ellisbrown/BDML25SP_hw1_processed_data

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• Mangroves to alleviate coastal
storm energy
• Water reservoirs to buffer
low-flows and water scarcity
Figure TS.4 \| There are options for risk reduction through adaptation. Adaptation can reduce risk by addressing one or more of the three ris k factors: vulnerability,
exposure, and/or hazard. The reduction of vulnerability, exposure, and/or hazard potential can be achieved through different po licy and action choices over time until limits
to adaptation might be reached. The ﬁgure builds on the conceptual framework of risk used in AR5 (for more details see Cross-Ch apter Box 2 in Chapter 1).

47Technical Summary
TSthe drivers of those changes, and the risks to marine, coastal, polar
and mountain ecosystems, occur on spatial and temporal scales that may not align within existing governance structures and practices (medium conﬁdence ). This report highlights the requirements
for transformative governance, international and transboundary
cooperation, and greater empowerment of local communities in the governance of the ocean, coasts, and cryosphere in a changing climate. {1.5, 1.7, Cross-Chapter Box 2 in Chapter 1, Cross-Chapter
Box 3 in Chapter 1}
Robust assessments of ocean and cryosphere change, and the
development of context-speciﬁc governance and response options, depend on utilising and strengthening all available knowledge systems ( high conﬁdence ). Scientiﬁc knowledge from
observations, models and syntheses provides global to local scale
understandings of climate change ( very high conﬁdence ). Indigenous
knowledge (IK) and local knowledge (LK) provide context-speciﬁc and
socio-culturally relevant understandings for effective responses and
policies ( medium conﬁdence ). Education and climate literacy enable
climate action and adaptation ( high conﬁdence ). {1.8, Cross-Chapter
Box 4 in Chapter 1}
Long-term sustained observations and continued modelling
are critical for detecting, understanding and predicting ocean
and cryosphere change, providing the knowledge to inform
risk assessments and adaptation planning ( high conﬁdence ).
Knowledge gaps exist in scientiﬁc knowledge for important regions, parameters and processes of ocean and cryosphere change, including for physically plausible, high impact changes like high end sea level
rise scenarios that would be costly if realised without effective
adaptation planning and even then may exceed limits to adaptation.
Means such as expert judgement, scenario building, and invoking
multiple lines of evidence enable comprehensive risk assessments
even in cases of uncertain future ocean and cryosphere changes.
{1.8.1, 1.9.2, Cross-Chapter Box 5 in Chapter 1}
TS.2 High Mountain Areas
The cryosphere (including, snow, glaciers, permafrost, lake and river ice) is an integral element of high mountain regions, which
are home to roughly 10% of the global population. Widespread
cryosphere changes affect physical, biological and human systems in the mountains and surrounding lowlands, with impacts evident even in the ocean. Building on the IPCC’s 5th Assessment Report (AR5), this chapter assesses new evidence on observed recent and projected changes in the mountain cryosphere as well as associated impacts, risks and adaptation measures related to natural and human systems. Impacts in response to climate changes independently of changes in
the cryosphere are not assessed in this chapter. Polar mountains are
included in Chapter 3, except those in Alaska and adjacent Yukon,
Iceland and Scandinavia, which are included in this chapter.Observations of cryospheric changes, impacts,
and adaptation in high mountain areas
Observations show general decline in low-elevation snow
cover ( high conﬁdence ) glaciers ( very high conﬁdence ) and
permafrost ( high conﬁdence ) due to climate change in recent
decades. Snow cover duration has declined in nearly all regions,
especially at lower elevations, on average by 5 days per decade,
with a likely range from 0–10 days per decade. Low elevation snow
depth and extent have declined, although year-to-year variation is high. Mass change of glaciers in all mountain regions (excluding the Canadian and Russian Arctic, Svalbard, Greenland and Antarctica)
was very likely –490 ± 100 kg m
–2 yr–1 (–123 ± 24 Gt yr–1) in 2006–
2015. Regionally averaged mass budgets were likely most negative
(less than –850 kg m–2 yr–1) in the southern Andes, Caucasus and the
European Alps/Pyrenees, and least negative in High Mountain Asia (–150 ± 110 kg m
–2 yr–1) but variations within regions are strong.
Between 3.6–5.2 million km2 are underlain by permafrost in the
eleven high mountain regions covered in this chapter corresponding
to 27–29% of the global permafrost area ( medium conﬁdence ).
Sparse and unevenly distributed measurements show an increase
in permafrost temperature ( high conﬁdenc e), for example, by
0.19ºC ± 0.05ºC on average for about 28 locations in the European
Alps, Scandinavia, Canada and Asia during the past decade. Other
observations reveal decreasing permafrost thickness and loss of ice
in the ground. {2.2.2, 2.2.3, 2.2.4, Figure TS.5}
Glacier, snow and permafrost decline has altered the frequency,
magnitude and location of most related natural hazards ( high
conﬁdence ). Exposure of people and infrastructure to natural
hazards has increased due to growing population, tourism and socioeconomic development ( high conﬁdence ). Glacier retreat
and permafrost thaw have decreased the stability of mountain slopes and the integrity of infrastructure ( high conﬁdence ). The number
and area of glacier lakes has increased in most regions in recent
decades ( high conﬁdence ), but there is only limited evidence that
the frequency of glacier lake outburst ﬂoods (GLOF) has changed. In
some regions, snow avalanches involving wet snow have increased
(medium conﬁdence ), and rain-on-snow ﬂoods have decreased at
low elevations in spring and increased at high elevations in winter
(medium conﬁdence ). The number and extent of wildﬁres have
increased in the Western USA partly due to early snowmelt ( medium
conﬁdence ). {2.3.2, 2.3.3}
Changes in snow and glaciers have changed the amount and
seasonality of runoff in snow-dominated and glacier-fed river
basins ( very high conﬁdence ) with local impacts on water
resources and agriculture ( medium conﬁdence ). Winter runoff
has increased in recent decades due to more precipitation falling as
rain ( high conﬁdence ). In some glacier-fed rivers, summer and annual
runoff have increased due to intensiﬁed glacier melt, but decreased
where glacier melt water has lessened as glacier area shrinks.
Decreases were observed especially in regions dominated by small
glaciers, such as the European Alps ( medium conﬁdence ). Glacier
retreat and snow cover changes have contributed to localized declines
in agricultural yields in some high mountain regions, including the
Hindu Kush Himalaya and the tropical Andes ( medium conﬁdence ).

