ellisbrown/BDML25SP_hw1_processed_data

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carbon dioxide and methane released from the microbial breakdown
of organic carbon, or the release of trapped methane. {3.4.1, 3.4.3}
Climate-related changes to Arctic hydrology, wildﬁre and
abrupt thaw are occurring ( high conﬁdence ), with impacts
on vegetation and water and food security. Snow and lake
ice cover has declined, with June snow extent decreasing 13.4
± 5.4% per decade (1967–2018) ( high conﬁdence ). Runoff into
the Arctic Ocean increased for Eurasian and North American rivers
by 3.3 ± 1.6% and 2.0 ± 1.8% respectively (1976–2017; medium
conﬁdence ). Area burned and frequency of ﬁres (including extreme
ﬁres) are unprecedented over the last 10,000 years (high conﬁdence ).
There has been an overall greening of the tundra biome, but also
browning in some regions of tundra and boreal forest, and changes
in the abundance and distribution of animals including reindeer and
salmon (high conﬁdence ). Together, these impact access to (and food

53Technical Summary
TSavailability within) herding, hunting, ﬁshing, forage and gathering
areas, affecting the livelihood, health and cultural identity of residents including Indigenous peoples ( high conﬁdence ). {3.4.1, 3.4.3, 3.5.2}
Limited knowledge, ﬁnancial resources, human capital and
organisational capacity are constraining adaptation in many human sectors in the Arctic (high conﬁdence ). Harvesters of
renewable resources are adjusting timing of activities to changes in seasonality and less safe ice travel conditions. Municipalities and industry are addressing infrastructure failures associated with ﬂooding and thawing permafrost, and coastal communities and cooperating agencies are in some cases planning for relocation (high conﬁdence ). In spite of these adaptations, many groups are
making decisions without adequate knowledge to forecast near- and
long-term conditions, and without the funding, skills and institutional
support to engage fully in planning processes ( high conﬁdence ).
{3.5.2, 3.5.4, Cross-Chapter Box 9}
It is extremely likely that the rapid ice loss from the Greenland
and Antarctic ice sheets during the early 21st century has
increased into the near present day, adding to the ice sheet
contribution to global sea level rise. From Greenland, the 2012–
2016 ice losses (–247 ± 15 Gt yr
–1) were similar to those from 2002
to 2011 (–263 ± 21 Gt yr–1) and extremely likely greater than from
1992 to 2001 (–8 ± 82 Gt yr–1). Summer melting of the Greenland
Ice Sheet (GIS) has increased since the 1990s (very high conﬁdence )
to a level unprecedented over at least the last 350 years, and two-to-ﬁvefold the pre-industrial level ( medium conﬁdence ). From
Antarctica, the 2012–2016 losses (–199 ± 26 Gt yr
–1) were extremely
likely greater than those from 2002 to 2011 (–82 ± 27 Gt yr–1) and
likely greater than from 1992 to 2001 (–51 ± 73 Gt yr–1). Antarctic
ice loss is dominated by acceleration, retreat and rapid thinning
of major West Antarctic Ice Sheet (WAIS) outlet glaciers ( very high
conﬁdence ), driven by melting of ice shelves by warm ocean waters
(high conﬁdence ). The combined sea level rise contribution from both
ice sheets for 2012–2016 was 1.2 ± 0.1 mm yr–1, a 29% increase on
the 2002–2011 contribution and a ~700% increase on the 1992–
2001 period. {3.3.1}
Mass loss from Arctic glaciers ( –212 ± 29 Gt yr–1) during
2006 –2015 contributed to sea level rise at a similar rate
(0.6 ± 0.1 mm yr–1) to the GIS (high conﬁdence ). Over the same
period in Antarctic and subantarctic regions, glaciers separate from
the ice sheets changed mass by –11 ± 108 Gt yr–1 (low conﬁdence ).
{2.2.3, 3.3.2}
There is limited evidence and high agreement that recent
Antarctic Ice Sheet (AIS) mass losses could be irreversible over decades to millennia. Rapid mass loss due to glacier ﬂow
acceleration in the Amundsen Sea Embayment (ASE) of West Antarctica and in Wilkes Land, East Antarctica, may indicate the beginning of Marine Ice Sheet Instability (MISI), but observational data are not yet sufﬁcient to determine whether these changes mark the beginning of irreversible retreat. {3.3.1, Cross-Chapter Box 8 in Chapter 3, 4.2.3.1.2}
6 Projections for ice sheets and glaciers in the polar regions are summarized in Chapters 4 and 2, respectively.The polar regions will be profoundly different in future compared with today, and the degree and nature of that difference will depend strongly on the rate and magnitude of global climatic change
6. This will challenge adaptation
responses regionally and worldwide.
It is very likely that projected Arctic warming will result in
continued loss of sea ice and snow on land, and reductions in
the mass of glaciers. Important differences in the trajectories of loss emerge from 2050 onwards, depending on mitigation measures taken ( high conﬁdence ). For stabilised global warming
of 1.5ºC, an approximately 1% chance of a given September being sea
ice free at the end of century is projected; for stabilised warming at
a 2ºC increase, this rises to 10–35% ( high conﬁdence ). The potential
for reduced (further 5–10%) but stabilised Arctic autumn and spring snow extent by mid-century for Representative Concentration
Pathway (RCP)2.6 contrasts with continued loss under RCP8.5 (a further 15–25% reduction to end of century) ( high conﬁdence ).
Projected mass reductions for polar glaciers between 2015 and 2100 range from 16 ± 7% for RCP2.6 to 33 ± 11% for RCP8.5 ( medium
conﬁdence ). {3.2.2, 3.3.2, 3.4.2, Cross-Chapter Box 6 in Chapter 2}
Both polar oceans will be increasingly affected by CO
2
uptake, causing conditions corrosive for calcium carbonate
shell-producing organisms ( high conﬁdence ), with associated
impacts on marine organisms and ecosystems ( medium
conﬁdence ). It is very likely that both the Southern Ocean and the
Arctic Ocean will experience year-round conditions of surface water
undersaturation for mineral forms of calcium carbonate by 2100
under RCP8.5; under RCP2.6 the extent of undersaturated waters
are reduced markedly. Imperfect representation of local processes
and sea ice interaction in global climate models limit the ability to
project the response of speciﬁc polar areas and the precise timing of
undersaturation at seasonal scales. Differences in sensitivity and the
scope for adaptation to projected levels of ocean acidiﬁcation exist
across a broad range of marine species groups. {3.2.1, 3.2.2.3, 3.2.3}
Future climate-induced changes in the polar oceans, sea ice,
snow and permafrost will drive habitat and biome shifts,
with associated changes in the ranges and abundance of ecologically important species ( medium conﬁdence ). Projected
shifts will include further habitat contraction and changes in abundance for polar species, including marine mammals, birds, ﬁsh, and Antarctic krill ( medium conﬁdence ). Projected range expansion
of subarctic marine species will increase pressure for high-Arctic
species ( medium conﬁdence ), with regionally variable impacts.
Continued loss of Arctic multi-year sea ice will affect ice-related and
pelagic primary production ( high conﬁdence ), with impacts for whole
ice-associated, seaﬂoor and open ocean ecosystems. On Arctic land,
projections indicate a loss of globally unique biodiversity as some
high Arctic species will be outcompeted by more temperate species
and very limited refugia exist ( medium conﬁdence ). Woody shrubs
and trees are projected to expand, covering 24–52% of the current
tundra region by 2050. {3.2.2.1, 3.2.3, 3.2.3.1, Box 3.4, 3.4.2, 3.4.3}

