While the concentrations of almost all greenhouse gases have been increasing since the Industrial Revolution, carbon dioxide has had the greatest effect on changing the climate. During the 1980s, humans released 5.5 billion tons of carbon (as carbon dioxide) into the atmosphere annually, by burning fossil fuels—coal, oil, and natural gas for heat, transportation, and electricity. An additional 1.6 billion tons was released from human-induced changes in land-use (clearing land for agriculture, pastures, etc.), mostly through deforestation in the tropics.
By the 1990s the average release of carbon dioxide from fossil fuels was 6.6 billion tons of carbon per year; and in the period 2000-2008, it was 7.7 billion tons of carbon per year. In 2008, 8.7 billion tons of carbon were released to the atmosphere from the combustion of fossil fuels. Emissions of carbon from deforestation were stable from 1980 to 2014, but since then, there has been a significant increase.
Where does that annual release of carbon go? Approximately four billion tons of carbon per year are accumulated in the atmosphere. Ocean modelers find that the oceans take up approximately 25 percent of emissions per year (2.3 billion tons), and the land takes up about three billion tons (or 33 percent of total emissions). These fluxes within the Global Carbon Cycle may be summarized using the formula:
Atmospheric increase = Emissions from fossil fuels + Net emissions from changes in land use – Oceanic uptake – Terrestrial carbon sink
 |
| This diagram of the carbon cycle shows the movement of carbon between land, atmosphere, and oceans. Yellow numbers are natural fluxes, and red are human contributions in gigatons of carbon per year. White numbers indicate stored carbon. (Diagram adapted from U.S. DOE, Biological and Environmental Research Information System by NASA Earth Observatory.)
Humans cause the release of carbon dioxide and other greenhouse gases to the atmosphere at rates much faster than the Earth can cycle them. Fossil fuels—oil, coal, natural gas, and their derivatives—were formed through the compression of organic (once living) material for millions of years, yet billions of tons of these fuels are now being burned each year. The CO2 expelled into the atmosphere through these activities will remain in the atmosphere for decades to centuries. This means that the CO2 emitted today will likely be affecting the climate for generations to come.
Despite widespread recognition of this, worldwide emission of fossil fuel continues to grow at an ever increasing rate (Le Quéré et al., 2009). Emissions will increase even more as the developing world moves towards greater industrialization. In 2007, China passed the United States in being the number one emitter of carbon dioxide, though the United States still leads in terms of per capita emissions.
Based on existing demographic, economic, social, and political conditions and trends, energy-related emissions of CO2are projected to increase from 7.9 billion tons of carbon in 2006 to 11.0 billion tons of carbon in 2030. Under business-as-usual scenarios, energy-related emissions of carbon from the Organisation for Economic Co-operation and Development(OECD) countries are predicted to increase by seven percent during this period, while the increase in emissions from non-OECD countries are predicted to increase by 68 percent (EIA, 2009). These emissions trajectories could be altered drastically, however, with improvements to the drivers of emissions, such as economic growth and climate change mitigation strategies.
|
Comments
Post a Comment