Clouds cover about 70% of the earth. In 1983 the world first satellite program, called International Satellite Cloud Climatology Project (ISCCP), was established. ISCCP use geostationary and polar orbiting satellites to cover the world every third hour. Moderate Resolution Imaging Spectroradiometer (MODIS), a new instrument, was introdused in the satellite Terra in 2000. MODIS has 36 band in the range 0.4μm − 14.4μm, while ISCCP has 3-8 bands. Terra and Aqua, both carrying MODIS, use 1-2 days to cover the earth.
Total cloud fraction, cloud optical thickness, high cloud fraction, cirrus fractionand cloud top pressure have been analysed. The data has been presented in color plots. Five year trends have been presented for the parameters for both dataset.
The results show that MODIS give higher values than ISCCP for all pa-rameters. The global trend for optical thickness was in good agreement. Se-ven areas; Atlantic ocean south and north, South-Norway, Central-Sahara,Central-Australia, south east Asia and Central-Pasific were more closely investigated. Statistical tests were performed to investigate if the trends for ISCCP and MODIS were significant different. ISCCP5 trends were not representative for the ISCCP21. The differences between ISCCP5 and ISCCP21 may indicate a real change in trends, but five year may be a too short term to give confident estimates for the future.