8.2 Topics on GHG Emissions and Global Carbon Budget
Global trends in GHGs are indicative of the imbalance between sources and sinks in
the gas budgets and are strictly related to atmospheric emissions on a global scale.
Among the gases targeted by the Kyoto Protocol are
(i) Carbon dioxide, emitted by burning solid waste, fossil fuels, woody and
non-woody products and biomasses, agricultural residues, and certain
chemical reactions (e.g., manufacture of cement). Carbon dioxide is also
sequestered from the atmosphere, for example, when it is absorbed by plant
photosynthesis as part of the biological carbon cycle. As mentioned in
Sect. 4.6, the CO 2 atmospheric concentration increased from 280 ppm at the
beginning of the Industrial Revolution around 1750, to about the current
407 ppm.
(ii) Methane emitted from livestock and other agricultural practices, decomposition of organic municipal waste landfills, or production and transport of
coal, natural gas, and oil.
(iii) Nitrous oxide (N 2 O) emitted by combustion of fossil fuels and solid wastes
from agricultural and industrial activities.
(iv) Fluorinated gases such as hydrofluorocarbons, perfluorocarbons, sulfur
hexafluoride, and nitrogen trifluoride which are synthetic, powerful greenhouse gases that are emitted from a variety of industrial processes. These
gases are typically emitted in smaller quantities but because they are potent
greenhouse gases, they can be referred to as high global warming potential
gases (e.g., https://whatsyourimpact.org/high-global-warming-potentialgases; global warming potential, Wikipedia).
The Earth has been at a nearly constant temperature during the past 100 million
years, with less than a 4% variation over that period. During this long period, the
incoming solar radiation was practically compensated for by emitted infrared
radiation, maintaining the temperature of the Earth’s system in a stable equilibrium.
Over the last 50 million years (Stull 2000), the Earth’s temperature oscillated
by ± 1 °C around the current average of 15 °C. These small variations of temperature can induce significant changes in, for example, the sea level and glaciations. Based on the available evidence, there is a larger consensus that GHG
emissions will continue to rise, under the prevalent climate change mitigation
policies. For example, AR4 reported that between 2000 and 2030 the increase of
GHG emissions would be about 25 and 90%, with fossil fuels maintaining the
dominant position by 2020 and beyond.
As GHG concentrations rise, net radiation flux changes, due to an increase in
infrared radiation which induces atmosphere warming (e.g., Stull 2000). In this
context, a fundamental concept for assessing the degree of climate change is the
so-called radiative forcing (RF) (e.g., AR4 Report 2008). This metric has been used
for many years by IPCC to evaluate the strength of the various mechanisms
affecting the Earth’s radiation balance. Aerosols partially offset the effects of
272
8 Fundamentals of Global Carbon Budgets and Climate Change
Global trends in GHGs are indicative of the imbalance between sources and sinks in
the gas budgets and are strictly related to atmospheric emissions on a global scale.
Among the gases targeted by the Kyoto Protocol are
(i) Carbon dioxide, emitted by burning solid waste, fossil fuels, woody and
non-woody products and biomasses, agricultural residues, and certain
chemical reactions (e.g., manufacture of cement). Carbon dioxide is also
sequestered from the atmosphere, for example, when it is absorbed by plant
photosynthesis as part of the biological carbon cycle. As mentioned in
Sect. 4.6, the CO 2 atmospheric concentration increased from 280 ppm at the
beginning of the Industrial Revolution around 1750, to about the current
407 ppm.
(ii) Methane emitted from livestock and other agricultural practices, decomposition of organic municipal waste landfills, or production and transport of
coal, natural gas, and oil.
(iii) Nitrous oxide (N 2 O) emitted by combustion of fossil fuels and solid wastes
from agricultural and industrial activities.
(iv) Fluorinated gases such as hydrofluorocarbons, perfluorocarbons, sulfur
hexafluoride, and nitrogen trifluoride which are synthetic, powerful greenhouse gases that are emitted from a variety of industrial processes. These
gases are typically emitted in smaller quantities but because they are potent
greenhouse gases, they can be referred to as high global warming potential
gases (e.g., https://whatsyourimpact.org/high-global-warming-potentialgases; global warming potential, Wikipedia).
The Earth has been at a nearly constant temperature during the past 100 million
years, with less than a 4% variation over that period. During this long period, the
incoming solar radiation was practically compensated for by emitted infrared
radiation, maintaining the temperature of the Earth’s system in a stable equilibrium.
Over the last 50 million years (Stull 2000), the Earth’s temperature oscillated
by ± 1 °C around the current average of 15 °C. These small variations of temperature can induce significant changes in, for example, the sea level and glaciations. Based on the available evidence, there is a larger consensus that GHG
emissions will continue to rise, under the prevalent climate change mitigation
policies. For example, AR4 reported that between 2000 and 2030 the increase of
GHG emissions would be about 25 and 90%, with fossil fuels maintaining the
dominant position by 2020 and beyond.
As GHG concentrations rise, net radiation flux changes, due to an increase in
infrared radiation which induces atmosphere warming (e.g., Stull 2000). In this
context, a fundamental concept for assessing the degree of climate change is the
so-called radiative forcing (RF) (e.g., AR4 Report 2008). This metric has been used
for many years by IPCC to evaluate the strength of the various mechanisms
affecting the Earth’s radiation balance. Aerosols partially offset the effects of
272
8 Fundamentals of Global Carbon Budgets and Climate Change