Cities are where more than half the world lives, and where all future population growth will occur. By many estimates, cities are already responsible for more than half of climate change. While Congress remains dysfunctional, cities are rapidly becoming the most interesting and innovative developers and adopters of programs to cut CO2 emissions. They increasingly are taking on the responsibility of achieving deep CO2 emission reductions that virtually all climate scientists tell us we must achieve.

I participated in the recent VERGE day-long City Summit, and was impressed by how much effort and innovation around climate change reduction is occurring in cities. More than 1,000 U.S. mayors, who represent some 60 million Americans, have signed on to the U.S. Conference of Mayors’ Climate Protection Agreement, committing to cut city-wide CO2 emissions below 1990 levels. Houston, Philadelphia and Los Angeles recently launched the Mayors’ Nation Climate Action Agenda (PDF), a joint commitment to an inter-city cap-and-trade program to reduce CO2 emissions by 80 percent by 2050.

For the most part, however, cities have not yet gotten serious about implementing substantial policies to cut CO2 emissions. Following are seven actions cities can and should take in order to reduce emissions by more than half while saving money.

1. Adopt cool roof, green roof and solar harvesting strategies

Half of city surfaces are roads, parking lots, sidewalks or roofs. These generally absorb over 75 percent of the sun’s energy, converting it into heat that increases urban temperature and global warming, both of which increase smog formation and energy bills. The low reflectivity of these surfaces imposes huge unnecessary social and environmental costs.

It is cost-effective today to double the reflectivity of most city roofs and paved areas. Through the work that Capital E is doing with Washington, D.C., the National Housing Trust, the American Institute of Architects and others, we have found that by adopting cool roofs, green roofs and solar PV on roofs, most cities dramatically can improve comfort and health while cutting energy costs.

Cool and green roofs and solar PV should be evaluated on a full costs and benefits basis — including health — to inform policies.

2. Integrate smart-building platforms with existing systems

City agencies commonly have different building energy management systems and a range of often incompatible energy using devices, controls and systems. Buildings — even LEED buildings — can be made to operate better if they are managed through a smart building platform that integrates with all existing systems, including building energy systems, controls and sensors, and uses near real-time data from these systems to optimize energy use and comfort.

A strategy such as ESCO 2.0 features integrated, near real-time, smart energy data, and controls and optimization to actively manage a portfolio of buildings. A recent NRDC study (PDF) of three efficient commercial buildings, including a newly commissioned LEED building, that adopted a smart-building optimization platform called AtSite cut energy use by 8 to 17 percent with almost no new equipment investment.

One advantage of an ESCO 2.0 strategy is that it allows a shift from expensive scheduled maintenance to maintenance triggered by near-real time equipment performance. Another benefit is improved comfort. This kind of open platform also allows virtually unlimited flexibility in adding in new equipment or applications.

3. Enter into long-term agreements to buy new renewable energy

Today a lot of cities, among other building owners, buy short-term (typically two-year) Renewable Energy Credits. These are in essence transferrable, inexpensive accounting claims for the environmental benefits associated with renewable energy. But in reality RECs are almost entirely from projects that are already completed (often many years earlier), and the RECs have little or no impact on driving new renewable energy investments.

To drive new renewable energy investments, cities should skip RECs and instead contract to buy renewable energy on terms long enough to actually allow new project financing. To do so, cities should enter into long-term purchase power agreements with renewable energy power developers to buy clean energy at fixed rates — typically below the rate they are currently paying.

This long-term purchase commitment means revenue certainty for the project developer, enabling equity and debt financing for project construction. Smaller cities can band together to do larger, joint PPAs for renewable energy, in turn bringing down the cost of clean energy.

These PPAs can be executed by almost any city today, would achieve real CO2 reductions and generally would cut the long-term cost of electricity. City government can invite in-city groups, such as schools and hospitals, to participate in city PPAs to enable even larger cost and environmental savings.

4. Insist that cities’ energy efficiency investments be counted in cap-and-trade programs

About half the U.S. population lives in states with cap-and trade programs (including California and members of the Regional Greenhouse Gas Initiative) that place a dollar value on CO2 as a way to encourage investments that cut CO2 emissions. But while large industries, corporations and utilities can participate, cities are excluded from these programs. This makes no sense.

A national initiative called CO2toEE seeks to allow energy efficiency investments by cities and other building owners to receive the value of the CO2 reductions that result from their energy efficiency investments. This initiative has broad and growing support from state and national real estate and energy organizations and NGO groups — and cities should join to push for this common-sense and important design change in carbon trading programs.

