1. An area and distance weighted analysis of the impacts of station exposure on the U.S. Historical Climatology Network temperatures and temperature trends
An updated evaluation of the
U.S. Historical Climate Network as it relates to siting biases
Supplement to Watts et al., 2012
Updated 8/3/12

2. Table of Contents INTRODUCTION ……………………………………………. page 2
STATION QUALITY RATINGS (“Microsite”) …………... page 3
GENERAL STATION ENVIRONMENT (“Mesosite”) ….. page 4
PART1 ………………………………………………………... page 5
All Rated Stations
PART 2 ……………………………………………………….. page 14
Airports Excluded
PART 3 ……………………………………………………….. page 24
Rural Stations Only
PART 4 ……………………………………………………….. page 33
PART 5 ……………………………………………………….. page 43
MMTS Equipment (modernized sensors) only

3. Introduction
This study compares of the rate of warming of well sited and poorly sited stations to determine whether improper location engenders spurious warming biases in the data trends.
There are two bases of comparison:
Microsite: Immediate surroundings
(Proximity to buildings, asphalt surfaces, etc.
Stations are rated from Class 1 to 5.)
Mesosite: General environment
(Rural, Semi-Urban, Urban, etc.)
Ideally, only properly sited, i.e., Class 1&2, Rural, Non-Airport, stations should be used to measure historical temperature trends.

4. Station Quality Ratings (Microsite)
Class 1&2 (Compliant)
Heat sinks cover under 10% of area within a 30-meter radius of sensor, under 1% of within 5 meters, and under 5% of an annulus from 5 to 10 meters.
Class 3 (Non-Compliant)
Heat sinks cover over 10% of area within a 30-meter radius but under 10% within 10 meters and under 5% within 5 meters.
Class 4 (Non-Compliant)
Heat sinks cover from 10% to 50% of area within a 10-meter radius of sensor but under 30% within 3 meters.
Class 5 (Non-Compliant)
Heat sinks cover over 50% or more area within a 10-meter radius of sensor or over 30% within 3 meters.

5. General Environment (Mesosite)
Rural
Semi-Urban
Urban
Airports

6. Part 1 Sample: All Stations
This includes all stations in place prior to 2003 that we were able to observe and rate.
Includes:
Rural
Semi-Urban
Urban
Airports
Sample size (All Stations, All Classes): 779
Compliant: 160
Non-Compliant: 619

7. Class 1\2 (Compliant) All Rated Stations
Gridded Average
Heat sinks cover under 10% of area within a 30-meter radius of sensor, under 1% of within 5 meters, and under 5% of an annulus from 5 to 10 meters. Airports and urbanized areas are included.
Sample size: 160

8. Class 3 (Non-Compliant) All Rated Stations
Gridded Average
Heat sinks cover over 10% of area within a 30-meter radius but under 10% within 10 meters and under 5% within 5 meters.
Sample size: 247

9. Class 4 (Non-Compliant) All Rated Stations
Gridded Average
Heat sinks cover from 10% to 50% of area within a 10-meter radius of sensor but under 30% within 3 meters. Airports and urbanized areas are included.
Sample size: 277

10. Class 5 (Non-Compliant) All Rated Stations
Gridded Average
Heat sinks cover over 50% or more area within a 10-meter radius of sensor or over 30% within 3 meters. Airports and urbanized areas are included.
Sample size: 95

11. Class 3\4\5 (All Non-Compliant) All Rated Stations
Gridded Average
Sample includes all Class 3, 4, and 5 stations. These stations are not in compliance with NOAA microsite requirements.
Sample size: 619

12. Class 1-5 (All Rated Stations) All Rated Stations
Gridded Average
Sample includes all rated stations, Class 1-5, including all NOAA compliant and non-compliant stations.
Sample size: 779

13. Class 1-5 (After NOAA Adjustments) All Rated Stations
Gridded Average
This is the data for all 779 rated stations as adjusted by NOAA. Instead of adjusting the poorly sited station trends downward to the levels of the well located stations, the well sited station trends are adjusted upward to match the poor station trends. The “official” trend data is higher even than that of the raw data for non-compliant stations.

