This article is adapted from Mark Schapiro’s recently published book, Carbon Shock: A Tale of Risk and Calculus From the Front Lines of the Disrupted Global Economy (Chelsea Green).

The Allegheny River pulses through the city of Pittsburgh, Pennsylvania, like a muscle. Along its waters traveled the steel that became the backbone to our railroads and skyscrapers, and the coal that fired up the factories fueling America’s twentieth-century industrial might.

In the 1980s and early ’90s, however, the steel started leaving. Today, some two decades after the flight of the last mill, the Allegheny has been transformed into a new kind of symbol—one of the modern “green” city. The river has been cleansed of many of the most toxic substances that formerly poured from those factories; now its meandering flow is featured in municipal sites against a glittering downtown skyline that hosts one of the highest concentrations of green buildings in the United States.

From green skyscrapers to a new “greenwalk” that snakes along the river, Pittsburgh has been attacking its polluting gases as if its survival depends on it—and it does. The city and surrounding communities once produced a significant portion of the steel in the United States. After the industry bottomed out, a coalition of businesspeople, city planners and environmental engineers staked out a development plan that positioned Pittsburgh as a hub of innovation in ecologically oriented design.

Today, the skyscraper windows are angled to maximize natural light, heat is piped in from thermal pools deep underground, and solar panels line the roofs far above the bustling sidewalks. The city has a full-time sustainability manager charged with shifting its energy sources away from fossil fuels by means of mass transit, urban planning, and municipal procurement policies that place a value on low-carbon alternatives. The city’s water-treatment system is considered a model even for other eco-conscious cities like San Francisco. Major property developers agreed to halve their 2003 carbon footprints by 2050; the city now has the highest concentration of LEED-certified buildings in the country.

The city’s transformation has been so complete that the G-20—the body representing developed countries, many of which have experienced similar declines in manufacturing—held its yearly conference there in 2009 and highlighted the city’s green strategy as a model for the postindustrial way forward. Pittsburgh is now one of the greenest of the midsize cities in America—a designation that would have been unthinkable even a decade ago.

“Back then, in the ’50s and into the ’80s, no one was thinking about climate change, and no one was asking about emissions of carbon dioxide,” says Aurora Sharrard, who served as the director of innovation for the Pittsburgh Climate Initiative, a collaboration among the business, municipal and scientific communities to devise emission-reduction strategies. From 1900 to 1970, the area experienced a steady annual increase in its industrial greenhouse-gas emissions, from 14 million tons to more than 30 million tons. But as industries fled the area, greenhouse-gas emissions dropped sharply—declining by at least 40 percent throughout the area from 1970 to 2000—and have continued on a downward trajectory.

By 2008, Pittsburgh’s emissions had declined to about 6.8 million tons. By 2013, the city was on the way toward its goal of reducing emissions 20 percent from 2003 levels, and it aims for progressively steeper declines over the decades to follow. In a country that is reliant on local improvisation to tackle the problem, with few legal guidelines from the federal government, Pittsburgh is considered among the leading urban climate innovators. It lost its manufacturing base and refashioned itself as a city far more reliant on brains than brawn.

But whatever happened to all those greenhouse gases that once came spewing from Pittsburgh?

They did not disappear.

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Welcome to Guangzhou, a city of over 15 million on China’s southeast coast. The freighters that come into the port here, and the two other ports servicing Guangdong province, are loaded with a container approximately every second—all carrying goods made in China to the United States, Europe and elsewhere around the world. Industrial clusters throughout the province are home to more than 1,000 steel manufacturing and trading companies. They produce skyscraper girders, auto parts, appliances, ships, refrigerators and even American bridges—steel products that were once made in Pittsburgh and other Midwestern cities during America’s century of industrial dominance.

Guangdong is also, in the United Nations’ estimation, one of the top ten carbon-emitting provinces in a country that is itself the leading emitter. Some 8,000 miles from Pittsburgh, the CO2 that used to come from that city now fumes into the atmosphere from Guangzhou. It wasn’t just Pittsburgh’s manufacturing jobs that migrated to China; the greenhouse gases associated with them went, too.

Today, the residents of this churning industrial center of China have a per capita annual footprint of 7.8 tons—quite a bit more than the average Pittsburgher. But there’s a story hidden in those numbers. Only 6 percent of Pittsburgh’s emissions, according to that city’s Climate Inventory, come from industrial sources. Yet emissions produced by the Chinese industrial sector account for 56 percent of the total—almost ten times higher, as a percentage, than those of Pittsburgh.

The huge discrepancy between the industrial emissions of Pittsburgh and those of Guangzhou, which started trading places in the 1980s, suggests that what has changed significantly is not so much the lifestyle choices of the people of Pittsburgh, but rather the region’s entire economic support system, based as it was on greenhouse-gas-intensive manufacturing.

