Cities, states, and provinces are not parties to the Paris Agreement, but most human-induced greenhouse gas emissions (and most of the actions to reduce emissions) occur in urban areas. So, when California formulated the most aggressive climate change action plan in the United States, it reflected the need for close coordination between the state and its 540 local governments and state investment in local action.

There was no agreement on exactly how they could do it.

In 2015, under the Paris Agreement, the world’s countries agreed to hold the increase in global average temperature to "well below" two degrees above pre-industrial levels and pursue efforts to limit it to 1.5 degrees above pre-industrial levels.

Climate change poses profound challenges to all levels of government and to communities in every jurisdiction. Under California law, the state must reduce its greenhouse gas emissions 40 per cent below 1990 levels by 2030 — in eleven years. The state’s electricity grid must be 100 per cent renewable by 2045, and energy efficiency in buildings must double by 2030. In addition, by executive order, California is to cut in half its use of oil by 2030 and become carbon neutral — emissions and carbon sequestration must balance at zero — by 2045.

Much of California’s multi-billion-dollar climate investment focuses on transportation and electricity, which combine for 75 per cent of the state’s emissions. Just as importantly, the state and cities are reformulating urban development for a carbon-constrained world, focusing on transit-oriented design and climate resilience.

One of California’s most innovative programs — called Transformative Climate Communities (TCC) — invests significant funds from the state’s cap and trade program (which creates a market for greenhouse gas emission reductions) in the most disadvantaged communities in the state. TCC focuses on individual neighborhoods, funding community-driven climate projects that reduce greenhouse gas emissions significantly, leverage additional funding sources, and provide additional health, environmental and economic benefits. Projects include affordable and sustainable housing developments, transit stations and facilities, bicycle and car share programs, residential weatherization and solar projects, water-energy efficiency installations, urban greening projects, bicycle and pedestrian facilities, and low-carbon transit vehicles and clean vehicle rebates. The investments are substantial — from $25 million to $140 million per community — in order to promote large-scale and meaningful change.

California’s climate actions impact housing, transportation, and all aspects of infrastructure. The state faces a severe housing shortage, especially for low and moderately priced units. A 2017 state law provides funding and technical assistance to all local governments in California for streamlined housing approvals and production, consistent with the principles of transit-oriented development, thereby reducing transportation impacts and impacts of suburban sprawl.

At the same time, California has changed how it evaluates the environmental impacts of development projects on transportation. For decades, local governments focused their reviews on traffic delay — the impact of a particular project on local traffic. As a result, projects in urban areas faced additional costs and barriers as they inevitably impact traffic more than development in greenfield areas at the urban edge. Now, local governments and developers must evaluate the project’s impact on vehicle miles traveled. Thus, a project on the outskirts of town likely adds more miles (and more climate and criteria pollution) than a project located in the central city, thereby changing incentives for urban and greenfield development, and promoting a stronger urban core. This is one example of a significant change in orientation.