BROWN, BLACK, GREEN AND BLUE CARBON
Brown and black carbon emissions from fossil fuels, biofuels global warming over the past century. Black carbon tends to
and wood burning are major contributors to global warming. remain in the atmosphere for days-weeks (Hansen and Naza-
Black carbon emissions have a large effect on radiation trans- rento, 2004) whereas CO
2
remains in the atmosphere for ap-
mission in the troposphere, both directly and indirectly via prox 100 years (IGSD, 2009).
clouds, and also reduce the snow and ice albedo.
The total CO
2
emissions of are estimated to be between 7,200
Black carbon is thought to be the second largest contributor to Tg C yr
–1
, and 10,000 Tg C yr
–1
(Trumper et al., 2009), and
global warming, next to brown carbon (the gases). Thus, reduc- the amount of carbon in the atmosphere is increasing by ap-
ing black carbon emission represents one of the most efficient proximately 2,000 Tg C yr
–1
(Houghton, 2007).
ways for mitigating global warming that we know today.
GREEN CARBON
Black carbon enters the ocean through aerosol and river deposi- Green carbon is carbon removed by photosynthesis and stored
tion. Black carbon can comprise up to 30% of the sedimentary in the plants and soil of natural ecosystems and is a vital part of
organic carbon (SOC) in some areas of the deep sea (Masiello the global carbon cycle. Sofar, however, it has mainly been con-
and Druffel, 1998) and may be responsible for 25% of observed sidered in the climate debate in terrestrial ecosystems, though
the issue of marine carbon sequestration has been known for
at least 30 years.
Actual and projected energy demand
A sink is any process, activity or mechanism that removes a
Gigatonnes of oil equivalent
greenhouse gas, an aerosol or a precursor of a greenhouse gas
or aerosol from the atmosphere. Natural sinks for CO
Projections
2
are for
15 example forests, soils and oceans.
Oil
12
Unlike many plants and most crops, which have short lives or
release much of their carbon at the end of each season, forest bio-
mass accumulates carbon over decades and centuries. Further-
9
Coal more, forests can accumulate large amounts of CO
2
in relatively
short periods, typically several decades. Afforestation and refores-
6
tation are measures that can be taken to enhance biological car-
Gas bon sequestration. The IPCC calculated that a global programme
3
Nuclear involving reduced deforestation, enhanced natural regeneration
Biomass Hydropower
of tropical forests and worldwide re-afforestation could seques-
Other
0 renewables
1980 1990 2000 2010 2020 2030
Figure 3: World greenhouse emission by sector. All transport
Note: All statistics refer to energy in its original form (such as coal) before being
transformed into more convenient energy (such as electrical energy).
accounts for approximately 13.5% of the total emissions, while
deforestation accounts for approximately 18%. However, esti-
Source: International Energy Agency (IEA), World Energy Outlook 2008.
mates of the loss of marine carbon-binding ecosystems have
Figure 2: Projected growth in energy demand in coming decades. previously not been included.
16
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