In the wake of President Trump’s decision to withdraw from the Paris agreement, a dozen states and more than 300 cities have pledged to reduce greenhouse-gas emissions in line with the Paris targets.

The move suggests a possible future for climate change policy in the Trump era: States and cities are taking on the brunt of climate responsibility, building green energy capabilities and meeting ambitious climate targets in the process.

There is no replacing the federal role in setting the larger climate agenda, without which the country is unlikely to meet more ambitious targets. But states and cities should still do all they can to fight for sensible climate policy in the absence of a sensible president. In many cases, that work is already underway and shows no signs of slowing.

States Are Already Abandoning Coal

Despite the president’s focus on bolstering the coal industry, the sector faced persistent declines over the past decade. This is important for reducing greenhouse-gas emissions since coal produces more carbon dioxide than other common forms of energy and is one of the leading causes of global warming.

Megawatt-hours of electricity production, by energy source 2b 1.5b Coal Natural gas 1b Nuclear 500m Hydro- electric Wind Other 0 1990 1995 2000 2005 2010 2015 Source: U.S. Energy Information Administration Megawatt-hours of electricity production, by energy source 2b 1.5b Coal Natural gas 1b Nuclear 500m Hydro- electric Wind Other 0 1990 1995 2000 2005 2010 2015 Source: U.S. Energy Information Administration

States have been lured away from coal by cheaper alternatives and an abundance of cleaner natural gas — market forces that are not easily manipulated by Trump’s policies. The rise of natural gas and decline of coal was partly responsible for falling CO2 emissions — 18 percent below projections made in 2008 by the Annual Energy Outlook.

Metric ton of CO2 emissions from energy consumption 6.5k AEO 2008 Forecast 6k 5.5k Actual 5k 4.5k 1990 1995 2000 2005 2010 2016 Sources: EIA, Rhodium Group analysis Metric ton of CO2 emissions from energy consumption 6.5k AEO 2008 Forecast 6k 5.5k Actual 5k 4.5k 1990 1995 2000 2005 2010 2016 Sources: EIA, Rhodium Group analysis

“Regulation will play a modest role in the future,” said Mark Muro, senior fellow at the Brookings Institution. “But the main effect here is simply price. Gas and renewables are simply becoming cheaper than coal for many plants and many situations.”

Federal regulations, if implemented, would force some states to replace older, dirtier sources of energy with cleaner fuels, or push them to find efficiency improvements in the grid and engage in emissions trading with other states. Those regulations would have included the Clean Power Plan, which set ambitious carbon emission reduction goals for high-polluting states, but Trump ordered the E.P.A. to roll back the plan in an executive order.

Percent change in net electricity generation from coal, 2004 to 2015 2004 2015 N.Y. Del. Calif. Conn. Nev. N.J. Mass. N.H. -77.0% -78.6% -83.0% -85.4% -85.9% -86.7% -87.4% -89.6% Maine Miss. S.D. Ga. Md. Va. Wash. Tenn. -47.3% -51.5% -51.7% -52.3% -53.6% -58.7% -63.4% -74.4% Ala. Ohio N.C. Pa. S.C. La. Ind. Fla. -33.9% -35.2% -35.9% -41.9% -44.0% -44.7% -44.8% -47.2% Mich. Okla. N.M. Kan. Minn. W.Va. Ill. Ore. -21.9% -22.3% -22.9% -26.4% -27.4% -28.9% -30.2% -33.1% Ky. Utah Ark. Mo. Hawaii Idaho Texas Iowa -12.9% -13.5% -14.3% -15.5% -15.7% -16.6% -18.4% -20.4% +18.2% Ariz. Mont. N.D. +2.9% Colo. Wyo. Alaska Wis. Neb. -0.6% -1.2% -7.9% -9.2% -11.8% -12.0% Only Alaska and Nebraska increased their net electricity generation from coal. Note: Excludes Rhode Island, which had no coal energy production. Coal measurements include anthracite, bituminous coal, subbituminous coal, lignite, waste coal, and synthetic coal Source: U.S. Energy Information Administration Percent change in net electricity generation from coal, 2004 to 2015 2004 ‘15 N.Y. Del. Calif. Conn. Nev. N.J. Mass. N.H. -77.0% -78.6% -83.0% -85.4% -85.9% -86.7% -87.4% -89.6% Maine Miss. S.D. Ga. Md. Va. Wash. Tenn. -47.3% -51.5% -51.7% -52.3% -53.6% -58.7% -63.4% -74.4% Ala. Ohio N.C. Pa. S.C. La. Ind. Fla. -33.9% -35.2% -35.9% -41.9% -44.0% -44.7% -44.8% -47.2% Mich. Okla. N.M. Kan. Minn. W.Va. Ill. Ore. -21.9% -22.3% -22.9% -26.4% -27.4% -28.9% -30.2% -33.1% Ky. Utah Ark. Mo. Hawaii Idaho Texas Iowa -12.9% -13.5% -14.3% -15.5% -15.7% -16.6% -18.4% -20.4% Ariz. Mont. N.D. +2.9% Colo. Wyo. Alaska Wis. Neb. -0.6% -1.2% -7.9% -9.2% +18.2% -11.8% -12.0% Only Alaska and Nebraska increased their net electricity generation from coal. Note: Excludes Rhode Island, which had no coal energy production. Coal measurements include anthracite, bituminous coal, subbituminous coal, lignite, waste coal, and synthetic coal Source: U.S. Energy Information Administration Percent change in net electricity generation from coal, 2004 to 2015 TOP FIVE DECREASES N.Y. Del. Calif. Conn. Nev. -85.4% -85.9% -86.7% -87.4% -89.6% ONLY ALASKA AND NEBRASKA SAW INCREASES +18.2% Alaska +2.9% Neb. Note: Coal measurements include anthracite, bituminous coal, subbituminous coal, lignite, waste coal, and synthetic coal Source: U.S. Energy Information Administration

