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REPORTS - ASSESSMENT REPORTS |
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Synthesis Report - Question 5
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Climate Change 2001: Synthesis Report |
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| 5.18 |
Inertia in the climate, ecological,
and socio-economic systems makes adaptation inevitable and already necessary
in some cases, and inertia affects the optimal mix of adaptation and
mitigation strategies.
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| 5.19 |
As a result of the time lags
and inertias inherent in the Earth system,including its social components,
some of the consequences of actions taken, or not taken, will only be felt
many years in the future. For example, the differences in the initial
trajectories of the various SRES and stabilization scenarios are small,
but the outcomes in terms of the climate in the year 2100 are large. The
choice of development path has consequences at all the affected time scales;
thus, long-term total costs and benefits may differ considerably from short-term
ones.
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 WGIII
TAR Section 8.4.2 |
| 5.20 |
In the presence of inertia,
well-founded actions to adapt to or mitigate climate change are more effective,
and under some circumstances may be cheaper, if taken earlier rather than
later. Time lags provide a breathing space between emissions and
impacts, thus allowing time for planned adaptation. The inertia of technology
development and capital stock replacement is an important argument for
gradual
mitigation. The essential point of inertia in economic structures and processes
is that deviation from any given trend incurs costs, and these costs rise
with the speed of deviations (e.g., the costs of early retirement of carbon-intensive
facilities). Earlier mitigation action may reduce the
risk of incurring severe lasting or irreversible impacts, while reducing
the need for more rapid mitigation later.Accelerated action may help to
drive down the costs of mitigation and adaptation in the long term by accelerating
technology development and the early realization of benefits currently
obscured
by market imperfections. Abatement over the next few years is economically
valuable if there is a significant probability of having to stay below
ceilings
that would otherwise be reached within the characteristic time scales of
the systems producing greenhouse gases. Climate change mitigation decisions
depend on the interplay of inertia and uncertainty, resulting in a sequential
decision-making process. Foresight and early adaptation will be most advantageous
in sectors with long-lived infrastructure, such as dams and bridges, and
large social inertia, such as misallocated property rights. Anticipatory
adaptive action can be very cost-effective if the anticipated trend materializes.
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WGII TAR Sections 1.3.4
& 2.7.1, WGIII
TAR Chapter 2, WGIII TAR Sections
10.1 & 10.4.2-3, &
WGIII TAR Table 10.7 |
| 5.21 |
The existence of time lags,
inertia, and irreversibility in the Earth system means that a mitigation
action or technology development can have different outcomes, depending
on when it is taken. For example, in one model analysis of the hypothetical
effect of reducing anthropogenic greenhouse gas emissions to zero in the
year 1995, on sea-level rise during the 21st century in the Pacific, showed
that the sea-level rise that would inevitably occur due to warming incurred
to 1995 (5 to 12 cm) would be substantially less than if the same emission
reduction occurred in the year 2020 (14 to 32 cm). This demonstrates the
increasing commitment to future sea-level rise due to past and present emissions,
and the effect of delaying the hypothetical emissions reduction.
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WGII TAR Sections 2.7.1
& 17.2.1 |
| 5.22 |
Technological
inertia in less developed countries can be reduced through "leapfrogging"
(i.e., adopting anticipative strategies to avoid the problems faced today
by industrial societies). It cannot be assumed that developing countries
will automatically follow the past development paths of industrialized countries.
For example, some developing countries have bypassed land-lines for communication,
and proceeded directly to mobile phones. Developing countries could avoid
the past energy-inefficient practices of developed countries by adopting
technologies that use energy in a more sustainable way, recycling more wastes
and products, and handling residual wastes in a more acceptable manner.
This may be easier to achieve in new infrastructure and energy systems in
developing countries since large investments are needed in any case. Transfer
of technology between countries and regions can reduce technological inertia.
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WGII TAR Chapter 2, WGIII
TAR Section 10.3.3, SRES
Section 3.3.4.8, & SRTT SPM |
| 5.23 |
Inertia and uncertainty in the climate, ecological,
and socio-economic systems imply that safety margins should be considered
in setting strategies, targets, and time tables for avoiding dangerous
levels of interference in the climate system. Stabilization target
levels of, for instance, atmospheric CO2 concentration, temperature,
or sea level may be affected by:
- The inertia of the climate system, which will cause climate change
to continue for a period after mitigation actions are implemented
- Uncertainty regarding the location of possible thresholds of irreversible
change and the behavior of the system in their vicinity
- The time lags between adoption of mitigation goals and their achievement.
Similarly, adaptation is affected by time lags involved in identifying
climate change impacts, developing effective adaptation strategies, and
implementing adaptive measures. Hedging strategies and sequential decision
making (iterative action, assessment, and revised action) may be appropriate
responses to the combination of inertia and uncertainty. Inertia has
different consequences for adaptation than for mitigation, with adaptation
being primarily oriented to address localized impacts of climate change,
while mitigation aims to address the impacts on the climate system. Both
issues involve time lags and inertia, with inertia suggesting a generally
greater sense of urgency for mitigation.
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WGII TAR Section 2.7.1
& WGIII TAR Sections
10.1.4.1-3 |
| 5.24 |
The pervasiveness of inertia
and the possibility of irreversibility in the interacting climate, ecological,
and socio-economic systems are major reasons why anticipatory adaptation
and mitigation actions are beneficial. A number of opportunities
to exercise adaptation and mitigation options may be lost if action is delayed.
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