The irony of lunch-bucket-turned-high-tech Pittsburgh hosting a global financial summit scheduled to tackle the daunting challenge of paying for a less carbon intensive energy future is rich on so many levels.

Perhaps nowhere in the world have industrial emissions been reduced and the skies cleared so much as in Pittsburgh, where the G-20 finance ministers will gather Thursday and Friday.

But know, too, that because carbon dioxide -- unlike some other greenhouse gases -- stays in the atmosphere so long, a component of the climate change problem billowed from Henry Clay Frick's coke ovens and Andrew Carnegie's steel mills.

The region's transformative changes during the last 50 years did not come easily or cheaply in either human or financial terms. And the changes that will be required to mitigate greenhouse gas emissions and address climate change on a global scale over the next 50 years promise to be even greater.

Maybe the Pittsburgh setting will provide context for taking the bold action that a scientific consensus says is necessary now. Certainly the region's rich environmental history gives leaders of current greening efforts a unique perspective on what can and should be done to make the massive and expensive transitions needed to address climate change.

Here are some thoughts about what they envision as the important next steps needed to address climate change locally, nationally or internationally:

Teresa Heinz, chair, Heinz Endowments, Heinz Family Philanthropies, said Pittsburgh is the perfect G-20 host city because the promises and realities of cooperatively embarking on a green, sustainable recovery will be all around them.

"One of the best ways we can address the threats of global climate change is to expand the innovation we've seen here across the country, investing in green technology, alternative energy and green chemistry that will create jobs, strengthen our infrastructure and power our nation through domestic sources that can develop right here at home. It's an optimistic reality that proves it's not a choice between the environment or jobs. Quite the contrary, the environment is jobs.

"For our efforts to combat climate change to be truly successful, however, we will need to forge binding agreements between regions, states and countries that control harmful emissions and hold each other to account as one region's activities and efforts now directly impact, or undermine, another's.

"Pittsburgh, even on its best days, has trouble with air quality compliance, not because of its own doing, but because of what its neighbors are doing. Pittsburgh stands as a powerful example of what we're all capable of and I hope the G-20 leaders can take something valuable home from our experience."

Jared L. Cohon, Carnegie Mellon University president, said Pittsburgh should make research and development of clean coal technologies the highest priority because despite its emissions problems the world will continue to rely on it while alternative energy sources are developed.

"If we, as a major center of coal production, want coal to be part of the longterm fuel mix for electricity generation, and if we care about the interim impacts, we must have a sense of urgency about developing ways to capture and store carbon generated from coal. Carnegie Mellon scientists and engineers are working on just these issues in collaboration with colleagues at the University of Pittsburgh, West Virginia University and the National Energy Technology Laboratory.

"With this kind of cooperative effort expanded in scope and participants, Pittsburgh and our region can make a very important contribution to reducing coal's impact on climate and the environment."

"For too long, the world has played a game of, 'I'll limit my emissions of carbon dioxide, if you'll limit yours.' It is time to lead by example and get the rest of the world to follow -- either because they get embarrassed or because we won't trade with them again until they do."

Kathleen McGinty, former state Department of Environmental Protection secretary, environmental official in the Clinton administration and advisor with Pittsburgh solar technology firm Plextronics Inc., said tackling climate change will take a mix of old and new technologies plus the old-fashioned work ethic Pittsburgh is known for.

"Solving the climate crisis isn't about some wondrous new technology or impossible to imagine inventions. It is about building and installing efficient boilers and ballasts and buildings. It is about bolting solar panels on roofs and hanging them on street lamps and utility poles. It is about steel towers in the ground with wind turbines on top. It is about cars charged with the new "lead carbon" super-batteries being made right here at home, right now. And it is about capturing carbon from our coal plants and using it to enrich the soil, even as we stop it from polluting the air.

"In other words, winning the battle against climate change is about the very things that the people of Pittsburgh are very good at and where the Pittsburgh area is second to none: Pittsburgh has abundant raw energy resources. Pittsburgh has the basic industries and the skill sets needed in steel and glass and aluminum. Pittsburgh has more green buildings than nearly any city in the country. And the region is now home to some of the most promising solar, wind, biofuel, clean coal, battery and efficient window companies anywhere. When it comes to solving the climate crisis, the people of Pittsburgh have all the right stuff."

