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2006 Bibliometric Analysis (Revised) for Papers on Topics Related to Global Change (GC) (papers Published 1998 to 2005)
March 2006 Report (RevisedJune 2007)

This is a revised bibliometric analysis of the papers prepared by intramural and extramural researchers of the U.S. Environmental Protection Agency (EPA) on topics related to global change (GC). This analysis was revised in June 2007 because the journals were initially categorized into the fields used by Thomson Scientifics Essential Science Indicators (ESI) using information provided in Thomsons Journal Citation Reports (JCR); for this revised analysis, the journals were categorized into ESI fields using the journal category list by ESI that is available on the Internet athttp://in-cites.com/journal-list/index.html. The Journal List for ESI was made available in 2006 and the current list contains all of the 12,734 journals covered for ESI up to December 31, 2006. This list is updated bimonthly by Thomson. This revised bibliometric analysis will allow comparison of the results of this 2005 analysis to those of the analysis performed in 2007.

This is a bibliometric analysis of the papers prepared by intramural and extramural researchers of on topics related to global change. For this analysis, 341 papers, reports, and books were reviewed, and they were published from 1998 to 2005. These publications were cited 3,694 times in the journals covered by Thomsons Web of Science.1 Of these 341 publications, 293 (86%) have been cited at least once in a journal.

Searches of Thomsons Web of Science, Scopus2 , and Google were conducted to obtain times cited data for the global change journal publications. The analysis was completed using Thomsons ESI and JCR as benchmarks. ESI provides access to a unique and comprehensive compilation of essential science performance statistics and science trends data derived from Thomsons databases. For influence and impact measures, ESI employs both total citation counts by field and cites per paper scores. The former reveals gross influence while the latter shows weighted influence, also called impact. JCR is a recognized authority for evaluating journals. It presents quantifiable statistical data that provide a systematic, objective way to evaluate the worlds leading journals and their impact and influence in the global research community. The two key measures used in this analysis to assess the journals in which the EPA global change papers are published are the Immediacy Index and the Impact Factor. The Immediacy Index is a measure of how quickly the average article in a journal is cited. This index indicates how often articles published in a journal are cited within the same year and it is useful in comparing how quickly journals are cited. The Impact Factor is a measure of the frequency with which the average article in a journal has been cited in a particular year. The Impact Factor helps evaluate a journals relative importance, especially when compared to other journals in the same field.

The report is divided into three sections. The first section presents an analysis of all 341 global change papers analyzed by ESI field (e.g., Environment/Ecology, Geosciences, Plant & Animal Science, Engineering). The second section presents an analysis of the global change papers by year of publication. The third section presents an analysis of the global change papers by focus area (e.g., air quality, regional assessment, ecosystems). In each section, a summary of the results is provided as well as the data evaluated and a description of the analysis.

I. Analysis of Global Change Publications by ESI Field

SUMMARY OF RESULTS

  1. About one-fifth of the global change publications are highly cited papers. A review of the citations indicates that 67 (19.6%) of the global change papers qualify as highly cited when using the ESI criteria for the top 10% of highly cited publications. This is nearly twice the number expected for a typical program. Eight (2.3%) of the global change papers qualify as highly cited when using the criteria for the top 1%, which is more than twice the number expected. One (0.3%) of these papers qualifies as very highly cited (in the top 0.1%), which is 3 times the number expected. It is not surprising that no papers actually meet the 0.01% threshold for the most highly cited papers because the expected number for this program is 0.03 papers in the most highly cited category.
  2. The global change papers are more highly cited than the average paper. Using the ESI average citation rates for papers published by field as the benchmark, in 9 of the 14 fields in which the EPA global change papers were published, the ratio of actual to expected cites is greater than 1, indicating that the global change papers are more highly cited than the average papers in those fields. For all 14 fields combined, the ratio of total number of cites to the total number of expected cites (3,694 to 2103.25) is 1.8, indicating that the global change papers are more highly cited than the average paper.
  3. Nearly one-third of the global change papers are published in very high impact journals. Ninety-nine (99) of the 341 papers were published in the top 10% of journals ranked by JCR Impact Factor, representing 29% of EPAs global change papers. This number is about 3 times higher than expected. One-hundred seven (107) of the 341 papers appear in the top 10% of journals ranked by JCR Immediacy Factor, representing 31% of EPAs global change papers. This number is more than 3 times higher than expected.
  4. Eight of the global change papers qualify as hot papers. Using the hot paper thresholds established by ESI as a benchmark, 8 hot papers, representing 2.4% of the global change papers, were identified in the analysis. Hot papers are papers that were highly cited shortly after they were published. The number of global change hot papers is 24 times higher than expected.
  5. The authors of the global change papers cite themselves much less than the average author. Two-hundred fifteen (215) of the 3,694 cites are author self-cites. This 5.8% author self-citation rate is well below the accepted range of 10-30% author self-citation rate.
  6. Twenty-seven of the authors of the global change papers are included in ISIHighlyCited.com, which is a database of the worlds most influential researchers who have made key contributions to science and technology during the period from 1981 to 1999.

