The NOAA Annual Greenhouse Gas Index (AGGI) · • The Annual Greenhouse Gas Index (AGGI), defined...
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The NOAA Annual Greenhouse Gas Index (AGGI) The NOAA Annual Greenhouse Gas Index (AGGI) David Hofmann, James Butler, Thomas Conway, Edward Dlugokencky, James Elkins, Kenneth Masarie, Stephen Montzka, Russell Schnell, and Pieter Tans NOAA Earth System Research Laboratory, Boulder, Colorado, USA Abstract. For the past 30 years, the U.S. National Oceanic and Atmospheric Administration (NOAA) has monitored climate-forcing and ozone-depleting atmospheric gases. These global measurements have provided input to climate and ozone assessments (e.g., the quadrennial IPCC Climate Reports and WMO/UNEP Ozone Assessments). Recently, efforts to make these data more useful and available have been undertaken through release of the NOAA Annual Greenhouse Gas Index (AGGI), http://www.esrl.noaa.gov/gmd/aggi and the Ozone Depleting Gas Index (ODGI) http://www.esrl.noaa.gov/gmd/odgi . These indices are designed to enhance the connection between scientists and society by providing a normalized standard that can be easily understood and followed. Measurements are made at baseline climate observatories (Pt. Barrow, Alaska; Mauna Loa, Hawaii; American Samoa; and the South Pole) and flask air samples are collected through global networks, including an international cooperative program for carbon gases. The concept of radiative climate forcing is used to determine the AGGI, which is normalized to 1.00 in 1990, the Kyoto Climate Protocol baseline year. For the year 2006, the AGGI was 1.23, i.e. global radiative forcing by long-lived greenhouse gases has increased 23% since 1990. As will be emphasized, the increase in carbon dioxide (CO 2 ) alone was about 32% over this time interval. Reductions in the growth rates of methane and the CFCs have effectively tempered the increase of CO 2 since 1990. November 2004 Surface Observatory Aircraft Tower Open symbol represents inactive site NOAA/ESRL GLOBAL COOPERATIVE CO 2 NETWORK These five gases account for about 97% of the direct radiative forcing by long-lived greenhouse gas increases since 1750. The remaining 3% is contributed by an assortment of 10 minor halogen gases, mainly HCFC-22, CFC-113 and CCl 4 . SUMMARY AND CONCLUSIONS • The Annual Greenhouse Gas Index (AGGI), defined as the ratio of the annual post-industrial radiative forcing by long-lived greenhouse gases to that which was present in 1990, was 1.23 for the year 2006, (an increase in total radiative forcing of 23% since 1990). • Since 1990, the radiative forcing due to CO 2 alone has increased about 32%. • Of the four major groups of long-lived greenhouse gases that contribute to radiative climate forcing, CO 2 and N 2 O are the only ones that continue to increase at a regular rate. • The contribution to radiative forcing by methane and CFCs has been nearly constant or declining in recent years. As a consequence, the contribution to the annual increase in the total radiative forcing of long-lived greenhouse gases due to CO 2 is now over 90%, up from about 50% before 1990. • Had the ozone-depleting gases not been regulated by the Montreal Protocol (1987) and its amendments, climate forcing is estimated to have been as much as 0.2 watt m -2 higher, or about one- half of the increase in radiative forcing due to CO 2 alone since 1990. RADIATIVE FORCING CALCULATIONS IPCC recommended expressions determined from radiative transfer models are used to convert greenhouse gas changes since 1750 to instantaneous radiative forcing. Only the direct forcing has been calculated. The uncertainty in these estimates is of the order of 5-10%, providing a benchmark for climate forcing. Forcing by short-lived, poorly known species such as atmospheric aerosols and tropospheric ozone, as well as model-dependent indirect effects, have not been included. Radiative forcing by carbon dioxide, relative to 1750, has increased by about 32% since 1990. Radiative Forcing and the Annual Greenhouse Gas Index (AGGI) RADIATIVE FORCING OF CLIMATE IPCC: An externally imposed perturbation in the radiative energy budget of the Earth climate system, e.g. through changes in solar radiation, changes