The 3% Solution

When it comes to keeping climate change at bay, we have our work cut out for us. Scientists can more or less pinpoint the atmospheric concentration of carbon dioxide beyond which some of the most dreaded worst-case scenarios start to become inevitable. The best estimate is 450 parts per million (ppm): if we can keep below that, we should be able to avoid irreversible changes such as the melting of Greenland’s ice sheet and parts of Antarctica—changes that would raise sea levels by more than 20 feet.

The bad news is that 450 ppm is not far from the current concentrations of 383 ppm. CO2 continues to rise because we are burning fossil fuels faster than the oceans, forests, and soils can remove them, and because of the century-long half-life of CO2 in the atmosphere. To keep concentrations to 450 ppm, we must reduce emissions 80 percent by 2050.

But if that sounds daunting—if such numbers seem to imply draconian belt-tightening, an end to modern conveniences, and a major restructuring of the economy—there is also good news. We could come close to our goal if every year we’d cut our carbon emissions by just three percent. We’d be at the 50 percent mark in 23 years and the 75 percent mark in 47 years. We’d attain our 80 percent reduction after 53 years.

I call this the Three Percent Solution to Climate Change, and we could implement it without forgoing the amenities we all value: fast transportation, electronics and entertainment, comfortable living spaces, good lighting, and refrigerated food and drink. We wouldn’t have to spend staggering sums, either. As our old, inefficient power plants, vehicles, buildings, and appliances wore out, we’d simply replace them with counterparts that produce fewer emissions.

Some estimates suggest that because the first 15 to 20 percent of changes could actually save money, we might achieve half of the total reductions required at no net economic cost. Beyond that, costs would depend on how rapidly technologies evolve and what kinds of policies we adopt—but estimates put the price tag at about one percent of gross domestic product.

In the next few pages, I’m going to outline some options for achieving three percent emissions reductions in each of three energy-intensive spheres of life: buildings, transportation, and the goods we purchase. I don’t claim that each proposed step will bring about a cut of precisely three percent. But in the aggregate, if broadly adopted over the long haul, these measures will ensure that we’re moving in the right direction, and at the right speed.

Buildings Let’s start with buildings—both because the heating, cooling, and lighting systems and appliances in them result in lots of CO2 emissions, and because buildings are where the most cost-effective emissions reductions can be achieved. The Intergovernmental Panel on Climate Change, of which I am a member, and McKinsey & Company (in its report titled “Reducing U.S. Greenhouse Gas Emissions: How Much at What Cost?”) have identified dozens of ways to improve the energy performance of buildings, often with payback times of months to a few years. Here are a few:

First, stop wasting electricity. Energy use can occupy a nearly twofold range in identical housing units, depending on how careful people are. Many air conditioners are highly inefficient, improperly sized, and set set to bone-chilling levels below 72 degrees Fahrenheit. Adjustments can bring savings of 10 to 50 percent. Better management of home heating can also save 10 percent or more.

Energy Star homes—those built or converted to meet the Environmental Protection Agency’s efficiency guidelines—lower energy use by at least 30 percent compared with structures that are merely built to code, and they do so at no additional cost. Some new homes and offices consume 80 to 90 percent less energy than code-built structures, thanks to such features as thicker walls with vapor barriers and more insulation, south-facing windows, and tight, highly efficient doors.

Adding insulation and weather stripping to existing houses can cut heating and cooling demand by 25 to 75 percent. Tight-fitting windows and doors can also save energy, but at a higher cost.

Replacing aging heating systems with modern furnaces that are 90 percent efficient or better can lower emissions by 20 to 35 percent. And new furnaces that generate both heat and electricity can cut emissions by more than half while providing both winter comfort and a significant fraction of your electricity. Ground-source heat pumps that extract stored solar energy from 6 to 100 feet underground can bring major reductions in emissions as well, although installing them can be expensive.

The proper orientation of buildings so that more than half of the window area is on the south side (in the northern hemisphere), with a decent roof overhang for summer shading, can reduce energy for heating, cooling, and lighting by 25 percent or more.

