Stratospheric aerosols from explosive volcanic eruptions lead to negative forcing that lasts a few years. Several explosive eruptions occurred in the periods 1880 to 1920 and 1960 to 1991, and no explosive eruptions since 1991. Enhanced stratospheric aerosol content due to volcanic eruptions, together with the small solar irradiance variations, result in a net negative natural radiative forcing over the past two, and possibly even the past four, decades.
Table 3: Direct Global Warming Potentials (GWPs) relative to carbon dioxide (for gases for which the lifetimes have been adequately characterised). GWPs are an index for estimating relative global warming contribution due to atmospheric emission of a kg of a particular greenhouse gas compared to emission of a kg of carbon dioxide. GWPs calculated for different time horizons show the effects of atmospheric lifetimes of the different gases. [Based upon Table 6.7] | ||||||
Gas |
Lifetime
(years) |
Global Warming Potential
(Time Horizon in years) |
||||
20 yrs
|
100 yrs
|
500 yrs
|
||||
Carbon dioxide | CO2 |
1
|
1
|
1
|
||
Methanea | CH4 |
12.0 b
|
62
|
23
|
7
|
|
Nitrous oxide | N2O |
114 b
|
275
|
296
|
156
|
|
Hydrofluorocarbons |
|
|
|
|||
HFC-23 | CHF3 |
260
|
9400
|
12000
|
10000
|
|
HFC-32 | CH2F2 |
5.0
|
1800
|
550
|
170
|
|
HFC-41 | CH3F |
2.6
|
330
|
97
|
30
|
|
HFC-125 | CHF2CF3 |
29
|
5900
|
3400
|
1100
|
|
HFC-134 | CHF2CHF2 |
9.6
|
3200
|
1100
|
330
|
|
HFC-134a | CH2FCF3 |
13.8
|
3300
|
1300
|
400
|
|
HFC-143 | CHF2CH2F |
3.4
|
1100
|
330
|
100
|
|
HFC-143a | CF3CH3 |
52
|
5500
|
4300
|
1600
|
|
HFC-152 | CH2FCH2F |
0.5
|
140
|
43
|
13
|
|
HFC-152a | CH3CHF2 |
1.4
|
410
|
120
|
37
|
|
HFC-161 | CH3CH2F |
0.3
|
40
|
12
|
4
|
|
HFC-227ea | CF3CHFCF3 |
33
|
5600
|
3500
|
1100
|
|
HFC-236cb | CH2FCF2CF3 |
13.2
|
3300
|
1300
|
390
|
|
HFC-236ea | CHF2CHFCF3 |
10
|
3600
|
1200
|
390
|
|
HFC-236fa | CF3CH2CF3 |
220
|
7500
|
9400
|
7100
|
|
HFC-245ca | CH2FCF2CHF2 |
5.9
|
2100
|
640
|
200
|
|
HFC-245fa | CHF2CH2CF3 |
7.2
|
3000
|
950
|
300
|
|
HFC-365mfc | CF3CH2CF2CH3 |
9.9
|
2600
|
890
|
280
|
|
HFC-43-10mee | CF3CHFCHFCF2CF3 |
15
|
3700
|
1500
|
470
|
|
Fully fluorinated species | ||||||
SF6 |
3200
|
15100
|
22200
|
32400
|
||
CF4 |
50000
|
3900
|
5700
|
8900
|
||
C2F6 |
10000
|
8000
|
11900
|
18000
|
||
C3F8 |
2600
|
5900
|
8600
|
12400
|
||
C4F10 |
2600
|
5900
|
8600
|
12400
|
||
C4F8 |
3200
|
6800
|
10000
|
14500
|
||
C5F12 |
4100
|
6000
|
8900
|
13200
|
||
C6F14 |
3200
|
6100
|
9000
|
13200
|
||
Ethers and Halogenated Ethers | ||||||
CH3OCH3 |
0.015
|
1
|
1
|
<<1
|
||
HFE-125 | CF3OCHF2 |
150
|
12900
|
14900
|
9200
|
|
HFE-134 | CHF2OCHF2 |
26.2
|
10500
|
6100
|
2000
|
|
HFE-143a | CH3OCF3 |
4.4
|
2500
|
750
|
230
|
|
HCFE-235da2 | CF3CHClOCHF2 |
2.6
|
1100
|
340
|
110
|
|
HFE-245fa2 | CF3CH2OCHF2 |
4.4
|
1900
|
570
|
180
|
|
HFE-254cb2 | CHF2CF2OCH3 |
0.22
|
99
|
30
|
9
|
|
HFE-7100 | C4F9OCH3 |
5.0
|
1300
|
390
|
120
|
|
HFE-7200 | C4F9OC2H5 |
0.77
|
190
|
55
|
17
|
|
H-Galden 1040x | CHF2OCF2OC2F4OCHF2 |
6.3
|
5900
|
1800
|
560
|
|
HG-10 | CHF2OCF2OCHF2 |
12.1
|
7500
|
2700
|
850
|
|
HG-01 | CHF2OCF2CF2OCHF2 |
6.2
|
4700
|
1500
|
450
|
|
a. The methane GWPs include an
indirect contribution from stratospheric H2O and O3
production. b. The values for methane and nitrous oxide are adjustment times, which incorporate the indirect effects of emission of each gas on its own lifetime. |
Other reports in this collection |