in the Earth albedo, or changes in atmospheric gases and aerosol particles. The perturbation that has the largest magnitude and the least scientific uncertainty is the forcing related to changes in atmospheric gases that absorb Earth infrared radiation (greenhouse gases) and that are long-lived and well-mixed in the atmosphere. These “major” greenhouse gases are carbon dioxide (CO 2 ), methane (CH 4 ), nitrous oxide (N 2 O) and the halocarbons (mainly CFCs). Method. Measurements of the long-lived greenhouse gases – carbon dioxide, methane, nitrous oxide and halocarbons (mainly CFCs) have minimal scientific uncertainty, being independent of climate models, and thus provide a climate benchmark free of controversy. All of these gases have been monitored around the world since the 1970’s mainly by NOAA’s Earth System Research Laboratory (ESRL), Global Monitoring Division (formerly CMDL), in Boulder, Colorado. To provide the data required for the AGGI, continuous measurements from five baseline climate observatories at Pt. Barrow, Alaska; Mauna Loa, Hawaii; Trinidad Head, California; American Samoa; and at the South Pole are maintained. In addition, flask air samples are collected through several global networks, including a cooperative program for carbon-containing and other greenhouse gases that provides samples from globally widespread clean air sites. All measurements are reported on World Calibration Scales, produced and maintained by NOAA/ESRL in Boulder. These data are used to calculate annual global average concentrations from which changes in radiative forcing of the global climate since the pre- industrial era (1750) for the 28-year period encompassing 1979 through 2006 are determined. This includes all major greenhouse gases and 10 minor halogenated gases. Results are normalized to radiative forcing in 1990, the baseline year for the Kyoto Climate Protocol, to produce the AGGI. Interannual Variation in Radiative Forcing by Greenhouse Gases Radiative Forcing by Carbon Dioxide 1978 1982 1986 1990 1994 1998 2002 2006 Parts per trillion (ppt) 100 200 300 400 500 600 CFC-12 CFC-11 1978 1982 1986 1990 1994 1998 2002 2006 Parts per billion (ppb) 298 302 306 310 314 318 322 1978 1982 1986 1990 1994 1998 2002 2006 Parts per million (ppm) 335 345 355 365 375 385 1978 1982 1986 1990 1994 1998 2002 2006 Parts per billion (ppb) 1550 1600 1650 1700 1750 1800 Carbon Dioxide Nitrous Oxide Methane 2006 AGGI = 1.23 Minor Greenhouse Gases Except for HFC-134a, which does not contain chlorine or bromine (used in auto air conditioners), these gases are also ozone- depleting gases and are regulated by the Montreal Protocol. In the figure, the lifetime in years and the global warming potential (CO 2 = 1) are given in the brackets. 0.0 0.5 1.0 1.5 2.0 2.5 3.0 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 Watts per square meter CO2 CH4 N2O CFC12 CFC11 10 Minor Total 0.01 0.10 1.00 10.00 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 Watts per square meter CO2 CH4 N2O CFC12 CFC11 10 Minor Total 1980 1985 1990 1995 2000 2005 Radiative Forcing Since 1750 (W m -2 ) 1.0 1.2 1.4 1.6 % From 1990 -30 -20 -10 0 10 20 30 1980 1984 1988 1992 1996 2000 2004 2008 Radiative Forcing Change (mW m -2 per year) 0 20 40 60 80 CO 2 CH 4 N 2 O CFC-12 Integrated Radiative Forcing Since 1750 (W m -2 ) 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 CFC-11 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 Radiative Forcing (W m -2 ) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 CO 2 CH 4 N 2 O CFC12 CFC11 10 Minor Annual Greenhouse Gas Index (AGGI) 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Global Carbon Dioxide Growth Rate From Monthly Average Data 1978 1983 1988 1993 1998 2003 2008 Parts Per Million Per Year 0 1 2 3 4 1990 1992 1994 1996 1998 2000 2002 2004 2006 Parts per trillion 0 25 50 75 100 125 150 175 CFC-113 HCFC-22 CH 3 CCl 3 CCl 4 HFC-134a 1990 1992 1994 1996 1998 2000 2002 2004 2006 Parts per trillion 0 5 10 15 20 HCFC-141b HCFC-142b H-1211 H1301 SF 6 (11.9, 1700) (35, 1800) (85, 6000) (4.8, 140) (13.8, 1300) (9.3, 700) (19, 2400) (3200, 22200) (11, 1300) (65, 6900)
Transcript of The NOAA Annual Greenhouse Gas Index (AGGI) · • The Annual Greenhouse Gas Index (AGGI), defined...