The value of the CO2 received by cities would offset a significant part of the capital cost of deeper energy efficiency investments, increasing the funding for deep energy efficiency investments.

By allowing city and building energy efficiency to participate, cap-and-trade markets also would become larger, deeper and more efficient, and would drive large additional investments into energy efficiency. This is essential if cities are to achieve deep reductions in their CO2 emissions.

5. Measure, count and reduce the CO2 embedded in cities’ buildings and roads

Most cities that count their CO2 emissions and invest in reducing CO2 still ignore the enormous volume of CO2 that results from constructing their buildings, roads and other infrastructure.

Cement production is responsible for about 6 percent of the world’s CO2 emissions. A recent review of California’s 500 mile high-speed train found that it would take about a decade of CO2 emissions reductions from rail trips replacing car, truck and plane trips to offset the CO2 emissions from the production of cement required to build the train’s infrastructure. And it can take an energy-efficient building six or eight years of operations to equal the CO2 emissions from the cement used in construction. In fact, the most recent release of the national green building design standard, LEED v4, awards points for reduction of embedded CO2.

What if, instead of generating CO2 emissions, cement sequestered CO2? What if cities measured their embedded CO2, and then used their infrastructure — roads, parking lots, sidewalks and their buildings — to sequester CO2?

6. Invest in new versions of ancient building products that can reduce or sequester CO2 in buildings

Wood sequesters CO2, and the recent development of advanced structural wood products such as cross-laminated timber allow 10 or 20 story buildings to be built of wood.

A much larger CO2 sequestration opportunity is low or negative carbon cement. Cement, first used by Mesopotamians and Romans, is also being reinvented. Cement produces almost a ton of CO2 per ton of cement (cement is made by burning limestone at over 2500 degrees.) Several companies produce low or negative carbon cement.

The most interesting of these companies is Blue Planet, which sequesters flue gas from power plants in cement, sand and aggregate (cement is combined with sand and aggregate to make concrete). Blue Planet can sequester up to 1,500 pounds of CO2 per ton of cement. In its current work at the DOE National Carbon Sequestration Center and in other partnerships, Blue Planet is targeting an 80-percent CO2 reduction from fossil fuel plants, such as natural-gas fired power plants. The process also sequesters other damaging pollutants, such as PM2.5, heavy metals and NOx.

7. Incorporate best-estimate CO2 costs into design and investment decisions

Even in places such as California that have active carbon markets, the market price for carbon is far below its real cost. Because climate change already imposes large costs, cities increasingly want to account for global-warming costs in their investment decisions.

A dozen federal agencies, including the Treasury Department and the Environmental Protection Agency, developed a rigorous cost analysis called the social cost of carbon (PDF). First released in 2010 and updated in 2013, it found the real cost of CO2 to be in the $40/ton range, with additional identified costs not included. Based on a Congressional request, the report and its methodology were extensively reviewed by the General Accounting Office, which a few months ago issued a report that entirely confirmed the social cost of carbon analysis and findings.

A good strategy — recently adopted by the Federal Green Building Advisory Committee which I chair — is to include the social cost of carbon in all construction and energy-related design decisions. In effect it is revenue neutral because it is used just to make better design decisions.

While this will take years to implement in federal agencies, cities can and should move rapidly to adopt this rigorous and conservative cost of carbon in their own design and investment decisions. This would allow better, more cost-effective investment and design decisions that reflect the real cost of climate change. (British Columbia’s adoption of a substantial cost of carbon helped achieve deeper CO2 reductions, lower overall taxes and faster economic growth than other Canadian provinces that did not adopt a carbon price.)

Enabled by organizations such as the Urban Sustainability Directors Network, C40 Cities and the Global Cool City Alliance, cities have become the most promising and important forum to drive deep CO2 reductions. Cities increasingly have the political will to get serious about climate change and to lead their countries to a very low-carbon future consistent with protecting the planet and future generations from the worst of climate change. The clock is ticking.

This article is based on a presentation Nov. 10 at the National Academy of Sciences/Institute of Medicine.

Disclosure: I work with several of the above companies and organizations as a board member/adviser/investor.

Greg Kats serves on the Board of the Global Cool Cities Alliance.

This article was originally posted on November 13, 2014 at GreenBiz.com. (http://www.greenbiz.com/article/7-actions-cities-seriously-address-climate-change)