Energy efficiency is a "key mitigation strategy" in keeping global carbon emissions within a safe range through the end of the century, according to a report issued Sunday by the United Nations' Intergovernmental Panel on Climate Change (IPCC). In the near term, it may be the most immediate and inexpensive way to curtail emissions while more costly and complex solutions get under way.
Smarter energy use alone won't solve global warming. The world will also need to quickly shift to carbon-free energy sources, and develop technologies that capture emissions from traditional fossil fuel sources, according to Sunday's report. But efficiency gains have already made large, low-cost contributions to making all energy sources less carbon-intensive, without the expensive and time-consuming infrastructure needs of solar, wind, and other renewables.
"Reducing energy use would give us more flexibility in the choice of low-carbon energy technologies, now and in the future," Ramón Pichs-Madruga, co-chair of the IPCC team behind Sunday's report, said in a press release. "It can also increase the cost-effectiveness of mitigation measures."
Buildings, for example, accounted for nearly a third of the world's total energy use in 2010 and 6.4 percent of greenhouse-gas emissions. As emerging economies across the globe continue to develop higher standards of living, energy demand for buildings is projected to double, and carbon dioxide emissions to increase by 50 percent to 150 percent by midcentury, the report found.
Retrofitting old buildings to become more efficient, and making sure new ones are built to higher standards, can help keep that energy demand in check, according to IPCC. By 2050, better everyday energy habits could cut in half the developed world's building energy demand from today's levels. Most of these measures are inexpensive and often recoup their upfront costs over time. They may have other side benefits like increased economic productivity and energy security.
Between 1950 and 2011, the energy intensity of the United States – measured as energy consumption per unit of gross domestic product – dropped by 58 percent per real dollar of GDP, according to the US Energy Information Administration. It's largely the result of Americans using more efficient cars and appliances, and energy intensity is expected to continue to decline in coming decades.
The challenge is getting a variety of different stakeholders to sign on to efficiency measures. People who rent their homes may not want to make permanent energy-saving upgrades, and landlords won't be motivated to do it if the tenants are the ones paying the utility bills.
There's also concern about a so-called rebound effect, where energy savings are diminished or even offset by an increase in overall consumption. For example, a person who buys a more efficient car may just end up driving it more, canceling out any emissions the car might save. That's why some economists believe the value of efficiency may be overestimated.
Still, Sunday's IPCC report emphasized saving energy as an immediate, inexpensive way to address a costly, long-term challenge.
"Using energy more sensibly not only reduces costs but can improve productivity and quality of life," Timothy Wirth, vice chairman of the United Nations Foundation, said in a statement responding to the report. "Cleaner energy sources – renewable energy, especially wind and solar, as well as the least carbon-intensive fossil fuel, natural gas – are increasing their penetration of the world’s energy markets, too slowly but with increasing momentum."