Countries around the globe have committed to decoupling economic growth and carbon dioxide emissions in an effort to curb the effects of global warming. States, too, have worked to cut emissions while growing their economies, but the degree to which they’ve succeeded in doing so varies greatly.

A new Brookings Institution report compares state’s recent economic growth to changes in carbon emissions. In all, 33 states and the District of Columbia achieved reductions in emissions while expanding their economies between 2000 and 2014. The others saw their emissions continue to rise.

The report comes at a time when federal leadership on the issue is set to experience a dramatic shift. President-elect Donald Trump rejects scientific evidence around global warming, has pledged to pull out of the Paris climate accord and nominated Oklahoma Attorney General Scott Pruitt, a leader in the legal battle against President Obama's climate change policies, to lead the U.S. Environmental Protection Agency. (For more on Pruitt, read this).

Nationally, carbon dioxide emissions have fluctuated in recent years, experiencing the largest declines during the Great Recession.

A dozen states -- many in the Northeast and Mid-Atlantic -- achieved particularly strong reductions in emissions, declining at least 15 percent since 2000. Maine saw its emissions drop 25 percent, the largest decline of any state, followed by Massachusetts and Alaska.

While Maine experienced notably slower economic growth, this wasn’t the case for most states with the largest emissions reductions: Nine of 12 still recorded real GDP gains exceeding 15 percent.

Another 22 states also managed to cut emissions between 2000 and 2014 but did so at a slower rate.

Cutting emissions did not appear to hinder steady economic growth. Over the 14-year period, all but two states -- Michigan and Maine -- recorded real GDP gains exceeding 10 percent.

The Brookings report contends that, given the policy reversal at the federal level, states will play an increasingly important role in combating climate change.

“National decarbonization is a state and local affair,” said Brookings’ Mark Muro, who co-authored the report. “That’s where industries and power plants are and where much of the public policy that affects outcomes resides.”

In 16 states, emissions still continue to climb, with Nebraska and North Dakota experiencing the steepest increases.

A range of factors help shed light on why states have headed in opposite directions.

The single largest driver of emissions reductions, according to Muro, is the shift from coal to natural gas, a result of the recent fracking boom. This is particularly true in the Northeastern states, which are generating more power from natural gas while also importing hydroelectric power from Canada.

Zero-emissions nuclear power plants, while not as prevalent, also played a role in pushing down emissions. In the Northeast, nuclear plants were responsible for 35 percent of electricity generation in 2014, the most of any region, according to Brookings. A slew of Southern states also experienced sizable expansions, such as North Carolina and Tennessee. Thirty-two states currently have at least a limited presence of nuclear power generation.

The study did not find a strong statistical relationship between states’ emissions reductions and use of wind or solar power generation. A select few Western states experienced sizable gains in wind generation. Still, though, the recent growth of renewables has yet to register as having a major effect on emissions nationally.

The industry mix present in each state further explains the extent to which they’ve decoupled emissions from economic growth. States with expanding service industries, rather than manufacturing or agricultural sectors, recorded among the largest corresponding declines in emissions. These included states like Delaware, Georgia, Maine, North Carolina and Virginia.

Despite the recent progress, Muro emphasized that states still have a long way to go in curbing emissions while continuing to grow their economies. To meet the goal of holding global average temperature increases to 2 degrees Celsius, the U.S. would need to achieve an annual decarbonization rate of 4.3 percent until 2030, according to an analysis by PricewaterhouseCoopers. So far, only North Dakota and the District of Columbia have met this benchmark since 2000.

“Going forward, as the coal switchout runs its course, states will need to look very closely at ramping up their renewables as well as considering nuclear,” said Muro. “[Decarbonization] will get harder rather than easier.”

State Decarbonization Rates

Another way to assess decarbonization is to measure carbon intensity, or emissions per dollar of GDP. Brookings computed each state's average annual change in carbon intensity between 2000 and 2014, shown below. For raw changes in carbon dioxide emissions, see the graphic here.