On Friday, May 2, 2014 NOAA released the latest Annual Greenhouse Gas Index (AGGI), showing that the warming influence from human-emitted gases continues to increase. This trend that began with the Industrial Revolution of the 1880s has accelerated in recent decades.

The AGGI Driven in large part by rising levels of carbon dioxide (CO2), increased 1.5 percent between 2012 and 2013. This means the combined heating effect of human-emitted, long-lived greenhouse gases currently in the atmosphere has increased by 1.5 percent in one year, and 34 percent since 1990.

"We continue to turn the dial up on this ‘electric blanket' of ours without knowing what the resulting temperatures will be," said James Butler, Ph.D., director of the Global Monitoring Division of NOAA's Boulder-based Earth System Research Laboratory (ESRL). "We know that the world is getting warmer on average because of our continued emissions of heat-trapping gases. Turning down the dial on this heating will become increasingly more difficult as concentrations of the long-lived greenhouse gases continue to rise each year."

Scientists at NOAA calculate the AGGI each year from several decades of atmospheric data collected through an international cooperative air-sampling network of up to 80 sites around the world. Researchers from CIRES, NOAA's Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder, work with NOAA's scientists at many stages ‒ from shipping air sampling flasks around the world to air sampling and data analysis. This index provides scientists and decision-makers with information useful for understanding climate change and its present-day and potential future impacts on our communities.

In 2013, carbon dioxide concentrations for the first time in recorded history exceeded 400 parts per million(ppm) at Mauna Loa -considered a "global benchmark" monitoring site-in early May. This year, CO2 exceeded 400 ppm at Mauna Loa in mid-March, two months earlier than last year. Concentrations at Mauna Loa have continued to top 400 ppm throughout much of April and are expected to stay at historic high levels through May and early June, dropping in early summer only as trees and plants in the Northern Hemisphere begin to take up CO2 during the growing season.

Carbon dioxide continues to be the largest greenhouse gas contributor to climate change, responsible for 87 percent of the increase this past year. The annual rise in CO2 is consistent with trends in fossil fuel emissions and carbon dioxide uptake by the ocean and land ecosystems. Historically, about half of the carbon dioxide emitted is removed from the atmosphere by the ocean and land vegetation.

Atmospheric methane concentrations stabilized during the late 1990s and early 2000s, but have been rising again since 2007. The largest sources of methane emissions are naturally occurring and come from wetlands in the tropics. Human-caused methane emissions come from the production of coal, oil and natural gas, livestock, rice agriculture and waste. Nitrous oxide continues to rise at a steady rate. Nitrous oxide occurs naturally in the atmosphere, but has been increasing in recent decades owing largely to human-driven emissions associated with fertilizer applications, vehicles, and industrial emissions. Chemicals developed to replace ozone-depleting chlorofluorocarbons, or refrigerants, that were banned by the Montreal Protocol two decades ago are making up a larger share of greenhouse gases each year.

NOAA researchers developed the AGGI in 2004 and have updated it annually since. Although it currently is calculated for years starting in 1978, atmospheric composition data from ice cores and other records could allow the record to be extended back centuries.

To learn more about the index, visit: http://www.esrl.noaa.gov/gmd/aggi/.

About AGGI

The AGGI is a measure of the warming influence of long-lived trace gases and how that influence is changing each year. The index was designed to enhance the connection between scientists and society by providing a normalized standard that can be easily understood and followed.

The warming influence of long-lived greenhouse gases is well understood by scientists and has been reported by NOAA through a range of national and international assessments. Nevertheless, the language of scientists often eludes policy makers, educators, and the general public. This index is designed to help bridge that gap. The AGGI provides a way for this warming influence to be presented as a simple index.

Source and Image Credit: NOAA

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