Global Analysis - April 2013

Contents of this Section:

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Note: GHCN-M Data Notice

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). 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.

The net result of this new version of GHCN-M reveals 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 version 3.2.1 is almost identical to the series from version 3.2.0 and that the 1895-2012 annual temperature trend remains 0.13°F/decade. 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.

More complete information about this issue is available at this supplemental page.

NCDC will not update the static reports from October through December 2012 and the 2012 U.S and Global annual reports, but will use the current dataset (GHCN-M v. 3.2.1 and MLOST v. 3.5.3) for the January 2013 report and other comparisons to previous months and years.

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Global Highlights

  • The combined average temperature over global land and ocean surfaces for April 2013 was the 13th warmest on record, at 0.52°C (0.94°F) above the 20th century average of 13.7°C (56.7°F).
  • The global land surface temperature was 0.71°C (1.28°F) above the 20th century average of 8.1°C (46.5°F), marking the 17th warmest April on record. For the ocean, the April global sea surface temperature was 0.44°C (0.79°F) above the 20th century average of 16.0°C (60.9°F), tying with 2001 and 2009 as the seventh warmest April on record.
  • The combined global land and ocean average surface temperature for the January–April period (year-to-date) was 0.56°C (1.01°F) above the 20th century average of 12.6°C (54.8°F), tying with 2009 as the eighth warmest such period on record.


Temperature anomalies and percentiles are shown on the gridded maps below. The anomaly map on the left is a product of a merged land surface temperature (Global Historical Climatology Network, GHCN) and sea surface temperature (ERSST.v3b) anomaly analysis developed by Smith et al. (2008). Temperature anomalies for land and ocean are analyzed separately and then merged to form the global analysis. For more information, please visit NCDC's Global Surface Temperature Anomalies page. The April 2013 Global State of the Climate report introduces percentile maps that complement the information provided by the anomaly maps. These new maps on the right provide additional information by placing the temperature anomaly observed for a specific place and time period into historical perspective, showing how the most current month, season or year compares with the past.

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In the atmosphere, 500-millibar height pressure anomalies correlate well with temperatures at the Earth's surface. The average position of the upper-level ridges of high pressure and troughs of low pressure—depicted by positive and negative 500-millibar height anomalies on the April 2013 height and anomaly mapApril 2013 map—is generally reflected by areas of positive and negative temperature anomalies at the surface, respectively.


The globally-averaged temperature across the world's land and ocean surfaces was 0.52°C (0.94°F) above the 20th century average, marking the 13th warmest April on record and coolest April since 2008. The average global land temperature was the 17th warmest for April, at 0.71°C (1.28°F) above average. The Northern Hemisphere land was 20th warmest for April, while the Southern Hemisphere land was 12th warmest. As indicated by the Temperature Percentiles map in the above right, temperatures were much warmer than average across much of Mexico, the coastal regions of South America, most of Argentina, southern Europe, parts of coastal Africa, far eastern Europe, and western Australia. Record warm temperatures were observed across the southern tip of South America, far western Brazil, the southern Philippines, and some locales in far eastern Russia. It was much cooler than average across a swath of central North America, central Paraguay, part of northwestern Canada, and much of Alaska, where the southeastern portion of Alaska had record cold April temperatures. According to the Temperature Anomalies map in the above left, the average April temperature was more than 5°C (9°F) below average in some of these regions.

Select national information is highlighted below:
  • April 2013 brought the fifth warmest April average maximum temperature on record to Australia since national records began in 1900, at 1.64°C (2.95°F) above the 1961–1990 average. At the state level, Western Australia reported its third highest monthly-averaged maximum temperature (2.41°C/4.34°F above average) and fifth highest monthly-averaged minimum temperature (1.50°C/2.70°F above average). Tasmania was the only state with a below-average monthly maximum temperature (-0.23°C/-0.41°F).

  • According to NIWA, April temperatures in New Zealand were "well above average" (more than 1.2°C/2.2°F above the 1971–2000 average) across most of the North Island. April temperatures were "above average" (+0.5°C/+0.9°F to +1.2°C/+2.2°F) across most of the South Island.

  • The average April temperature across the United Kingdom was 1.1°C (2.0°F) below the 1981–2010 average, tying with 2012 as the coolest April since 1989.

