Demonstrators protest President Trump’s decision to exit the Paris climate change accord June 2 in Chicago. (Scott Olson/Getty Images)

“I was elected to represent the citizens of Pittsburgh, not Paris,” President Trump said last week as he announced the U.S. withdrawal from the Paris climate accord. Pittsburgh’s mayor quickly tweeted his rebuke:

This tweet was just the beginning. Soon many local and state government leaders were announcing their own commitments to the Paris accord. One group declared it would create its own climate plan to submit to the United Nations. As the New York Times reports, “[this group] includes 30 mayors, three governors, more than 80 university presidents and more than 100 businesses.” Oregon’s Gov. Kate Brown tweeted:

Will more state and local governments do the same? My research indicates that many will. But their efforts are unlikely to be enough to replace federal policy.

Here are some things worth considering in the era of state and local climate action we are about to enter.

When George W. Bush stepped back from the Kyoto Protocol, cities and states stepped in. 

Subnational governments often step in when national leaders send a clear signal of inaction. For example, in 2001, President George W. Bush announced that his administration would not ratify the Kyoto Protocol. Beginning immediately and continuing over the next eight years, state governments responded by passing a myriad of climate change policies.

By now, 34 states have a climate action plan, which identifies ways the state can pursue climate change mitigation,  while 29 states have enacted a renewable portfolio standard, a regulation that mandates utilities increase the percentage of energy they sell from renewable sources by a specified amount and date. California has taken the lead, enacting tough automobile emissions standards and lofty targets for the state’s share of energy production that comes from renewables.

Many other states have followed California’s example, and now have laws, regulations or policies that require monitoring emissions, improving building standards to mandate energy conservation and creating “climate action plans” for those efforts. In fact, all 50 states have at least one climate change mitigation law in place. Many have 10 or more.

Some states have worked together in their climate-policy pursuits. For instance, nine northeastern states — Maine, Connecticut, Delaware, Maryland, Massachusetts, New Hampshire, New York, Rhode Island and Vermont — are part of a CO2 cap and trade system that began in 2009.

What makes cities, states and regions likely to take unilateral climate action?

To answer this, my co-authors J.S. Butler, John Poe, Whitney Davis and I collected data on which states adopted climate change mitigation policies between 1994 and 2009. What we found will surprise no one. Our research indicates that the states that aggressively establish  climate change policies are likely to have a more liberal population, a state legislature led by Democrats and higher per capita income. In particular, when a state’s citizens have a particularly high rate of Sierra Club membership, that state is especially likely to commit itself to policies that mitigate climate change.

Further, liberal state governments try to learn from and copy other liberal states’ successful policies, which spreads policies across states.

Here’s another finding that may seem obvious, but is in fact somewhat subtle. My research with John Poe shows that as citizens become more attentive to and concerned with climate change, state governments become more likely to pass climate legislation. For example, we find that increases in Google searches for environmental issues in a state increases the likelihood that the state will adopt climate policy.

Consider the fact that Utah wasn’t an early bird on climate change policy. But between 2007 and 2009, as Utah faced severe droughts and wildfires that many linked to climate change, the state legislature promulgated more regulations. States that face very observable new weather patterns linked to climate change are now acutely aware of the federal government’s lack of action — and are positioned to try to fill this gap.

Trump’s withdrawal from the Paris accords will mobilize groups, municipalities and states to act more aggressively to slow climate change. 

We can expect the Sierra Club and other environmental groups to use Trump’s withdrawal to get their supporters to press their state and local governments to get to work on climate change. Public officials with an election coming up are more likely to act on issues the public is highly attentive to. Expect new climate change laws in states where many citizens belong to environmental groups.

That action should continue as long as climate change is in the news — which is likely to continue through both the midterms and the next presidential election, since the U.S. cannot officially withdraw from the Paris climate accord until November 2020.

Which climate change policies should we expect from local and state governments?

My research with James Stoutenborough and Arnold Vedlitz finds that the public largely supports individual climate change policies, such as investing in renewable energy and reducing auto emissions. But policymakers might wish to stay away from the term “climate change,” which is politically polarizing; only Democrats report that they trust climate science’s conclusion that human use of fossil fuels is what’s changing the climate.

Sometimes state renewable energy policy is effective at reducing carbon emissions and increasing the share of renewable energy production. However, how stringent the policy is and what number and type of energy policies are implemented matters. For example, state net metering programs give consumers credit if they produce surplus energy through wind, solar or other methods. But these programs vary in the types of energy production they include, the ease at which consumers can connect to the grid and whether a fee is required — all of which make a difference in carbon emission reduction.

State and local governments can also make renewable energy investments and encourage the renewable industry through greenhouse gas targets and renewable portfolio standards. Again, these standards vary widely. Some states institute weak voluntary standards; South Carolina has a goal of a two-percent renewable energy share by 2021. Others aim very high, with Hawaii aiming for a target of 100 percent by 2045, with substantial increases in between.

But those patchwork efforts, while important, are no substitutes for national action. The federal government can negotiate internationally in a way that state and local governments simply cannot. And federal standards can require every state to get involved, not just the most motivated states. Without a federal mandate, many states will continue to sit on their hands.

Rebecca Bromley-Trujillo is an assistant professor in the Martin School of Public Policy and Administration at the University of Kentucky.