National Academies Press: OpenBook

Verifying Greenhouse Gas Emissions: Methods to Support International Climate Agreements (2010)

Chapter: Appendix B: Estimates of Signals Created in the Atmosphere by Emissions

« Previous: Appendix A: UNFCCC Inventories of Industrial Processes and Waste
Suggested Citation:"Appendix B: Estimates of Signals Created in the Atmosphere by Emissions." National Research Council. 2010. Verifying Greenhouse Gas Emissions: Methods to Support International Climate Agreements. Washington, DC: The National Academies Press. doi: 10.17226/12883.
×

Appendix B
Estimates of Signals Created in the Atmosphere by Emissions

To determine how well national emissions can be quantified from atmospheric measurements, it is necessary to first estimate the mole fraction signals produced over a country by its emissions, then compare the result to technical capabilities. The average emissions are defined as the total national emissions divided by the area, and they are expressed in units of moles per square meter per second (mol m–2 s–1). An air mass with a certain thickness, traveling over a region, collects emissions during its transit. The transit time is estimated as the fetch divided by the wind speed. The fetch is taken as the square root of the area, and a wind speed of 5 m s–1 is assumed. When trace gas emissions are mixed into the air mass, its mole fraction changes (denoted by ); the change is smaller when the trace gas is diluted into a larger air mass. The latter is expressed as moles per square meter in the column of air into which the trace is being mixed (equation 1).

(1)

At sea level the total atmospheric column contains ~356,000 mol m–2 of air. The lowest 1 km, a typical height of the atmospheric boundary layer, contains ~40,000 mol m–2 of air at sea level, or ~11 percent of the total atmosphere. In Table B.1 the total column and the boundary layer masses assume the surface to be sea level for each country. At an average wind speed of 5 m s–1, air moves 430 km in 24 hours, so it takes 4.6 days to traverse a fetch of 2,000 km. Air usually remains in the boundary layer 3-5 days. For longer fetches it becomes increasingly unlikely that all of the emissions remain confined to the boundary layer, and the mole fraction change is then overestimated for those cases.

Table B.1 compares national carbon dioxide (CO2) emissions and the estimated atmospheric signal for the 20 largest CO2-emitting nations, which represent more than 80 percent of estimated global emissions. The numbers in the last two columns are typical, but will vary greatly in practice because they are inversely proportional to wind speed. How do the estimates in Table B.1 compare with observations? Based on a very limited number of 14C measurements of CO2 in small aircraft off the coast of Cape May and New Hampshire, the average component of CO2 from recent fossil-fuel combustion is ~3 parts per million (ppm) in the boundary layer.

It is striking to note in Table B.1 how small, relative to background, the mole fraction signals are when averaged over an entire country, and also that the signals for Japan, Germany, and Korea are comparable to those for the two largest emitters: the United States and China. That is due to the higher emissions intensity (per square meter) in the three smaller countries.

Table B.2 presents data from the same 20 countries, for methane (CH4), nitrous oxide (N2O), and sulfur hexafluoride (SF6), estimated in the same way as in Table B.1. When comparing these estimates with U.S. observations from the National Oceanic and Atmospheric Administration network, the estimated

Suggested Citation:"Appendix B: Estimates of Signals Created in the Atmosphere by Emissions." National Research Council. 2010. Verifying Greenhouse Gas Emissions: Methods to Support International Climate Agreements. Washington, DC: The National Academies Press. doi: 10.17226/12883.
×

TABLE B.1 National CO2 Emissions and Estimated Atmospheric Signal

Country

Area (1,000 km2)

Fetch (km)

CO2(Mton yr–1)

Population (millions)

Average Emissions (μmol m–2s–1)

Total Column (ppm)

Boundary Layer 1 km (ppm)

