Satellites play vital role in understanding the carbon cycle     FAPAR (Fraction of Absorbed Photosynthetically Active Radiation) derived from MERIS over Europe in May 2005. FAPAR - the fraction of incoming solar radiation useful for photosynthesis that is actually absorbed by vegetation - is recognised as an essential climate variable by international organisations and is regularly used in diagnostic and predictive models to compute the primary productivity of the vegetation canopies.   Comparison between oxygen (top) and carbon dioxide figures derived from SCIAMACHY.   Carbon dioxide and oxygen mixing ratio derived from SCIAMACHY. Envisat's SCIAMACHY instrument is the first space sensor capable of measuring the most important greenhouse gases with high sensitivity down to the Earth’s surface because it observes the spectrum of sunlight shining through the atmosphere in ‘nadir’ looking operations on a global scale.   Global CO2 columns derived from SCIAMACHY for July and October 2003. The data shows the Earth 'breathing' from space. The blue colours represent low values of CO2, while the green colours represent normal values. The levels in July are lower because plants draw down the CO2 during the growing season and release some of it back when the leaves fall off in autumn. Release date: 28 February 2012