48Technical Summary
TSThere is limited evidence of impacts on operation and productivity
of hydropower facilities resulting from changes in seasonality and both increases and decreases in water input, for example, in the European Alps, Iceland, Western Canada and USA, and the tropical Andes. {2.3.1}
Species composition and abundance have markedly changed
in high mountain ecosystems in recent decades ( very high
conﬁdence ), partly due to changes in the cryosphere ( high
conﬁdence ). Habitats for establishment by formerly absent species
have opened up or been altered by reduced snow cover ( high

• Mangroves to alleviate coastal

storm energy

• Water reservoirs to buffer

low-flows and water scarcity

Figure TS.4 | There are options for risk reduction through adaptation. Adaptation can reduce risk by addressing one or more of the three ris k factors: vulnerability,

exposure, and/or hazard. The reduction of vulnerability, exposure, and/or hazard potential can be achieved through different po licy and action choices over time until limits

to adaptation might be reached. The ﬁgure builds on the conceptual framework of risk used in AR5 (for more details see Cross-Ch apter Box 2 in Chapter 1).

47Technical Summary

TSthe drivers of those changes, and the risks to marine, coastal, polar

and mountain ecosystems, occur on spatial and temporal scales that may not align within existing governance structures and practices (medium conﬁdence ). This report highlights the requirements

for transformative governance, international and transboundary

cooperation, and greater empowerment of local communities in the governance of the ocean, coasts, and cryosphere in a changing climate. {1.5, 1.7, Cross-Chapter Box 2 in Chapter 1, Cross-Chapter

Box 3 in Chapter 1}

Robust assessments of ocean and cryosphere change, and the

development of context-speciﬁc governance and response options, depend on utilising and strengthening all available knowledge systems ( high conﬁdence ). Scientiﬁc knowledge from

observations, models and syntheses provides global to local scale

understandings of climate change ( very high conﬁdence ). Indigenous

knowledge (IK) and local knowledge (LK) provide context-speciﬁc and

socio-culturally relevant understandings for effective responses and

policies ( medium conﬁdence ). Education and climate literacy enable

climate action and adaptation ( high conﬁdence ). {1.8, Cross-Chapter

Box 4 in Chapter 1}

Long-term sustained observations and continued modelling

are critical for detecting, understanding and predicting ocean

and cryosphere change, providing the knowledge to inform

risk assessments and adaptation planning ( high conﬁdence ).

Knowledge gaps exist in scientiﬁc knowledge for important regions, parameters and processes of ocean and cryosphere change, including for physically plausible, high impact changes like high end sea level

rise scenarios that would be costly if realised without effective

adaptation planning and even then may exceed limits to adaptation.

Means such as expert judgement, scenario building, and invoking

multiple lines of evidence enable comprehensive risk assessments

even in cases of uncertain future ocean and cryosphere changes.