United States

9,827

3,134

5,892

307.0

0.432

0.76

6.8

China

9,571

3,093

5,577

1,329.0

0.420

0.73

6.5

Russia

17,075

4,132

1,568

142.0

0.066

0.15

1.4

Japan

378

614

1,249

128.0

2.379

0.82

7.3

India

3,166

1,779

1,222

1169.0

0.278

0.28

2.5

Germany

357

597

829

82.6

1.672

0.56

5.0

Canada

9,985

3,159

559

32.8

0.040

0.07

0.6

UK

244

493

539

60.8

1.591

0.44

3.9

Italy

301

548

477

58.9

1.141

0.35

3.1

South Korea

99

314

475

48.2

3.455

0.61

5.4

Iran

1,648

1,283

447

71.2

0.195

0.14

1.3

Mexico

1,964

1,401

411

106.5

0.151

0.12

1.1

France

544

737

399

61.6

0.528

0.22

1.9

Australia

7,682

2,771

382

20.7

0.036

0.06

0.5

Indonesia

1,905

1,380

367

232.0

0.139

0.11

1.0

Spain

506

711

367

44.3

0.522

0.21

1.9

Brazil

8,547

2,923

352

192.0

0.030

0.05

0.4

South Africa

1,219

1,104

337

48.6

0.199

0.12

1.1

Saudi Arabia

2,240

1,496

333

24.8

0.107

0.09

0.8

Ukraine

604

777

303

46.2

0.361

0.16

1.4

NOTES: Mton CO2 = million metric ton of CO2. The totals include electricity generation, heating, transportation, manufacturing and construction, and other fuel combustion, but not bunker fuels, land-use change, or waste.

SOURCES: National totals for 2005 from the World Resources Institute. Area and population are from the CIA Fact book.

TABLE B.2 National Emissions of CH4, N2O, and SF6 and Estimated Atmospheric Signals

 

CH4

N2O

SF6

Country

Emissions (Mton yr–1)

Average (nmol m–2s–1)

Total Column (ppb)

Boundary Layer 1 km (ppb)

Emissions (Mton yr–1)

Average (pmol m–2s–1)

Total Column (ppb)

Boundary Layer 1 km (ppb)

Emissions (ton yr–1)

Average (fmol m–2s–1)

Total Column (ppt)

Boundary Layer 1km (ppt)

United States

20.84

4.20

7.4

65

1.261

92

0.163

1.4

842

18.60

0.0327

0.29

China

34.13

7.06

12.3

109

2.296

172

0.300

2.7

364

8.25

0.0143

0.13

Russia

12.58

1.46

3.4

30

0.193

8

0.019

0.2

175

2.22

0.0052

0.05

Japan

0.84

4.40

1.5

13

0.119

226

0.078

0.7

57

32.73

0.0113

0.10

India

21.91

13.70

13.7

121

0.239

54

0.054

0.5

92

6.31

0.0063

0.06

Germany

2.74

15.20

5.1

45

0.213

429

0.144

1.3

35

21.28

0.0071

0.06

Canada

4.08

0.81

1.4

12

0.194

13

0.025

0.2

110

2.39

0.0042

0.04

UK

1.85

15.01

4.2

37

0.153

451

0.125

1.1

22

19.57

0.0054

0.05

Italy

1.38

9.08

2.8

24

0.150

358

0.111

1.0

18

12.98

0.0040

0.04

South Korea

1.34

26.80

4.7

42

0.057

414

0.073

0.7

96

210.45

0.0372

0.33

Iran

3.83

4.60

3.3

29

0.077

33

0.024

0.2

22

2.90

0.0021

0.02

Mexico

7.39

7.45

5.9

52

0.090

32

0.026

0.2

35

3.87

0.0030

0.03

France

2.44

8.88

3.7

32

0.268

354

0.147

1.3

18

7.18

0.0030

0.03

Australia

5.16

1.33

2.1

18

0.107

10

0.016

0.1

31

0.88

0.0014

0.01

Indonesia

7.32

7.61

5.9

52

0.142

53

0.042

0.4

18

2.05

0.0016

0.01

Spain

1.46

5.71

2.3

20

0.097

138

0.055

0.5

9

3.86

0.0015

0.01

Brazil

15.56

3.61

5.9

52

0.888

74

0.123

1.1

75

1.90

0.0031

0.03

South Africa

2.21

3.59

2.2

19

0.078

46

0.029

0.3

35

6.23

0.0039

0.03

Saudi Arabia

1.11

0.98

0.8

7

0.038

12

0.010

0.1

22

2.13

0.0018

0.02

Ukraine

6.14

20.13

8.8

78

0.091

108

0.047

0.4

31

11.14

0.0049

0.04

NOTES: nmol = nanomol, 10–9 mol; pmol = picomol, 10–12 mol; fmol = femtomol, 10–15 mol.

SOURCE: National emissions for 2005 from the World Resources Institute.

