National Overview - January 2013
v 3.2.1 Transition

« National Overview - January 2013


v 3.2.1 Transition

An omission in processing a correction algorithm led to some small errors on the Global Historical Climatology Network-Monthly dataset (GHCN-M v3.2.0; the US Historical Climatology Network, from which the CONUS temperature is calculated, is part of GHCN-M). This led to small errors in the reported land surface temperatures in the October, November, December and Annual U.S. and global climate reports. On February 14, 2013, NCDC fixed this error in its software, included an additional improvement (described below), and implemented both changes as GHCN-M version 3.2.1. With this update to GHCN-M, the Merged Land and Ocean Surface Temperature dataset also is subsequently revised as MLOST version 3.5.3.

This new version of GHCN-M shows very small changes in temperature and ranks. The 2012 U.S. temperature is 0.01°F higher than reported in early January, but still remains approximately 1.0°F warmer than the next warmest year, and approximately 3.25°F warmer than the 20th century average. The U.S. annual time series from GHCN-M is almost identical to the series from version 3.2.0, and the 1895-2012 annual temperature trend remained 1.3°F/century. The trend for certain calendar months changed more than others (discussed below). For the globe, ranks of individual years changed in some instances by a few positions, but global land temperature trends changed no more than 0.01°C/century for any month since 1880.

NCDC uses two correction processes to remove inhomogeneities associated with factors unrelated to climate such as changes in observer practices, instrumentation, and changes in station location and environment that have occurred through time. The first correction for time of observation changes in the United States was inadvertently disabled during late 2012. That algorithm provides for a physically based correction for observing time changes based on station history information. NCDC also routinely runs a .pairwise correction. algorithm that addresses such issues, but in an indirect manner. It successfully corrected for many of the time of observation issues, which minimized the effect of this processing omission.

The version 3.2.1 release also includes the use of updated data to improve quality control and correction processes of other U.S. stations and neighboring stations in Canada and Mexico.

Compared to analyses released in January 2013, the trend for certain calendar months has changed more than others. This effect is related to the seasonal nature of the reintroduced time-of-observation correction. Trends in U.S. winter temperature are higher while trends in summer temperatures are lower. For the globe, ranks of individual years changed in some instances by a few positions, but global temperature trends changed no more than 0.01°C/century for any month since 1880.

Differences in CONUS Temperature: v3.2.1 versus v3.2.0

These graphics depict the Contiguous United States Temperature timeseries as departures ("anomalies") from the 20th century average. The thick black trace depicts version 3.2.0 (as reported in the Annual 2012 report). The red-dotted trace represents v3.2.1, as reported in the January 2013 report. The difference between the two (from 3.2.0 to 3.2.1) is expressed as a blue line.

Differences in Global Land Surface Temperature: v3.2.1 versus v3.2.0

These graphics depict the Global Land Surface Temperature timeseries as departures ("anomalies") from the 20th century average. The thick black trace depicts the v3.2.0 land surface temperature series (as reported in the Annual 2012 report). The red-dotted trace represents v3.2.1, as reported in the January 2013 report. The difference between the two (from 3.2.0 to 3.2.1) is expressed as a green line.


The Effect Upon Ranks in CONUS Temperature

NCDC and other centers often express a month's, season's or year's temperature anomaly as a rank, or how the period "ranked" among its history (for example, 23rd warmest of 118 on record). Expressing a value as a rank provides an easily-understandable depiction of the relative placement of the month, season or year, but using rankings is very sensitive to even small changes in the values. For example, imagine a footrace with 118 runners. In most cases, many of the runners finish very near to each other ("in a pack"), where the slightest change could result in a "bump" in rank of several positions within the pack. In the same way, annual temperature anomalies feature a few outstanding (warm or cold) years, and a large "pack". Slight changes to any one year can result in a "bump" in rank in the "middle of the pack". This sensitivity to slight changes is one of the criticisms of using the ranking method, despite its known utility for quickly conveying how a single month, season or year compares to others in history.