In turn, what the Chinese numbers tell us is that legions of urban residents there have a far smaller personal footprint as a percentage of the overall total than do their Pittsburgh counterparts. As Chinese consumption grows, that footprint will grow—but at this stage and for some time to come, it is production, not consumption, that accounts for the overwhelming bulk of Chinese emissions. Indeed, as much as 60 percent of China’s exports are manufactured by China-based affiliates of multinational corporations, many of them American and European. The Chinese, in short, are producing greenhouse gases on our behalf.

China was responsible for about 10 percent of the world’s greenhouse-gas emissions in 1990; by 2013, its global contribution was more like 30 percent. But greenhouse gases end up in the same atmosphere wherever they are generated. Does it matter where they come from? On one level, it does not. But on another, more fundamental level—the level at which we decide who is responsible for reducing those emissions—it matters quite significantly.

Climate scientists say that to avoid a potentially catastrophic rise of 4°C by 2050, each of us should ideally be emitting no more than two tons of greenhouse gases annually. Consider this finding from the Carnegie Institution for Science at Stanford University: Americans’ per capita footprint would jump by 2.4 tons annually if their consumption—mostly of goods made in China—is taken into account.

Globalization has flipped the calculus on the central question of who is accountable for greenhouse-gas emissions. Richard Feldon headed up a team working with the International Council for Local Environmental Initiatives to devise a set of 2012 protocols for American cities seeking to limit their emissions. He told me that including consumption in their calculations was one of the most controversial issues they faced. That’s because it blurs the line between our contribution as consumers and industry’s contribution as producers, and gives a new way to understand our “greenest” of green cities.

“Let’s say Pittsburgh still had its industrial base, and that steel from Pittsburgh was being used in a city like San Francisco,” Feldon explained. “Well, it would be unfair to say that San Francisco, under that scenario, is a greener city than Pittsburgh.” The same equation, he said, applies to Pittsburgh and Guangzhou—or the United States and Europe, jointly the world’s biggest consumers, and China, its biggest producer. This also means that when you do the numbers, the United States trades places with China to become the world’s worst emitter of greenhouse gases.

Most of us are urban dwellers—70 percent of the world’s population will be by 2020—so reducing those emissions, city by city, is one of the fundamental challenges the world faces in devising a new energy system that keeps greenhouse gases to at least livable levels. Just because emissions aren’t happening in our backyard doesn’t mean that they’re not ours—a reality that at least one of the world’s cities is facing head-on.

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Welcome to Manchester, birthplace of the Industrial Revolution. This city in the northwest of England was at the center of Britain’s industrial rise and has experienced a trajectory similar to Pittsburgh’s ever since. Like Pittsburgh, Manchester has dropped from being one of Britain’s leading greenhouse- gas emitters to a center for high-tech innovation, and it is now host to a cluster of leading universities conducting cutting-edge research into renewable energy.

The legacies of both cities are deeply interwoven with the evolution of greenhouse gases and their contribution to climate change. Pittsburgh was the center of American steel; Manchester, for its part, was home to the world’s first steam-driven factory, which of course was reliant on coal. In the eighteenth century, that coal-fired energy was put into the service of processing the vast amounts of cotton that Britain was obtaining from its colonies in Asia and North Africa. Indeed, one can see Manchester as having assumed the industrial greenhouse-gas contribution on behalf of the British colonies, which were expected only to send raw materials to the mother country for processing and manufacture. By 1850, Manchester was widely considered a model of the modern industrial city. “From this foul drain,” wrote Alexis de Tocqueville of his visit to the city, “the greatest form of human industry flows out to fertilize the whole world. From this filthy sewer pure gold flows.”

As with other imperial cycles, Manchester’s dominion came home to roost. The textile companies disappeared—many of them relocated to India and China—and by the 1990s, the city had skyrocketing unemployment. Practically an entire generation of workers in Manchester was compelled either to leave the city or live on the dole. Their greenhouse gases went with them.

Then, in 1996, in the center of downtown Manchester, the Irish Republican Army set off one of the most powerful bombs in the history of its conflict with Britain. More than 200 people were injured, and the neighborhood around the City Hall devastated. And it was then, according to Sarah Davies, the person in charge of environment strategies for the Greater Manchester Combined Authority, that the city was compelled to decide how it wanted to rebuild itself.

Davies told me there was a “shift in the mindset” of the city’s traumatized leaders, who met as the world prepared for negotiations over what would become the Kyoto Protocol. Manchester would return to its role as a center for technological innovation, but this time that innovation would serve the emerging vision of a new low-carbon economy. “There’s the sense,” Davies added, “that we created the energy-hungry economy, and now we have some responsibility for finding our way out of it.”

