Global Temperatures
| Global
temperatures in 2003 were 0.56°C (1.01°F) above the
long-term (1880-2003) average**, ranking 2003 the second warmest
year on record, which tied 2002. The warmest year on record is 1998
with an anomaly of +0.63°C (+1.13°F). Land temperatures in
2003 were 0.83°C (1.50°F) above average, ranking third in
the period of record while ocean temperatures ranked as second
warmest with 0.44°C (0.80°F) above the 1880-2003 mean. |
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The map of temperature anomalies (above right) contains data
from an in-situ and satellite blended data set of land and ocean
temperatures. The period of record for this data set is 1988-2002,
a relatively warm period compared to the base period used in the
creation of the land
only map of temperature anomalies below. Some minor differences
in the land surface anomalies between these two maps result from
the differences in base periods and data that are used to construct
the two maps.
The
Northern Hemisphere temperature averaged near record levels in
2003 at 0.64°C (1.15°F) above the long-term average. The
Southern Hemisphere temperature also reflected the globally
warmer conditions, with a positive anomaly near 0.45°C
(0.81°F).
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In 2003, warmer
temperatures and shifts in atmospheric circulation patterns
contributed to a second straight year of extremely low Arctic sea
ice extent in September, according to the
National Snow and Ice Data Center. Northern Hemisphere sea ice
extent was almost as low as that observed in September 2002, the
lowest since satellite monitoring began in 1978. |
Annual anomalies in excess of +2.0°C (3.6°F) were
widespread across much of North America, Asia and Europe.
Additional details on temperatures throughout the world are
included below.
**The 1880-2003 average combined land and ocean annual
temperature is 13.9°C (56.9°F), the annually averaged land
temperature for the same period is 8.5°C (47.3°F), and the
long-term annually averaged sea surface temperature is 16.1°C
(60.9°F).
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ENSO Conditions
| The year began with
the equatorial Pacific Ocean in an El Niño/Southern
Oscillation (ENSO) warm event. This El Niño warming began in
mid-2002, and reached its maturity in November 2002 when the
sea-surface temperature (SST) anomalies in the Niño
3.4 region (map of
Niño regions) reached their warmest condition with a
+1.54°C (+2.77°F) SST anomaly. |
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| Beginning in January of 2003, the anomalously warm
waters in the oceanic mixed-layer in the eastern equatorial Pacific
began to slowly cool. Between December 2002 and January 2003, the
SST anomaly in the Niño 3.4 region decreased from
+1.42°C (+2.55°F) to +0.66°C (+1.18°F). This
cooling spread westward, and had affected the ocean conditions
basin-wide in the February monthly mean ocean temperatures. The
trend in SST anomalies was also evident in the western Pacific
Ocean, reflected in the anomalies measured in the Niño
4 region. The observed cooling trend in basin-wide SSTs
continued through March. The dissipation of the warm event and the
transition to near-neutral ENSO conditions occurred in April, when
the SST anomalies cooled to near-normal across the equatorial
Pacific basin. However, the atmospheric signal lagged the ocean,
with the
Southern Oscillation Index (SOI) remaining negative through
June (see discussion below). This trend in ocean temperatures is
illustrated in the loop of
Equatorial Pacific SSTs, which shows the mean and anomalous
conditions across the tropical Pacific Ocean for the period
December 2002 through December 2003. |
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After the El
Niño event dissipated in April, ocean surface and
sub-surface temperatures began to rapidly cool. This cooling
suggested the development of a La Niña cold event in the
eastern and central equatorial Pacific. By the end of
May, SST anomalies in the eastern and central equatorial
Pacific had cooled to below -1.5 °C adjacent to the South
American coast. The cold anomaly in the Niño
3.4 region was -0.63°C (-1.13°F) in May. The rapid
cooling was generated by the return of easterly trade winds across
the near-equatorial region, which increased equatorial upwelling in
the eastern Pacific in April and May. |
| The colder than normal SST anomalies extended into
the middle of June, but were abruptly halted when a strong westerly
wind event propagated across the equatorial Pacific basin. This
westerly wind event (often referred to as wind bursts) is evident
in the
zonal wind (U-component wind) anomalies averaged over 5-day
periods in the equatorial zone. The westerly wind event was first
observed in early May in the far western Pacific, and then moved
eastward during June. This event generated an eastward propagating
oceanic Kelvin
wave that eroded the cold SST anomalies that had developed in
the central and eastern Pacific during the previous two
months. |
| Since the cessation of
the cold SST anomalies in June, the equatorial Pacific region has
slowly warmed. This observed warming did not develop into an El
Niño by the end of 2003, but the SST anomalies have been
consistently warm since July in both Niño regions (map of
Niño regions). Anomalously warm SSTs have been been
measured in the Niño
3.4 region for the past 6 months, and the SST anomaly had
reached +0.56 °C (+1.01 °F) for the
December mean. The warm oceanic conditions were also present in
the sub-surface measurements from NOAA's array of moored buoys.