Highly Cited Global Change Publications

The 341 global change papers reviewed for this analysis covered 14 of the 22 ESI fields. The distribution of the papers among these 14 fields and the number of citations by field are presented in Table 1.

Table 1. Global Change Papers by ESI Fields


ESI Field

No. of Citations

No. of EPA GC Papers

Average Cites/Paper

Environment/Ecology

1,521

148

10.28

Geosciences

680

54

12.59

Plant & Animal Science

462

48

9.62

Multidisciplinary

419

7

59.86

Clinical Medicine

211

19

7.00

Engineering

203

41

4.95

Microbiology

85

4

21.25

Biology & Biochemistry

60

8

7.50

Immunology

20

2

10.0

Social Sciences, general

14

5

2.80

Economics & Business

11

2

5.50

Agricultural Sciences

6

1

1.00

Physics

2

1

2.00

Computer Science

0

1

0.00

Total = 3,694

Total = 341

10.83

There are 67 (19.65% of the papers analyzed) highly cited EPA global change papers in 7 of the 14 fieldsEnvironment/Ecology, Geosciences, Multidisciplinary, Plant & Animal Science, Engineering, Clinical Medicine, and Economics & Businesswhen using the ESI criteria for the top 10% of papers. Table 2 shows the number of EPA papers in those 7 fields that meet the top 10% threshold in ESI. Eight (2.35%) of the papers analyzed qualify as highly cited when using the ESI criteria for the top 1% of papers. These papers cover five fieldsMultidisciplinary, Environment/Ecology, Geosciences, Plant & Animal Science, and Engineering. Table 3 shows the 8 papers by field that meet the top 1% threshold in ESI. The citations for these 10 papers are provided in Tables 4 through 8. There was 1(0.3%) very highly cited global change paper in the Multidisciplinary field. This paper, which met the top 0.1% threshold in ESI, is listed in Table 9. None of the global change papers actually met the top 0.01% threshold in ESI, which is to be expected.

Table 2.


ESI Field

Citations

No. of Papers

Average Cites/Paper

% of EPA Papers in Field

Environment/Ecology

773

27

28.63

18.24%

Geosciences

485

13

37.31

24.07%

Multidisciplinary

405

5

81.00

71.43%

Plant & Animal Science

262

11

23.82

22.92%

Engineering

128

7

18.26

17.07%

Clinical Medicine

126

3

42.00

15.79%

Economics & Business

10

1

10.00

50.00%

Total = 2,189

Total = 67

32.67

19.65%

Number of Highly Cited Global Change Papers by Field (top 10%)

Table 3. Number of Highly Cited Global Change Papers by Field (top 1%)


ESI Field

Citations

No. of Papers

Average Cites/Paper

% of EPA Papers in Field

Multidisciplinary

304

2

152.0

28.57%

Environment/Ecology

215

2

107.5

1.35%

Geosciences

134

2

67.00

3.70%

Plant & Animal Science

79

1

79.00

2.08%

Engineering

52

1

52.00

2.44%

Total = 784

Total = 8

98.0

2.35%

Table 4. Highly Cited Global Change Papers in the Field of Multidisciplinary (top 1%)


No. of Cites

First Author

Paper

236

Root TL

Fingerprints of global warming on wild animals and plants. Nature 2003;421(6918):57-60.

68

Pascual M

Cholera dynamics and El Nino-Southern Oscillation. Science 2000;289(5485):1766-1769.

Table 5. Highly Cited Global Change Papers in the Field of
Environment/Ecology (top 1%)


No. of Cites

First Author

Paper

141

National Assessment Team

Climate Change Impacts on the United States: The Potential Consequences of Climate Variability and Change (Overview and Foundation reports), 2001.

74

Marsh DM

Metapopulation dynamics and amphibian conservation. Conservation Biology 2001;15(1):40-49.

Table 6. Highly Cited Global Change Papers in the Field of Geosciences (top 1%)


No. of Cites

First Author

Paper

61

Pielke RA

Influence of the spatial distribution of vegetation and soils on the prediction of cumulus convective rainfall. Reviews of Geophysics 2001;39(2):151-177.

73

Chase TN

Simulated impacts of historical land cover changes on global climate in northern winter. Climate Dynamics 2000;16(2-3):93-105.

Table 7. Highly Cited Global Change Paper in the Field of
Plant & Animal Science (top 1%)


No. of Cites

First Author

Paper

79

Moran MA

Carbon loss and optical property changes during long-term photochemical and biological degradation of estuarine dissolved organic matter. Limnology and Oceanography 2000;45(6):1254-1264.

Table 8. Highly Cited Global Change Papers in the Field of Engineering (top 1%)


No. of Cites

First Author

Paper

52

Douglas EM

Trends in floods and low flows in the United States: impact of spatial correlation. Journal of Hydrology 2000;240(1-2):90-105.

Table 9. Very Highly Cited Global Change Paper in the
Field of Multidisciplinary (top 0.1%)


No. of Cites

First Author

Paper

236

Root TL

Fingerprints of global warming on wild animals and plants. Nature 2003;421(6918):57-60.