The NOAA Annual Greenhouse Gas Index (AGGI) The NOAA Annual Greenhouse Gas Index (AGGI) David Hofmann, James Butler, Thomas Conway, Edward Dlugokencky, James Elkins, Kenneth Masarie, Stephen Montzka, Russell Schnell, and Pieter TansNOAA Earth System Research Laboratory, Boulder, Colorado, USA
Abstract. For the past 30 years, the U.S. National Oceanic and Atmospheric Administration (NOAA) has monitored climate-forcing and ozone-depleting atmospheric gases. These global measurements have provided input to climate and ozone assessments (e.g., the quadrennial IPCC Climate Reports and WMO/UNEP Ozone Assessments). Recently, efforts to make these data more useful and available have been undertaken through release of the NOAA Annual Greenhouse Gas Index (AGGI), http://www.esrl.noaa.gov/gmd/aggi and the Ozone Depleting Gas Index (ODGI) http://www.esrl.noaa.gov/gmd/odgi . These indices are designed to enhance the connection between scientists and society by providing a normalized standard that can be easily understood and followed. Measurements are made at baseline climate observatories (Pt. Barrow, Alaska; Mauna Loa, Hawaii; American Samoa; and the South Pole) and flask air samples are collected through global networks, including an international cooperative program for carbon gases. The concept of radiative climate forcing is used to determine the AGGI, which is normalized to 1.00 in 1990, the Kyoto Climate Protocol baseline year. For the year 2006, the AGGI was 1.23, i.e. global radiative forcing by long-lived greenhouse gases has increased 23% since 1990. As will be emphasized, the increase in carbon dioxide (CO2) alone was about 32% over this time interval. Reductions in the growth rates of methane and the CFCs have effectively tempered the increase of CO2 since 1990.
Nov
embe
r 200
4SurfaceObservatoryAircraftTower
Open symbol represents inactive site
NOAA/ESRL GLOBAL COOPERATIVE CO2 NETWORK
These five gases account for about 97% of the direct radiative forcing by long-lived greenhouse gas increases since 1750. The remaining 3% is contributed by an assortment of 10 minor halogen gases, mainly HCFC-22, CFC-113 and CCl4.
SUMMARY AND CONCLUSIONS
• The Annual Greenhouse Gas Index (AGGI), defined as the ratio of the annual post-industrial radiative forcing by long-lived greenhouse gases to that which was present in 1990, was 1.23 for the year 2006, (an increase in total radiative forcing of 23% since 1990).• Since 1990, the radiative forcing due to CO2 alone has increased about 32%.• Of the four major groups of long-lived greenhouse gases that contribute to radiative climate forcing, CO2 and N2O are the only ones that continue to increase at a regular rate.• The contribution to radiative forcing by methane and CFCs has been nearly constant or declining in recent years. As a consequence, the contribution to the annual increase in the total radiative forcing of long-lived greenhouse gases due to CO2 is now over 90%, up from about 50% before 1990.• Had the ozone-depleting gases not been regulated by the Montreal Protocol (1987) and its amendments, climate forcing is estimated to have been as much as 0.2 watt m-2 higher, or about one-half of the increase in radiative forcing due to CO2 alone since 1990.
RADIATIVE FORCING CALCULATIONSIPCC recommended expressions determined from radiative transfer models are used to convert greenhouse gas changes since 1750 to instantaneous radiativeforcing. Only the direct forcing has been calculated. The uncertainty in these estimates is of the order of 5-10%, providing a benchmark for climate forcing. Forcing by short-lived, poorly known species such as atmospheric aerosols and tropospheric ozone, as well as model-dependent indirect effects, have not been included.
Radiative forcing by carbon dioxide, relative to 1750, has increased by about 32% since 1990.
Radiative Forcing and the Annual Greenhouse Gas Index (AGGI)
RADIATIVE FORCING OF CLIMATEIPCC: An externally imposed perturbation in the radiative energy budget of the Earth climate system, e.g. through changes in solar radiation, changes in the Earth albedo, or changes in atmospheric gases and aerosol particles. The perturbation that has the largest magnitude and the least scientific uncertainty is the forcing related to changes in atmospheric gases that absorb Earth infrared radiation (greenhouse gases) and that are long-lived and well-mixed in the atmosphere. These “major” greenhouse gases are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and the halocarbons (mainly CFCs).
Method. Measurements of the long-lived greenhouse gases – carbon dioxide, methane, nitrous oxide and halocarbons (mainly CFCs) have minimal scientific uncertainty, being independent of climate models, and thus provide a climate benchmark free of controversy. All of these gases have been monitored around the world since the 1970’s mainly by NOAA’s Earth System Research Laboratory (ESRL), Global Monitoring Division (formerly CMDL), in Boulder, Colorado. To provide the data required for the AGGI, continuousmeasurements from five baseline climate observatories at Pt. Barrow, Alaska; Mauna Loa, Hawaii; Trinidad Head, California; American Samoa; and at the South Pole are maintained. In addition, flask air samples are collected through several global networks, including a cooperative program for carbon-containing and other greenhouse gases that provides samples from globally widespread clean air sites. All measurements are reported on World Calibration Scales, produced and maintained by NOAA/ESRL in Boulder. These dataare used to calculate annual global average concentrations from which changes in radiative forcing of the global climate since the pre-industrial era (1750) for the 28-year period encompassing 1979 through 2006 are determined. This includes all major greenhouse gases and 10 minor halogenated gases. Results are normalized to radiative forcing in 1990, the baseline year for the Kyoto Climate Protocol, to produce the AGGI.
