Climate Change and Cities: What We Need to Do

On October 6, 2018, the International Panel on Climate Change (IPCC) released a special report in support of a global response to keep global warming to less than 1.5ºC above pre-industrial levels. Widely reported in popular media, the Summary for Policymakers (SMP) provided a clear warning ­­- we need to act fast and decisively.

The October 2018 IPCC Summary to Policymakers indicates we must reduce our GHG emissions by 45% before 2030 and reach net zero emissions by 2075.

Climate Scientists’ Projections

The IPCC scientific team’s current projections indicate we have little over a decade to drastically reduce greenhouse gas emissions to avoid catastrophic climate change. We need to make a “rapid and far-reaching transition in energy, land, urban and infrastructure (including transport and buildings), and industrial systems” to avoid surpassing a 1.5ºC increase in global temperatures by 2050. Meeting the 1.5ºC or less target is critical for reducing climate impacts and reducing the costs for adaptation.

The latest report indicates we must reduce greenhouse gas (GHG) emissions 45% by 2030 and reach net zero emissions by 2075. Based on our current efforts, these seem like audacious goals. However, not meeting them means we can expect continued increase in extreme weather events and coastal flooding, impacts on food security and loss of biodiversity and unique ecosystems that also support people.

Meeting the goals is ambitious but not impossible. In fact, we already know a lot about what we need to do. Mostly, it will require rethinking the way we live, work and travel around the world’s cities, which account for about 75% of global greenhouse gas emissions. Interesting efforts already are underway.

Four Broad Pathways to Net Zero

The report defines four broad “pathways” to reach that goal, along with the potential outcomes for each. These include (P1) lower energy demand, (P2) broad focus on sustainability, (P3) changing the way we produce energy and (P4) continuing a resource-intensive path. Pathways 1, 2, and 3 would require large-scale efforts, although they are not unprecedented in terms of speed. Pathway 4 requires very large investments in bioenergy with carbon capture and storage.

The mitigation strategies within the pathways include potential synergies or co-benefits when comparing the interrelationships between energy demand, energy supply and land use. For example, energy demand and supply strategies have synergies with responsible consumption and production, but there are tradeoffs when considering clean water and sanitation. While synergies like these seem logical, researchers continue to quantify co-benefits of relationships between climate actions and quality of life indicators.

Pathways to Net Zero at the Local Level

Cities on every continent are setting aggressive GHG reduction targets that are changing their policies and investment in their operations, building stock and infrastructure. The IPCC established protocols for assessing and measuring national GHG emissions. World Resource Institute, C40, and International Council for Local Environmental Initiatives collaborated with the World Bank and others to prepare a framework to allow cities to measure their GHG inventories in a consistent way in order to more easily align local climate protocols with those used by the IPCC. The Global Protocol for Community-Scale Greenhouse Gas Emissions has been piloted by 33 international cities. Other international networks, such as Resilient 100 Cities, C40 Cities, and EcoDistricts.org, are providing technical assistance and peer-to-peer mentoring.

Demand Reduction and Supply Strategies

Cities are pursuing broad community-scale strategies focusing on land use, energy used in the building sector, transportation, infrastructure (especially paving) and embodied emissions. These can be viewed as demand and supply-side strategies (below).

Land Use Strategies

The patterns in which cities are built contribute to their GHG emissions. Compact, connected and concentric walkable cities enable other reduction strategies. They more easily provide transportation options, more efficient infrastructure and building types that use less energy. They can also cut down on loss of farm and natural landscapes that store carbon and shorten farm-to-market supply chains.

Embodied Emissions

Building and infrastructure have embodied emissions. These are from the energy required to construct them, including that consumed to ship materials and equipment to the building site. Buildings that use locally sourced materials, as well as materials that do not require a lot of energy to manufacture and can be recycled or reused, have lower embodied GHG emissions. "Green infrastructure," such as parks and open spaces designed as a continuous stormwater system, can serve a more compactly planned city reducing embodied emissions found in traditional concrete "gray infrastructure."

Building Energy Strategies

In the United States, buildings account for 40% of all GHG emissions. Incorporating more energy-efficient technology into buildings and using locally developed renewable energy can dramatically reduce urban greenhouse gas emissions. In addition to incorporating new active technologies, better passive strategies including deliberate solar orientation, thermal insulation and ventilation can also improve building energy performance.

Cities need to define their own pathways to mitigate their GHG emissions by reducing the demand for energy, developing greener energy supplies, and supporting more sustainable lifestyles.

Transportation Strategies

The second highest source of global urban GHG emissions is the transportation sector. There are three general strategies for reducing emissions from transportation: reducing vehicle miles traveled, improving vehicle technologies and switching to cleaner-burning fuels. By developing “walk first” cities we can greatly reduce emissions. Well-connected and comfortable pedestrian systems enable intermodal transportation systems providing mobility options for residents.

Supply-side Strategies

Cities can employ green energy technologies and sources that reduce emission from the power sector. At the scale of the regional grid, cities can negotiate purchase of greener energy or benefit from national policies regarding reducing the amount of carbon dioxide and other damaging emissions in the power supply. Municipal power companies are developing greener portfolios by adding waste-to-energy, wind and solar technologies. At a local or site scale, cities and building managers/operators can employ smart micro-grid technologies or renewable technologies. These might include rooftop solar or ground source geothermal technologies. To meet net zero GHG emission goals, supply-side strategies are most cost effective when used in concert with demand reduction strategies.

Cities are Acting

We are at a serious tipping point in the earth’s capacity to absorb additional heat. While the international efforts are discussed, local communities can take action, and many are. They are joining peer communities, learning from each other and developing polices that reduce their climate impact. They are developing GHG inventories to understand where reductions are needed, establishing reduction targets and goals, and pursuing strategies and supporting actions. They are following their own pathways to reduce emissions, developing greener energy supplies, and supporting more sustainable lifestyles.

In future blog posts I will share strategies cities are employing to reduce their GHG emissions and discuss their effectiveness.