Ratio of Actual Cites to Expected Citation Rates

The expected citation rate is the average number of cites that a paper published in the same journal in the same year and of the same document type (article, review, editorial, etc.) has received from the year of publication to the present. Using the ESI average citation rates for papers published by field as the benchmark, in 9 of the 14 fields in which the EPA global change papers were published, the ratio of actual to expected cites is greater than 1, indicating that the global change papers are more highly cited than the average papers in those fields (see Table 10).

Table 10. Ratio of Actual Cites to Expected Cites for Global Change Papers by Field


ESI Field

Total Cites

Expected Cite Rate

Ratio

Agricultural Sciences

6

6.98

0.86

Biology & Biochemistry

60

64.12

0.94

Clinical Medicine

211

148.50

1.42

Computer Science

0

0.63

0.00

Economics & Business

11

2.36

4.66

Engineering

203

112.83

1.80

Environment/Ecology

1,521

1,041.40

1.46

Geosciences

680

354.04

1.92

Immunology

20

28.94

0.69

Microbiology

85

53.17

1.60

Multidisciplinary

419

28.97

14.46

Physics

2

3.96

0.50

Plant & Animal Science

462

247.31

1.87

Social Sciences, general

14

10.07

1.39

JCR Benchmarks

Impact Factor. The JCR Impact Factor is a well known metric in citation analysis. It is a measure of the frequency with which the average article in a journal has been cited in a particular year. The Impact Factor helps evaluate a journals relative importance, especially when compared to others in the same field. The Impact Factor is calculated by dividing the number of citations in the current year to articles published in the 2 previous years by the total number of articles published in the 2 previous years.

Table 11 indicates the number of global change papers published in the top 10% of journals, based on the JCR Impact Factor. Ninety-nine (99) of 341 papers were published in the top 10% of journals, representing 29.0% of EPAs global change papers. This indicates that nearly one-third of the global change papers are published in the highest quality journals as determined by the JCR impact factor, which is nearly 3 times the expected percentage.

Table 11. Global Change Papers in Top 10% of Journals by JCR Impact Factor


EPA Global Change Papers in that Journal

Journal

Impact Factor
(IF)

JCR IF Rank

10

Environmental Health Perspectives

3.929

439

9

Journal of Geophysical ResearchAtmospheres

2.839

831

7

Ecological Applications

3.287

623

7

Ecosystems

3.241

642

6

Global Change Biology

4.333

358

6

Journal of Climate

3.500

558

5

Epidemiology

3.840

459

5

Conservation Biology

3.672

504

5

Environmental Science & Technology

3.557

540

4

Lancet

21.713

20

4

Proceedings of the National Academy of Sciences of the United States of America

10.452

88

4

Limnology and Oceanography

3.024

737

3

Applied and Environmental Microbiology

3.810

470

2

Nature

32.182

9

2

Ecology

4.104

394

2

Plant Cell and Environment

3.634

517

2

New Phytologist

3.355

603

2

American Journal of Public Health

3.241

642

2

Bioscience

3.041

730

1

Science

31.853

10

1

JAMAJournal of the American Medical Association

24.831

15

1

Reviews of Geophysics

8.667

114

1

British Medical Journal

7.038

169

1

Emerging Infectious Diseases

5.643

230

1

Trends in Parasitology

5.497

239

1

Journal of Infectious Diseases

4.943

287

1

American Journal of Epidemiology

4.933

290

1

Microbes and Infection

3.753

480

1

Climate Dynamics

3.497

561

1

Oecologia

2.899

800

1

Agricultural and Forest Meteorology

2.811

844

Total = 99

 

 

Immediacy Index. The JCR Immediacy Index is a measure of how quickly the average article in a journal is cited. It indicates how often articles published in a journal are cited within the year they are published. The Immediacy Index is calculated by dividing the number of citations to articles published in a given year by the number of articles published in that year.

Table 12 indicates the number of global change papers published in the top 10% of journals, based on the JCR Immediacy Index. One-hundred seven (107) of the 341 papers appear in the top 10% of journals, representing 31.4% of the global change papers. This indicates that approximately one-third of the global change papers are published in the highest quality journals as determined by the JCR immediacy index, which is more than 3 times higher than the expected percentage.

Table 12. Global Change Papers in Top 10% of Journals by JCR Immediacy Index


EPA Papers in that Journal

Journal

Immediacy Index
(II)

JCR II Rank

17

Climatic Change

1.235

195

10

Environmental Health Perspectives

1.202

202

9

Journal of Geophysical ResearchAtmospheres

0.617

630

7

Ecosystems

2.048

76

7

Ecological Applications

0.747

466

6

Journal of Climate

0.528

795

5

Epidemiology

0.864

354

5

Conservation Biology

0.744

468

5

Environmental Science & Technology

0.623

617

4

Lancet

5.017

12

4

Proceedings of the National Academy of Sciences of the United States of America

1.923

89

3

Journal of Biogeography

0.514

827

2

Nature

6.089

5

2

New Phytologist

0.876

349

2

Bioscience

0.863

356

2

American Journal of Public Health

0.723

489

2

Plant Cell and Environment

0.605

653

2

Ecology

0.590

676

1

Science

7.379

3

1

JAMAJournal of the American Medical Association

5.499

9

1

British Medical Journal

3.039

35

1

Reviews of Geophysics

1.714

110

1

Ambio

1.435

156

1

Emerging Infectious Diseases

1.350

169

1

Journal of Infectious Diseases

1.105

229

1

American Journal of Epidemiology

0.842

373

1

Trends in Parasitology

0.819

393

1

Aquatic Sciences

0.800

413

1

Hydrobiologia

0.681

532

1

Tellus Series B-Chemical and Physical Meteorology

0.610

646

1

Theoretical and Applied Climatology

0.564

720

Total = 107

 

