Microwave Sounding Unit Data

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Temperatures measured in the lowest 8 km (5 miles) of the troposphere were 0.17°C (0.31°F) above the long term average (1979-1998). This was the 4th warmest April, but far below the record anomaly of 0.75°C (1.35°F) set during the strong El Niño of 1998.

Over the Northern Hemisphere, temperatures in April above the surface were also 4th warmest, with a positive departure of 0.28°C (0.50°F). Southern Hemisphere temperatures were near to the long term average, with temperatures averaging just 0.06°C (0.11°F) above the mean.

In the lower stratosphere, the global temperature was 0.37°C (0.67°F) cooler than the average, which ranked as the 5th coolest April during the satellite period of record which began in 1979. This was the 8th consecutive April with below average stratospheric temperatures. Both the Northern and Southern Hemispheric temperatures were below the average, with departures of -0.45°C (-0.81°F) and -0.29°C (-0.52°F), respectively.

Lower 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.