Annual temperature anomalies: Contiguous United States
Anomalies based on the 20th century average
Colors defined in the Climatological Rankings DYK
Year3.2.0 Anomaly3.2.0 Rank
20123.25118
20111.1298
20100.9393
20090.3080
20080.2376
20071.58111
20062.23116
20051.56110
20041.0495
20031.22102
20021.1499
20011.61112
20001.20101
19991.86114
19982.25117
19970.2074
1996-0.1847
19950.6488
19940.8291
1993-0.8015
19920.5586
19911.1197
19901.49108
1989-0.2646
19880.5887
19871.32106
19861.29104
1985-0.7716
1984-0.0363
1983-0.1355
1982-0.7017
19811.1096
19800.3582
1979-1.128
1978-0.989
19770.5385
1976-0.5426
1975-0.5328
19740.2577
19730.2778
1972-0.6519
1971-0.3340
1970-0.4035
1969-0.5426
1968-0.7017
1967-0.2744
1966-0.5525
1965-0.3637
1964-0.3439
19630.2275
1962-0.1355
1961-0.1552
1960-0.5823
19590.0971
1958-0.0761
19570.0569
19560.3181
1955-0.3340
19541.30105
19531.35107
19520.2879
1951-0.9113
1950-0.6420
19490.0164
1948-0.4234
1947-0.1058
19460.9292
1945-0.2942
1944-0.1454
19430.0770
1942-0.1648
19410.6989
1940-0.1648
19391.24103
19381.17100
1937-0.4831
19360.1173
1935-0.1552
19342.06115
19330.9894
1932-0.2744
19311.52109
1930-0.0363
1929-1.167
1928-0.1059
19270.1173
1926-0.0766
19250.4984
1924-1.444
1923-0.3637
19220.0165
19211.74113
1920-0.9612
1919-0.4732
1918-0.1648
1917-1.961
1916-1.196
1915-0.5823
1914-0.1648
1913-0.4533
1912-1.732
19110.0266
19100.3983
1909-0.6121
19080.0569
1907-0.5328
1906-0.2843
1905-0.989
1904-0.8514
1903-1.335
1902-0.3736
1901-0.1355
19000.7990
1899-0.9711
1898-0.6121
1897-0.4930
18960.0569
1895-1.533
Annual temperature anomalies: Contiguous United States
Anomalies based on the 20th century average
Colors defined in the Climatological Rankings DYK
Year3.2.1 Anomaly3.2.1 Rank
20123.26118
20111.1298
20100.9493
20090.3181
20080.2477
20071.59111
20062.24117
20051.55110
20041.0495
20031.21102
20021.1399
20011.60112
20001.19101
19991.84114
19982.23116
19970.1874
1996-0.2047
19950.6288
19940.8291
1993-0.8015
19920.5486
19911.0997
19901.48108
1989-0.2842
19880.5687
19871.29106
19861.27104
1985-0.7816
1984-0.0462
1983-0.1354
1982-0.7017
19811.0896
19800.3482
1979-1.148
1978-1.009
19770.5285
1976-0.5524
1975-0.5327
19740.2376
19730.2678
1972-0.6619
1971-0.3539
1970-0.4134
1969-0.5426
1968-0.7017
1967-0.2645
1966-0.5524
1965-0.3736
1964-0.3637
19630.1975
1962-0.1650
1961-0.1748
1960-0.6121
19590.0770
1958-0.0860
19570.0365
19560.2980
1955-0.3440
19541.28105
19531.34107
19520.2779
1951-0.9113
1950-0.6320
19490.0466
1948-0.4035
1947-0.1058
19460.9392
1945-0.2842
1944-0.1552
19430.0668
1942-0.1748
19410.6989
1940-0.1650
19391.23103
19381.16100
1937-0.4930
19360.1073
1935-0.1552
19342.06115
19330.9894
1932-0.2744
19311.52109
1930-0.0363
1929-1.166
1928-0.1257
19270.0972
1926-0.0761
19250.4884
1924-1.444
1923-0.3637
19220.0164
19211.75113
1920-0.9710
1919-0.4930
1918-0.1354
1917-1.931
1916-1.157
1915-0.5327
1914-0.1354
1913-0.4333
1912-1.732
19110.0466
19100.4183
1909-0.5923
19080.0770
1907-0.5029
1906-0.2645
1905-0.9710
1904-0.8414
1903-1.315
1902-0.3440
1901-0.1058
19000.7990
1899-0.9612
1898-0.6022
1897-0.4632
18960.0668
1895-1.523