Hot Papers

ESI establishes citation thresholds for hot papers, which are selected from the highly cited papers in different fields, but the time frame for citing and cited papers is much shorterpapers must be cited within 2 years of publication and the citations must occur in a 2-month time period. Papers are assigned to 2-month periods and thresholds are set for each period and field to select 0.1% of papers. There were no hot papers identified for the current 2-month period (i.e., January-February 2006), but there were a number of hot papers identified from previous periods.

Using the hot paper thresholds established by ESI as a benchmark, 8 hot papers, representing 2.4% of the global change papers, were identified in five fieldsEnvironment/Ecology, Engineering, Multidisciplinary, Plant & Animal Science, and Geosciences. The hot papers are listed in Table 13.

Table 13. Hot Papers Identified Using ESI Thresholds


Field

ESI Hot Papers Threshold

No. of Cites in 2-Month Period

Paper

Environment/ Ecology

4

8 cites in May 2000

Polsky C, et al. The Mid-Atlantic Region and its climate: past, present, and future. Climate Research 2000;14(3):161-173.

4

5 cites in May 2000

Rose A, et al. Simulating the economic impacts of climate change in the Mid-Atlantic Region. Climate Research 2000;14(3):175-183.

4

5 cites in May 2000

Fisher A, et al. The Mid-Atlantic Regional Assessment: motivation and approach. Climate Research 2000;14(3):153-159.

4

4 cites in October-November 2001

Patz JA, et al. The potential health impacts of climate variability and change for the United States: executive summary of the health sector of the US National Assessment. Environmental Health Perspectives 2000;108(4):367-376.

Engineering

5

7 cites in June-July 2002

Douglas EM, et al. Trends in floods and low flows in the United States: impact of spatial correlation. Journal of Hydrology 2000;240(1-2):90-105.

Multidisciplinary

9

9 cites in September-October 2003

Root TL, et al. Fingerprints of global warming on wild animals and plants. Nature 2003;421(6918):57-60.

Plant & Animal Science

4

5 cites in December 2002

Sousounis PJ, Grover EK. Potential future weather patterns over the Great Lakes region. Journal of Great Lakes Research 2002;28(4):496-520.

Geosciences

4

4 cites in October-November 2001

Hogrefe C, et al. Simulating regional-scale ozone climatology over the eastern United States: model evaluation. Atmospheric Environment 2004;38(17):2627-2638.

Author Self-Citation

Self-citations are journal article references to articles from that same author (i.e., the first author). Because higher author self-citation rates can inflate the number of citations, the author self-citation rate was calculated for the global change papers. Of the 3,694 total cites, 215 are author self-citesa 5.8% author self-citation rate. Garfield and Sher3 found that authors working in research-based disciplines tend to cite themselves on the average of 20% of the time. MacRoberts and MacRoberts4 claim that approximately 10% to 30% of all the citations listed fall into the category of author self-citation. Kovacic and Misak5 recently reported a 20% author self-citation rate for medical literature. Therefore, the 5.8% self-cite rate for the global change papers is well below the range for author self-citation.

Highly Cited Researchers

A search of Thomsons ISIHighlyCited.com revealed that 27 (3.5%) of the 773 authors of the global change papers are highly cited researchers. ISIHighlyCited.com is a database of the worlds most influential researchers who have made key contributions to science and technology during the period from 1981 to 1999. The highly cited researchers identified during this analysis of the global change publications are presented in Table 14.

Table 14. Highly Cited Researchers Authoring Global Change Publications


Highly Cited Researcher

Affiliation

ESI Field

Ankley, Gerald T

U.S. EPA

Environment/Ecology

Brown, Sandra L

Winrock International

Environment/Ecology

Caldwell, Martyn M

Utah State University

Environment/Ecology

Callaghan, Terry V

University of Sheffield

Environment/Ecology

Chase, Thomas N

NINDS

Neuroscience

Colwell, Rita R

Canon U.S. Life Sciences

Microbiology

Ehleringer, James

University of Utah

Environment/Ecology

Elliott, Edward T

University of Nebraska

Environment/Ecology

Giorgi, Filippo

Abdus Salam International Centre for Theoretical Physics

Geosciences

Goldberg, Richard

Columbia University

Plant & Animal Science

Jacob, Daniel J

Harvard University

Geosciences

Lauenroth, William K

Colorado State University

Environment/Ecology

Lugo, Ariel E

USDA

Environment/Ecology

Ojima, Dennis S

Colorado State University

Environment/Ecology

Pacala, Stephen

Princeton University

Ecology/Environment

Palmer, T.N.

