Amicus Curiae Brief presented by ClientEarth 21 November 2016 78. This section sets out why the Commission may accept that greenhouse gas emissions from a range of different sources (expressed in tonnes of carbon dioxide equivalent) contribute equally to global warming. 79. The evidence of the IPCC is clear and unequivocal. Climate change is a global problem by its very nature. It is caused by the release of greenhouse gasses, of which methane and carbon dioxide are the most potent, into the earth's atmosphere, as well as land use changes that have increased deforestation, and affect the planet’s ability to absorb excess carbon dioxide via natural processes. These two processes and their acceleration since the start of the industrial revolution have caused a build up of gasses in the earth's upper atmosphere, trapping radiative heat from the sun in the earth's atmosphere and warming the surface of the planet. A build up of carbon dioxide in the atmosphere also causes ocean acidification which has potentially significant negative impacts on marine environments and the people who depend on them. 63 80. The AR5 concluded that: "[a]nthropogenic greenhouse gas emissions have increased since the preindustrial era, driven largely by economic and population growth, and are now higher than ever. This has led to atmospheric concentrations of carbon dioxide, methane and nitrous oxide that are unprecedented in at least the last 800,000 years. Their effects, together with those of other anthropogenic drivers, have been detected throughout the climate system and are extremely likely to have 63 http://climate.nasa.gov/evidence/ 40