14. Class 1-5 (After NOAA Adjustments)
Comparison All Rated Stations What the compliant thermometers actually say: What the non-compliant thermometers say: What NOAA says: +.309
Class 1\2 (Compliant)
Class 1-5 (After NOAA Adjustments)
Class 3\4\5 (All Non-Compliant)

15. Part 2 Airports Excluded
This includes stations in place prior to 2003 that we were able to observe and rate.
Includes:
Rural
Semi-Urban
Urban
(Airports Excluded)
Sample size (All Stations, All Classes): 727
Compliant: 126
Non-Compliant: 601

16. Class 1\2 (Compliant) Airports Excluded
Gridded Average
Heat sinks cover under 10% of area within a 30-meter radius of sensor, under 1% of within 5 meters, and under 5% of an annulus from 5 to 10 meters. Airports are excluded, urbanized areas are included.
Sample size: 126

17. Class 3 (Non-Compliant) Airports Excluded
Gridded Average
Heat sinks cover over 10% of area within a 30-meter radius but under 10% within 10 meters and under 5% within 5 meters. Airports are excluded, urbanized areas are included.
Sample size: 238

18. Class 4 (Non-Compliant) Airports Excluded
Gridded Average
Heat sinks cover from 10% to 50% of area within a 10-meter radius of sensor but under 30% within 3 meters. Airports are excluded, and urbanized areas are included.
Sample size: 269

19. Class 5 (Non-Compliant) Airports Excluded
Gridded Average
Heat sinks cover over 50% or more area within a 10-meter radius of sensor or over 30% within 3 meters. Airports are excluded, urbanized areas are included.
Sample size: 94

20. Class 3\4\5 (All Non-Compliant) Airports Excluded
Gridded Average
Sample includes all Class 3, 4, and 5 stations. These stations are not in compliance with NOAA microsite requirements.
Sample size: 601

21. Class 1-5 (All Rated Stations) Airports Excluded
Gridded Average
Sample excludes airports, urbanized areas are included. Class 1-5, including both NOAA compliant and non-compliant stations.
Sample Size: 727

22. Class 1-5 (After NOAA Adjustments) Airports Excluded
Gridded Average
This is the data for the 727 non-airport stations as adjusted by NOAA. The well sited station trends are adjusted upward to match the poor station trends (also adjusted upward. The adjusted trend data is higher even than that of the raw data for non-compliant stations.

23. Class 1-5 (After NOAA Adjustments)
Comparison Airports Excluded What the compliant thermometers actually say: What the non-compliant thermometers say: What NOAA says: +.308
Class 1\2 (Compliant)
Class 1-5 (After NOAA Adjustments)
Class 3\4\5 (All Non-Compliant)

24. Comparison Airports vs. Non-Airports Compliant Stations, Non-Airports:
Comparison Airports vs. Non-Airports Compliant Stations, Non-Airports: .124 Compliant Stations, Airports: .251
Class 1\2 (Compliant)
AIRPORTS REMOVED
Class 1\2 (Compliant)
AIRPORTS ONLY

25. Part 3 Rural Only
This includes stations in place prior to 2003 that we were able to observe and rate.
Includes:
Rural
Rural Airports
(Semi-Urban Excluded)
(Urban Excluded)
Sample size (All Stations, All Classes): 502
Compliant: 105
Non-Compliant: 397

26. Class 1\2 (Compliant) Rural Only
Gridded Average
Heat sinks cover under 10% of area within a 30-meter radius of sensor, under 1% of within 5 meters, and under 5% of an annulus from 5 to 10 meters. Rural airports are included, all urbanized areas are excluded.
Sample size: 105

27. Class 3 (Non-Compliant) Rural Only
Gridded Average
Heat sinks cover over 10% of area within a 30-meter radius but under 10% within 10 meters and under 5% within 5 meters. Rural airports are included, all urbanized areas are excluded.
Sample size: 158

28. Class 4 (Non-Compliant) Rural Only
Gridded Average
Heat sinks cover from 10% to 50% of area within a 10-meter radius of sensor but under 30% within 3 meters. Rural airports are included, all urbanized areas are excluded.
Sample size: 187