European Center for Medium Range Weather Forecasts

Geosciences

Parton, William J

Colorado State University

Environment/Ecology

Pielke, Roger A

Colorado State University

Geosciences

Rind, David H

NASA Goddard

Geosciences

Running, Steven W

University of Montana

Environment/Ecology

Sala, Osvaldo E

Brown University

Environment/Ecology

Schimel, David S

National Center for Atmospheric Research

Environment/Ecology

Schwartz, Joel D

Harvard University

Environment/Ecology

Shugart, Herman H

University of Virginia

Environment/Ecology

Teramura, Alan H

University of Hawaii

Plant & Animal Science

Zeger, Scott L

Johns Hopkins University

Mathematics

Zepp, Richard G

U.S. EPA

Environment/Ecology

Total = 27

II. Analysis of Global Change Publications by Year of Publication

SUMMARY OF RESULTS
  1. About one-fifth of the global change publications are highly cited papers (this is twice the number expected for a typical program). From 1998 to 2005, the percentage of global change papers that qualified as highly cited when using the ESI criteria for the top 10% of highly cited publications ranges from a low of 7.4% to a high of 30.9%. From 2000 to 2003, there were 8 papers that qualified as very highly cited when using the ESI criteria for the top 1%, with the percentages ranging from 2.4% to 7.7%. These percentages are, on average, about 2.6 times higher than would be expected for a typical program. One paper published in 2003 meets the ESI criteria for the top 0.1%, which is about 3 times higher than would be expected for a typical program. None of the global change papers meet the ESI criteria for the most highly cited papers (top 0.01%). The expected number of papers in this top category for a program of this size would be 0.03 papers, so the absence of papers in this top category is not surprising.
  2. The global papers are more highly cited than the average paper. Using the ESI average citation rates for papers published by field as the benchmark, the ratio of actual to expected cites is greater than 1 for all but one of the years analyzed (i.e.,2004). This indicates that the global change papers are more highly cited than the average papers published in these fields.
  3. Nearly one-third of the global change papers are published in high impact journals as determined by the JCR Impact Factor of the journals in which the papers are published. For every year analyzed the number of global change papers published in high impact journals (the top 10% of journals) exceeds the expected 10% as determined by the JCR Impact Factor and Immediacy Index of the journals. The percentage of papers in high impact journals (by Impact Factor) ranges from 14.3% to 45.2%, which is 1.4 to 4.5 times higher than expected. The percentage of papers in high impact journals (by Immediacy Index) ranges from 14.3% to 38.1%, which is 1.4 to 3.8 times higher than expected.
  4. The percentage of publications cited one or more times is consistently high from 1998 to 2003. The number declines as expected in the more recent years (i.e., 2004 and 2005) because most publications are not cited until a year or longer after they are published.
  5. The authors of the global change papers cite themselves less than the average self-citation rate. The author self-citation rate for most years is well below the accepted range of 10-30% author self-citation rate. The only exception is in 2005, which is expected because most publications are not cited by other researchers until a year or longer after they are published.
6. There were hot papers published in 2000, 2002, 2003, and 2004. The absence of hot papers in 2005 is not surprising given the fact that the period during which the citations analyzed for determining hot paper status was incomplete.

This section of the report presents an analysis of the global change papers by year of publication from 1998 to 2005. The data are presented by year in Table 15, which includes eight key bibliometric parameters.

The results of the analysis are presented below and the numbers link the findings with the corresponding data in Table 15.

1. No. of Global Change Papers AnalyzedThe number of global change publications has ranged from 27 to 56 per year over the period analyzed (i.e., 1998 to 2005).

2. Total No. of Highly Cited PublicationsESI identifies four thresholds of highly cited papersthose in the top 10%, 1%, 0.1%, and 0.01%. It is extraordinary for a publication to meet the threshold for the top 0.01%; these publications are rare and should not be expected in every program. Using the ESI thresholds for the top 10% cited papers, about 20% of the global change publications are highly cited papers (this is twice the number expected for a typical program). From 1998 to 2005, the percentage of global change papers that qualify as highly cited when using the ESI criteria for the top 10% of highly cited publications ranges from a low of 7.4% to a high of 30.9%. From 2000 to 2003, there were 8 papers that qualify as very highly cited when using the ESI criteria for the top 1%, with the percentage ranging from 0% to 7.7%. These percentages are, on average, about 3,5 times higher than would be expected for a typical program. One paper published in 2003 meets the ESI criteria for the top 0.1%, which is about 3 times higher than would be expected for a typical program. None of the global change papers meet the ESI criteria for the most highly cited papers (top 0.01%). The expected number of papers in this top category for a typical program of this size would be 0.03 papers, so the absence of papers in this top category is not surprising.

3. Ratio of Actual to Expected CitesThe global papers are more highly cited than the average paper. Using the ESI average citation rates for papers published by field as the benchmark, the ratio of actual to expected cites is greater than 1 for all but two of the years analyzed (i.e., 2004 and 2005). This indicates that the global change papers are more highly cited than the average papers published in these fields.

4. No. of Papers in High Impact Journals by Impact FactorNearly one-third of the global change papers are published in high impact journals as determined by the JCR Impact Factor of the journals in which the papers are published. For every year analyzed, the number of global change papers published in high impact journals (the top 10% of journals) exceeds the expected 10% as determined by the JCR Impact Factor of the journals. The percentage of papers in high impact journals (by Impact Factor) ranges from 14.3% to 45.2%, which is 1.4 to 4.5 times higher than expected.

