"What percentage of the CO2 in the atmosphere has been produced by human beings through the burning of fossil fuels?"
"... In the following calculations, we will express atmospheric concentrations of CO2 in units of parts per million by volume (ppmv). Each ppmv represents 2.13 X1015 grams, or 2.13 petagrams of carbon (PgC) in the atmosphere. According to Houghton and Hackler, land-use changes from 1850-2000 resulted in a net transfer of 154 PgC to the atmosphere. During that same period, 282 PgC were released by combustion of fossil fuels, and 5.5 additional PgC were released to the atmosphere from cement manufacture. This adds up to 154 + 282 + 5.5 = 441.5 PgC, of which 282/444.1 = 64% is due to fossil-fuel combustion.
Atmospheric CO2 concentrations rose from 288 ppmv in 1850 to 369.5 ppmv in 2000, for an increase of 81.5 ppmv, or 174 PgC. In other words, about 40% (174/441.5) of the additional carbon has remained in the atmosphere, while the remaining 60% has been transferred to the oceans and terrestrial biosphere.
The 369.5 ppmv of carbon in the atmosphere, in the form of CO2, translates into 787 PgC, of which 174 PgC has been added since 1850. From the second paragraph above, we see that 64% of that 174 PgC, or 111 PgC, can be attributed to fossil-fuel combustion. This represents about 14% (111/787) of the carbon in the atmosphere in the form of CO2." See the full text article at Carbon Dioxide Information Analysis Center. (CDIAC)
Source: CDIAC http://cdiac.ornl.gov/faq.html#Q7 Last accessed 1/5/2012.)
Source: Tables:US Energy Information Administration, http://www.eia.gov/emeu/international/carbondioxide.html Last Accessed 1/5/2012 .
World per capita carbon dioxide from consumption and flaring of fossil fuels 1980-2006
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World carbon dioxide emissions from the consumption and flaring of fossil fuels 1980-2006
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"The above question pertains to all 'Greenhouse Gases' Indicators, however, the information on these pages (overview, graphics, references and metadata) relates specifically to 'U.S. Greenhouse Gas Emissions'. ..." See the full text article at The United States Environmental Protection Agency.
Source: The United States Environmental Protection Agency http://cfpub.epa.gov/eroe/index.cfm?fuseaction=detail.viewInd&lv=list.listByAlpha&r=224026&subtop=342 Last accessed 1/5/2012.
Source: Global Climate Change - NASA's Eyes on the Earth http://climate.nasa.gov/keyIndicators/#landIce Last accessed 1/5/2012.
"Yes, there is strong evidence that global sea level gradually rose in the 20th century and is currently rising at an increased rate, after a period of little change between AD 0 and AD 1900. Sea level is projected to rise at an even greater rate in this century. The two major causes of global sea level rise are thermal expansion of the oceans (water expands as it warms) and the loss of land-based ice due to increased melting. ..." See the full text article at IPCC AR4 2007.
Source: "Intergovernmental Panel on Climate Change Fourth Assessment Report Climate Change 2007" http://www.ipcc.ch/publications_and_data/ar4/wg1/en/faq-5-1.html Last accessed 1/5/2012.
"Observations show a global-scale decline of snow and ice over many years, especially since 1980 and increasing during the past decade, despite growth in some places and little change in others (Figure 1). Most mountain glaciers are getting smaller. Snow cover is retreating earlier in the spring. Sea ice in the Arctic is shrinking in all seasons, most dramatically in summer. Reductions are reported in permafrost, seasonally frozen ground and river and lake ice. Important coastal regions of the ice sheets on Greenland and West Antarctica, and the glaciers of the Antarctic Peninsula, are thinning and contributing to sea level rise. The total contribution of glacier, ice cap and ice sheet melt to sea level rise is estimated as 1.2 ± 0.4 mm yr–1 for the period 1993 to 2003. ..." See the full text article at IPCC AR4 2007.
Source: "Intergovernmental Panel on Climate Change Fourth Assessment Report Climate Change 2007," http://www.ipcc.ch/publications_and_data/ar4/wg1/en/faq-4-1.html Last accessed 1/5/2012.
"Instrumental observations over the past 157 years show that temperatures at the surface have risen globally, with important regional variations. For the global average, warming in the last century has occurred in two phases, from the 1910s to the 1940s (0.35°C), and more strongly from the 1970s to the present (0.55°C). An increasing rate of warming has taken place over the last 25 years, and 11 of the 12 warmest years on record have occurred in the past 12 years. Above the surface, global observations since the late 1950s show that the troposphere (up to about 10 km) has warmed at a slightly greater rate than the surface, while the stratosphere (about 10–30 km) has cooled markedly since 1979. This is in accord with physical expectations and most model results. Confirmation of global warming comes from warming of the oceans, rising sea levels, glaciers melting, sea ice retreating in the Arctic and diminished snow cover in the Northern Hemisphere. ..." See the full text article at IPCC AR4 2007.
Source: "Intergovernmental Panel on Climate Change Fourth Assessment Report Climate Change 2007," http://www.ipcc.ch/publications_and_data/ar4/wg1/en/faq-3-1.html Last accessed 1/5/2012.