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TSThe projected effects of climate-induced stressors on
polar marine ecosystems present risks for commercial and subsistence ﬁsheries with implications for regional economies, cultures and the global supply of ﬁsh, shellﬁsh, and Antarctic krill ( high conﬁdence ). Future impacts for linked human
systems depend on the level of mitigation and especially the responsiveness of precautionary management approaches (medium conﬁdence ). Polar regions support several of the
world’s largest commercial ﬁsheries. Speciﬁc impacts on the stocks
and economic value in both regions will depend on future climate change and on the strategies employed to manage the effects on
stocks and ecosystems ( medium conﬁdence ). Under high emission
scenarios current management strategies of some high-value stocks
may not sustain current catch levels in the future ( low conﬁdence );
this exempliﬁes the limits to the ability of existing natural resource
management frameworks to address ecosystem change. Adaptive
management that combines annual measures and within-season
provisions informed by assessments of future ecosystem trends
reduces the risks of negative climate change impacts on polar
ﬁsheries ( medium conﬁdenc e). {3.2.4, 3.5.2, 3.5.4}
Widespread disappearance of Arctic near-surface permafrost
is projected to occur this century as a result of warming ( very
high conﬁdence ), with important consequences for global
climate. By 2100, near-surface permafrost area will decrease
by 2–66% for RCP2.6 and 30–99% for RCP8.5. This is projected to release 10s to 100s of billions of tons (Gt C), up to as much as 240 Gt C, of permafrost carbon as carbon dioxide and methane to
the atmosphere with the potential to accelerate climate change.
Methane will contribute a small proportion of these additional carbon
emissions, on the order of 0.01–0.06 Gt CH
4 yr–1, but could contribute
40–70% of the total permafrost-affected radiative forcing because of
its higher warming potential. There is medium evidence but with low
agreement whether the level and timing of increased plant growth
and replenishment of soil will compensate these permafrost carbon
losses. {3.4.2, 3.4.3}
Projected permafrost thaw and decrease in snow will affect
Arctic hydrology and wildﬁre, with impacts on vegetation and
human infrastructure ( medium conﬁdence ). About 20% of Arctic
land permafrost is vulnerable to abrupt permafrost thaw and ground
subsidence, which is expected to increase small lake area by over
50% by 2100 for RCP8.5 ( medium conﬁdence ). Even as the overall
regional water cycle intensiﬁes, including increased precipitation,
evapotranspiration, and river discharge to the Arctic Ocean, decreases
in snow and permafrost may lead to soil drying ( medium conﬁdence ).
Fire is projected to increase for the rest of this century across most
tundra and boreal regions, while interactions between climate and shifting vegetation will inﬂuence future ﬁre intensity and frequency (medium conﬁdence ). By 2050, 70% of Arctic infrastructure is located
in regions at risk from permafrost thaw and subsidence; adaptation
measures taken in advance could reduce costs arising from thaw and
other climate change related impacts such as increased ﬂooding,
precipitation, and freeze-thaw events by half ( medium conﬁdence ).
{3.4.1, 3.4.2, 3.4.3, 3.5.2}Response options exist that can ameliorate the impacts of
polar change, build resilience and allow time for effective mitigation measures. Institutional barriers presently limit their efﬁcacy.
Responding to climate change in polar regions will be more
effective if attention to reducing immediate risks (short-term
adaptation) is concurrent with long-term planning that builds resilience to address expected and unexpected impacts ( high
conﬁdence ). Emphasis on short-term adaptation to speciﬁc problems
will ultimately not succeed in reducing the risks and vulnerabilities to
society given the scale, complexity and uncertainty of climate change.
Moving toward a dual focus of short- and long-term adaptation involves knowledge co-production, linking knowledge with decision
making and implementing ecosystem-based stewardship, which
involves the transformation of many existing institutions ( high
conﬁdence ). {3.5.4}
Innovative tools and practices in polar resource management
and planning show strong potential in improving society’s capacity to respond to climate change ( high conﬁdence ).
Networks of protected areas, participatory scenario analysis, decision
support systems, community-based ecological monitoring that
draws on local and indigenous knowledge, and self assessments
of community resilience contribute to strategic plans for sustaining
biodiversity and limit risk to human livelihoods and wellbeing. Such
practices are most effective when linked closely to the policy process.
Experimenting, assessing, and continually reﬁning practices while
strengthening the links with decision making has the potential to
ready society for the expected and unexpected impacts of climate
change ( high conﬁdence ). {3.5.1, 3.5.2, 3.5.4}
Institutional arrangements that provide for strong multiscale
linkages with Arctic local communities can beneﬁt from including indigenous knowledge and local knowledge in the formulation of adaptation strategies ( high conﬁdence ). The
tightly coupled relationship of northern local communities and their
environment provide an opportunity to better understand climate
change and its effects, support adaptation and limit unintended
consequences. Enabling conditions for the involvement of local
communities in climate adaptation planning include investments in
human capital, engagement processes for knowledge co-production
and systems of adaptive governance. {3.5.3}
The capacity of governance systems in polar regions to
respond to climate change has strengthened recently, but
the development of these systems is not sufﬁciently rapid or robust to address the challenges and risks to societies posed
by projected changes ( high conﬁdence ). Human responses
to climate change in the polar regions occur in a fragmented
governance landscape. Climate change, new polar interests from
outside the regions, and an increasingly active role played by informal
organisations are compelling stronger coordination and integration between different levels and sectors of governance. The governance
landscape is currently not sufﬁciently equipped to address cascading
risks and uncertainty in an integrated and precautionary way within
existing legal and policy frameworks ( high conﬁdence ). {3.5.3, 3.5.4}