5. No. of Papers in High Impact Journals by Immediacy Index Nearly one-third of the global change papers are published in high impact journals as determined by the JCR Immediacy Index of the journals in which the papers are published. For every year analyzed, the number of global change papers published in high impact journals (the top 10% of journals) exceeds the expected 10% as determined by the JCR Immediacy Index of the journals. The percentage of papers in high impact journals (by Immediacy Index) ranges from 14.3% to 38.1%, which is 1.4 to 3.8 times higher than expected.

6. Total No. of Publications Cited One or More TimesThe percentage of publications cited one or more times is consistently high (88% or greater) from 1998 to 2003. The number declines as expected in the more recent years (i.e., 2004 and 2005) because most publications are not cited until a year or longer after they are published.

7. Total No. of Author Self CitesThe authors of the global change papers cite themselves less than the average self-citation rate. The author self-citation rates in Table 15 are well below the accepted range of 10-30% author self-citation rate. The only exception is in 2005, which is expected because most publications are not cited by other researchers until a year or longer after they are published.

8. No. of Hot PapersUsing the hot paper thresholds established by ESI as a benchmark, there were hot papers published in 2000, 2002, 2003, and 2004. Because only the top 0.1% of papers are selected as hot papers for each ESI field, the percentages of global change hot papers identified in Table 15 are 18 to 96 times higher than expected for these years. The percentage of hot papers in 2004 and 2005 is probably low because this analysis was conducted before the 2 year period in which hot papers must be cited was completed. ESI establishes citation thresholds for hot papers, which are selected from the highly cited papers in different fields, but the time frame for citing and cited papers is much shorterpapers must be cited within 2 years of publication and the citations must occur in a 2-month time period. Papers are assigned to 2-month periods and thresholds are set for each period and field to select 0.1% of papers. For papers published in 2004, the 2-year period of consideration would not conclude until 2006. Similarly, for papers published in 2005, the 2-year period of consideration would not conclude until 2007. The original bibliometric analysis was completed in March 2006; therefore, the number of hot papers among those published in 2004 and 2005 would be expected to be lower than if the analysis was completed in January 2008.

Table 15. Key Bibliometric Parameters for Global Change Papers By Year (1998 to 2005)


ANALYSIS PARAMETERS

1998

1999

2000

2001

2002

2003

2004

2005

1. No. of Global Change Papers Analyzed

35

42

52

42

56

41

46

27

2. No. of Highly Cited Publications That Met the Top 10% Threshold
(Percentage)

9
(25.7%)

9
(21.4%)

9 (17.3%)

13
(30.9%)

12 (21.4%)

9
(21.9%)

4
(8.7%)

2
(7.4%)

No. of Highly Cited Publications That Met the Top 1% Threshold
(Percentage)

0
(0%)

0
(0%)

4
(7.7%)

3
(7.1%)

0
(0%)

1
(2.4%)

0
(0%)

0
(0%)

No. of Highly Cited Publications That Met the Top 0.1% Threshold
(Percentage)

0
(0%)

0
(0%)

0
(0%)

0
(0%)

0
(0%)

1 (2.4%)

0
(0%)

0
(0%)

No. of Highly Cited Publications That Met the Top 0.01% Threshold
(Percentage)

0
(0%)

0
(0%)

0
(0%)

0
(0%)

0
(0%)

0
(0%)

0
(0%)

0
(0%)

3. Expected No. of Citations Calculated Using the Average Citation Rate

376.59

382.38

489.43

328.86

295.71

144.18

78.10

8.00

Total No. of Times Cited for All Publications

630

528

817

791

434

419

67

8

Ratio of Actual Cites to Expected Cites

1.67

1.38

1.67

2.41

1.47

2.91

0.86

1.00

4. No. of Papers in High Impact Journals by Impact Factor
(Percentage)

5 (14.3%)

7 (16.7%)

17 (32.7%)

19 (45.2%)

20 (35.7%)

8 (19.5%)

14 (30.4%)

9 (33.3%)

  1. No. of Papers in High Impact Journals by Immediacy Index

(Percentage)

6 (17.1%)

6
(14.3%)

14
(26.9%)

16
(38.1%)

19
(33.9%)

13
(31.7%)

15
(32.6%)

9 (33.3%)

6. No. of Publications Cited One or More Times
(Percentage)

34 (97.1%)

40 (95.2%)

51 (98.1%)

41 (97.6%)

54 (96.4%)

36 (87.8%)

31 (67.4%)

6 (22.2%)

7. Total No. of Author Self Cites (Percentage)

61
(9.7%)

49 (9.3%)

35 (4.3%)

26 (3.3%)

25 (5.8%)

10 (2.4%)

5
(7.5%)

4 (50.0%)

8. No. of Hot Papers
(Percentage)

0
(0%)

0
(0%)

5
(9.6%)

0
(0%)

1
(1.8%)

1 (2.4%)

1
(2.2%)

0
(0%)

III. Analysis of Global Change Publications by Focus Area

This section of the report presents an analysis of the global change papers by focus area (i.e., air quality, ecosystems, human health, regional assessment, and water quality). The data are presented by focus area in Table 16, which includes eight key bibliometric parameters.