Suggested Citation:"Appendix B: Estimates of Signals Created in the Atmosphere by Emissions." National Research Council. 2010. Verifying Greenhouse Gas Emissions: Methods to Support International Climate Agreements. Washington, DC: The National Academies Press. doi: 10.17226/12883.
×

enhancement of greenhouse gas mole fractions is not far from, but on the high side of, observed values for the lowest 1 km, consistent with the fact that over long fetches the emissions tend not to remain confined to the boundary layer. For CH4, the observed annual average enhancement in the boundary layer of the United States, relative to background values, is 20-60 parts per billion (ppb), with large standard deviation of midday means of 20-30 ppb. For N2O, these numbers are 0.2-0.4 ppb, and daily standard deviation of 0.3-0.7 ppb; for SF6, the average enhancement is 0.05-0.2 parts per trillion (ppt), with daily variability of 0.07 to 0.13 ppt. For N2O, the highest observed enhancement is 0.7 ppb over Iowa, which is indicative of intense regional emissions. The World Meteorological Organization-recommended accuracies for in situ measurements are 2 ppb for CH4, 0.1 ppb for N2O, and 0.02 ppt for SF6.

Table B.3 explores expected enhancements of the CO2 mole fraction over metropolitan areas. The signal expected to be produced over a single large city relative to its surroundings is comparable to, and in many cases larger than, the average produced by an entire country. Note that the observed average fossil-fuel CO2 enhancement at the surface in Los Angeles based on 14C measurements of plants (Figure 4.5) is about five times larger over part of the basin than the number estimated in Table B.3.

The latter is derived with a standard assumption of a steady 5 m s–1 average wind vector, which would imply that the residence time of air over the metropolitan area would be ~4 hours. Because Los Angeles is surrounded by mountains on three sides, the residence time over the city is much longer.

SIGNAL FROM A 1 GW(E) COAL FIRED POWER PLANT

One gigawatt (GW) corresponds to 8.76 109 kWh yr–1. Applying the U.S. average 25 mol C kWh–1, the plant would produce 2.19 1011 mol yr–1, or 6,900 mol s–1. If the perpendicular distance across the plume is 1.7 km at some distance downwind, and the wind speed is 5 m s–1, then 1 second of CO2 emissions is diluted into 1,700 × 5 m2 s–1 × 3.56 105 mol of air per square meter (full atmospheric column). The number 1.7 km is chosen to correspond to the 3 km2 footprint of a single Orbiting Carbon Observatory (OCO) sounding. The CO2 increase in the total column is then 2.3 ppm.

SIGNAL FROM A GEOLOGICAL SEQUESTRATION LEAK

Significant quantities of CO2 may one day be captured at large point sources in the utility and industrial sectors and injected into storage sites in the Earth, rather than released to the atmosphere. If this occurs, it will be important to monitor both the quantity of CO2 that is injected into storage sites and the amount of any CO2 that leaks from these sites (IPCC, 2005). Leaks from geological sequestration are relatively easy to detect. The emissions are at the surface and are not buoyant like those from a power plant. At night they

TABLE B.3 Expected CO2 Signals for Selected Metropolitan Areas

City

Area (km2)a

Emissions (Mton CO2yr–1)

Emissions (μmol m–2s–1)

Total Column (ppm)

Boundary Layer 1 km (ppm)

Los Angeles

3,700

73.2

14.2

0.49

4.3

Chicago

2,800

79.1

20.3

0.60

5.4

Houston

3,300

101.8

22.2

0.72

6.4

Indianapolis

900

20.1

16.1

0.27

2.4

Tokyo

1,700

64

27

0.63

5.6

Seoul

600

43

52

0.71

6.3

Beijing

800

74

67

1.1

9.4

Shanghai

700

112

116

1.8

15

NOTES: Mton CO2 is million metric tons of CO2.

aArea represents the contiguous area of intense and activity and was estimated using Google maps in “satellite” mode, which shows built up areas by color and road density.

SOURCES: Emissions in 1998 for four east Asian cities from Dhakal et al. (2003). U.S. estimates are from the VULCAN emissions inventory for 2002 (<www.purdue.edu/eas/carbon/vulcan>).

