State of the Climate
Global Analysis
April 2004

National Oceanic and Atmospheric Administration

National Climatic Data Center

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Global Highlights:

Based on preliminary data for April 2004, global average combined land and sea surface temperature was third warmest on record
April temperatures were above average throughout Scandinavia, the western United States, Alaska and India, with below average temperatures in the southern U.S., western Russia and the Carribean
Precipitation during April was above average across the southern Great Plains of the U.S., western Europe and the United Kingdom with drier than average conditions across Japan, coastal Brazil and the Pacific Northwest of the U.S.
Near-normal SSTs across the central and eastern equatorial Pacific basin are indicative of neutral ENSO conditions.

The data presented in this report are preliminary. Ranks and anomalies may change as more complete data are received and processed. The most current data may be accessed via the Global Surface Temperature Anomalies page.

Introduction

The map below uses anomalies that were calculated from the Global Historical Climatology Network (GHCN) data set of land surface stations using a 1961-1990 base period. This map indicates above average temperatures across eastern Asia, most of Australia, Alaska and the western United States, while cooler than average temperatures occurred in Mexico, portions of Canada and the southeastern U.S.

The mean position of upper level ridges of high pressure and troughs of low pressure (depicted by positive and negative 500 millibar height anomalies during April 2004) are generally reflected by areas of positive and negative temperature anomalies at the surface, respectively. For other Global products see the Climate Monitoring Global Products page.

Click here for current month's Temperature Dot map

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Temperature Rankings and Graphics

Current Month / Year-to-date

April	Anomaly	Rank	Warmest Year on Record
Global Land Ocean Land and Ocean	+0.84°C (+1.51°F) +0.39°C (+0.70°F) +0.52°C (+0.94°F)	5th warmest 3rd warmest 3rd warmest	1998 (+1.24°C/2.32°F) 1998 (+0.51°C/0.92°F) 1998 (+0.73°C/1.31°F)
Northern Hemisphere Land Ocean Land and Ocean	+0.79°C (+1.42°F) +0.47°C (+0.85°F) +0.60°C (+1.08°F)	9th warmest warmest 3rd warmest	1998 (+1.26°C/2.27°F) 1998 (+0.78°C/1.40°F)
Southern Hemisphere Land Ocean Land and Ocean	+0.74°C (+1.33°F) +0.35°C (+0.63°F) +0.42°C (+0.76°F)	4th warmest 7th warmest 5th warmest	1998 (+1.09°C/1.96°F) 1998 (+0.56°C/1.01°F) 1998 (+0.66°C/1.19°F)

Click here for Global Land and Ocean Triad plot

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Click here for Global Hemisphere Triad plot

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January-April	Anomaly	Rank	Warmest Year on Record
Global Land Ocean Land and Ocean	+1.01°C (+1.82°F) +0.40°C (+0.72°F) +0.59°C (+1.06°F)	3rd warmest 4th warmest 3rd warmest	2002 (+1.38°C/2.49°F) 1998 (+0.52°C/0.94°F) 1998 (+0.73°C/1.31°F)
Northern Hemisphere Land Ocean Land and Ocean	+1.12°C (+2.02°F) +0.45°C (+0.81°F) +0.72°C (+1.30°F)	4th warmest 2nd warmest 3rd warmest	2002 (+1.61°C/2.90°F) 1998 (+0.51°C/0.92°F) 2002 (+0.86°C/1.55°F)
Southern Hemisphere Land Ocean Land and Ocean	+0.58°C (+1.04°F) +0.39°C (+0.70°F) +0.43°C (+0.77°F)	6th warmest 7th warmest 6th warmest	1998 (+0.88°C/1.58°F) 1998 (+0.54°C/0.97°F) 1998 (+0.60°C/1.08°F)

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

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Precipitation

The maps below represent anomaly values based on the GHCN data set of land surface stations using a base period of 1961-1990. The map to the left is precipitation anomalies measured in millimeters, the map to the right is the percentage of average (1961-1990) precipitation. During April 2004, much above average precipitation fell across the southern Great Plains of the U.S., France, southeastern Brazil and Uruguay. Below average precipitation was observed across Malaysia, the southeastern U.S., the northern Great Plains of the U.S. and Japan.

