Saturday, July 22, 2017
 
NOAA’s greenhouse gas index up 40 percent since 1990

NOAA’s greenhouse gas index up 40 percent since 1990

Tuesday, July 11, 2017

NOAA’s Annual Greenhouse Gas Index, which tracks the warming influence of long-lived greenhouse gases, has increased by 40 percent from 1990 to 2016 -- with most of that attributable to rising carbon dioxide levels, according to NOAA climate scientists.

The role of greenhouse gases on influencing global temperatures is well understood by scientists, but it’s a complicated topic that can be difficult to communicate. In 2006, NOAA scientists introduced the Annual Greenhouse Gas Index as a way to help policymakers, educators and the public understand changes in the direct climate warming influence exerted by greenhouse gas levels over time.

“The greenhouse gas index is based on atmospheric data, so it’s telling us what is happening to Earth’s climate right now.” said James Butler, director of NOAA’s Global Monitoring Division.

NOAA bases the AGGI on precise measurements of long-lived atmospheric gases in samples collected from a network of sites around the globe. The index is proportional to the change in the direct warming influence exerted by long-lived greenhouse gases since 1750, which is the accepted date for onset of the industrial revolution. 

2016 Annual Greenhouse Gas Index

2016 Annual Greenhouse Gas Index

The NOAA Annual Greenhouse Gas Index tracks the change in radiative forcing of all the long-lived greenhouse gases relative to 1750.

The five primary gases tracked by the AGGI are carbon dioxide, methane, nitrous oxide, and two chlorofluorocarbons that were banned by the Montreal Protocol because they damage Earth’s protective ozone layer. These five primary greenhouse gases account for about 96 percent of the increased climate warming influence since 1750. Fifteen secondary greenhouse gases also tracked by the AGGI account for the remaining 4 percent.

Scientists who created the AGGI assigned a value of zero to the year 1750. Analysis of air trapped in ice and snow in Antarctica by NOAA and others demonstrate that after this date, atmospheric carbon dioxide concentrations departed from a relatively stable 280 parts per million observed during the previous 10,000 years, climbing to 403 parts per million by the end of 2016.  

An AGGI value of 1.0 was assigned to the year 1990, the baseline year of the Kyoto Protocol, an international treaty calling for the reduction in greenhouse gas emissions. In 2016, the AGGI rose to a value of 1.4.

Carbon dioxide is most important greenhouse gas

CO2 is by far the most important greenhouse gas in both total amount and rate of increase. It is responsible for 80 percent of the increased warming influence captured by the AGGI since 1990.

The amount of COin the atmosphere grew by 2.9 parts per million (ppm) in 2016, roughly equal to the record rise observed in 2015. During calendar year 2016, the global average for CO2 was approximately 403 parts per million, which represents a 45-percent increase since the start of the industrial era.

The direct warming influence exerted by all five primary and 15 secondary gases measured by the AGGI are equivalent to the warming influence of 489 ppm of CO2.

In April 2017, CO2 levels on Mauna Loa averaged 409 ppm.

The direct warming influence exerted by all five primary and 15 secondary gases measured by the AGGI are equivalent to the warming influence of 489 ppm of CO2.

One of many climate change indicators

The Greenhouse Gas Index is one of numerous indicators tracked by NOAA that demonstrate how the Earth’s climate is changing, including:

"We know that rising greenhouse gas emissions are continuing to trap more and more of the sun's heat in the Earth system," Butler said.

Access the complete AGGI for 2016 online at https://esrl.noaa.gov/gmd/aggi/aggi.html.


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