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Anthropogenic CO2 increase[edit]

While CO2 absorption and release is always happening as a result of natural processes, the recent rise in CO2 levels in the atmosphere is known to be mainly due to human activity.[26] Researchers know this both by calculating the amount released based on various national statistics, and by examining the ratio of various carbon isotopes in the atmosphere,[26] as the burning of long-buried fossil fuels releases CO2 containing carbon of different isotopic ratios to those of living plants, enabling them to distinguish between natural and human-caused contributions to CO2 concentration.

Burning fossil fuels such as coal and petroleum is the leading cause of increased anthropogenic CO2; deforestation is the second major cause. In 2010, 9.14 gigatonnes of carbon (33.5 gigatonnes of CO2) were released from fossil fuels and cement production worldwide, compared to 6.15 gigatonnes in 1990.[27] In addition, land use change contributed 0.87 gigatonnes in 2010, compared to 1.45 gigatonnes in 1990.[27] In 1997, human-caused Indonesian peat fires were estimated to have released between 13% and 40% of the average carbon emissions caused by the burning of fossil fuels around the world in a single year.[28][29][30] In the period 1751 to 1900, about 12 gigatonnes of carbon were released as carbon dioxide to the atmosphere from burning of fossil fuels, whereas from 1901 to 2008 the figure was about 334 gigatonnes.[31]

This addition, about 3% of annual natural emissions, as of 1997, is sufficient to exceed the balancing effect of sinks.[32] As a result, carbon dioxide has gradually accumulated in the atmosphere, and as of 2013, its concentration is almost 43% above pre-industrial levels.[33][34] Various techniques have been proposed for removing excess carbon dioxide from the atmosphere in carbon dioxide sinks.

Global fossil carbon emissions 1800–2007.

False-color image of smoke and ozone pollution from Indonesian fires, 1997.

Biosphere CO2 flux in the northern hemisphere summer (NOAA Carbon Tracker).

Biosphere CO2 flux in the northern hemisphere winter (NOAA Carbon Tracker).

Sources[edit]

Main article: Life-cycle greenhouse-gas emissions of energy sources

Lifecycle greenhouse gas emissions by electricity source.[35]

Technology

Description

50th percentile (g CO2/kWhe)

Hydroelectric Reservoir 4 Wind Onshore 12 Nuclear Various generation II reactor types 16 Biomass Various 18 Solar thermal Parabolic trough 22 Geothermal Hot dry rock 45 Solar PV Polycrystalline silicon 46 Natural gas Various combined cycle turbines without scrubbing 469 Coal Various generator types without scrubbing 1001

Total CO2 emissions Main article: List of countries by carbon dioxide emissions

Countries with the highest CO2 emissions

Country

Carbon dioxide emissions per year (106 Tons) (2006)

Percentage of global total

Avg. emission per km2 of its land (tons)

Carbon dioxide emissions per year (Tons per person) (2007)

China 6,103 21.5% 636 4.9 United States 5,752 20.2% 597 19.3 Russia 1,564 5.5% 91 11.6 India 1,510 5.3% 459 1.4 Japan 1,293 4.6% 3421 9.8 Germany 805 2.8% 2254 9.6 United Kingdom 568 2.0% 2338 8.9 Canada 544 1.9% 54 16.5 South Korea 475 1.7% 4758 10.5 Italy 474 1.7% 1573 7.7

Per capita CO2 emissions[36] Main article: List of countries by carbon dioxide emissions per capita

Countries with the highest per capita CO2 emissions

Country

Carbon dioxide emissions per year (Tons per person) (2006)

Qatar 56.2 United Arab Emirates 32.8 Kuwait 31.2 Bahrain 28.8 Trinidad and Tobago 25.3 Luxembourg 24.5 Netherlands Antilles 22.8 Aruba 22.3 United States 19 Australia 18.1

United States According to Washington DC, Carbon Monitoring for Action (CARMA).[notes 1] In the United States, power generators produce 40%[37] of all CO2 emissions. Globally power generators contribute 25 per cent of emissions.[37] Carbon dioxide accounted for the 95 per cent of direct greenhouse gas emissions (GGE). [38] In November 2007 the Scherer Plant was the only American power plant on the list of the world’s top 25 carbon dioxide emitters ranking 20th out of 25.[39] Scherer Plant in Juliette, Georgia is the largest CO2 emitter in the U.S.[37]

Irreversibility and uniqueness of carbon dioxide[edit]

Carbon dioxide has unique long-term effects on climate change that are largely "irreversible" for one thousand years after emissions stop (zero further emissions) even though carbon dioxide tends toward equilibrium with the ocean on a scale of 100 years. The greenhouse gases methane and nitrous oxide do not persist over time in the same way as carbon dioxide. Even if human carbon dioxide emissions were to completely cease, atmospheric temperatures are not expected to decrease significantly in the short term.[56][57][58][59]

The concentration of carbon dioxide (CO2) in Earth's atmosphere determines its contribution to the greenhouse effect and the rates of plant and algal photosynthesis. The concentration has increased markedly in the 21st century, at a rate of 2.0 ppm/yr during 2000–2009 and faster since then.[1][2] It was 280 ppm (parts per million) in pre-industrial times, and has risen to 395 ppm in 2013[3] (with a daily average at Mauna Loa recording 400 ppm as of 10 May 2013,[4]) with the increase largely attributed to anthropogenic sources.[5] About 57% of the CO2 emissions go to increase the atmospheric level, with much of the remainder contributing to ocean acidification. Carbon dioxide is used in photosynthesis (in plants and other photoautotrophs), and is also a prominent greenhouse gas. Despite its relatively small overall concentration in the atmosphere, CO2 is an important component of Earth's atmosphere because it absorbs and emits infrared radiation at wavelengths of 4.26 µm (asymmetric stretching vibrational mode) and 14.99 µm (bending vibrational mode), thereby playing a role in the greenhouse effect.[6] The present level is the highest in the past 800,000 years[7] and likely the highest in the past 20 million years[8].