors where the world’s cities can take rapid action to address consumption-based emissions: food, construction, clothing, vehicles, aviation, and electronics. There is significant potential to cut consumption-based emissions in these sectors.

Together these actions would save around 1.5 GtCO₂e per year by 2030. When combined with existing city climate commitments, this would deliver 35% of necessary reductions in consumption-based emissions needed to put C40 cities on a 1.5°C trajectory.

• Vehicles: Mayors, business, and citizens in C40 cities could together take actions to reduce consumption-based emissions from private transport by 28% by 2030. This could be through interventions reducing and eventually nearly eliminating the need for car ownership, which would reduce costs and free up space on the streets for people. This could be achieved by strengthening public transport or making shared or hire car access in cities easy and cost-effective. Cities can also work with manufacturers in maximizing car lifespans and increasing materials efficiency.

• Aviation: Mayors, business, and citizens in C40 cities could together take actions to reduce consumption-based emissions from aviation by 26% by 2030. Part of this will be delivered by technology interventions, such as sustainable aviation fuel. However, since this will take time to reach maturity, in order to deliver the necessary carbon targets, there must be an average 28% reduction in the number of flights across C40 cities. The greatest reductions would be required where flying is most common. Such a convergence would help ensure climate-safe travel for all, rather than just a small proportion of the world flying extensively and most not at all. This can be facilitated through providing viable alternatives like affordable high-speed rail.

• Food: Mayors, business, and citizens in C40 cities could together take actions to reduce consumption-based emissions from food by an average of 31-37% by 2030, depending on the target level, by moving to a plant-based diet, eating healthy quantities and avoiding waste. Actions might include “meat free Mondays” at schools and public buildings, community gardens to encourage activity, local cohesion, and healthy diets, regulation to prevent excessive targeting of children for fast food, or supporting healthy food retailers to avoid food deserts where citizens have to travel long distances to get quality healthy food. This could help reduce meat consumption to a maximum of 16 kg per person per year and dairy to 90 kg per person per year, down from an average of 58 kg of meat and 155 kg of dairy at present, and eventually to even lower levels of consumption that can further reduce emissions.

• Construction: Mayors, business, and citizens in C40 cities could together take actions to reduce consumption-based emissions from buildings and infrastructure by 26% by 2030. Regulations and incentives to use less building materials could reduce steel and cement use by 35% and 56%, respectively. Ensuring all buildings are being used to their full capacity could lead to a 20% reduction in the need for new buildings. Switching to lower-impact materials such as sustainable timber (as a part replacement for concrete) is needed for 90% of homes and 70% of offices being built.

• Clothing: Mayors, business, and citizens in C40 could together take actions to reduce consumption-based emissions from clothing and textiles by 39% by 2030 through interventions such as encouraging new clothing business models focused on recycling, upgrading, renting, and reuse of clothes. This would allow a reduction in new items of clothing to as low as 3 per person, per year, and reduce waste, costs, and impact. A 75% reduction in supply chain waste will also be needed to realize the full emissions reduction potential.

• Electronics: Mayors, business, and citizens in C40 cities could together take actions to reduce consumption-based emissions from electronics and consumer goods by 18% by 2030 by prolonging the lives of products ideally for at least 7 years, saving money and waste. This could be accomplished through interventions such as community workshops to repair electronics and appliances or “tool libraries” where tools can be borrowed only when needed.

This research was made possible thanks to Citi Foundation. C40 is a network of the world’s megacities committed to addressing climate change.