Warmer than normal conditions were evident in the mixed-layer
during
December across the entire Pacific basin, although the observed
ocean temperatures were well below the peak warmth observed during
the 2002-2003
El Niño event. |
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Loop
of 2003 Sub-Surface Temperatures
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The atmospheric
indices measured during the latter half of 2003 in the Pacific
region showed mixed signals regarding their response to the
observed warming in the oceanic mixed-layer. The
Southern Oscillation Index (SOI) was consistently negative
during the first 6 months of 2003, which lagged the dissipation of
the El Niño event. The SOI remained negative through much of
the year but was strongly positive in December (see the latest
SOI
graph). Deep tropical convection in the western and central
equatorial Pacific typically responds to the warm waters associated
with ENSO warm events, and this is measured by
Outgoing Longwave Radiation (OLR) across the western and
central Pacific region. OLR anomalies were strongly negative in
early 2003, in response to the warm SSTs during the El Niño.
However, they have remained positive since April, despite the more
recent warming in the equatorial Pacific Ocean observed since July
(see the latest OLR
Anomaly graph). Through much of the year, the atmospheric
signal was mixed, with the SOI reflecting the warm SST anomalies,
and the OLR remaining positive and reflecting a weak La Niña
type signature. Please link to the ENSO
Monitoring page for the latest ENSO conditions in the tropical
Pacific. |
Temperature Trends
| During the past century, global
surface temperatures have increased at a rate near
0.6°C/century (1.1°F/century) but this trend has increased
to a rate approaching 2°C/century (3.6°F/century) during
the past 25 to 30 years. There have been two sustained periods of
warming, one beginning around 1910 and ending around 1945, and the
most recent beginning about 1976. Temperatures during the latter
period of warming have increased at a rate comparable to the rates
of warming projected to occur during the next century with
continued increases of anthropogenic greenhouse gases
(IPCC, 2001).
Data collected by NOAA's polar orbiting satellites and analyzed
for NOAA by the University of Alabama in Huntsville (UAH) and
Remote Sensing Systems (RSS, Santa Rosa, California) indicate that
temperatures in the lower troposphere from the surface to an
altitude of five miles ranked 2003 the third warmest year for the
globe. The average middle troposphere temperature for 2003 (the
layer which is centered in the mid-troposphere at an altitude of 2
to 6 miles, but which includes the lower stratosphere) is also
ranked as the third warmest year on record.
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| Analysis of the
satellite record that began in 1979 shows that the global average
temperature in the middle troposphere has increased, but differing
analysis techniques have yielded different trends. While trends are
positive in both cases, the increase in the UAH time series is
0.04°C/decade (0.08°F/decade), while the trend in the RSS
series is larger; 0.12°C/decade (0.22°F/decade). Trends in
both cases are less than the trend in global surface temperatures,
which increased at a rate near 0.17°C/decade
(0.30°F/decade) during the same 25 year period. Research toward
reconciling differences in trends between surface and
troposphere temperatures has been undertaken by the National
Academy of Sciences and continues to be addressed by the world's
leading climate change scientists. |
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While lower
tropospheric temperatures as measured by the MSU indicate
increasing temperatures over the last 2 decades, stratospheric (14
to 22 km / 9 to 14 miles) temperatures have been decreasing. This
is consistent with the depletion of ozone in the lower
stratosphere. The large increase in 1982 was caused by the volcanic
eruption of El Chichon, and the increase in 1991 was caused by the
eruption of Mt. Pinatubo in the Philippines. |
Regional Temperatures
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Annual temperatures
were above average across most land areas. The adjacent figure
depicts warmer than average temperatures (for a 1961-1990 base
period) that were widespread across much of the contiguous United
States and Alaska, as well as most of Europe and Asia. Temperatures
in these regions were 2-5°C (3.6-9.0°F) above the 1961-1990
average. This map was created using data from the Global
Historical Climatology Network, a network of more than 7,000
land surface observing stations. The only widespread areas of
negative anomalies were across parts of the eastern U.S., coastal
areas of Australia and far western Asia where temperatures were
between 1 and 3°C (1.8-5.4°F) cooler than average. |
| Notable temperature extremes during 2003 included a severe
heatwave during summer of 2003 across Europe. Daily maximum
temperatures ranged from 30-37°C (90-99°F) across France,
Switzerland and the Mediterranean region, killing approximately
25,000 people. France had its warmest summer on record, and
according to news reports, more than 14,000 people died of
heat-related causes during the peak of the heat wave in late July
and August. In North America, extreme cold winter temperatures
resulted in an unusually high ice concentration across the Great
Lakes. More than 90 percent of lakes Superior, Erie and Huron were
frozen by March 10th, the most ice cover since February 1994.
