Importing fossil fuel is one solution, but the environmentally minded Swedes are unhappy about the greenhouse-gas implications of burning more coal, oil and natural gas.

ECONOMIST: Geothermal energy

Those heat-trapping gases are from the burning of fossil fuels like coal, oil and gas.

NPR: World Warm Last Year, But Not Like Record US Heat

Human sources come principally from the burning of fossil fuels such as coal, oil and gas.

BBC: Scientists call for action to tackle CO2 levels

Because of the burning of fossil fuels, such as oil and coal, carbon dioxide levels have gone up by that amount in just 55 years.

NPR: Greenhouse Gas Milestone; CO2 Levels Set Record

The burning of fossil fuels, such as coal for electricity and oil for gasoline, has caused the overwhelming bulk of the man-made increase in carbon in the air, scientists say.

NPR: Experts: CO2 Record Illustrates 'Scary' Trend

Carbon monoxide is a colourless, odourless gas produced by the burning of fuels, including gas, oil, wood and coal.

BBC: Fire service sees rise in carbon monoxide poisoning cases

The background level of tropospheric ozone is inexorably rising as volatile organic compounds are released from burning coal and oil.

FORBES: Protesters To Target Koch Brothers' Secretive 'Billionaires Caucus'

Scientists say it's apparent that human activity -- namely burning coal, oil and natural gas -- has been driving a rapid rise of carbon dioxide levels in the atmosphere.

CNN: CO2 levels hit new peak at key observatory