Complex sentence: From the beginning of the satellite record in late 1978 into 1998 it apparently showed a net global cooling trend, although ground measurements and instruments carried aloft by balloons showed warming in many of the areas where those measurements were taken.
Split into simpler sentences: From the beginning of the satellite record in late 1978 well into 1998 it showed a net global cooling trend. Ground measurements and instruments carried aloft by balloons showed warming in many of the areas where those measurements were taken.