Unseasonably cold weather affected Bangladesh, India and much of
Asia in January, leading to the deaths of more than 1,000 people.
Average minimum temperatures were as low as 2-4°C
(36-39°F), in a region where minimum temperatures are usually
12-14°C (54-57°F). In the Peruvian highlands, temperatures
dropped below -20°C (-5°F) during the Southern Hemisphere
winter month of July, which led to the reported deaths of more than
200 people. For more information on temperature extremes during
2003 see the annual report of Significant
Events |
Global Snow Cover Extent
| As shown in the time
series to the right, mean Northern Hemisphere snow cover extent
during the winter season (December-February) was the second highest
since records began in 1967. Mean Northern Hemisphere winter snow
cover extent for the 1967-2003 period of record is 4.6 million
square kilometers. (Blue bars indicate seasons with below average
snow cover and red bars indicate seasons with above average snow
cover. Data were provided by David Robinson, Rutgers University).
Colder than normal conditions contributed to greater than
average snow cover across large parts of western and southern Asia
as well as Eastern Europe. Measurements from the Special Sensor
Microwave Imager (SSM/I) indicate the presence of higher than
average snow cover in these regions during December,
January,
and February. |
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However, higher than
average temperatures in northern and western regions of North
America, and
below average precipitation in some regions led to below
average winter season snow cover extent for the continent. This is
seen in the time series of winter snow cover extent anomalies for
North America to the left. Mean North America winter snow cover
extent for the 1967-2003 period of record is 1.7 million square
kilometers. Data were provided by David Robinson, Rutgers
University. |
| Northern Hemisphere
snow cover extent was also above average during the March-May
spring season, but only marginally so. As shown in the time series
graph to the right, spring snow cover extent in the Northern
Hemisphere has been below average in 14 of the past 16 years as a
trend to warmer spring temperatures has led to more rapid loss of
snow cover during the transition season between winter and summer.
Mean Northern Hemisphere spring snow cover extent is 3.1 million
square kilometers for the 1967-2003 period of record. |
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Spring snow cover
extent has also been below average across North America in much of
the past two decades. Snow cover extent was below average for the
spring 2003 season, the 14th below average year since 1985. Mean
North America spring snow cover extent is 1.3 million square
kilometers for the 1967-2003 period of record. |
Global Precipitation
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Global precipitation
was below the 1961-1990 average in 2003 for the third year in a
row. Drought was widespread across much of eastern Australia during
the first half of the year. India monsoon rainfall was 102 percent
above normal, bringing relief to areas that were plagued with
drought for much of 2002. Western Asia's rainfall was 80 percent
above average, alleviating long-term drought conditions. In
Zimbabwe, severe drought affected 900,000 people, one of Zimbabwe's
worst droughts in 50 years. Other drought-affected areas included
the western United States where the multi-year drought continued to
ravage the region. |
| In contrast to drought conditions, Denver, CO had it's second
biggest snowstorm on record when 31.80 inches of snow fell in
March. In February, a snowstorm hit the northeastern U.S., breaking
numerous 24-hour snowfall records. Heavy rainfall in mountainous
regions of southwest Asia's mountain region ameliorated long-term
drought conditions but caused a landslide in the village of
Kara-Taryk, Kyrgyzstan killing 38 people. In Sante Fe, Argentina
the reported worst flooding to occur since 1573 occurred in April
of 2003. Several days of heavy rainfall caused local rivers to rise
as much as 20 inches in one hour, killing 23 people and forcing the
evacuation of 45,000. By early May, flooding was so severe, Sante
Fe was characterized as an island. For more information about
precipitation extremes during 2003 see the annual report of
Significant
Events. |
Additional information on other notable weather events can be
found in the Significant
Events section of this report.
References
IPCC, 2001: Climate Change 2001: The Scientific Basis,
Contribution of Working Group I to the Third Assessment Report of
the Intergovernmental Panel of Climate Change. J.T. Houghton, Y.
Ding, D.J. Griggs, M. Noguer, P.J. vander Linden, X.Dai, K.
Maskell, and C.A. Johnson (Eds.), Cambridge University Press, 881
pp.
NOAA's National Climatic Data Center is the world's largest
active archive of weather data. The preliminary temperature and
precipitation rankings are available from the center by calling:
828-271-4800.
NOAA works closely with the academic and science communities on
climate-related research projects to increase the understanding of
El Niño and improve forecasting techniques. NOAA's Climate
Prediction Center monitors, analyzes and predicts
climate events ranging from weeks to seasons for the nation.
NOAA also operates the network of data buoys and satellites that
provide vital information about the ocean waters, and initiates
research projects to improve future climate forecasts.
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