More and more people around the world are installing air conditioners to keep cool. If current economic and climate trends continue, 70 percent of homes could have air conditioning by 2100, up from 13 percent today. But a new study linking climate change, incomes, and air conditioning suggests a serious side effect: namely, the adjacent increases in energy demands and the flow of carbon dioxide into the atmosphere.
"Our results point to the enormous potential impacts from air conditioning," write University of California-Berkeley professors Lucas Davis and Paul Gertler in a paper published today in Proceedings of the National Academy of Sciences.
Davis and Gertler wanted to look at how climate and income influenced air-conditioner ownership and in turn how that would affect energy usage. To do so, they began with a database of electricity bills for 25 million households from across Mexico. They linked that information with weather data from the United States National Climatic Data Center that would tell them how much increasing temperatures affect energy usage.
If current economic and climate trends continue, 70 percent of homes could have air conditioning by 2100.
Next, they turned to a 2010 in-home survey of about 27,000 Mexicans to find out how income and local climate affected the decision to own an air conditioner. Davis and Gertler combined the results gleaned from the first two datasets with long-term forecasts from climatewizard.org. This allowed them to estimate how a changing climate would ultimately affect energy consumption.
The data analysis revealed three main findings. First, energy consumption on days when temperatures top 90ºF is 3.2 percent higher than on a typical day in Mexico, when the temperatures are around 65ºF or 70ºF. Temperatures below the average didn't affect energy use very much, Davis and Gertler found.
Second, income has a powerful influence on whether a household had an air conditioner, but only in hotter regions. There, AC adoption went up 27 percentage points for every $10,000 (U.S. currency) increase in income, topping out at around 75 percent adoption among those making $25,000 (U.S.) or more. (That's a lot in Mexico.) In cooler areas, AC ownership stayed below 10 percent even at the highest income levels.
Putting those two results together with long-term climate forecasts, and supposing incomes increase by two percent per year, Davis and Gertler estimate air conditioning will reach 71 percent of households by the end of the century, even under the assumption that carbon emissions slow down somewhat over that time.
Further analysis revealed that higher temperature did contribute to the predicted increase in air-conditioned homes, "but income growth by itself explains the lion's share," Davis and Gertler write.
"Whether or not these forecasts will prove accurate depends on the pace of technological change," Davis and Gertler write, noting "dramatic improvements in energy efficiency over the last several decades." On the other hand, the price of a basic air conditioner is also likely to fall. If so, it's likely more homes will have air conditioners, energy consumption will climb, and so too will the amount of carbon floating around the atmosphere.
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