Larger units are not more efficient -- buy the smallest A/C recommended for the room. Whether they’re window-mounted room units, central cooling systems or portable machines, air conditioners emit greenhouse gases, a class of chemicals that scientists believe depletes the Earth’s ozone layer. The gradual weakening of this protective stratum increases the amount of harmful ultraviolet radiation that reaches Earth’s surface, permanently elevating the planet's temperature in a process dubbed global warming. To slow this effect, the U.S. government and air conditioning manufacturers have required A/C units to be more energy efficient and less damaging to the environment. How A/C Units Work Air conditioners employ an electric pump and two internal electric coils to transfer air between the outdoors and indoors. The cooling apparatus, called the evaporator, transmits cooler air into your home, while the hot coil, the condenser, releases warm air outside. A compressor pump moves refrigerant between the evaporator and condenser, alternately transforming it from liquid to gas to move the cooler and warmer air.

The refrigerant is the source of the ozone-depleting greenhouse gas. Greenhouse Gases Released Air conditioners manufactured in the second half of the 20th century typically used chlorofluorocarbons, or CFCs, under the trade name Freon, as the liquid refrigerant. In the 1970s, scientists began quantifying the ozone-depleting characteristics of CFCs; in 1987, the Montreal Protocol called for an international reduction in CFC use. Since 1995, A/C units in the U.S. have used halogenated chlorofluorocarbons, or HCFCs, as refrigerant. Because HCFCs still contribute to ozone depletion — on a lesser level when compared with CFCs — the U.S. will phase out all production of HCFCs by 2030. Effects of Greenhouse Gases Climate change caused by greenhouse gases has the potential to affect all animal and plant life on earth —from marine plankton to humans, from algae to complex rainforest ecosystems. A few of the interrelated consequences of emitting greenhouse gases into Earth’s atmosphere are changes in plant growth and reproduction, which can alter food chains;

elevated ocean levels and warmer ocean temperatures, which can increase flooding and destroy coastal ecosystems; and greater incidence of skin cancers and cataracts in humans. Reducing the output of these gases may slow the process of global warming. Increasing A/C Efficiency The Energy Star program, a joint effort of the U.S. Environmental Protection Agency and the Department of Energy, sets standards for energy efficiency and encourages consumers to buy eco-friendly home appliances. Energy Star air conditioners use 10 percent less energy than conventional units, and may feature timers to better regulate energy use when cooling your home. You can also increase the efficiency of central cooling systems by sealing ducts and improving insulation in your home; for window units, make sure the air conditioner’s adjustable louvers are tightly fitted inside the window frame. References U.S. Department of Energy: How Air Conditioners WorkUnited Nations Environment Programme, Ozone Secretariat: Handbook for the Montreal Protocol on Substances that Deplete the Ozone Layer -- 7th Edition (2006)EPA: Health and Environmental Effects of Ozone Layer DepletionEnergyStar: Room Air Conditioning Photo Credits Yamini Chao/Digital Vision/Getty Images Suggest a Correction

There's no putting a chill on the worldwide air conditioning boom that's expected to heat up to historic levels over the next decade. Nations with emerging economies and spiking populations — including India, Indonesia and Brazil — are seeing air conditioner sales grow 10 to 15 percent a year. used ac units for rvThat means the world's supply of A/C units could increase from about 900 million in 2015 to roughly 1.6 billion by 2030, according to a recent Berkeley National Laboratory study.ac unit fell Mario Tama / Getty Images, filewhy are some ac units on the roof So instead of simply trying to shut off the inexorable growth, scientists are working to find fresh energy-efficient technologies that could offset the effects A/C units have on the climate.

That's one of the purposes of the Clean Energy Ministerial, a two-day conference this Wednesday and Thursday in San Francisco that will be attended by two dozen of the world's major countries. U.S. Energy Secretary Ernest Moniz will host the event, and a so-called Advanced Cooling Challenge is on the agenda to discuss developing super-efficient, climate-friendly and cost-effective solutions. That means cutting down on the use of hydrofluorocarbons — typically found in supermarket refrigerators and air conditioners. HFCs are among the fastest-growing greenhouse gases with "global warming potentials thousands of times higher" than carbon dioxide, according to the Berkeley study. Reducing the amount of HFCs in the environment would be a better alternative to mitigating climate change than trying to control CO2 use alone, the researchers say. In the United States, where two-thirds of homes have air conditioners, roughly 100 million tons of carbon dioxide are released into the air each year, according to the Energy Department.

Scientists worry energy use and emissions will only worsen once countries such as India — known for its extreme heat, but which is still playing catch-up in terms of A/C use — bring millions of units on the grid as a refuge from the rising temperatures. The issue could reach a crisis point around 2060, when the Netherlands Environmental Assessment Agency predicts the amount of energy used worldwide in cooling will overtake that used in heating. By then, over 2.5 billion A/C units could make up the global stock, the Berkeley study says. "The more cooling you have, the more heat air-conditioning systems release into the urban environment, which then elevates the ambient temperature and further increases the cooling demand," Afshin Afshari, a professor with the Abu Dhabi-based Masdar Institute's research team said this month. "It's a vicious cycle."Environ Sci Technol. 2012 Dec 4;46(23):12977-85. Epub 2012 Nov 20.Galka MD1, Lownsbury JM, Blowers P.Author information1Department of Chemical and Environmental Engineering The University of Arizona, Tucson, Arizona 85721-0011, USA.

AbstractIn this work, potential replacement refrigerants for window-mounted room air conditioners (RACs) in the U.S. have been evaluated using a greenhouse gas (GHG) emissions analysis. CO(2)-equivalent emissions for several hydrofluoroethers (HFEs) and other potential replacements were compared to the most widely used refrigerants today. Included in this comparison are pure refrigerants that make up a number of hydrofluorocarbon (HFC) mixtures, pure hydrocarbons, and historically used refrigerants such as propane and ammonia. GHG emissions from direct and indirect sources were considered in this thermodynamic analysis. Propylene, dimethyl ether, ammonia, R-152a, propane, and HFE-152a all performed effectively in a 1 ton window unit and produced slightly lower emissions than the currently used R-22 and R-134a. The results suggest that regulation of HFCs in this application would have some effect on reducing emissions since end-of-life emissions remain at 55% of total refrigerant charge despite EPA regulations that mandate 80% recovery.