55Technical Summary
TSTS.4 Sea Level Rise and Implications for Low-
lying Is lands, Coasts and Communities
This chapter assesses past and future contributions to global, regional
and extreme sea level changes, associated risk to low-lying islands, coasts, cities, and settlements, and response options and pathways to resilience and sustainable development along the coast.
Observations
Global mean sea level (GMSL) is rising ( virtually certain )
and accelerating ( high conﬁdence )7. The sum of glacier and
ice sheet contributions is now the dominant source of GMSL rise ( very high conﬁdence ). GMSL from tide gauges and altimetry
observations increased from 1.4 mm yr
–1 over the period 1901–1990
to 2.1 mm yr–1 over the period 1970–2015 to 3.2 mm yr–1 over

TSThe projected effects of climate-induced stressors on

polar marine ecosystems present risks for commercial and subsistence ﬁsheries with implications for regional economies, cultures and the global supply of ﬁsh, shellﬁsh, and Antarctic krill ( high conﬁdence ). Future impacts for linked human

systems depend on the level of mitigation and especially the responsiveness of precautionary management approaches (medium conﬁdence ). Polar regions support several of the

world’s largest commercial ﬁsheries. Speciﬁc impacts on the stocks

and economic value in both regions will depend on future climate change and on the strategies employed to manage the effects on

stocks and ecosystems ( medium conﬁdence ). Under high emission

scenarios current management strategies of some high-value stocks

may not sustain current catch levels in the future ( low conﬁdence );

this exempliﬁes the limits to the ability of existing natural resource

management frameworks to address ecosystem change. Adaptive

management that combines annual measures and within-season

provisions informed by assessments of future ecosystem trends

reduces the risks of negative climate change impacts on polar

ﬁsheries ( medium conﬁdenc e). {3.2.4, 3.5.2, 3.5.4}

Widespread disappearance of Arctic near-surface permafrost

is projected to occur this century as a result of warming ( very

high conﬁdence ), with important consequences for global

climate. By 2100, near-surface permafrost area will decrease

by 2–66% for RCP2.6 and 30–99% for RCP8.5. This is projected to release 10s to 100s of billions of tons (Gt C), up to as much as 240 Gt C, of permafrost carbon as carbon dioxide and methane to

the atmosphere with the potential to accelerate climate change.

Methane will contribute a small proportion of these additional carbon

emissions, on the order of 0.01–0.06 Gt CH

4 yr–1, but could contribute

40–70% of the total permafrost-affected radiative forcing because of

its higher warming potential. There is medium evidence but with low

agreement whether the level and timing of increased plant growth

and replenishment of soil will compensate these permafrost carbon

losses. {3.4.2, 3.4.3}

Projected permafrost thaw and decrease in snow will affect

Arctic hydrology and wildﬁre, with impacts on vegetation and

human infrastructure ( medium conﬁdence ). About 20% of Arctic

land permafrost is vulnerable to abrupt permafrost thaw and ground

subsidence, which is expected to increase small lake area by over

50% by 2100 for RCP8.5 ( medium conﬁdence ). Even as the overall

regional water cycle intensiﬁes, including increased precipitation,

evapotranspiration, and river discharge to the Arctic Ocean, decreases

in snow and permafrost may lead to soil drying ( medium conﬁdence ).

