26
climate change contribution. Yet, climate change is the paradigmatic global environmental problem, as anthropogenic GHG emissions are produced in all countries
by innumerable entities. No one country or entity can be deemed to be the cause of
climate change. Nonetheless, some countries and corporations are more substantial
contributors to atmospheric GHG emissions than others.
This acquires peculiar relevance in the context of climate change lawsuits
brought under various permitting legislation (e.g., Environmental Impact Assessment
regulations), inasmuch as such pieces of legislation somewhat encompass GHG
emissions—or, more generally, climate change aspects—as a significant impact of
specific projects. In fact, in this field of litigation defendants often invoke the “drop
in the ocean” argument, whereby GHG emissions stemming from a particular activity cannot be said to cause climate change harm and/or have a significant environmental impact in global terms, and therefore should be negligible for the purposes
of the given permitting or planning procedure.
Against this backdrop, the existing carbon budgets calculations aim to unfold the
cumulative amount of CO 2 emissions permitted over a period of time to avoid overshoot of the “well below 2°C” above pre-industrial levels overshoot, consistently
with the objectives agreed globally and officially endorsed in the 2015 UNFCCC
Paris Agreement.
1
In sum, relying on Integrated Assessment Models or Earth Models, CO 2 budgets
draw from life cycle emission estimates, which fundamentally determine the anthropogenic CO 2 input to the atmosphere as balanced by output in the carbon reservoirs
on land or in the ocean, while taking into account also other factors beyond combustion—e.g., the differing degrees of carbon capture and storage (CCS) deployment.
Several carbon budgets have been published over the last decade. The most
authoritative carbon budgets come as a result of scenarios developed in international
policy documents, such as the IEA’s World Energy Outlook, IPCC’s Assessment
Reports, as well as independent academic endeavours, such as the Global Carbon
Project (Le Queré et al. 2018).
2
According to IPCC’s carbon budget calculations contained in the 1.5° Report, to
ensure a greater than 66% probability of limiting global average temperature rise to
no more than 2 °C, cumulative human CO 2 emissions since 1870 through year 2100
must be less than 1000 Gt (Rogelj et al. 2018, p. 104). If non-CO 2 greenhouse gases
1 Relevant, specifying the level of ‘pre-industrial emissions’ aims to provide a baseline from which
anthropogenic activity began influencing greenhouse gas (GHG) concentrations in the atmosphere.
How the ‘pre-industrial level’ is interpreted, however, can vary. To date, 1850–1900 has been the
preferred baseline by institutions including the IPCC. However, some studies have suggested a
1720–1800 baseline would be more appropriate because GHG concentrations have been increasing since industrialisation began around 1750. Others argue that baselines should be taken from
natural climate model simulations, i.e. those that exclude anthropogenic forces.
2 It is also worth noting that carbon budget calculations differ in terms of scope and range. For
example, IEA’s carbon budget refers to budgets for the energy sector only—the largest single
source of CO 2 emissions through the burning of coal, oil and gas. In contrast, the IPCC’s budgets
account for all anthropogenic sources of CO 2 , thus including, inter alia, budgets for heavy industries and land use, land use change and forestry (LULUCF).
M. Fermeglia
climate change contribution. Yet, climate change is the paradigmatic global environmental problem, as anthropogenic GHG emissions are produced in all countries
by innumerable entities. No one country or entity can be deemed to be the cause of
climate change. Nonetheless, some countries and corporations are more substantial
contributors to atmospheric GHG emissions than others.
This acquires peculiar relevance in the context of climate change lawsuits
brought under various permitting legislation (e.g., Environmental Impact Assessment
regulations), inasmuch as such pieces of legislation somewhat encompass GHG
emissions—or, more generally, climate change aspects—as a significant impact of
specific projects. In fact, in this field of litigation defendants often invoke the “drop
in the ocean” argument, whereby GHG emissions stemming from a particular activity cannot be said to cause climate change harm and/or have a significant environmental impact in global terms, and therefore should be negligible for the purposes
of the given permitting or planning procedure.
Against this backdrop, the existing carbon budgets calculations aim to unfold the
cumulative amount of CO 2 emissions permitted over a period of time to avoid overshoot of the “well below 2°C” above pre-industrial levels overshoot, consistently
with the objectives agreed globally and officially endorsed in the 2015 UNFCCC
Paris Agreement.
1
In sum, relying on Integrated Assessment Models or Earth Models, CO 2 budgets
draw from life cycle emission estimates, which fundamentally determine the anthropogenic CO 2 input to the atmosphere as balanced by output in the carbon reservoirs
on land or in the ocean, while taking into account also other factors beyond combustion—e.g., the differing degrees of carbon capture and storage (CCS) deployment.
Several carbon budgets have been published over the last decade. The most
authoritative carbon budgets come as a result of scenarios developed in international
policy documents, such as the IEA’s World Energy Outlook, IPCC’s Assessment
Reports, as well as independent academic endeavours, such as the Global Carbon
Project (Le Queré et al. 2018).
2
According to IPCC’s carbon budget calculations contained in the 1.5° Report, to
ensure a greater than 66% probability of limiting global average temperature rise to
no more than 2 °C, cumulative human CO 2 emissions since 1870 through year 2100
must be less than 1000 Gt (Rogelj et al. 2018, p. 104). If non-CO 2 greenhouse gases
1 Relevant, specifying the level of ‘pre-industrial emissions’ aims to provide a baseline from which
anthropogenic activity began influencing greenhouse gas (GHG) concentrations in the atmosphere.
How the ‘pre-industrial level’ is interpreted, however, can vary. To date, 1850–1900 has been the
preferred baseline by institutions including the IPCC. However, some studies have suggested a
1720–1800 baseline would be more appropriate because GHG concentrations have been increasing since industrialisation began around 1750. Others argue that baselines should be taken from
natural climate model simulations, i.e. those that exclude anthropogenic forces.
2 It is also worth noting that carbon budget calculations differ in terms of scope and range. For
example, IEA’s carbon budget refers to budgets for the energy sector only—the largest single
source of CO 2 emissions through the burning of coal, oil and gas. In contrast, the IPCC’s budgets
account for all anthropogenic sources of CO 2 , thus including, inter alia, budgets for heavy industries and land use, land use change and forestry (LULUCF).
M. Fermeglia