Last updated July 12, 2017

Greenhouse Gas Emissions

Greenhouse gases from human activities—mainly the burning of fossil fuels like coal and gas—are likely responsible for all the observed warming since 1950. The fundamental physics of heat-trapping greenhouse gases has been understood since the nineteenth century. Scientists have known since the late 1970s that humans—by increasing the atmospheric concentration of greenhouse gases from 280 parts per million in preindustrial times to what is now over 400 ppm—have effectively wrapped the Earth in a thicker blanket, trapping more of the Earth’s infrared energy close to the surface.

Global trends

“Anthropogenic greenhouse gas emissions have increased since the pre-industrial era, driven largely by economic and population growth, and are now higher than ever. This has led to atmospheric concentrations of carbon dioxide, methane and nitrous oxide that are unprecedented in at least the last 800,000 years. Their effects, together with those of other anthropogenic drivers, have been detected throughout the climate system and are extremely likely to have been the dominant cause of the observed warming since the mid-20th century.”[1] 

“If not for human activities, global climate would actually have cooled slightly over the past 50 years. The pattern of temperature change through the layers of the atmosphere, with warming near the surface and cooling higher up in the stratosphere, further confirms that it is the buildup of heat-trapping gases (also known as “greenhouse gases”) that has caused most of the Earth’s warming over the past half century.”[2]