54Technical Summary

carbon dioxide and methane released from the microbial breakdown

of organic carbon, or the release of trapped methane. {3.4.1, 3.4.3}

Climate-related changes to Arctic hydrology, wildﬁre and

abrupt thaw are occurring ( high conﬁdence ), with impacts

on vegetation and water and food security. Snow and lake

ice cover has declined, with June snow extent decreasing 13.4

± 5.4% per decade (1967–2018) ( high conﬁdence ). Runoff into

the Arctic Ocean increased for Eurasian and North American rivers

by 3.3 ± 1.6% and 2.0 ± 1.8% respectively (1976–2017; medium

conﬁdence ). Area burned and frequency of ﬁres (including extreme

ﬁres) are unprecedented over the last 10,000 years (high conﬁdence ).

There has been an overall greening of the tundra biome, but also

browning in some regions of tundra and boreal forest, and changes

in the abundance and distribution of animals including reindeer and

salmon (high conﬁdence ). Together, these impact access to (and food

53Technical Summary

TSavailability within) herding, hunting, ﬁshing, forage and gathering

areas, affecting the livelihood, health and cultural identity of residents including Indigenous peoples ( high conﬁdence ). {3.4.1, 3.4.3, 3.5.2}

Limited knowledge, ﬁnancial resources, human capital and

organisational capacity are constraining adaptation in many human sectors in the Arctic (high conﬁdence ). Harvesters of

renewable resources are adjusting timing of activities to changes in seasonality and less safe ice travel conditions. Municipalities and industry are addressing infrastructure failures associated with ﬂooding and thawing permafrost, and coastal communities and cooperating agencies are in some cases planning for relocation (high conﬁdence ). In spite of these adaptations, many groups are

making decisions without adequate knowledge to forecast near- and

long-term conditions, and without the funding, skills and institutional

support to engage fully in planning processes ( high conﬁdence ).

