AR5 Highlights - Working Group III

Working Group III contribution to the
IPCC Fifth Assessment Report
CLIMATE CHANGE 2014
Mitigation of Climate Change
©Ocean/Corbis
Youba SOKONA
Co-Chair, Working Group III
Highlights of the IPCC Fifth Assessment Report
23 February 2015, Nairobi, Kenya

1 Summary for Policymakers
1 Technical Summary
16 Chapters
235 Authors
800+ Reviewers
Close to 1500 pages
Close to 10,000 references
More than 38,000 comments
IPCC reports are the result of extensive work of many scientists
from around the world.
2

3
Climate change is a global commons problem
that requires international cooperation and
coordination across scales.
©ESA/NASA

There is far more carbon in the ground than emitted in any
baseline scenario.
4
Based on SRREN Figure 1.7

5
GHG emissions growth has accelerated
despite reduction efforts.

GHG emissions growth between 2000 and 2010 has been larger
than in the previous three decades.
6
Based on Figure 1.3

About half of the cumulative anthropogenic CO2 emissions
between 1750 and 2010 have occurred in the last 40 years.
7
Based on Figure 5.3

Regional patterns of GHG emissions are shifting along with
changes in the world economy.
8
Based on Figure 1.6

Regional patterns of GHG emissions are shifting along with
changes in the world economy.
9
Based on Figure 1.6

GHG emissions rise with growth in GDP and population.
10
Based on Figure 1.7

The long-standing trend of decarbonization has reversed.
11
Based on Figure 1.7

Limiting warming involves substantial technological,
economic and institutional challenges.

13
Based on WGII AR5 Figure 19.4
Without additional mitigation, global mean surface temperature
is projected to increase by 3.7 to 4.8°C over the 21st century.

Stabilization of atmospheric GHG concentrations requires
moving away from business as usual.
14
Based on Figure 6.7

Lower ambition mitigation goals require similar reductions of
GHG emissions.
15
Based on Figure 6.9

Mitigation involves substantial upscaling of low-carbon energy.
16
Based on Figure 7.16

Mitigation involves substantial upscaling of low-carbon energy.
17

Many scenarios make it at least about as likely as not that
warming will remain below 2°C relative to pre-industrial levels.
18
Based on Figures 6.32 and 7.16

Still, between 2030 and 2050, emissions would have to be
reduced at an unprecedented rate...
19

...implying a rapid scale-up of low-carbon energy.
20

Delaying emissions reductions increases the difficulty and
narrows the options for mitigation.
21

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24
Mitigation cost estimates vary, but global
GDP growth may not be strongly affected.

Global costs rise with the ambition of the mitigation goal.
25
Based on Table SPM.2

Mitigation can result in co-benefits for human health
and other societal goals.
26

Climate change mitigation can result in co-benefits for human
health and other societal goals.
27

• These influences can be substantial, although often difficult to
quantify, and have not yet been thoroughly assessed in the
literature.
• Co-benefits and adverse side-effects depend on local
circumstances as well as on the implementation practice, pace
and scale.
• Behaviour, lifestyle and culture have a considerable influence on
emissions, with high mitigation potential in some sectors, in
particular when complementing technological and structural
change.
• Enhancing co-benefits and avoiding adverse side-effects: good
governance, transparency, stakeholder participation, cross-
sectoral analysis and design, etc.
28
Key points about co-benefits and adverse side effects

29
Low stabilization scenarios depend on a full
decarbonization of energy supply.

Baseline scenarios suggest rising GHG emissions in all sectors,
except for CO2 emissions from the land‐use sector.
30
Based on Figure TS.15

Mitigation requires changes throughout the economy. Systemic
approaches are expected to be most effective.
31
Based on Figure TS.17

32
Effective mitigation will not be achieved if
individual agents advance their own interests
independently.

• No single country can protect ‘its own’ climate by reducing its
own emissions.
• Countries must persuade other countries to help it solve its
climate problem.
• A country thus reduces its own emissions – and cooperates in
other ways – for the sake of inducing reciprocal effort, i.e.,
getting other countries to do likewise.
• A country is more likely to be successful if it is perceived as
doing its fair share of the effort.
• Thus, a cooperative agreement with equitable effort-sharing is
more likely to be agreed and successfully implemented.
33
Climate change as a global commons problem: Equitable
outcomes can lead to more effective cooperation.

Substantial reductions in emissions require significant
changes in investment patterns and appropriate policies.
34

Climate change mitigation is a necessary, but not a sufficient
condition for sustainable development.
• Effort-sharing is fundamental to international cooperation in a
global commons problem.
• There is a small set of broadly invoked ethical principles relating to
equitable effort-sharing.
• Mitigation measures interact broadly (and sometimes strongly)
with other sustainable development objectives, creating co-
benefits or adverse side-effects.
• Highly context specific, difficult to quantify yet nonetheless
significant both in welfare and political terms. Managing these
interactions implies mainstreaming mitigation.

There has been a considerable increase in national and sub-
national mitigation policies since AR4.
36

Sector-specific policies have been more widely used than
economy-wide policies.
37

Climate change mitigation is a global commons problem that
requires international cooperation across scales.
38

AR5 Highlights - Working Group III

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Editor's Notes