Larry Schweiger, president of the National Wildlife Federation, former executive director of the Western Pennsylvania Conservancy and author of a new book, "Last Chance," about the impact of climate changes on life and wildlife on Earth, said the G-20 must provide focus to a world on the edge of catastrophic climate change.

"First, I hope they reach a collective commitment on strong reduction targets for carbon dioxide proportional to their emissions. I think that type of commitment will be much easier to get with 20 nations in the room than at Copenhagen where there will be 100 nations.

"Second, we need to make available technology to help developing nations adapt to changes in sea level, storms, desertification and displaced populations that climate change will cause, helping them skip over old 20th century technologies in favor of better environmental technologies, including solar. And third we need to help make on the ground adaptations to protect people, including moving them back from oceans and waterways, before there is a crisis situation.

"The U.S. needs to do more because it caused much of the problem. We cannot walk away from that responsibility because it will not put us in the right place."

M. Granger Morgan, head of the Department of Engineering and Public Policy at Carnegie Mellon University where he directs the Center for Climate Decision Making, said local research leadership can translate into job and economic benefits if leaders act boldly.

"To stop climate change, by mid-century the world must reduce its emissions roughly 80 percent. Doing that's going to take everything we've got: more efficient use of energy, coal plants that capture their carbon dioxide and safely put it a mile underground, more wind and nuclear plants, and plug-electric hybrid vehicles that get their power from the U.S., not the Middle East.

"Pittsburgh has a great start on most of these activities. We have many new energy efficient green buildings -- but we need to figure out how to make our older buildings, and the appliances in them, use less energy.

"Our National Energy Technology Lab, located in the South Hills, leads the world in research on carbon capture and sequestration (CCS) -- but we need to build some CCS plants here. We have several wind farms just to our east but we need more, and our universities need to come up with affordable ways to add large amounts of variable wind into out power system without causing blackouts.

"Westinghouse Electric, in our eastern suburbs, is building safe and modern nuclear power plants all over the world. We need to build some here.

"Toyota is supporting research at Carnegie Mellon on hybrid cars, including cars that drive most of the time on electricity. We need to replace more of our gas guzzling clunkers with cars like the Prius. In about a year, Chevrolet will release the Volt, its new plug hybrid. Pittsburgh's Chevy dealers should start planning now to make our region the sales leader in the nation.

"There are no "silver bullets" -- no single technology or strategy that will solve the problem of climate change. Meeting that challenge will take everything we've got -- and in the process create many new jobs.

"If we lead, the rest of the world will follow. If we sit on our hands and wait for others, our grandchildren will not thank us!"

Matthew Mehalik, Sustainable Pittsburgh program manager, said climate change is a complex issue that the region's Business Climate Coalition is working on from a sustainable perspective that does not disadvantage local industries.

"We want to be on the right side of history when we approach climate change and we have to factor climate issues into our regional planning process. But it's complex. The cost of transitioning away from fossil fuels is great but we can't continue to rely on coal. On the other hand, we need to take advantage of our wealth. I have the feeling that the G-20 may try to reduce a complex situation to good guys and bad guys, but these companies recognize they need to start changing their business model.

"There is also a need to keep shining a light on business operations to motivate change."

Joel A. Tarr, the Caliguiri University Professor of History and Policy at Carnegie Mellon University and author of "Devastation and Renewal," an environmental history of Pittsburgh and its region, said leadership and some calculated risk taking is needed and, if history is any guide, change won't come easily.

"Pittsburgh has accomplished major environmental improvements in the past half-century but does this history provide any clues to strategies that might be followed in order to achieve future goals? Critical to their accomplishment was political and private leadership willing to take risks, unafraid of challenging powerful vested interests, and allied with citizens groups.

"This leadership must be willing to challenge the status quo and to educate the public to their real interests in regard to health and the environment in order to achieve significant environmental goals."

Patricia M. DeMarco, Rachel Carson Homestead Association executive director, said climate change solutions must be found in how we produce energy and also in how we limit its use.

"We waste two thirds of the fuel we burn through inefficiencies in the conversion process, and inefficiencies at the point of use. We need to re-think our approach to using energy to perform necessary work. Finding least energy use solutions for space conditioning in buildings, moving people, and goods, communications, and industrial processes has received very little applied research attention.

