This publication explores how enabling policy frameworks at the national level can support critical urban action to combat climate change.
The key messages are:

Cities have a unique ability to address global climate change challenges: The report argues that choices made in cities today about long-lived urban infrastructure will determine the extent and impact of climate change, the ability to achieve emission reductions and adapt to changing circumstances.
National frameworks can either empower or slow down city-level action; therefore, supportive national and regional policies and incentives are required to ensure city-level initiatives have sufficient resources.
National policies often establish what cities can and cannot do in terms of climate policy action: National and regional governments should ensure that their policy frameworks are well-aligned and work to support city-level action.
National support is needed to help cities establish policy frameworks and minimum standards and to garner the required resources and technical information. This could come in the form of environmental goals and incentives in national policies.
Identifying national policies that conflict with or prevent local climate action is an important way in which national governments can improve their alignment with local climate initiatives.
Investing in low-carbon, climate-resilient urban infrastructure has low incremental costs and provides multiple local benefits.
Public sector financing will not be sufficient; therefore, the report argues that cities need to encourage private investment to fill funding gaps for green urban infrastructure projects. It argues that national level policies must be in place that improve the enabling environment for private investments in green urban infrastructure and the risk-return profile of these investments.

[Adapted from source]