Fire is projected to increase for the rest of this century across most

tundra and boreal regions, while interactions between climate and shifting vegetation will inﬂuence future ﬁre intensity and frequency (medium conﬁdence ). By 2050, 70% of Arctic infrastructure is located

in regions at risk from permafrost thaw and subsidence; adaptation

measures taken in advance could reduce costs arising from thaw and

other climate change related impacts such as increased ﬂooding,

precipitation, and freeze-thaw events by half ( medium conﬁdence ).

{3.4.1, 3.4.2, 3.4.3, 3.5.2}Response options exist that can ameliorate the impacts of

polar change, build resilience and allow time for effective mitigation measures. Institutional barriers presently limit their efﬁcacy.

Responding to climate change in polar regions will be more

effective if attention to reducing immediate risks (short-term

adaptation) is concurrent with long-term planning that builds resilience to address expected and unexpected impacts ( high

conﬁdence ). Emphasis on short-term adaptation to speciﬁc problems

will ultimately not succeed in reducing the risks and vulnerabilities to

society given the scale, complexity and uncertainty of climate change.

Moving toward a dual focus of short- and long-term adaptation involves knowledge co-production, linking knowledge with decision

making and implementing ecosystem-based stewardship, which

involves the transformation of many existing institutions ( high

conﬁdence ). {3.5.4}

Innovative tools and practices in polar resource management

and planning show strong potential in improving society’s capacity to respond to climate change ( high conﬁdence ).

Networks of protected areas, participatory scenario analysis, decision

support systems, community-based ecological monitoring that

draws on local and indigenous knowledge, and self assessments

of community resilience contribute to strategic plans for sustaining

biodiversity and limit risk to human livelihoods and wellbeing. Such

practices are most effective when linked closely to the policy process.

Experimenting, assessing, and continually reﬁning practices while

strengthening the links with decision making has the potential to

ready society for the expected and unexpected impacts of climate

change ( high conﬁdence ). {3.5.1, 3.5.2, 3.5.4}

Institutional arrangements that provide for strong multiscale

linkages with Arctic local communities can beneﬁt from including indigenous knowledge and local knowledge in the formulation of adaptation strategies ( high conﬁdence ). The

tightly coupled relationship of northern local communities and their

environment provide an opportunity to better understand climate

change and its effects, support adaptation and limit unintended

consequences. Enabling conditions for the involvement of local

communities in climate adaptation planning include investments in

human capital, engagement processes for knowledge co-production

and systems of adaptive governance. {3.5.3}

The capacity of governance systems in polar regions to

respond to climate change has strengthened recently, but

the development of these systems is not sufﬁciently rapid or robust to address the challenges and risks to societies posed

by projected changes ( high conﬁdence ). Human responses

to climate change in the polar regions occur in a fragmented

governance landscape. Climate change, new polar interests from

outside the regions, and an increasingly active role played by informal

organisations are compelling stronger coordination and integration between different levels and sectors of governance. The governance

landscape is currently not sufﬁciently equipped to address cascading

risks and uncertainty in an integrated and precautionary way within

existing legal and policy frameworks ( high conﬁdence ). {3.5.3, 3.5.4}

55Technical Summary

TSTS.4 Sea Level Rise and Implications for Low-

lying Is lands, Coasts and Communities

This chapter assesses past and future contributions to global, regional

and extreme sea level changes, associated risk to low-lying islands, coasts, cities, and settlements, and response options and pathways to resilience and sustainable development along the coast.

Observations

Global mean sea level (GMSL) is rising ( virtually certain )

and accelerating ( high conﬁdence )7. The sum of glacier and

ice sheet contributions is now the dominant source of GMSL rise ( very high conﬁdence ). GMSL from tide gauges and altimetry

observations increased from 1.4 mm yr

–1 over the period 1901–1990

to 2.1 mm yr–1 over the period 1970–2015 to 3.2 mm yr–1 over