The Climate City

Reaching the goals of the 2015 Paris Agreement will require ambitious actions from all sectors and levels of our society, but especially in our cities. More than 55% of people already live in urban areas, and this is forecast to rise to 68% by mid-century. 1Urban areas account for more than 60–70% of the world’s greenhouse gas (GHG) emissions, consuming 66–78% of the world’s energy, while occupying less than 2% of the land. 2Even as we decouple economic growth from emissions – already achieved by over twenty countries before – the sheer scale of the amount of people living in cities means that climate leadership by cities requires ambition and talent at city-scale as much as ever before in history.

But ambition on its own will not be enough. A mayor will always fall short when simply citing “a net-zero city” as a strategic goal. It may sound good, but without clarity in describing that destination it may even come to be seen as just a PR stunt that sounds good but lacks substance (Figure 1.3). At the other extreme, a crystal-clear set of cautious environmental objectives is simply not going to be bold enough in this time of climate emergency. So, how do we retain the ambition but increase the clarity on what cities can and should be aiming for to lead on climate?

Figure 1.3 The need for both ambition and clarity will drive success. ( Source : Boyd, P. and Pickett, C., 2020. Climate Ambition: A Case for Net-Zero Clarity . Yale Center for Business and the Environment. https://cbey.yale.edu/research/defining-net-zero.)

As I’ve argued with co-author Casey R. Pickett in a recent paper 3– from which this paper draws – we need a consistent definition of “Net-Zero” that cities (and organizations, companies, and countries) can use and measure progress against. If we are to maximize the probability of a just transition to a sustainable society, all actors have to explain what they mean by “net-zero” in addition to their intended deadlines and paths . We suggest four measurable criteria for any undertaking of “net-zero” to be worthy of capitalizing to “Net-Zero”.

In a refreshed and robust definition, a strategy for “Net-Zero” GHG emissions earns its capital letters if it is: Fully Scoped , Science-Based , Paris-Agreement-Compliant , and Cumulative . Each descriptive term imparts a dimension of clarity. “Net-Zero” can be a powerful and useful goal at the city level if the city embraces a concept of “Net-Zero” that is:

1 Fully Scoped: articulating the city’s defined scope of responsibility. This should include all GHG emissions from scope 1 (GHG emissions from sources located within the city boundary); scope 2 (GHG emissions occurring as a consequence of the use of grid-supplied electricity, heat, steam, and/or cooling within the city boundary); and scope 3 (all other GHG emissions that occur outside the city boundary as a result of activities taking place within the city boundary).4

2 Science-Based: incorporating a destination-based5 target for “Net-Zero” that demonstrates the city is assuming bold, appropriate responsibility for emissions reductions consistent with the Paris Agreement and at least proportional to its contribution to climate change.6

3 Paris-Agreement-Compliant: specifying if and to what extent carbon credits and external investments in carbon removal factor into the strategy. Any offsetting investments should be linked to the global carbon budget as defined in the Paris Agreement.

4 Cumulative: acknowledging the city’s historical emissions of GHGs, not just their current level.

We will unpack each of the terms above and what it means for cities, but we should first explain the “and Beyond” of the title, as its meaning is designed to be taken in at least two ways. For cities to set climate action goals solely through a lens of GHG emissions would be too narrow and not recognize the complex set of interconnected goals and stakeholders. All climate goals in a municipal environment are often phrased within the Brundtland Commission definition of sustainability, 7encompassing sustainability for social, economic, and environmental benefit. The UN Sustainable Development Goals (SDGs) have built on this important work over decades, and we have since heard most sustainability targets referring to not only the destination but also the nature of the transition, and the ambition to make the transition a just one. Beyond climate and human equity, biodiversity, water, and land stewardship are also critical considerations for any city.

The second intended orientation of setting “Net-Zero and Beyond” goals is leaving the “Net-Zero” market behind in the past. Cities hopefully become “Climate Positive” rather than just aiming for “Net-Zero”. “Climate positive” is an increasingly used alternative to “carbon negative” that emphasizes the benefits of aggressive climate action. “Net-Zero” hopefully becomes a well-defined marker that many cities leave behind – and ideally well before 2050. 8

Providing net-zero context at the global level, the Paris Agreement, agreed in 2015 and ratified the following year, created a vital destination-based target for the world. It set the objective of “Holding the increase in the global average temperature to well below 2°C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5°C …” by achieving “a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases in the second half of the century, on the basis of equity, and in the context of sustainable development and efforts to eradicate poverty”. 9

While the first phrase, from Article 2, outlines the temperature target, Article 4 effectively defines net-zero GHG emissions as reducing human-caused emissions to the level that natural climate solutions and other methods of CO 2storage and removal can effectively absorb. It succinctly describes a global state of ecological balance, even if the results of past emissions have not been fully absorbed. If this state is achieved by mid-century, and if emissions decline further to net-negativity in the back half of the century, maintaining a 1.5°C world becomes likely. 10

Paris-Agreement goals build on strong conclusions from the Intergovernmental Panel on Climate Change’s recent assessment 11and the US government’s own 4th National Climate Assessment. 12A recent report released in BioScience 13listing 11,000 scientists as contributing authors was equally unequivocal. We must adjust course dramatically and achieve net-zero emissions by 2050 if we are to avert the worst impacts of climate change and remain on target for 1.5°C of warming. These global goals transmit across language, culture, and ideology. They are vital to the transition to a sustainable world, but their applicability and measurability tend to burn off on impact as they enter a single enterprise.

City mayors have been stepping up and leading through a variety of fora, most notably the Global Covenant of Mayors for Climate & Energy, C40, and the International Council for Environmental Initiatives (ICLEI). In the former, 9,000 municipalities could potentially achieve savings of 1.4–2.8 GtCO 2e versus “business as usual” if their combined pledges are achieved. C40’s “Deadline 2020” is a commitment from the world’s leading cities to urgently pursue high-ambition climate and has attracted 119 committed cities at time of writing.