{3.5.2, 3.5.4, Cross-Chapter Box 9}

It is extremely likely that the rapid ice loss from the Greenland

and Antarctic ice sheets during the early 21st century has

increased into the near present day, adding to the ice sheet

contribution to global sea level rise. From Greenland, the 2012–

2016 ice losses (–247 ± 15 Gt yr

–1) were similar to those from 2002

to 2011 (–263 ± 21 Gt yr–1) and extremely likely greater than from

1992 to 2001 (–8 ± 82 Gt yr–1). Summer melting of the Greenland

Ice Sheet (GIS) has increased since the 1990s (very high conﬁdence )

to a level unprecedented over at least the last 350 years, and two-to-ﬁvefold the pre-industrial level ( medium conﬁdence ). From

Antarctica, the 2012–2016 losses (–199 ± 26 Gt yr

–1) were extremely

likely greater than those from 2002 to 2011 (–82 ± 27 Gt yr–1) and

likely greater than from 1992 to 2001 (–51 ± 73 Gt yr–1). Antarctic

ice loss is dominated by acceleration, retreat and rapid thinning

of major West Antarctic Ice Sheet (WAIS) outlet glaciers ( very high

conﬁdence ), driven by melting of ice shelves by warm ocean waters

(high conﬁdence ). The combined sea level rise contribution from both

ice sheets for 2012–2016 was 1.2 ± 0.1 mm yr–1, a 29% increase on

the 2002–2011 contribution and a ~700% increase on the 1992–

2001 period. {3.3.1}

Mass loss from Arctic glaciers ( –212 ± 29 Gt yr–1) during

2006 –2015 contributed to sea level rise at a similar rate

(0.6 ± 0.1 mm yr–1) to the GIS (high conﬁdence ). Over the same

period in Antarctic and subantarctic regions, glaciers separate from

the ice sheets changed mass by –11 ± 108 Gt yr–1 (low conﬁdence ).

{2.2.3, 3.3.2}

There is limited evidence and high agreement that recent

Antarctic Ice Sheet (AIS) mass losses could be irreversible over decades to millennia. Rapid mass loss due to glacier ﬂow

acceleration in the Amundsen Sea Embayment (ASE) of West Antarctica and in Wilkes Land, East Antarctica, may indicate the beginning of Marine Ice Sheet Instability (MISI), but observational data are not yet sufﬁcient to determine whether these changes mark the beginning of irreversible retreat. {3.3.1, Cross-Chapter Box 8 in Chapter 3, 4.2.3.1.2}

6 Projections for ice sheets and glaciers in the polar regions are summarized in Chapters 4 and 2, respectively.The polar regions will be profoundly different in future compared with today, and the degree and nature of that difference will depend strongly on the rate and magnitude of global climatic change

6. This will challenge adaptation

responses regionally and worldwide.

It is very likely that projected Arctic warming will result in

continued loss of sea ice and snow on land, and reductions in

the mass of glaciers. Important differences in the trajectories of loss emerge from 2050 onwards, depending on mitigation measures taken ( high conﬁdence ). For stabilised global warming

of 1.5ºC, an approximately 1% chance of a given September being sea

ice free at the end of century is projected; for stabilised warming at

a 2ºC increase, this rises to 10–35% ( high conﬁdence ). The potential

for reduced (further 5–10%) but stabilised Arctic autumn and spring snow extent by mid-century for Representative Concentration

Pathway (RCP)2.6 contrasts with continued loss under RCP8.5 (a further 15–25% reduction to end of century) ( high conﬁdence ).

Projected mass reductions for polar glaciers between 2015 and 2100 range from 16 ± 7% for RCP2.6 to 33 ± 11% for RCP8.5 ( medium

conﬁdence ). {3.2.2, 3.3.2, 3.4.2, Cross-Chapter Box 6 in Chapter 2}

Both polar oceans will be increasingly affected by CO

2

uptake, causing conditions corrosive for calcium carbonate

shell-producing organisms ( high conﬁdence ), with associated

impacts on marine organisms and ecosystems ( medium

conﬁdence ). It is very likely that both the Southern Ocean and the

Arctic Ocean will experience year-round conditions of surface water

undersaturation for mineral forms of calcium carbonate by 2100

under RCP8.5; under RCP2.6 the extent of undersaturated waters

are reduced markedly. Imperfect representation of local processes

and sea ice interaction in global climate models limit the ability to

project the response of speciﬁc polar areas and the precise timing of

undersaturation at seasonal scales. Differences in sensitivity and the

scope for adaptation to projected levels of ocean acidiﬁcation exist

across a broad range of marine species groups. {3.2.1, 3.2.2.3, 3.2.3}

Future climate-induced changes in the polar oceans, sea ice,

snow and permafrost will drive habitat and biome shifts,

with associated changes in the ranges and abundance of ecologically important species ( medium conﬁdence ). Projected

shifts will include further habitat contraction and changes in abundance for polar species, including marine mammals, birds, ﬁsh, and Antarctic krill ( medium conﬁdence ). Projected range expansion

of subarctic marine species will increase pressure for high-Arctic

species ( medium conﬁdence ), with regionally variable impacts.

Continued loss of Arctic multi-year sea ice will affect ice-related and

pelagic primary production ( high conﬁdence ), with impacts for whole

ice-associated, seaﬂoor and open ocean ecosystems. On Arctic land,

projections indicate a loss of globally unique biodiversity as some

high Arctic species will be outcompeted by more temperate species

and very limited refugia exist ( medium conﬁdence ). Woody shrubs

and trees are projected to expand, covering 24–52% of the current

tundra region by 2050. {3.2.2.1, 3.2.3, 3.2.3.1, Box 3.4, 3.4.2, 3.4.3}

54Technical Summary