10.1.2.2 The Problem Is Long Term
It is concentrations not emissions that matter
Climate change is related to the concentration of GHGs and not to any individual
years emissions. Carbon dioxide (CO2) concentrations are closely
related to the net accumulation of emissions over long periods of time. That
is, it is the sum of emissions over time that determines the atmospheric concentration.
Any individual years emissions are only marginally important1.
Average residence times for GHGs can range up to thousands of years for some
of the anthropogenic species. Strategies to control net emissions must account
for long periods of time in a meaningful way. The ultimate objective of the
UNFCCC is the stabilization of GHG concentrations in the atmosphere at
a level that would prevent dangerous anthropogenic interference with the climate
system (UNFCCC 1993, Article 2).
Intergenerational transfers are inevitable
The consequences of climate change will be visited primarily on those who are
alive in the future. The present generation has inherited its atmosphere and
associated climate from its ancestors. While individuals and governments make
many decisions that affect future generations, most of these decisions are undertaken
inadvertently. It is impossible to avoid the intergenerational wealth-transfer
issue when addressing the climate problem. That most of the affected parties
are not present to participate in the decision-making process raises complicated
ethical questions. The implications of their absence are not immediately obviously.
Future generations have a stake both in the environmental resources, such as
climate, that they inherit, and in other wealth that is passed down to them.
Sacrifices that are made by the present generation for the good of its descendants
will alter the composition of wealth (e.g., environmental versus material) that
is transferred from the present to the future, as well as the magnitude of the
transfer. As climate change is anticipated to be greater in the future than
it is at present, those who live in the future will reap most of the benefits
that accrue to near-term actions to limit emissions. Intergenerational asymmetry
can lead to a form of public goods problem in which the willingness to undertake
emissions mitigation in the near-term may be less than would have been the case
if the decision makers lived infinitely. Also implied is a greater sensitivity
to emission-limitation costs than would be the case if the present generation
lived to benefit from its emissions-mitigation actions.
To limit the concentration of atmospheric carbon dioxide, global carbon
emissions must eventually peak and then decline
This result follows from the nature of the carbon cycle, as it is presently
understood. While non-CO2 GHGs with relatively short life times,
such as methane (CH4), have an atmospheric concentration that is
stable with a stable rate of annual emission, CO2 does not. The cumulative
net introduction of carbon emissions from terrestrial reservoirs, such as fossil
fuels or biological carbon, through (for example) energy production and use
or land-use change, determines the long-term, steady state, atmospheric CO2
concentration. Carbon cycle models require net emissions to asymptotically approach
zero, though the process can take centuries. Most, but not all, emissions scenarios
anticipate that, in the absence of a concern for climate change, future GHG
emissions will continue to rise rather than fall (IPCC, 2000b). Where reference
emissions scenarios exhibit increasing emissions over time, most of the emissions
mitigation required to stabilize the concentration of carbon must occur in the
future, with the deviation from the profile required for stabilization growing
While emissions limitation is a policy response, it is not the only policy
response available to decision makers
In addition to emissions limitations, policymakers have a wide array of other
tools at their disposal including knowledge gathering, research and development
of technologies to reduce emissions and enhancing the resilience of societies
experiencing climate change. The optimal and actual mix of policy responses
will vary over time.