SUMMARY OF RESULTS
  1. About one-fifth of the global change publications are highly cited papers (this is twice the number expected for a typical program). The percentage of global change papers that qualify as highly cited when using the ESI criteria for the top 10% of highly cited publications ranges from 2.4% for the air quality papers to 35.0% for the water quality papers. The water quality and human health focus areas have the highest percentages of highly cited publications when using the ESI criteria for the top 10%, and the number of highly cited papers in these areas is 3.5 to 2.9 times higher than expected. The ecosystems and water quality focus areas hold the lead positions when using the ESI criteria for the top 1% of papers, and the number of very highly cited papers in these areas is 2.9 to 2.5 times higher than expected. Only one paper in the ecosystems focus area meets the ESI criteria for the top 0.1% of papers, which is 6 times higher than the expected number for this focus area. None of the global change papers meet the ESI criteria for the most highly cited papers (top 0.01%), which is expected.
  2. The global papers are more highly cited than the average paper. Using the ESI average citation rates for papers published by field as the benchmark, the ratio of actual to expected cites is greater than 1 for all but the air quality focus area. This indicates that the global change papers are more highly cited than the average papers published in these fields.
  3. Nearly one-third of the global change papers are published in high impact journals as determined by the JCR Impact Factor and Immediacy Index of the journals in which the papers are published. For every year analyzed, the number of global change papers published in high impact journals (the top 10% of journals) exceeds the expected 10% as determined by the JCR Impact Factor and Immediacy Index of the journals. The percentage of papers in high impact journals (by Impact Factor) for air quality, ecosystems, and human health ranges from 21.4% to 75.6%, which is 2 to 8 times higher than expected. The percentage of water quality papers published in high impact journals (by Impact Factor) is the same as that expected (i.e., 10%). None of the regional assessment papers are published in high impact journals, but this could be attributed to the fact that this focus area had more non-journal publications than the other focus areas. The percentage of papers in high impact journals (by Immediacy Index) for all five focus areas is higher than expected, ranging from 11.4% to 65.8%, which is 1.1 to 7 times higher than expected.
  4. In four of the five focus areas (i.e., ecosystems, human health, regional assessment, and water quality) the percentage of publications cited one or more times is very high (i.e., 88% to 95%). For the air quality focus area the percentage drops to approximately 60%, but this is attributed to high percentage of air quality papers published after 2003.
  5. The authors of the global change papers cite themselves less than the average self-citation rate. The author self-citation rates range from 3.4% to 23.4%. The rates for the ecosystems, human health, regional assessment, and water quality focus areas are well below the accepted range of 10-30% author self-citation rate, and the rate for the air quality papers is 23.4%, which is within the accepted range.
  6. There were hot papers published in each of the five focus areas. The highest percentage of hot papers (i.e., 9.1%) is in the regional assessment focus area, and the percentage of hot papers in the three of the other focus areas is consistent (i.e., approximately 2.4%). These percentages are 24 to 91 times higher than expected.

The results of the analysis are presented below and the numbers link the findings with the corresponding data in Table 16.

1. No. of Global Change Papers AnalyzedMore than half of the global change publications fall under the ecosystems focus area. The number of global change publications for the remaining focus areas is approximately the same.

2. Total No. of Highly Cited PublicationsESI identifies four thresholds of highly cited papersthose in the top 10%, top 1%, top 0.1%, and top 0.0.1%. It is extraordinary for a publication to meet the threshold for the top 0.01%; these publications are rare and should not be expected in every program. Using the ESI thresholds, about 20% of the global change publications are highly cited papers (this is 2 times the number expected for a typical program). The percentage of global change papers that qualify as highly cited when using the ESI criteria for the top 10% of highly cited publications ranges from 2.4% for the air quality papers to 35.0% for the water quality papers. The water quality and human health focus areas have the highest percentages of highly cited publications when using the ESI criteria for the top 10%, and the number of highly cited papers in these areas is 3.5 and 2.9 times higher than expected. The ecosystems and water quality focus areas hold the lead positions when using the ESI criteria for the top 1% of papers, and the number of very highly cited papers in these areas is 2.9 and 2.5 times higher than expected. Only one paper in the ecosystems focus area meets the ESI criteria for the top 0.1% of papers, which is 6 times higher than the expected number for this area. None of the global change papers meet the ESI criteria for the most highly cited papers (top 0.01%). The expected number of papers in this top category for a typical program of this size would be 0.03 papers, so the absence of papers in this category is not surprising.

3. Ratio of Actual to Expected CitesThe global papers are more highly cited than the average paper. Using the ESI average citation rates for papers published by field as the benchmark, the ratio of actual to expected cites is greater than 1 for all but one of the focus areas (i.e., air quality). This indicates that the global change papers are more highly cited than the average papers published in these fields.

