GHG emissions, GHG
Greenhouse gas emissions cause dangerous anthropogenic climate change. Emissions include CO2, fluoridated gases, methane which are emitted by human activity such as deforestation and burning fossil fuels, and water vapour.
A greenhouse gas (abbrev. GHG) is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Without greenhouse gases, the average temperature of Earth's surface would be about −18 °C (0 °F), rather than the present average of 15 °C (59 °F). In the Solar System, the atmospheres of Venus, Mars and Titan also contain gases that cause a greenhouse effect. Human activities since the beginning of the Industrial Revolution (taken as the year 1750) have produced a 40% increase in the atmospheric concentration of carbon dioxide, from 280 ppm in 1750 to 400 ppm in 2015. This increase has occurred despite the uptake of a large portion of the emissions by various natural "sinks" involved in the carbon cycle. Anthropogenic carbon dioxide (CO2) emissions (i.e. emissions produced by human activities) come from combustion of carbon-based fuels, principally coal, oil, and natural gas, along with deforestation, soil erosion and animal agriculture. It has been estimated that if greenhouse gas emissions continue at the present rate, Earth's surface temperature could exceed historical values as early as 2047, with potentially harmful effects on ecosystems, biodiversity and the livelihoods of people worldwide. Recent estimates suggest that on the current emissions trajectory the Earth could pass a threshold of 2°C global warming, which the United Nations' IPCC designated as the upper limit for "dangerous" global warming, by 2036.
Source: Wikipedia - Greenhouse gas
Wikipedia definition (similar term):
As of 2012 the Department of Energy projected United States' greenhouse gas (GHG) emissions from the US energy industry to drop 28 percent from its 2007 value by 2030, due to the recession and the hydraulic fracturing boom in natural gas which releases less carbon dioxide into the Earth's atmosphere than coal or oil. While the Bush administration opted against Kyoto-type policies, the Obama administration and various state, local, and regional governments have attempted to adopt some Kyoto Protocol goals on a local basis. For example, the Regional Greenhouse Gas Initiative (RGGI) founded in January 2007 is a state-level emissions capping and trading program by nine northeastern U.S. states. In December 2009 President Obama set a target for reducing U.S. greenhouse gas (GHG) emissions in the range of 17% below 2005 levels by 2020. The U.S. State Department offered a nation-level perspective in the Fourth US Climate Action Report (USCAR) to the United Nations Framework Convention on Climate Change, including measures to address climate change. The report showed that the country was on track to achieve President Bush's goal of reducing greenhouse gas emissions per unit of gross domestic product) by 18 percent from 2002 to 2012. Over that same period, actual GHG emissions were projected to increase by 11 percent. The report estimated that in 2006, U.S. GHG emissions decreased 1.5 percent from 2005 to 7,075.6 million tonnes of carbon dioxide equivalent. This was an increase of 15.1 percent from the 1990 levels of 6,146.7 million tonnes (or 0.9 percent annual increase), and an increase of 1.4 percent from the 2000 levels of 6,978.4 million tonnes. By 2012 GHG emissions were projected to increase to more than 7,709 million tonnes of carbon dioxide equivalent, which would be 26 percent above 1990 levels.