  • According to Austria's national meteorological agency ZAMG, a new record the was set in Vienna, Austria for the shortest timeframe between the last ice day (temperatures remaining below freezing all day) and the first day of summer (defined as when the temperature reaches 25°C)—25 days (March 24th – April 18th). Records date back to 1872. Overall, April in Austria was 1.3°C (2.3°F) above the 1981–2010 average.
  • April temperatures across Hungary ranged from near-normal up to 3°C (5.°F) above the 1971–2000 average. According to maps provided by Orszagos Meteorologai Szolgalat (Hungary's national meteorological service), no regions of the country observed below-average temperatures.

  • As reported by the Icelandic Meteorological Office, all listed observation stations in Iceland had average April temperatures below the 1961–1990 average. Departures from average ranged from -0.7°C (-1.3°F) at Stykkishólmur to -2.1°C (-3.8°F) at Egilsstaðir (fourth coldest in the 58-year period of record at this station).

  • April was warmer than average across all of Croatia, with much of the country experiencing "very warm" temperatures (91st – 98th percentiles) and parts of the south observing "extremely warm" temperatures (greater than 98th percentile) compared tothe normal for April.

  • The average April temperature across South Korea was 1.9°C (3.4°F) below the 1981–2010 average, marking the third coldest April since national records began in 1973. The average maximum temperature was also third coldest, while the average mimimum temperature was second coldest on record.

The April global sea surface temperature was 0.44°F (0.79°F) above the long-term average, tying with 2001 and 2009 as the seventh warmest April in the 134-year period of record. Temperatures were much warmer than average across the equatorial Atlantic Ocean, northern and southeastern Indian Ocean, and much of the southwestern Pacific Ocean. Ocean surface temperatures surrounding most of the Philippine Islands and to the south and southeast of Australia were record warm for April. The only much-cooler-than-average region was in part of the northwestern Pacific Ocean near Russia. Near-average sea surface temperatures were observed during April across most of the equatorial Pacific Ocean, with below-average SSTs in the far eastern equatorial Pacific. According to NOAA's Climate Prediction Center, ENSO-neutral conditions continue to be favored into the late Northern Hemisphere summer 2013. Images of sea surface temperature conditions are available for all weeks during 2013 from the weekly SST page.

April Anomaly Rank
(out of 134 years)
°C °F Year(s) °C °F
Land +0.71 ± 0.11 +1.28 ± 0.20 Warmest 17ᵗʰ 2007 +1.49 +2.68
Coolest 118ᵗʰ 1905 -0.81 -1.46
Ocean +0.44 ± 0.05 +0.79 ± 0.09 Warmest 7ᵗʰ 1998, 2010 +0.57 +1.03
Coolest 128ᵗʰ 1911 -0.53 -0.95
Ties: 2001, 2009
Land and Ocean +0.52 ± 0.08 +0.94 ± 0.14 Warmest 13ᵗʰ 2010 +0.77 +1.39
Coolest 122ⁿᵈ 1909 -0.53 -0.95
Northern Hemisphere
Land +0.71 ± 0.11 +1.28 ± 0.20 Warmest 20ᵗʰ 2012 +1.80 +3.24
Coolest 115ᵗʰ 1905 -1.06 -1.91
Ocean +0.44 ± 0.05 +0.79 ± 0.09 Warmest 6ᵗʰ 2010 +0.59 +1.06
Coolest 129ᵗʰ 1911 -0.52 -0.94
Ties: 2007
Land and Ocean +0.54 ± 0.11 +0.97 ± 0.20 Warmest 15ᵗʰ 2012 +0.92 +1.66
Coolest 120ᵗʰ 1909 -0.62 -1.12
Southern Hemisphere
Land +0.70 ± 0.14 +1.26 ± 0.25 Warmest 12ᵗʰ 2010 +1.14 +2.05
Coolest 123ʳᵈ 1917 -0.72 -1.30
Ocean +0.46 ± 0.06 +0.83 ± 0.11 Warmest 9ᵗʰ 1998 +0.62 +1.12
Coolest 126ᵗʰ 1911 -0.53 -0.95
Ties: 2005
Land and Ocean +0.50 ± 0.06 +0.90 ± 0.11 Warmest 10ᵗʰ 1998, 2010 +0.66 +1.19
Coolest 125ᵗʰ 1911 -0.52 -0.94

The most current data may be accessed via the Global Surface Temperature Anomalies page.