"The most important way Pittsburgh can contribute to climate change remedies is to apply the significant concentration of academic and industrial capability to the problem of reducing the use of fossil fuels through demand improvements. Distributed power based on renewable resources, building designs that require almost no externally supplied energy, community designs around mass transit and pedestrian convenience all can dramatically reduce our fossil fuel use.

"The benefits of moving to a post-fossil fuel economy include the potential for large health improvements. One in four Americans suffer from asthma and chronic allergies, one in 150 children are born with autism syndrome. Both have been linked to particulate and chemical contaminant emissions from fossil fuel combustion in vehicles and power plants. We need to count the health cost of fossil fuel extraction and combustion in the avoided cost for converting to renewable and sustainable energy systems."

"Rachel Carson's environmental ethic provides four principles to guide our path to a sustainable future: live in harmony with nature; preserve and learn from natural places; minimize the impact of synthetic chemicals on the natural systems of the world; and consider the implications of human actions on the global web of life.

"We have issued a Rachel Carson Legacy Challenge asking people, institutions, governments and businesses to make permanent, measurable changes in their lifestyle consistent with Rachel Carson's principles. We ask everyone to take at least one specific step to move toward a more responsible and less wasteful pattern of resource consumption.

"Overcoming the inertia to change is difficult. Once we begin to move together toward a pattern of sustainability and a value system that seeks to use a minimum of resources for all of our needs, each subsequent step becomes easier.

John Hanger, DEP secretary and former president and chief executive officer of Citizens for Pennsylvania's Future, said Pennsylvania, which emits about 1 percent of the world's heat-trapping gases, has a big role as the climate change drama plays out.

"Though our economy has grown greatly since 1960 and we have added more than 1 million people to our population, our emissions have not increased much at all over the last 50 years. Why? Cars today get about twice as many miles per gallon as those on the road 50 years ago. New appliances and buildings today are much more energy efficient than 50 years ago. About a half of our electricity generation now comes from zero carbon technologies like nuclear, wind, solar, biomass, as well as natural gas that emits less carbon than other fossil fuels when 50 years ago all of our electricity came from burning coal and oil.

"To continue this progress, we must use both law and markets. Laws like building codes and vehicle mileage standards must boost energy efficiency as well as low-carbon fuels and electricity; competitive markets must operate to produce efficiently cleaner appliances, electricity, vehicles; and public-private partnerships must develop new and better technologies like carbon capture and storage for coal plants."

Scott Van de Mark, director of special projects for the Pennsylvania Environmental Council, is working with Allegheny County to help reduce its global warming emissions footprint.

"From a local and regional standpoint, the most cost-effective and direct way for homeowners, businesses and governments to reduce their carbon footprint is to improve the energy efficiency of our homes, businesses and government buildings. With an older building stock in a colder climate in the Pittsburgh region, there are multiple opportunities to retrofit buildings and reduce energy usage and cost by upgrading insulation, replacing light bulbs or choosing to construct new facilities or renovate existing facilities in accordance with the LEED green building certification program.

"The Pennsylvania Environmental Council is honored to be assisting Allegheny County with the development of a greenhouse gas emissions inventory for county-owned and operated facilities and vehicle fleets. The inventory will be followed by a set of recommended actions for the county to reduce its greenhouse gas emissions including several cost-effective actions to improve the efficiency of heating, cooling and lighting county facilities. This effort follows and benefits from the City of Pittsburgh Greenhouse Gas Emissions Inventory issued in 2006 and the Pittsburgh Climate Action Plan issued in 2008."

Devra L. Davis, former director of the Center for Environmental Oncology at the University of Pittsburgh Cancer Institute, professor of epidemiology at Pitt's Graduate School of Public Health and author of many books, including "When Smoke Ran Like Water," an account of the 1948 Donora disaster, said Pittsburgh has transformed itself and the world can, too.

"Once one of the most polluted zones on the planet, the Pittsburgh region has turned its former moniker as 'hell with the lid off' into a force synonymous with major environmental awareness and green policy. . .

"Like the steel and coke produced in massive quantities for the first half of the last century and like the hard-charging athletes who are regularly cheered on by legions of die-hard fans, the town still has a tough edge to it.

"But, today the kind folks of this great region are steeped in the promise of the future, justly proud of the symphony and other major artistic accomplishments, and still struggling with the need to balance the freedom to study a problem with the duty to do something about it."