In 2012, fresh off his win in the presidential race, Barack Obama started talking about climate change. Just not in the way his base wanted.

“If the message is somehow we’re going to ignore jobs and growth simply to address climate change, I don’t think anybody is going to go for that. I won’t go for that,” he said in his first press conference after the election.

Obama was slammed by the left for his “lame” comments implying that economic growth and climate action are mutually exclusive. (This was before John Podesta joined the White House and made climate a top-tier issue for the president.)

Although very few people realized it, by that point America had proven that cutting carbon emissions didn’t have to come at the expense of economic output. In 2006, 2010, 2011 and 2012, the U.S. grew its GDP while also reducing carbon emissions. It happened again in 2015. This year will be the same. 

From 2000 to 2015, America’s national GDP grew by 30 percent while emissions declined 10 percent.

Meanwhile, carbon emissions are flattening globally

The reasons are complex and often contested. But it’s clear that a combination of economic restructuring (good and bad), consumer behavior, and fuel switching in the energy and industrial sectors is responsible.

According to a new analysis from the Brookings Institution, 33 U.S. states have now decoupled their emissions from economic growth. And the trend is only strengthening.

From 2000 and 2014, 33 states plus the District of Columbia increased GDP while lowering carbon pollution. Collectively, these states dropped emissions by 12 percent and grew their economies by 22 percent. 

As more studies show that dozens of countries around the world are separating growth from emissions, the Brookings experts wanted to “look under the hood” to see what is driving the trend locally within the U.S. 

“Emissions decoupling has clearly become more frequent amid the ongoing large-scale switch from coal to natural gas -- driven by the hydraulic fracturing (“fracking”) boom. At the same time, numerous other factors are clearly influencing outcomes, ranging from changes in the structure and growth of the national economy to investment decisions and technology change to land-use change and the availability of clean new energy resources, including renewables,” wrote Devashree Saha and Mark Muro, co-authors of the report. 

Their findings bring “license for a modest degree of optimism,” said Saha, a senior policy associate with Brookings and lead author of the report, in an interview.

“Changes are already underway -- and market forces may actually be more important at this juncture,” she said.

By market forces, she specifically meant natural-gas fuel switching. According to the research, 60 percent of all carbon reductions in the states came from natural gas -- either from retrofitting coal plants to burn gas, or an increase in consumption within the industrial sector. (A 2013 study from CO2 Scorecard suggested that efficiency accounted for two-thirds of the drop in carbon emissions nationwide in 2012, but the study was an outlier.)

“It’s impossible to overestimate the impact of coal replacement,” said Muro, a senior fellow at Brookings, in an interview.

The upside: We’re burning much less coal. That’s good for public health.

The downside: We don’t know how much this is increasing emissions of methane, a greenhouse gas 25 times more effective at trapping heat than carbon dioxide.

The shift to a service economy is also playing a role. And this is also an economic mixed bag.

“In fact, almost all of the states that experienced the largest shift toward services industries also registered large declines in their carbon emissions during 2000-2014. For example, as Maine’s service sector’s share of real GDP (in millions of chained 2009 dollars) expanded from 75 percent in 2000 to 83 percent in 2014, its carbon emissions declined by 25 percent. Similarly, Delaware, Georgia, North Carolina and Virginia all experienced some of the largest relative expansions of their service sectors among states and likewise achieved substantial carbon emissions declines of 20 percent, 17 percent, 15 percent and 15 percent, respectively,” wrote Saha and Muro.

The upside: America’s service-sector shift will continue to lower emissions intensity.

The downside: Almost every service-sector job -- from cashier to truck driver -- is under threat from automation and artificial intelligence. The steady march of technological progress will help states decarbonize while improving output, but that may spell doom for yet another class of workers.

So where are renewables in all of this? They’re playing a surprisingly small role so far. 

Saha and Muro explain more in the study: “Wind and solar generation have yet to register as broad an impact on decoupling as might be expected -- even in the green West. In this regard, while solar and wind’s share of electricity generation has been on the rise, [their] large-scale growth in some states dates only to the last decade, and so this analysis does not find a strong statistical relationship between states’ emissions reductions and solar and wind’s share of power generation.”

Even with such extraordinary growth rates, solar is still a tiny fraction of most states’ electricity generation mix. And in Midwestern states with a lot of wind installed, coal power is still a dominant source of electricity -- making decarbonization harder. 

“Renewables are becoming more visible though. The question is where more decarbonization is going to come from -- and renewables will come into the foreground then,” said Muro in an interview.

Assuming that America doesn’t ditch the Paris climate deal under President Trump, it will need to do more to lower emissions. The country is currently on pace to drop carbon emissions by 2.1 percent a year -- but it will need to achieve a rate of 3.5 percent a year to meet international targets. There are 20 states that haven’t even hit the 2 percent decarbonization rate. 

This research started long before Donald Trump won the presidency. In the weeks since the election, federal energy policy has been thrown into uncertainty -- and it appears that Obama’s signature climate plan will be dismantled

The possibility of federal policy chaos troubles Saha and Muro. But their findings do bring some hopeful signs for the coming years.

“Local factors (not just federal ones) matter a lot to how this happens. Moreover, the trends depicted here suggest that while federal policy reversals could be traumatic, progress on decarbonizing the nation’s economy will likely continue regardless of Donald Trump, driven by technology advances, market dynamics, and state policy.”

In other words: Our next president does matter, but the trend toward decarbonization will likely happen with or without his explicit support.