Clean Air Task Force

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photo of Earth's atmosphere
Courtesy of Getty Images

Human activity—especially the burning of fossil fuels for energy—is the primary cause of global warming. In the past 300 years, industrial, economic, and social activity has released more than 1.5 trillion tons of CO2 and other greenhouse gases into the atmosphere. Earth’s 20 hottest years since 1880 have all been in the last 27 years. Scientists say that the Earth could warm by an additional 7.2°F during the 21st century if we fail to reduce fossil fuel emissions.

Because nature’s processes for removing CO2 are relatively slow, a large portion of the CO2 already emitted will remain in the atmosphere for hundreds of years to come, setting our planet on a warming cycle from which ecological impacts are inevitable. Increases in the Earth’s surface temperature from pre-industrial times have already occurred, and will continue unabated based on CO2 emissions already released into the atmosphere. As emissions escalate, so too does the potential environmental devastation, while our chances of mitigating them rapidly slip away. It is now well established in climate science that CO2 emissions globally must stop, by the middle of this century, to avoid the worst cataclysms of global warming.