4. No. of Papers in High Impact Journals by Impact FactorNearly one-third of the global change papers are published in high impact journals as determined by the Impact Factor of the journals in which the papers are published. The percentage of papers in high impact journals for air quality, ecosystems, and human health ranges from 21.4% to 75.6%, which is 2 to 8 times higher than expected for these three focus areas. The percentage of water quality papers published in high impact journals is the same as that expected (i.e., 10%). None of the regional assessment papers are published in high impact journals, but this could be attributed to the fact that this focus area had more non-journal publications than the other focus areas.

5. No. of Papers in High Impact Journals by Immediacy IndexNearly one-third of the global change papers are published in high impact journals as determined by the Immediacy Index of the journals in which the papers are published. The percentage of papers published in high impact journals ranges from 11.4% to 65.8%, which is 1.1 to 7 times higher than expected for these five focus areas.
6. Total No. of Publications Cited One or More TimesIn four of the five focus areas (i.e., ecosystems, human health, regional assessment, and water quality) the percentage of publications cited one or more times is very high (i.e., 88% to 95%). For the air quality focus area, the percentage drops to approximately 60%, but this can be attributed to the fact that 74% of the air quality papers are published after 2003 compared to 4% of the regional assessment papers. In fact, 20% of the air quality papers were published in 2005, and only 6 of the 27 (22%) global change papers published in 2005 (all focus areas combined) have been cited one or more times.

7. Total No. of Author Self CitesThe authors of the global change papers cite themselves less than the average self-citation rate. The author self-citation rates range from 3.4% to 23.4%. The rates for the ecosystems, human health, regional assessment, and water quality focus areas are well below the accepted range of 10-30% author self-citation rate, and the rate for the air quality papers is 23.4%, which is within the accepted range.

8. No. of Hot PapersUsing the hot paper thresholds established by ESI as a benchmark, there were hot papers published in each of the five focus areas. The highest percentage of hot papers (i.e., 9.1%) is in the regional assessment focus area, and the percentage of hot papers in three of the other focus areas is consistent (i.e., approximately 2.4%). Because only the top 0.1% of papers are selected as hot papers for each ESI field, the percentages of global change hot papers identified in Table 16 are 24 to 91 times higher than expected.

Table 16. Key Bibliometric Parameters for Global Change Papers by Focus Area


ANALYSIS PARAMETERS

Focus Areas

Air Quality

Ecosystems

Human Health

Regional Assessment

Water Quality

1. No. of Global Change Papers Analyzed

42

174

41

44

40

2. No. of Highly Cited Publications That Met the Top 10% Threshold (Percentage)

1 (2.4%)

35 (20.1%)

12 (29.3%)

5 (11.4%)

14 (35.0%)

No. of Highly Cited Publications That Met the Top 1% Threshold (Percentage)

0 (0%)

5 (2.9%)

1 (2.4%)

1 (2.3%)

1 (2.5%)

No. of Highly Cited Publications That Met the Top 0.1% Threshold (Percentage)

0 (0%)

1 (0.6%)

0 (0%)

0 (0%)

0 (0%)

No. of Highly Cited Publications That Met the Top 0.01% Threshold (Percentage)

0 (0%)

0 (0%)

0 (0%)

0 (0%)

0 (0%)

3. Expected No. of Citations Calculated Using the Average Citation Rate

94.18

1,082.61

332.93

284.56

308.97

Total No. of Times Cited for All Publications

64

2,034

655

356

585

Ratio of Actual Cites to Expected Cites

0.68

1.88

1.97

1.25

1.89

4. No. of Papers in High Impact Journals by Impact Factor
(Percentage)

9 (21.4%)

55 (31.6%)

31 (75.6%)

0 (0%)

4 (10.0%)

5. No. of Papers in High Impact Journals by Immediacy Index (Percentage)

11 (26.2%)

58 (33.3%)

27 (65.8%)

5 (11.4%)

6 (15.0%)

6. No. of Publications Cited One or More Times (Percentage)

25 (59.5%)

154 (88.5%)

36 (87.8%)

42 (95.4%)

36 (90.0%)

7. Total No. of Author Self Cites (Percentage)

15 (23.4%)

115 (5.6%)

29 (4.4%)

12 (3.4%)

44 (7.5%)

8. No. of Hot Papers
(Percentage)

1 (2.4%)

1 (0.57%)

1 (2.4%)

4 (9.1%)

1 (2.5%)

1 Thomsons Web of Science provides access to current and retrospective multidisciplinary information from approximately 8,700 of the most prestigious, high impact research journals in the world. Web of Science also provides cited reference searching.

2 Scopus is a large abstract and citation database of research literature and quality Web sources designed to support the literature research process. Scopus offers access to 15,000 titles from 4,000 different publishers, more than 12,850 academic journals (including coverage of 535 Open Access journals, 750 conference proceedings, and 600 trade publications), 27 million abstracts, 245 million references, 200 million scientific Web pages, and 13 million patent records.

3 Garfield E, Sher IH. New factors in the evaluation of scientific literature through citation indexing. American Documentation 1963;18(July):195-210.

4 MacRoberts MH, MacRoberts BR. Problems of citation analysis: a critical review. Journal of the American Society of Information Science 1989;40(5):342-349.

5 Kavaci N, Misak A. Author self-citation in medical literature. Canadian Medical Association Journal 2004;170(13):1929-1930.

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