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A heat wave that struck Europe in 2003 resulted in power cuts that left some passengers stranded on the London Tube network. See more green science pictures.

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The weather forecast calls for hazy, hot and humid but if you're like many people, you only notice it as you walk from your cooled house to your cooled car to your cooled office. What would you do during the summer months without your air conditioning?

American homeowners spend more than $15 billion on home cooling, and roughly 5 percent of all the electricity produced in the United States is consumed by conventional air conditioning units. All that cooling releases an estimated 140 million tons (127 million metric tons) of carbon dioxide (CO2), a greenhouse gas known to contribute to climate change [source: American Council for an Energy-Efficient Economy].

Greenhouse gas emissions have increased by 25 percent in the 150 years since the industrial revolution. Today, fossil fuels supply 85 percent of the energy consumed in the United States; burning petroleum and coal are responsible for 80 percent of CO2 emissions in the United States [source: Energy Information Administration].

Demand for air conditioning is expected to grow as temperatures increase. Heat waves cause blackouts, health problems and in some cases even death -- during the summer of 2003, at least 35,000 people died from a heat wave that baked Europe. Seven of the eight hottest years on record happened since 2001; the 10 hottest years have all been since 1995 [source: National Climatic Data Center]. Global surface temperatures have increased by 1.4 degrees F (0.8 degree C) since 1920, and scientists predict temperatures could increase an average of 2 to 11.5 degrees F (1.1 to 6.4 degrees C) by the end of the 21st century [source: Pew Center on Global Climate Change and EPA].

Reducing the use of fossil fuels and replacing them with renewable resources for energy is key to putting the brakes on the effects of climate change. The only option for reducing the energy consumed by air conditioning has been to simply turn it off -- until now. Solar air conditioners take advantage of the sun at its brightest and use its energy to cool you during the hottest part of the day.