29. Class 5 (Non-Compliant) Rural Only
Gridded Average
Heat sinks cover over 50% or more area within a 10-meter radius of sensor or over 30% within 3 meters. Rural airports are included, all urbanized areas are excluded.
Sample size: 52

30. Class 3\4\5 (All Non-Compliant) Rural Only
Gridded Average
Sample includes all Class 3, 4, and 5 stations. These stations are not in compliance with NOAA microsite requirements. Rural airports are included, all urbanized areas are excluded.
Sample size: 397

31. Class 1-5 (All Rated Stations) Rural Only
Gridded Average
Sample includes rural airports; all urbanized areas are excluded. Class 1-5, including both NOAA compliant and non-compliant stations.
Sample Size: 502

32. Class 1-5 (After NOAA Adjustments) Rural Only
Gridded Average
This is the data for the 502 rural stations, as adjusted by NOAA. The well sited station trends are adjusted upward to match the poor station trends (also adjusted upward. The adjusted trend data is higher even than that of the raw data for non-compliant stations.

33. Class 1-5 (After NOAA Adjustments)
Comparison Rural Only What the compliant thermometers actually say: What the non-compliant thermometers say: What NOAA says: +.304
Class 1\2 (Compliant)
Class 1-5 (After NOAA Adjustments)
Class 3\4\5 (All Non-Compliant)

34. Part 4 Rural, Airports Excluded
This includes stations in place prior to 2003 that we were able to observe and rate.
Includes:
Rural, Non-Airport
(All Airports, including Rural, Excluded)
(Semi-Urban Excluded)
(Urban Excluded)
Sample size (All Stations, All Classes): 491
Compliant: 98
Non-Compliant: 393

35. Class 1\2 (Compliant) Rural, no Airports
Gridded Average
Heat sinks cover under 10% of area within a 30-meter radius of sensor, under 1% of within 5 meters, and under 5% of an annulus from 5 to 10 meters. All airports and urbanized areas are excluded.
Sample size: 98

36. Class 3 (Non-Compliant) Rural, no Airports
Gridded Average
Heat sinks cover over 10% of area within a 30-meter radius but under 10% within 10 meters and under 5% within 5 meters. All airports and urbanized areas are excluded.
Sample size: 157

37. Class 4 (Non-Compliant) Rural, no Airports
Gridded Average
Heat sinks cover from 10% to 50% of area within a 10-meter radius of sensor but under 30% within 3 meters. All airports and urbanized areas are excluded.
Sample size: 185

38. Class 5 (Non-Compliant) Rural, no Airports
Gridded Average
Heat sinks cover over 50% or more area within a 10-meter radius of sensor or over 30% within 3 meters. All airports and urbanized areas are excluded.
Sample size: 51

39. Class 3\4\5 (All Non-Compliant) Rural, no Airports
Gridded Average
Sample includes all Class 3, 4, and 5 stations. These stations are not in compliance with NOAA microsite requirements. All airports and urbanized areas are excluded.
Sample size: 393

40. Class 1-5 (All Rated Stations) Rural, no Airports
Gridded Average
Sample includes rural non-airports; all urbanized areas and airports are excluded. Class 1-5, including both NOAA compliant and non-compliant stations.
Sample Size: 491

41. Class 1-5 (After NOAA Adjustments) Rural, no Airports
Gridded Average
This is the data for the 491 rural non-airport stations, as adjusted by NOAA. The well sited station trends are adjusted upward to match the poor station trends (also adjusted upward. The adjusted trend data is higher even than that of the raw data for non-compliant stations.

42. Class 1-5 (After NOAA Adjustments)
Comparison Rural, no Airports What the compliant thermometers actually say: What the non-compliant thermometers say: What NOAA says: +.307
Class 1\2 (Compliant)
Class 1-5 (After NOAA Adjustments)
Class 3\4\5 (All Non-Compliant)

43. Rural, no Airports, NOAA ADJUSTED
Comparison Rural, no Airports Compliant Raw vs. Compliant Adjusted Compliant Stations, Raw Data: .108 Compliant Stations, NOAA Adjusted Data: .310
Class 1\2 (Compliant)
Rural, no Airports, RAW
Class 1\2 (Compliant)
Rural, no Airports, NOAA ADJUSTED

