Starting at the Bottom: The Potential Impact of Climate Action by Sub-National Entities in the United States

Above Image: The United States Capitol, seat of the legislative branch of the United States government. Source: Wikipedia

Article: Hultman NE, Clarke L, Frisch C et al. Fusing subnational with national climate action is central to decarbonization: the case of the United States. Nat Commun 11, 5255 (2020).


In the United States, particularly in the autumn, and especially so during presidential election years like 2020, national-level politics dominates news coverage. This includes legislation, policies, and actions of the national government since the last election (in 2016). One of the more controversial decisions undertaken by the current presidential administration is announcing the withdrawal the United States from the Paris Agreement signed in 2016. The withdrawal is set to take place in November 2020.

                While the decisions of the national government affect the United States as a whole, the American system of federalism means that there are many additional levels of government below the national level. These include state, county, and city/town/village governments, along with Native American tribes who have varying level of autonomy in their own affairs. 

                These sub-national governments oversee policies within their jurisdictions and also in partnership with other similar governments. Many of these governments have enacted their own goals and policies regarding climate change action. They have done so separate from, and now in spite of, national-level United States policy.  Many non-governmental entities, like businesses, have also pursued their own goals and policies.

                Thus, despite there being no unified national policy, there is currently quite a bit of climate change policies and directed actions at various sub-national levels in the United States.

                A recent paper published in Nature Communications presents an analysis of the impact of these policies, and also the potential impact of combining them with potential national-level policies.

Paper Summary:

The researchers first studies the specific sub-national entities (both governmental and non-governmental) that currently have made specific commitments to climate goals. Their findings are shown below in Figure 1 from the article. Part a shows the location of the various entities throughout the United States. Part B shows the growth of the entities as a whole, along with the proportion of national GDP (71%), national population (68%), and emissions (51%) they represent. As stated in the article, the combined entities represent the world’s second-largest economy – only the United States economy as a whole is larger.  

Figure 1 from Hultman NE, Clarke L, Fritsch C et al, 2020

                The impact of the various policies enacted by these entities is significant, and can be greater if they continue to be enhanced beyond that of the present, and even greater still if they were to be combined with impactful national-level policies. Currently, no national-level policies on climate change action exist. The effects of these three different scenarios of emissions in the United Sates is shown below. The numbers in red, blue, and green to the right of the graph shows the reduction of emissions in 2030 compared to 2020 levels by current sub-national measures, enhanced sub-national measures, and combined national and sub-national measures.

Figure 2 from Hultman NE, Clarke L, Fritsch C et al, 2020

                This overall reduction in emissions is even more noteworthy if broken down into various economic sectors, as shown below in Figure 3 from the paper. If national-level policies were to be enacted along with enhanced current subnational-policies across all economic sectors, the United States carbon dioxide emissions could be reduced to nearly half of 2020 levels.

Figure 3 from Hultman NE, Clarke L, Fritsch C et al, 2020


The national government in the United States has a lot of power in entering and exiting international agreements and enacting national-level domestic policy. However, the system of government in the United States has allowed various sub-national governments much autonomy in pursuing climate goals and climate change-related policies independently of the national governments. Many non-governmental entities are doing so, also. Their combined policies are already on track to result in significantly reduced carbon emissions by 2030. If existing policies were enhanced, emissions would be reduced even further. If (currently non-existent) national-level climate-change policies were to be enacted also, the reduction in carbon emissions would be drastically reduced by 2030, compared to current levels.

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Munim Deen

Munim is an epidemiologist and cartographer. His primary interests are infectious disease outbreaks and their intersection with the environment, public policy, and society at large. A geographic information system (GIS) devotee, he incorporates mapping and spatial analysis into his work whenever possible. A former newspaper columnist, he holds a bachelor's degree in microbiology and a master's degree in epidemiology.

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