Lighting is the place where we can meet the 2050 emissions goal right away. Incandescent light bulbs will be banned in the United States starting in 2012, to be replaced with lamps that are 70 percent more efficient. The new generation of compact fluorescent lamps meets that standard, using only a quarter to a fifth the electricity of incandescents. Granted, the purchase price is higher, but they last six to ten times as long and save $100 over the life of the lamp. A shift to compact fluorescents now will immediately reduce emissions from your total electricity consumption by more than 10 percent.

Appliances are the energy hogs in buildings. Replacing a pre-1993 refrigerator with a new Energy Star model will cut electricity in half, as long as you properly dispose of the older fridge. (If instead you follow the time-honored custom of using it to store large amounts of beverages that won’t fit in your new fridge, your emissions will go up by half, not down.) Avoiding accessories such as icemakers, through-door water dispensers, and less efficient side-by-side freezer-fridge options can cut emissions even more.

Horizontal-spin washers can use just one-third the electricity and water that a top-loading machine uses, and dishwashers vary by a factor of three in energy efficiency. Compare the energy tags and avoid energy-consuming “feature creep.”

Plasma screen TVs are notorious energy consumers compared with LCD screens. Also, check the amount of electricity used while the unit is turned off. Some LCD units use less than 0.1 watt, while others use much more.

Once buildings have been made super-efficient, they can be powered at least in part with solar electricity from the roofs or walls. Wind or geothermal energy might also supply electricity. This is expensive, but it will bring you immediately to zero emissions, and, at current electricity prices, payback can be expected in about 10 to 25 years. For homeowners, the most cost-effective way to tap solar energy is to invest in a solar hot-water heater. At current energy prices, these often have a payback of less than 10 years.

Some 55 percent of U.S. electricity is generated by coal plants, which emit prodigious amounts of carbon dioxide over their average lifetime of 40 to 50 years. Right now we’re making critical decisions about how to replace these fossil-fuel power stations with either highly efficient gas turbines or zero-emission wind, large-scale thermal solar, geothermal, or hydro power. Individuals can encourage this transition and reduce their own emissions by purchasing low- or zero-carbon “green electricity” that is generated by renewable technology. It’s available from local utilities at a small premium of about two cents per kilowatt hour. About one-third of U.S. emissions come from electric power, so reductions here are significant.

Transportation Another third of U.S. emissions come from transportation. Emissions are determined by the inherent efficiency of vehicles, the number of vehicle miles traveled, and the choice of fuel. Some industrywide shifts are making it easier for consumers to cut CO2 emissions. The use of ethanol in fuel, for example, can cut emissions (although, as I’ll explain in a minute, not all ethanol is created equal). Another encouraging development is the new U.S. fuel standard that will enter into force in 2020. It raises the average fuel economy of new cars to 35 miles per gallon, a big leap from today’s 25 miles per gallon, though still way behind Europe, Japan, and China.

The easiest way to effect a three percent reduction per year in emissions may be to drive three percent less, or about 30 fewer miles per month. That could mean taking public transportation now and then, ride sharing to work once or twice a month, or walking or cycling for errands when possible. Driving a bit slower or less aggressively can also reduce emissions by three percent or more.

When you replace your average-efficiency car with a vehicle that gets double the mileage—a Toyota Prius or Honda Civic hybrid—you reduce your emissions by five percent per year over the average life of that vehicle, well ahead of the three percent goal. Older vehicles should be disposed of, not kept on the road. Also bear in mind that although the Prius and the Civic are more efficient than the average vehicle, most other hybrids, including many hybrid SUVs, are not.

Diesel vehicles are 20 to 40 percent more efficient than the average vehicle and produce correspondingly lower CO2 emissions.

While air transport is becoming more efficient and producing fewer emissions per mile, the number of miles traveled is growing. The only way to address this problem is through “carbon offsets” that reduce emissions elsewhere (see “Should You Buy Carbon Offsets?”).

