If climate change mitigation is instead viewed as fundamentally
a problem of assessing shares of liability for protecting
the vulnerable against climate-related harm by reducing
current greenhouse emissions or otherwise coming to their
aid, other conceptions of justice emerge. Here, the overall focus
is on the economic costs or other burdens associated with carbon
abatement, combinedwith one of several sets of facts that
can assess liability for shares of those costs or burdens. If, for
example, one was to apply a conception of justice based in
responsibility to climate change mitigation, the focus would
be on each party's total contributions toward the problem and
would require a further judgment concerning the role of fault
in assessing the liability of various parties. Under a strict liability
standard, each party's cumulative and net greenhouse
emissions would determine its share of overall remedial liability,
thus focusing on its historical and current emissions
along with its land use changes or other carbon sequestration
efforts, which can affect net emissions. If a fault-based liability
standard is used, the focus would shift from causal contribution
to excusing conditions that justify subtractions from
cumulative emissions in calculating each party's remedial liability,
on grounds that it cannot be faulted for those contributions.
Under such a standard, pre-1990 emissions might be
exempted, as occurring before governments could be expected
to adequately know the relationship between greenhouse pollution
and climate change, or those emissions associated with
the meeting of basic needs might likewise be exempted as
unavoidable and therefore faultless.
By contrast, if remedial liability is assessed according to
the differentiated capabilities of various parties, then the focus
turns away from the historical facts and ethical judgments
central to responsibility-based justice, and toward largely economic
and political facts concerning the relative capacities of
various parties. Those countries viewed as being in a position
to more easily reduce their current emissions, whether because
of the lower socialwelfare opportunity costs of diverting funds
toward climate change mitigation that can be associated with
general affluence, or on the basis of the different marginal
abatement costs that result from variable past efforts in harvesting
the "low-hanging fruit" of carbon abatement opportunities
as well as national differences in built infrastructure
and access to low-carbon energy resources or sequestration
options, would be assigned, by this standard, relatively higher
mitigation burdens. Even among burden-sharing approaches,
the features of various potentially liable parties that each
focuses on is significantly different, as would be the prescriptions
that each justice principle issues on the basis of a fixed
set of facts.