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Year-to-date (January–April)

With ENSO-neutral conditions holding during the first four months of 2013, the January–April global temperature across land and ocean surfaces tied with 2009 as the eighth warmest on record, at 0.56°C (1.01°F) above the 20th century average. The global land temperature ranked 10th warmest, with the Southern Hemisphere observing its fifth warmest such period and the Northern Hemisphere having its 13th warmest January–April temperature over land on record. Part of southern Ethiopia, southern Cameroon, northern Gabon, part of southern Chile, and far southern Australia were record warm for the period. The global ocean temperature was eighth warmest for January–April, with the Indian Ocean south of Australia, the southern Caspian Sea, small sections of the Arctic Ocean, and part of the seas surrounding Indonesia having record warmth. No record cold regions over land or water were observed for the January–April period.

Select national information is highlighted below:
  • In Australia, January–April was the second warmest such period on record for maximum and mean temperatures (behind 2005 for maximum temperature and behind 1998 for mean temperature).
  • January–April Anomaly Rank
    (out of 134 years)
    °C °F Year(s) °C °F
    Land +0.95 ± 0.21 +1.71 ± 0.38 Warmest 10ᵗʰ 2007 +1.42 +2.56
    Coolest 125ᵗʰ 1893 -1.03 -1.85
    Ocean +0.42 ± 0.05 +0.76 ± 0.09 Warmest 8ᵗʰ 1998, 2010 +0.56 +1.01
    Coolest 127ᵗʰ 1911 -0.51 -0.92
    Land and Ocean +0.56 ± 0.10 +1.01 ± 0.18 Warmest 8ᵗʰ 2010 +0.72 +1.30
    Coolest 127ᵗʰ 1911 -0.54 -0.97
    Ties: 2009
    Northern Hemisphere
    Land +0.99 ± 0.24 +1.78 ± 0.43 Warmest 13ᵗʰ 2007 +1.62 +2.92
    Coolest 122ⁿᵈ 1893 -1.26 -2.27
    Ties: 2008
    Ocean +0.41 ± 0.06 +0.74 ± 0.11 Warmest 7ᵗʰ 2010 +0.55 +0.99
    Coolest 128ᵗʰ 1911 -0.47 -0.85
    Ties: 2003
    Land and Ocean +0.63 ± 0.13 +1.13 ± 0.23 Warmest 10ᵗʰ 2007 +0.91 +1.64
    Coolest 125ᵗʰ 1893 -0.72 -1.30
    Southern Hemisphere
    Land +0.83 ± 0.15 +1.49 ± 0.27 Warmest 5ᵗʰ 2010 +1.11 +2.00
    Coolest 130ᵗʰ 1917 -0.77 -1.39
    Ocean +0.44 ± 0.05 +0.79 ± 0.09 Warmest 10ᵗʰ 1998 +0.60 +1.08
    Coolest 125ᵗʰ 1911 -0.53 -0.95
    Ties: 2009
    Land and Ocean +0.50 ± 0.07 +0.90 ± 0.13 Warmest 8ᵗʰ 2010 +0.66 +1.19
    Coolest 127ᵗʰ 1911 -0.54 -0.97

    The most current data may be accessed via the Global Surface Temperature Anomalies page.

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    The maps below represent precipitation percent of normal (left) and precipitation percentiles (right) based on the GHCN dataset of land surface stations using a base period of 1961–1990. As is typical, precipitation anomalies during April 2013 varied significantly around the world. As indicated by the April precipitation percentiles map below, record wetness was observed over part of the north central United States, eastern Burkina Faso, and part of eastern Russia. Record dryness was scattered across several locales around the globe, including northern Chile, central Colombia, southeastern Egypt, and part of northern Sudan.

    • Following the declaration of drought conditions in March across much of New Zealand, more than double normal April rainfall was recorded in upper South Island and Tauranga. Motueka received 267 percent of its normal April rainfall, with almost half of this occurring in one day.

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Peterson, T.C. and R.S. Vose, 1997: An Overview of the Global Historical Climatology Network Database. Bull. Amer. Meteorol. Soc., 78, 2837-2849.

Quayle, R.G., T.C. Peterson, A.N. Basist, and C. S. Godfrey, 1999: An operational near-real-time global temperature index. Geophys. Res. Lett., 26, 333-335.

Smith, T.M. and R.W. Reynolds, 2005: A global merged land air and sea surface temperature reconstruction based on historical observations (1880-1997), J. Clim., 18, 2021-2036.

Smith et al., 2008, Improvements to NOAA's Historical Merged Land-Ocean Surface Temperature Analysis (1880-2006), J. Climate., 21, 2283-2293.

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Citing This Report

NOAA National Centers for Environmental Information, State of the Climate: Global Analysis for April 2013, published online May 2013, retrieved on July 30, 2016 from