{1.8.1, 1.9.2, Cross-Chapter Box 5 in Chapter 1}

TS.2 High Mountain Areas

The cryosphere (including, snow, glaciers, permafrost, lake and river ice) is an integral element of high mountain regions, which

are home to roughly 10% of the global population. Widespread

cryosphere changes affect physical, biological and human systems in the mountains and surrounding lowlands, with impacts evident even in the ocean. Building on the IPCC’s 5th Assessment Report (AR5), this chapter assesses new evidence on observed recent and projected changes in the mountain cryosphere as well as associated impacts, risks and adaptation measures related to natural and human systems. Impacts in response to climate changes independently of changes in

the cryosphere are not assessed in this chapter. Polar mountains are

included in Chapter 3, except those in Alaska and adjacent Yukon,

Iceland and Scandinavia, which are included in this chapter.Observations of cryospheric changes, impacts,

and adaptation in high mountain areas

Observations show general decline in low-elevation snow

cover ( high conﬁdence ) glaciers ( very high conﬁdence ) and

permafrost ( high conﬁdence ) due to climate change in recent

decades. Snow cover duration has declined in nearly all regions,

especially at lower elevations, on average by 5 days per decade,

with a likely range from 0–10 days per decade. Low elevation snow

depth and extent have declined, although year-to-year variation is high. Mass change of glaciers in all mountain regions (excluding the Canadian and Russian Arctic, Svalbard, Greenland and Antarctica)

was very likely –490 ± 100 kg m

–2 yr–1 (–123 ± 24 Gt yr–1) in 2006–

2015. Regionally averaged mass budgets were likely most negative

(less than –850 kg m–2 yr–1) in the southern Andes, Caucasus and the

European Alps/Pyrenees, and least negative in High Mountain Asia (–150 ± 110 kg m

–2 yr–1) but variations within regions are strong.

Between 3.6–5.2 million km2 are underlain by permafrost in the

eleven high mountain regions covered in this chapter corresponding

to 27–29% of the global permafrost area ( medium conﬁdence ).

Sparse and unevenly distributed measurements show an increase

in permafrost temperature ( high conﬁdenc e), for example, by

0.19ºC ± 0.05ºC on average for about 28 locations in the European

Alps, Scandinavia, Canada and Asia during the past decade. Other

observations reveal decreasing permafrost thickness and loss of ice

in the ground. {2.2.2, 2.2.3, 2.2.4, Figure TS.5}

Glacier, snow and permafrost decline has altered the frequency,

magnitude and location of most related natural hazards ( high

conﬁdence ). Exposure of people and infrastructure to natural

hazards has increased due to growing population, tourism and socioeconomic development ( high conﬁdence ). Glacier retreat

and permafrost thaw have decreased the stability of mountain slopes and the integrity of infrastructure ( high conﬁdence ). The number

and area of glacier lakes has increased in most regions in recent

decades ( high conﬁdence ), but there is only limited evidence that

the frequency of glacier lake outburst ﬂoods (GLOF) has changed. In

some regions, snow avalanches involving wet snow have increased

(medium conﬁdence ), and rain-on-snow ﬂoods have decreased at

low elevations in spring and increased at high elevations in winter

(medium conﬁdence ). The number and extent of wildﬁres have

increased in the Western USA partly due to early snowmelt ( medium

conﬁdence ). {2.3.2, 2.3.3}

Changes in snow and glaciers have changed the amount and

seasonality of runoff in snow-dominated and glacier-fed river

basins ( very high conﬁdence ) with local impacts on water

resources and agriculture ( medium conﬁdence ). Winter runoff

has increased in recent decades due to more precipitation falling as

rain ( high conﬁdence ). In some glacier-fed rivers, summer and annual

runoff have increased due to intensiﬁed glacier melt, but decreased

where glacier melt water has lessened as glacier area shrinks.

Decreases were observed especially in regions dominated by small

glaciers, such as the European Alps ( medium conﬁdence ). Glacier

retreat and snow cover changes have contributed to localized declines

in agricultural yields in some high mountain regions, including the

Hindu Kush Himalaya and the tropical Andes ( medium conﬁdence ).

48Technical Summary

TSThere is limited evidence of impacts on operation and productivity

of hydropower facilities resulting from changes in seasonality and both increases and decreases in water input, for example, in the European Alps, Iceland, Western Canada and USA, and the tropical Andes. {2.3.1}

Species composition and abundance have markedly changed

in high mountain ecosystems in recent decades ( very high

conﬁdence ), partly due to changes in the cryosphere ( high

conﬁdence ). Habitats for establishment by formerly absent species

have opened up or been altered by reduced snow cover ( high