Suggested Citation:"Appendix B: Estimates of Signals Created in the Atmosphere by Emissions." National Research Council. 2010. Verifying Greenhouse Gas Emissions: Methods to Support International Climate Agreements. Washington, DC: The National Academies Press. doi: 10.17226/12883.
×

will tend to stay at the surface. Assume that the CO2 from a 1 GW(e) power plant is captured and injected into a well. If 0.1 percent escapes during the injection, there would be a point source of 6.9 mol s–1 of CO2. At a point 1 km downstream, with a wind speed of 5 m s–1 and a plume width of 100 m and plume height of 100 m, the CO2 enhancement would be 3.3 ppm, causing a 14C depletion of 0.89 percent. A second scenario is escape from the geological formation into which the CO2 has been stored. If 0.2 percent of the sequestered CO2 escapes per year (residence time 500 years), the leak would increase over time as more CO2 is pumped into the formation. After 1 year the leak rate would be 14 mol s–1, after 2 years 28 mol s–1, and so on. In addition, when the escaping CO2 goes through soil, the CO2 mole fraction in soil air would become very high, eventually depriving the vegetation of sufficient oxygen in the root zone and leading to plant death, which should be easily detectable.

REFERENCES

Dhakal, S., S. Kaneko, and H. Imura, 2003, CO2 emissions from energy use in East-Asian mega-cities, in Proceedings of the International Workshop on Policy Integration Towards Sustainable Urban Use for Cities in Asia, February 4-5, East-West Center, Honolulu, Hawaii, available at <http://enviroscope.iges.or.jp/ contents/6/index.html>.

IPCC (Intergovernmental Panel on Climate Change), 2005, Carbon Dioxide Capture and Storage, IPCC Special Report, prepared by Working Group III of the Intergovernmental Panel on Climate Change, B. Metz, O. Davidson, H.C. de Coninck, M. Loos, and L.A. Meyer, eds., Cambridge University Press, New York, 442 pp.

Suggested Citation:"Appendix B: Estimates of Signals Created in the Atmosphere by Emissions." National Research Council. 2010. Verifying Greenhouse Gas Emissions: Methods to Support International Climate Agreements. Washington, DC: The National Academies Press. doi: 10.17226/12883.
×
Page 89
Suggested Citation:"Appendix B: Estimates of Signals Created in the Atmosphere by Emissions." National Research Council. 2010. Verifying Greenhouse Gas Emissions: Methods to Support International Climate Agreements. Washington, DC: The National Academies Press. doi: 10.17226/12883.
×
Page 90
Suggested Citation:"Appendix B: Estimates of Signals Created in the Atmosphere by Emissions." National Research Council. 2010. Verifying Greenhouse Gas Emissions: Methods to Support International Climate Agreements. Washington, DC: The National Academies Press. doi: 10.17226/12883.
×
Page 91
Suggested Citation:"Appendix B: Estimates of Signals Created in the Atmosphere by Emissions." National Research Council. 2010. Verifying Greenhouse Gas Emissions: Methods to Support International Climate Agreements. Washington, DC: The National Academies Press. doi: 10.17226/12883.
×
Page 92
Next: Appendix C: Current Sources of Atmospheric and Oceanic Greenhouse Gas Data »
Verifying Greenhouse Gas Emissions: Methods to Support International Climate Agreements Get This Book
×
Buy Paperback | $41.00 Buy Ebook | $32.99
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

The world's nations are moving toward agreements that will bind us together in an effort to limit future greenhouse gas emissions. With such agreements will come the need for all nations to make accurate estimates of greenhouse gas emissions and to monitor changes over time. In this context, the present book focuses on the greenhouse gases that result from human activities, have long lifetimes in the atmosphere and thus will change global climate for decades to millennia or more, and are currently included in international agreements. The book devotes considerably more space to CO2 than to the other gases because CO2 is the largest single contributor to global climate change and is thus the focus of many mitigation efforts. Only data in the public domain were considered because public access and transparency are necessary to build trust in a climate treaty.

The book concludes that each country could estimate fossil-fuel CO2 emissions accurately enough to support monitoring of a climate treaty. However, current methods are not sufficiently accurate to check these self-reported estimates against independent data or to estimate other greenhouse gas emissions. Strategic investments would, within 5 years, improve reporting of emissions by countries and yield a useful capability for independent verification of greenhouse gas emissions reported by countries.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    Switch between the Original Pages, where you can read the report as it appeared in print, and Text Pages for the web version, where you can highlight and search the text.

    « Back Next »
  6. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  7. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  8. ×

    View our suggested citation for this chapter.

    « Back Next »
  9. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!