* * *

Pittsburgh’s and Manchester’s industrial histories may be similar, but the way that the two cities deal with their greenhouse-gas accounting is not. The divergence can be seen in their official climate strategies. According to the Pittsburgh Climate Initiative, “Emissions resulting from many personal and business-related activities and decisions that might be evaluated in an individual, carbon-footprint-style inventory are excluded from a city-level GHG inventory approach.” In other words, the city isn’t counting the carbon embodied in the goods and services its residents consume or generated by their travel.

By contrast, the plan published by the Manchester City Council calls for counting and reducing emissions produced by city residents “wherever those emissions take place.” This includes the energy needed in the growth and transport of food; the extraction and processing of oil used by automobiles and factories; the emissions generated through the manufacture of electrical devices; and estimates of aviation emissions by residents flying out of town. Taking these consumption-based emissions into consideration adds roughly 30 percent to each citizen’s carbon contribution to the atmosphere—for a total of some 15.7 tons per person, according to a 2011 estimate.

The Greater Manchester Combined Authority, representing some 3 million people in the city and surrounding communities, launched an initiative to reduce the city’s footprint not only at home, but also along the global supply chain. Its room to maneuver is limited, of course, but its procurement policies now favor imported goods with lower greenhouse-gas impacts than their competitors, and the city has embarked on an effort to educate employers and homeowners on precisely why purchasing goods closer to home, and reducing energy use, is good for the city’s economy as well as for the planet.

Davies, whose office sponsors the Carbon Literacy Project, identified a central principle of that effort—providing a motive beyond some vague sense of well-being. “You have to ask, ‘What is it that people want?’ They want to earn more, pay less, have a decent quality of life—that’s what people aspire to. So carbon literacy must be put through these channels. They need to see prosperity as ‘green.’” Manchester is trying to make saving carbon desirable: the city’s long-term goal is to reduce emissions by 41 percent from 2005 levels—a goal that Davies argues makes economic and environmental sense. “Having this target makes us more attractive to investors,” she explains. Siemens has established a green-technology center in Manchester, as have many other European and Japanese firms; and textile companies are being lured back to the city from India and China, attracted by the new fuel-efficient ink-and-dye technologies developed with the assistance of city subsidies to the university. This provides a double bonus: creating jobs and seriously decreasing the money spent on greenhouse-gas-intensive transportation. Between 2007 and ‘12, the city created 37,000 new jobs in its evolving green economy, representing $7.5 billion passing through Manchester that otherwise would have gone elsewhere. The Greater Manchester economy grew 4 percent in 2012, fed largely by the infusion of green investments, Davies says, at a time when growth in the rest of the United Kingdom was flat.

In this way, consumption-based greenhouse-gas accounting prompts a fundamental change in our understanding of globalization. “You cannot decouple production from consumption,” says Cindy Isenhour, an associate professor at the University of Maine, who has conducted extensive research on a variety of environmental issues. Yet far too many governments insist on doing just that: the Center for International Climate and Environmental Research in Oslo concluded that virtually every developed country on the planet—including the United States—has underestimated its emissions by about 25 percent by failing to include increased consumption.

“We’re talking about changing habits and lifestyles,” says Alice Bows, a researcher at the University of Manchester’s Sustainable Consumption Institute. “People think they have a choice…. But choice is always constrained—limited by circumstances, financial and other realities. So we need to alter the concept, the circle of possibilities, included in ‘choice.’”

And so this tale of three cities brings us back to the most discomfiting realization of all. If you follow the many circuits of production, or the trail of greenhouse gases rising into the atmosphere, you will ultimately alight upon each of us, making our own individual choices about what to consume and from where. Thus, at what stage we act—at the point of production, or the point of consumption—will be a matter of how directly we face our contributions to climate change.

The outsourcing of emissions presents a challenge akin to the outsourcing of gruesome labor conditions. Pittsburgh and Manchester are signatories to a commitment that includes more than 300 cities around the world, all of which have agreed to seriously reduce their greenhouse-gas contributions. Both Pittsburgh and Manchester are largely unheralded leaders among the world’s cities in facing up to the challenges of climate change. Manchester, however, is at the forefront in attempting to account accurately for its outsourced emissions—a forward-looking approach to what is bound to become an increasingly volatile question as individual jurisdictions (cities, states, regions and whole nations) are left to improvise in the absence of a global climate accord.

Of course, local and national governments are limited in the influence they can have over the production practices in other countries. The means of regulating greenhouse gases, to the extent that they’re regulated at all, remain entrenched in traditional ideas of national sovereignty and jurisdiction. But just as climate change is altering the fundamental conditions here on earth, it is also altering our sense of the limits to those traditional notions. Manchester’s approach suggests a way for cities to wrestle with their emissions while addressing underlying inequities in the fight to stave off climate disaster.