Green Technologies Are More Affordable

Median price per watt for distributed solar systems Net solar electricity generation, megawatt-hours 15m $15 CA $10 10m 5 5m $4.1 AZ NV NC 0 0 2000 2005 2010 2015 2000 2005 2010 2015 Note: The system installed price is the upfront cost for photovoltaic solar energy, not including any financial incentives, in 2015 dollars. Energy production includes solar thermal and photovoltaic but excludes rooftops. Sources: Lawrence Berkeley National Laboratory (price); U.S. Energy Information Administration (production) Median price per watt for distributed solar systems $15 $10 5 $4.1 0 2000 2005 2010 2015 Net solar electricity generation, megawatt-hours 15m CA 10m 5m AZ NV NC 0 2000 2005 2010 2015 Note: The system installed price is the upfront cost for photovoltaic solar energy, not including any financial incentives, in 2015 dollars. Energy production includes solar thermal and photovoltaic, but excludes rooftops. Sources: Lawrence Berkeley National Laboratory (price); U.S. Energy Information Administration (production)

Once prohibitively expensive, renewable energy is becoming increasingly affordable, especially in sunnier and windier parts of the country. The price of solar cells, for example, plummeted in recent years, allowing states like California — a role model for climate policy at the state level — to substantially increase investment in that technology.

An analysis by the University of Texas Energy Institute found that for most of the country, natural gas and wind power are the cheapest forms of new energy capacity. But when other factor costs like health, availability of water and government regulations are factored in, solar, wind, nuclear and other greener energies prove even cheaper in some parts of the country. The institute based its findings on 2015 data, and some of those technologies are probably even more cost effective now.

Cheapest source of potential new electricity, by county ...but that changes when considering local rules, conditions, health costs and pollution costs: If counties were looking to add electricity- generating capacity, natural gas and wind turbines would be the cheapest option for many of them... Solar (large arrays or rooftop) Wind Natural gas Coal Nuclear Nuclear Natural gas Wind Natural gas Note: These maps use 2015 estimates for solar panel prices, which have dropped since then. Government subsidies, which lower costs, are not included. Source: University of Texas Energy Institute Cheapest source of potential new electricity, by county If counties were looking to add electricity-generating capacity, natural gas plants and wind turbines would be the cheapest option for many of them... ...But that changes when considering local rules, conditions, health costs and pollution costs: Solar (large arrays or rooftop) Wind Natural gas Nuclear Coal Nuclear Natural gas Wind Natural gas Note: These maps use 2015 estimates for solar panel prices, which have dropped since then. Government subsidies, which lower costs, are not included. Source: University of Texas Energy Institute Cheapest source of potential new electricity, by county If counties were looking to add electricity- generating capacity, natural gas plants and wind turbines would be the cheapest option for many of them... Coal Nuclear Natural gas Wind Natural gas ...but that changes when considering local rules, conditions, health costs and pollution costs: Solar (large arrays or rooftop) Wind Natural gas Nuclear Note: These maps use 2015 estimates for solar panel prices, which have dropped since then. Government subsidies, which lower costs, are not included. Source: University of Texas Energy Institute

It’s clear that Trump’s policies won’t affect the economic calculus states are facing: for many of them, green energy is the better option.

Investing in Green Energy Makes Economic Sense

A standard criticism of climate policy is the supposed negative impact on the economy. Trump cited this among his justifications for leaving the Paris accord.

“The Paris Agreement handicaps the United States’ economy in order to win praise from the very foreign capitals and global activists that have long sought to gain wealth at our country’s expense,” Trump said in his speech from the White House Rose Garden.

But findings from the Sierra Club, an environmental organization, showed clean energy account for more than double the number of jobs from coal, oil and gas combined. The growth is led by California, which has nearly half a million people employed in solar, wind and other clean energy jobs.

Jobs by energy sector, 2016 Clean energy* 2.8m Oil 533.8k Gas 398.2k Coal 160.1k *Includes solar, wind, storage, energy efficiency and smart grid Source: The Department of Energy; The Sierra Club Jobs by energy sector, 2016 Clean energy* 2.8m Oil 533.8k Gas 398.2k Coal 160.1k *Includes solar, wind, storage, energy efficiency and smart grid Source: The Department of Energy; The Sierra Club

At the state level, there’s growing evidence that cutting carbon dioxide emissions can be accomplished while accelerating gross domestic product. The Brookings Institution found more than 30 states have done this in recent years. The process, known as “decoupling,” has also happened in at least 35 countries — including the United States.

While the G.D.P. rose higher in states where CO2 increased, the ability to grow the economy while reducing harmful pollutants is a reality for many states. Trump’s actions, no matter how harmful, can’t stop that progress.