Query: Just 1.25 per cent of the carbon dioxide in the atmosphere-ocean system has been released by ­humans in the past 250 years.

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Planetary boundaries <=SEP=> Planetary boundaries is the central concept in an Earth system framework proposed by a group of Earth system and environmental scientists led by Johan Rockström from the Stockholm Resilience Centre and Will Steffen from the Australian National University . In 2009 , the group proposed a framework of `` planetary boundaries '' designed to define a `` safe operating space for humanity '' for the international community , including governments at all levels , international organizations , civil society , the scientific community and the private sector , as a precondition for sustainable development . This framework is based on scientific research that indicates that since the Industrial Revolution , human actions have gradually become the main driver of global environmental change . The scientists assert that once human activity has passed certain thresholds or tipping points , defined as `` planetary boundaries '' , there is a risk of `` irreversible and abrupt environmental change '' . The group identified nine Earth system processes which have boundaries that , to the extent that they are not crossed , mark the safe zone for the planet . However , because of human activities some of these dangerous boundaries have already been crossed , while others are in imminent danger of being crossed .   Rockström and Steffen collaborated with 26 leading academics , including Nobel laureate Paul Crutzen , Goddard Institute for Space Studies climate scientist James Hansen and the German Chancellor 's chief climate adviser Hans Joachim Schellnhuber . The group identified nine `` planetary life support systems '' essential for human survival , and attempted to quantify just how far seven of these systems have been pushed already . They then estimated how much further we can go before our own survival is threatened ; beyond these boundaries there is a risk of `` irreversible and abrupt environmental change '' which could make Earth less habitable . Estimates indicate that three of these boundaries -- climate change , biodiversity loss , and the biogeochemical flow boundary -- appear to have been crossed . The boundaries are `` rough , first estimates only , surrounded by large uncertainties and knowledge gaps '' that interact in ways that are complex and not well understood . Boundaries can help identify where there is room and define a `` safe space for human development '' , which is an improvement on approaches which aim at just minimizing human impacts on the planet . The 2009 report was presented to the General Assembly of the Club of Rome in Amsterdam . An edited summary of the report was subsequently published as the featured article in a special edition of Nature . Nature also published critical commentary from leading academics they invited to comment on each of the seven planetary boundaries which had been quantified , including comments from Nobel laureate Mario J. Molina and biologist Cristián Samper . In 2015 , a second paper was published in Science updating the Planetary Boundaries concept . The findings were presented at the World Economic Forum in Davos , January 2015 .

Carbon dioxide <=SEP=> Carbon dioxide ( chemical formula ) is a colorless gas with a density about 60 % higher than that of air ( 1.225 g/L ) that is odorless at normally encountered concentrations . Carbon dioxide consists of a carbon atom covalently double bonded to two oxygen atoms . It occurs naturally in Earth 's atmosphere as a trace gas at a concentration of about 0.04 percent ( 400 ppm ) by volume . Natural sources include volcanoes , hot springs and geysers , and it is freed from carbonate rocks by dissolution in water and acids . Because carbon dioxide is soluble in water , it occurs naturally in groundwater , rivers and lakes , ice caps , glaciers and seawater . It is present in deposits of petroleum and natural gas .   As the source of available carbon in the carbon cycle , atmospheric carbon dioxide is the primary carbon source for life on Earth and its concentration in Earth 's pre-industrial atmosphere since late in the Precambrian has been regulated by photosynthetic organisms and geological phenomena . Plants , algae and cyanobacteria use light energy to photosynthesize carbohydrate from carbon dioxide and water , with oxygen produced as a waste product .   Carbon dioxide is produced by all aerobic organisms when they metabolize carbohydrates and lipids to produce energy by respiration . It is returned to water via the gills of fish and to the air via the lungs of air-breathing land animals , including humans . Carbon dioxide is produced during the processes of decay of organic materials and the fermentation of sugars in bread , beer and winemaking . It is produced by combustion of wood and other organic materials and fossil fuels such as coal , peat , petroleum and natural gas .   It is a versatile industrial material , used , for example , as an inert gas in welding and fire extinguishers , as a pressurizing gas in air guns and oil recovery , as a chemical feedstock and in liquid form as a solvent in decaffeination of coffee and supercritical drying . It is added to drinking water and carbonated beverages including beer and sparkling wine to add effervescence . The frozen solid form of , known as `` dry ice '' is used as a refrigerant and as an abrasive in dry-ice blasting .   Carbon dioxide is the most significant long-lived greenhouse gas in Earth 's atmosphere . Since the Industrial Revolution anthropogenic emissions - primarily from use of fossil fuels and deforestation - have rapidly increased its concentration in the atmosphere , leading to global warming . Carbon dioxide also causes ocean acidification because it dissolves in water to form carbonic acid .