greenhouse gases and are the main contributors to the uncertainty associated with
the estimates of total radiative forcing.
CO 2 emissions were the largest contributors to the increased anthropogenic
radiative forcing or net radiation, in every decade since the 1960s. According to the
AR5 Report (2015), GHG emissions, driven by economic and population growth,
have increased since the pre-industrial era leading to unparalleled atmospheric
concentrations of CO 2 , methane, and nitrous oxide.
The long-term increase in CO 2 atmospheric concentration was mainly due to
accumulated emissions of about 2040 ± 310 Gt CO 2 , from which about 880 ± 35
Gt CO 2 remained in the atmosphere. The last 40 years accounted for about half of
the accumulated emissions over the two and a half centuries. It is estimated that
global emissions, which may be permissible worldwide, without a high likelihood
of dangerous climate change are about 2900 Gt CO 2 (e.g., Quiggin 2019).
Despite increased public awareness and climate mitigation policies, the global
yearly anthropogenic GHG emissions increased between 1970 and 2010, reaching
an estimated 49 Gt CO 2 -eq. (e.g., AR5 IPPC Report). Also, the yearly growths of
GHG emissions, in the period 1970–2000 and in the decade 2000–2010, were
about 1.3 and 2.2%, respectively. The contribution from fossil fuel combustion and
conversion was about 78% in these two periods.
While the contribution of population growth for CO 2 emissions from fossil fuels
remained constant in the period 1980–2010, the global economic growth rose
drastically over the same period. Therefore, according to the AR5 Report, typical
values of total annual anthropogenic GHG emissions were 27 Gt CO 2 -eq.y
−1 , 38 Gt
CO 2 -eq.y
−1 , and 49 Gt CO 2 -eq.y
−1 in 1970, 1990, and 2010 respectively, indicating
an increasing trend over this period.
Emissions of GHG, mainly CO 2 and CH 4 , have continuously increased since the
eighteenth century to 405 ppm and 1803 ppb in 2018, both higher by 40 and 150%
comparable to 1750 (e.g., AR5; Le Quéré et al. 2018). The stabilization of CO 2
atmospheric concentration to 550 ppm would theoretically increase the atmospheric
temperature by about 2–3 °C above the current level. Also, since the onset of the
industrial era, ocean uptake of CO 2 has resulted in increased acidification of the
oceans with a decrease of the pH of the ocean surface at the order of 0.1, corresponding to a 26% rise in acidity, measured as hydrogen ion concentration (e.g.,
AR5 Report 2015).
In general, the global carbon budget is considered to have six main components:
emissions by fossil fuel applications (EF), emissions from land-use due to land
human activities, including those leading to land-use changes (ELU), variations in
the atmospheric CO 2 concentration (△CAt), and uptake of carbon dioxide by the
oceans (UCO) and by land (UCL). A sixth closure budget component (CBC) is due
to imbalances resulting from divergences in the estimates for the other components.
The available information about these carbon budget components (Le Quéré
et al. 2018) relies on data sets from experimental observations or measurements and
from modeling projections that consider several dynamic global vegetation models
(Fig. 8.3).
8.2 Topics on GHG Emissions …
273
the estimates of total radiative forcing.
CO 2 emissions were the largest contributors to the increased anthropogenic
radiative forcing or net radiation, in every decade since the 1960s. According to the
AR5 Report (2015), GHG emissions, driven by economic and population growth,
have increased since the pre-industrial era leading to unparalleled atmospheric
concentrations of CO 2 , methane, and nitrous oxide.
The long-term increase in CO 2 atmospheric concentration was mainly due to
accumulated emissions of about 2040 ± 310 Gt CO 2 , from which about 880 ± 35
Gt CO 2 remained in the atmosphere. The last 40 years accounted for about half of
the accumulated emissions over the two and a half centuries. It is estimated that
global emissions, which may be permissible worldwide, without a high likelihood
of dangerous climate change are about 2900 Gt CO 2 (e.g., Quiggin 2019).
Despite increased public awareness and climate mitigation policies, the global
yearly anthropogenic GHG emissions increased between 1970 and 2010, reaching
an estimated 49 Gt CO 2 -eq. (e.g., AR5 IPPC Report). Also, the yearly growths of
GHG emissions, in the period 1970–2000 and in the decade 2000–2010, were
about 1.3 and 2.2%, respectively. The contribution from fossil fuel combustion and
conversion was about 78% in these two periods.
While the contribution of population growth for CO 2 emissions from fossil fuels
remained constant in the period 1980–2010, the global economic growth rose
drastically over the same period. Therefore, according to the AR5 Report, typical
values of total annual anthropogenic GHG emissions were 27 Gt CO 2 -eq.y
−1 , 38 Gt
CO 2 -eq.y
−1 , and 49 Gt CO 2 -eq.y
−1 in 1970, 1990, and 2010 respectively, indicating
an increasing trend over this period.
Emissions of GHG, mainly CO 2 and CH 4 , have continuously increased since the
eighteenth century to 405 ppm and 1803 ppb in 2018, both higher by 40 and 150%
comparable to 1750 (e.g., AR5; Le Quéré et al. 2018). The stabilization of CO 2
atmospheric concentration to 550 ppm would theoretically increase the atmospheric
temperature by about 2–3 °C above the current level. Also, since the onset of the
industrial era, ocean uptake of CO 2 has resulted in increased acidification of the
oceans with a decrease of the pH of the ocean surface at the order of 0.1, corresponding to a 26% rise in acidity, measured as hydrogen ion concentration (e.g.,
AR5 Report 2015).
In general, the global carbon budget is considered to have six main components:
emissions by fossil fuel applications (EF), emissions from land-use due to land
human activities, including those leading to land-use changes (ELU), variations in
the atmospheric CO 2 concentration (△CAt), and uptake of carbon dioxide by the
oceans (UCO) and by land (UCL). A sixth closure budget component (CBC) is due
to imbalances resulting from divergences in the estimates for the other components.
The available information about these carbon budget components (Le Quéré
et al. 2018) relies on data sets from experimental observations or measurements and
from modeling projections that consider several dynamic global vegetation models
(Fig. 8.3).
8.2 Topics on GHG Emissions …
273