44. Part 5 Rural MMTS, Airports Excluded
This includes stations in place prior to 2003 that we were able to observe and rate.
Includes:
Rural MMTS, Non-Airport
(All Non-MMTS post 1994 or plurality CRS or ASOS Excluded)
(All Airports, including Rural, Excluded)
(Semi-Urban Excluded)
(Urban Excluded)
Sample size (All Stations, All Classes): 312
Compliant: 56
Non-Compliant: 256

45. Class 1\2 (Compliant) Rural MMTS, no Airports
Gridded Average
Heat sinks cover under 10% of area within a 30-meter radius of sensor, under 1% of within 5 meters, and under 5% of an annulus from 5 to 10 meters. All non-MMTS, airports, and urbanized areas are excluded.
Sample size: 56

46. Class 3 (Non-Compliant) Rural MMTS, no Airports
Gridded Average
Heat sinks cover over 10% of area within a 30-meter radius but under 10% within 10 meters and under 5% within 5 meters. All non-MMTS, airports, and urbanized areas are excluded.
Sample size: 97

47. Class 4 (Non-Compliant) Rural MMTS, no Airports
Gridded Average
Heat sinks cover from 10% to 50% of area within a 10-meter radius of sensor but under 30% within 3 meters. All non-MMTS, airports, and urbanized areas are excluded.
Sample size: 132

48. Class 5 (Non-Compliant) Rural MMTS, no Airports
Gridded Average
Heat sinks cover over 50% or more area within a 10-meter radius of sensor or over 30% within 3 meters. All non-MMTS, airports, and urbanized areas are excluded.
Sample size: 27

49. Class 3\4\5 (All Non-Compliant) Rural MMTS, no Airports
Gridded Average
Sample includes all Class 3, 4, and 5 stations. These stations are not in compliance with NOAA microsite requirements. All non-MMTS, airports, and urbanized areas are excluded.
Sample size: 256

50. Class 1-5 (All Rated Stations) Rural MMTS, no Airports
Gridded Average
Sample excludes all non-MMTS equipment, urbanized areas, and airports. Class 1-5, including both NOAA compliant and non-compliant stations.
Sample Size: 312

51. Class 1-5 (After NOAA Adjustments) Rural MMTS, no Airports
Gridded Average
This is the data for the 312 rural non-airport MMTS stations, as adjusted by NOAA. The well sited station trends are adjusted upward to match the poor station trends (also adjusted upward. The adjusted trend data is higher even than that of the raw data for non-compliant stations.

52. Class 1-5 (After NOAA Adjustments)
Comparison Rural MMTS, no Airports What the compliant thermometers actually say: What the non-compliant thermometers say: What NOAA says: +.300
Class 1\2 (Compliant)
Class 1-5 (After NOAA Adjustments)
Class 3\4\5 (All Non-Compliant)

53. CONCLUSIONS
It is inescapably demonstrated that stations with poor microsite (Class 3, 4, 5) have significantly higher warming trends than well sited stations (Class 1, 2): This is true for, in all nine geographical areas of all five data samples. The odds of this result having occurred randomly are small.

54. It is demonstrated that stations with poor mesosite (airports and urbanized areas) show an increase in temperature trends of both well and poorly microsited stations, alike. Over a third of all stations are located in a poor mesosite environment. This is extremely unrepresentative of the topography the stations purport to represent. Poor mesosite has its greatest effect on Class 1, 2 stations (over 40% spurious exaggeration of trend), as so many of them are located in airports.

55. NOAA adjustment procedure fails to address these issues
NOAA adjustment procedure fails to address these issues. Instead, poorly sited station trends are adjusted sharply upward (not downward), and well sited stations are adjusted upward to match the already-adjusted poor stations. Well sited rural, non-airport stations show a warming nearly three times greater after NOAA adjustment is applied.

56. There is the further issue of equipment inhomogeneity
There is the further issue of equipment inhomogeneity. Modern MMTS sensors show a significantly lower warming trend than the obsolete CRS shelters. Yet rather than lowering the trends of CRS stations, the trends of MMTS stations are sharply adjusted upwards. (It is difficult, however, to be certain of the true effect thanks to the relatively small number of Class 1,2, rural, non-airport stations.)