Ultimately, we must design our communities to require less driving. We need modern transit systems like Singapore’s, in which the subways are clean and safe, with fast, frequent service covering high-density living and working neighborhoods. This work needs to start now. Citizens can help by using public transportation and by insisting that it be upgraded—and by supporting smart growth zoning initiatives that discourage sprawl.

Of course, if we developed biofuels such as ethanol from urban and agricultural waste—and everybody adopted them—we could reach the 80 percent reduction goal for transportation within 10 years. Brazil has taken a step in that direction: 40 percent of its fuel for cars comes from efficiently produced sugarcane ethanol. In contrast, the corn-based ethanol we use in the United States is much more energy intensive to produce and has pretty high emissions.

A similar leap forward could come from the development of 100-mile-per-gallon plug-in hybrids. And that day may not be far off. Already, several manufacturers have promised plug-in hybrids for 2010 that will get 50 to 80 miles per gallon.

Purchases The goods we purchase may look innocent enough sitting on our shelves, but if we consider the emissions it has taken to produce them and convey them to our door, we can grasp that they, too, give us an opportunity to shrink our carbon footprint.

Many items made of aluminum, steel, and concrete—materials whose production generates large CO2 emissions—can be replaced by wood. Not only are wood products manufactured with very low emissions, but trees actually absorb carbon dioxide. Similarly, plastics such as polyethylene can be used in place of copper pipe, resulting in much lower carbon emissions.

Recycled aluminum uses just 10 percent of the energy used by aluminum from ore, and produces an even smaller fraction of carbon dioxide.

Products from recycled steel and paper result in less than half the emissions that products from virgin materials do.

Crop production generates lower emissions than meat production, and of all meats, beef releases the most heat-trapping gases, while poultry and fish release the least. Grass-fed beef, however, produces fewer emissions than grain-fed beef does.

The average food calorie in America travels more than 1,500 miles. Locally grown produce requires less energy to deliver. Tropical agriculture is less fossil-fuel dependent, so it is not always possible to determine emissions solely on the distance food has traveled. But checking the label for origin, and tallying up the miles does provide a reasonable first approximation of the heat-trapping gases our groceries represent.

As you can see, none of these carbon-cutting measures requires putting on a hair shirt, but they do mean that we have to make deliberate decisions. To reach the goal of an 80 percent emissions reduction in about 50 years, everyone in the developed world must participate, starting now, and India, China, and other developing economies will need to join us within a few decades. China will be key, since it is already the world’s largest user of coal. Every year, it opens as many coal-burning electric power plants as are operating in Great Britain.

Still, the United States has pumped more CO2 into the atmosphere than any other nation, and, for the moment, we continue to lead in annual emissions. If we want carbon emissions to drop, it is up to us to demonstrate how it can be done.

Change of the magnitude we’re talking about is hardly unheard of in human history. In fact, the world passed through an equally dramatic, equally improbable energy revolution just 100 years ago. In 1905, 25 years after Thomas Edison produced his electric light bulb, only three percent of American homes had electric lighting. That same year, Henry Ford was producing just 14 cars per day in his two-year-old factory. Who would have imagined that by the middle of the twentieth century, every U.S. home would be illuminated by electricity, or that the automobile would have replaced the horse and carriage and redefined the suburbs?

Today, less than three percent of U.S. electricity is generated by non-hydro renewable technology such as wind, solar, biomass, and geothermal energy. The number of highly efficient gasoline-electric hybrids on the roads amounts to a mere trickle. But if enough individuals choose to limit their carbon emissions, and if producers respond to those new priorities, the mid-twenty-first-century world could look quite different. It could be a world that runs largely on carbon-free fuels and efficient technologies. A world where people live in very comfortable but low-energy homes. Better still, it could be a world where climate change is no longer a looming threat.

WILLIAM MOOMAW is a professor of international environmental policy and director of the Center for International Environment and Resource Policy at the Fletcher School. He is a member of the United Nations Intragovernmental Panel on Climate Change, which shared the 2007 Nobel Peace Prize with Al Gore. He also codirects the Tufts Climate Initiative, the program that enables the university to meet Kyoto Protocol emission reductions.