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Click here for Percent Precipitation Dot map

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ENSO SST Analysis

Click Here for the last week of the month's ENSO condtions Map

Click here for animated loop

Sea surface temperatures were again near-normal over much of the central and eastern equatorial Pacific (as shown in the adjacent animation of weekly sea surface temperature anomalies). A consensus of indices suggest neutral ENSO conditions. A comprehensive summary of April 2004 ENSO conditions can be found on the ENSO monitoring page. For the latest advisory on ENSO conditions go to NOAA's Climate Prediction Center (CPC) and the CPC ENSO Diagnostic Discussion
Images of sea surface temperature conditions are available for all months to date during 2004 at the weekly SST page

Troposphere

The tables below contain mid-tropospheric conditions for April 2004. These temperatures are for the atmospheric layer centered in the mid-troposphere (approximately 2-6 miles above the Earth's surface) which also includes a portion of the lower stratosphere. (The MSU channel used to measure mid-tropospheric temperatures receives about 25 percent of its signal above 6 miles.) Analysis of the satellite record that began in 1979 indicates that global temperatures are increasing in the mid-troposphere, but the magnitude of the trend differs based on the analysis methods used in adjusting for factors such as orbital decay and inter-satellite differences. The 1979-2004 trend for April is 0.04°C/decade based on data from the University of Alabama at Huntsville (UAH) and 0.13°C/decade based on data provided by Remote Sensing Systems (RSS). The base period used in both data sets is 1979-1998.

April	Anomaly	Rank	Warmest Year on Record
UAH mid-troposphere	+0.11°C (+0.20°F)	6th warmest	1998 (+0.71°C/1.28°F)
RSS mid-troposphere	+0.32°C (+0.58°F)	3rd warmest	1998 (+0.74°C/1.33°F)

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Stratosphere

The tables below display stratospheric conditions for April 2004. The stratosphere is located between 10-14 miles above the Earth's surface. Over the last decade, stratospheric temperatures have been below average in large part due to the depletion of ozone. The large increase in temperature in 1982 was caused by the volcanic eruption of El Chichon in Mexico, and the increase in 1991 was a result of the eruption of Mt. Pinatubo in the Philippines. Therefore the base period used in both data sets is 1984-1990 which was chosen to avoid contamination by these eruptions.

April	Anomaly	Rank	Warmest Year on Record
UAH stratosphere	-0.33°C (-0.60°F)	7th coolest	1983 (+0.91°C/1.64°F)
RSS stratosphere	-0.29°C (-0.52°F)	8th coolest	1992 (+0.84°C/1.51°F)

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Mid-tropospheric and lower stratospheric temperature data are collected by NOAA's TIROS-N polar-orbiting satellites and adjusted for time-dependent biases by NASA and the Global Hydrology and Climate Center at the University of Alabama in Huntsville (UAH). An independent analysis is also performed by Remote Sensing Systems (RSS).

For additional details on precipitation and temperatures in April, see the Global Hazards page .

References:

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

Questions?

For questions on technical or scientific content of this report, please contact:

Ahira Sánchez-Lugo:
Ahira.Sanchez-Lugo@noaa.gov

For general climate monitoring questions, please contact:

CMB.Contact@noaa.gov

For climate data orders, please contact the National Climatic Data Center's Climate Services and Monitoring Division:

NCDC.Orders@noaa.gov

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State of the ClimateGlobal AnalysisApril 2004

National Oceanic and Atmospheric Administration

National Climatic Data Center

Global Highlights:

Contents of this Section:

Introduction

Temperature Rankings and Graphics

Precipitation

ENSO SST Analysis

Troposphere

Stratosphere

Questions?

State of the Climate
Global Analysis
April 2004