Interannual Variation in Radiative Forcing by Greenhouse Gases
Radiative Forcing by Carbon Dioxide
1 9 7 8 1 9 8 2 1 9 8 6 1 9 9 0 1 9 9 4 1 9 9 8 2 0 0 2 2 0 0 6
Part
s pe
r tril
lion
(ppt
)
1 0 0
2 0 0
3 0 0
4 0 0
5 0 0
6 0 0C F C - 1 2C F C - 1 1
1 9 7 8 1 9 8 2 1 9 8 6 1 9 9 0 1 9 9 4 1 9 9 8 2 0 0 2 2 0 0 6
Part
s pe
r bill
ion
(ppb
)
2 9 8
3 0 2
3 0 6
3 1 0
3 1 4
3 1 8
3 2 2
1 9 7 8 1 9 8 2 1 9 8 6 1 9 9 0 1 9 9 4 1 9 9 8 2 0 0 2 2 0 0 6
Part
s pe
r mill
ion
(ppm
)
3 3 5
3 4 5
3 5 5
3 6 5
3 7 5
3 8 5
1 9 7 8 1 9 8 2 1 9 8 6 1 9 9 0 1 9 9 4 1 9 9 8 2 0 0 2 2 0 0 6
Part
s pe
r bill
ion
(ppb
)
1 5 5 0
1 6 0 0
1 6 5 0
1 7 0 0
1 7 5 0
1 8 0 0
C a r b o n D io x id e N i t r o u s O x id e
M e t h a n e
2006 AGGI= 1.23
Minor Greenhouse Gases
Except for HFC-134a, which does not contain chlorine or bromine (used in auto air conditioners), these gases are also ozone-depleting gases and are regulated by the Montreal Protocol. In the figure, the lifetime in years and the global warming potential (CO2 = 1) are given in the brackets.
0.0
0.5
1.0
1.5
2.0
2.5
3.0
1979
19811983198519
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931995199719
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ts p
er s
quar
e m
eter CO2
CH4N2OCFC12CFC1110 MinorTotal
0.01
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1.00
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1979198119
831985198719
89199119931995199719992001200320
05
Wat
ts p
er s
quar
e m
eter CO2
CH4N2OCFC12CFC1110 MinorTotal
1980
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1990
1995
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2005
Rad
iativ
e Fo
rcin
g Si
nce
1750
(W m
-2)
1.0
1.2
1.4
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% F
rom
199
0
-30
-20
-10
0
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1980 1984 1988 1992 1996 2000 2004 2008
Rad
iativ
e Fo
rcin
g C
hang
e (m
W m
-2 p
er y
ear)
0
20
40
60
80CO2 CH4
N2O CFC-12
Inte
grat
ed R
adia
tive
Forc
ing
Sin
ce 1
750
(W m
-2)
1.7
1.8
1.9
2.0
2.1
2.2
2.3
2.4
2.5
2.6
2.7CFC-11
1979
1980
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Rad
iativ
e Fo
rcin
g (W
m-2
)
0.0
0.5
1.0
1.5
2.0
2.5
3.0CO2
CH4
N2OCFC12CFC1110 Minor
Annu
al G
reen
hous
e G
as In
dex
(AG
GI)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
Global Carbon Dioxide Growth RateFrom Monthly Average Data
1978 1983 1988 1993 1998 2003 2008
Par
ts P
er M
illion
Per
Yea
r
0
1
2
3
4
1990 1992 1994 1996 1998 2000 2002 2004 2006
Parts
per
trilli
on
0
25
50
75
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150
175
CFC-113HCFC-22CH3CCl3CCl4HFC-134a
1990 1992 1994 1996 1998 2000 2002 2004 2006
Par
ts p
er tr
illio
n
0
5
10
15
20
HCFC-141bHCFC-142bH-1211H1301SF6
(11.9, 1700)
(35, 1800)
(85, 6000)
(4.8, 140)
(13.8, 1300)
(9.3, 700)
(19, 2400)
(3200, 22200)
(11, 1300)
(65, 6900)
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