Before about 60 people at Kroon Hall on Tuesday, David MacKay, the chief scientist for Britain’s Department of Energy and Climate Change, outlined his plan to reduce global energy consumption to sustainable levels.

MacKay said focusing on just reducing energy consumption will not significantly slow down climate change, but by focusing on creating alternative energy technologies as well, energy use can be reduced to sustainable levels.

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MacKay said his intention is not to produce statistics that might scare people into reducing energy use, but to inform people how much energy they use individually. MacKay said even if one does not believe in climate change’s existence, fossil fuels release carbon dioxide into the atmosphere. If countries do not develop alternative energy resources, fossil fuels will soon be depleted, he said.

“Everything I’m telling you is backed up by data, and we need to think about things this way,” he said. “I’m pro-arithmetic.”

As an example, MacKay calculated the reduction in energy from turning off a cell phone charger for a day, which amounted to less than a second of the energy consumed by driving a car.

To dispel popular myths about the efficiency of various alternative energy technologies, MacKay gave an analysis of the energy efficiency of wind turbines, biofuels, solar panels, nuclear energy and tide pools. He concluded that some popular technologies like wind turbines are not as effective as solar panels and nuclear energy, though solar energy is slightly less efficient than coal.

MacKay showed a map of how much land alternative energy technologies would need to cover to sustain current levels of energy consumption in the United States. For wind turbines to power the country, they would need to cover an area 49 times the size of New Jersey, MacKay said.

“To make a difference, renewable facilities have to be country-sized,” MacKay said.

MacKay spent the rest of the talk outlining ways individuals could reduce energy consumption. He urged the audience to drive small electric or hybrid cars such as the Chevy Volt instead of gas-guzzling sport utility vehicles, pad their houses with foam to reduce heat leakage, and turn thermostats down. MacKay added that developed countries should focus on clean coal, nuclear energy, and collaboration with other countries to produce the most efficient technology possible.

The one thing that audience members could do once they went home, he said, is to install a device that monitors energy consumption in their households. MacKay said he installed this kind of device in his home and reduced his energy consumption by more than 50 percent.

Three audience members said they enjoyed the talk and found it informative. Rick Walting, a resident of Long Island who drove to New Haven to hear MacKay speak, said he was particularly impressed with his “dispassionate” approach to the subject.

“He really takes the emotion out of the climate issue and just looks at facts,” Waling said. “That’s the most important thing.”

In 2009, MacKay published a book called “Sustainable Energy: Without the Hot Air.”