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REPORT
M-625 | 2016
The Impacts of 1.5°C
A science briefing
COLOPHON
Executive institution
Climate Analytics
Project manager for the contractor
Carl-Friedrich Schleussner
M-no
Year
625
2016
Contact person in the Norwegian Environment Agency
Maria Malene Kvalevåg
Pages
19
Contract number
16088182
Publisher
Norwegian Environment Agency/
Miljødirektoratet
The project is funded by
Norwegian Environment Agency/
Miljødirektoratet
Author(s)
Carl-Friedrich Schleussner
Title – Norwegian and English
The impacts of 1.5C – a scientific briefing
Summary – sammendrag
This report reviews the current state of the literature on the differences in climate impact
projections between 1.5°C and 2°C. There are discernible differences for extreme weather events in
particular on the regional level, impacts on unique and threatened systems such as coral reefs, water
availability and tropical crop yields as well as abrupt shifts in the climate system and long-term sealevel rise risks. Limiting warming to 1.5°C would substantially reduce the impacts of climate change
for the most vulnerable in particular in the Tropics, as well as in high-latitude regions. More science
is required to improve our understanding of the impacts of climate change at 1.5°C and the avoided
impacts when limiting warming to 1.5°C compared to 2°C or higher levels to provide a robust basis
for the IPCC special report. Coordinated efforts by the scientific community are underway to address
these issues and a wealth of new studies can be expected in time for the 1.5°C special report.
4 emneord
Effekter av klimaendringene, global
oppvarming, 1.5 graders, Parisavtalen
4 subject words
Climate impacts, global warming, 1.5 degrees,
Paris agreement
Front page photo
Jørgensen, Bjørn, Scanpix
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Content
Executive Summary ............................................................................................ 3
1. Introduction ................................................................................................. 3
2. Climate Impact Projections at 1.5°C ................................................................... 4
2.1 Extreme Weather Events ............................................................................ 5
2.1.1 Extreme Temperatures ...................................................................... 5
2.1.2 Extreme Precipitation ....................................................................... 6
2.1.3 Droughts ........................................................................................ 6
2.1.4 Tropical Cyclones ............................................................................. 6
2.1.5 Quasi-resonant amplified mid-latitude planetary waves .............................. 6
2.1.6 El Niño Southern Oscillation ................................................................ 7
2.2 Impacts on Ecosystems .............................................................................. 7
2.3 Water Availability and Crop Yields ................................................................ 8
3. Climate Impacts Byond 2100 and Abrupt Shifts in the Climate System ........................... 9
3.1 Long-term Sea-level Rise............................................................................ 9
3.2 Tipping elements and abrupt shifts in the Earth System .................................... 10
4. Vulnerability, livelihoods and sustainable development .......................................... 11
4.1 Impacts on health and labour productivity .................................................... 12
5. Scenario dependence of impacts at 1.5°C scenarios ............................................... 13
6. Key research questions and planned scientific activities for the 1.5°C Special Report ..... 14
7. References ................................................................................................. 15
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Executive Summary
International climate action is guided by and evaluated against targets to limit the
increase in global average temperature above preindustrial levels. The Paris
Agreement includes a long-term global temperature goal of “holding the increase in
the global average temperature to well below 2 °C… and pursuing efforts to limit the
temperature increase to 1.5 °C above pre-industrial levels, recognizing that this
would significantly reduce the risks and impacts of climate change.” Climate impacts
at 1.5°C, however, have not been a focus of the scientific community so far including
in the most recent fifth Assessment Report of the IPCC. The upcoming IPCC Special
Report on 1.5°C will aim to fill this gap. Here we review the current state of the
literature on the differences in climate impact projections between 1.5°C and 2°C.
We find discernible differences for extreme weather events in particular on the
regional level, impacts on unique and threatened systems such as coral reefs, water
availability and tropical crop yields as well as abrupt shifts in the climate system and
long-term sea-level rise risks. Limiting warming to 1.5°C would substantially reduce
the impacts of climate change for the most vulnerable in particular in the Tropics, as
well as in high-latitude regions. More science is required to improve our
understanding of the impacts of climate change at 1.5°C and the avoided impacts
when limiting warming to 1.5°C compared to 2°C or higher levels to provide a robust
basis for the IPCC special report. Coordinated efforts by the scientific community are
underway to address these issues and a wealth of new studies can be expected in
time for the 1.5°C special report.
1. Introduction
At its 43rd plenary, the IPCC decided “to accept the invitation from the UNFCCC to provide a
Special Report in 2018 on the impacts of global warming of 1.5°C above pre- industrial levels
and related global greenhouse gas emission pathways, and decides to prepare a Special
Report on this topic in the context of strengthening the global response to the threat of
climate change, sustainable development and efforts to eradicate poverty.”(IPCC, 2016).
By doing so, the IPCC followed an invitation by the UNFCCC spelled out in its decision
paragraph 21, 1/CP.21 on this matter. In addition to that, also decision 10/CP.21 on the 20132015 Review of the long-term global goal and the overall progress made towards it addresses
these questions. Paragraph 8, 10/CP.21: “Encourages the scientific community to address
information and research gaps identified during the structured expert dialogue, including
scenarios that limit warming to below 1.5 °C relative to pre-industrial levels by 2100 and the
range of impacts at the regional and local scales associated with those scenarios.” (UNFCCC,
2015a).
It is important to note that when the IPCC 43rd plenary agreed to the 1.5°C special report,
many developing countries expressed their wish that this report should also include the
implications for sustainable development. There is therefore an expectation that the
assessment of impacts at 1.5°C will necessarily include an assessment of implications for a
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wide range of sustainable development parameters and metrics. The context for this is that
some developing countries are concerned that mitigation could interfere with their ability to
develop and to eradicate poverty, while for others the impacts of climate change are a main
obstacle for sustainable development. It is thus important that the design of the special
report includes assessment of these issues, including the effects of climate impacts on
poverty eradication and sustainable development, the co-benefits of mitigation and any
linkages to impacts, vulnerability and adaptation.
These decisions have been informed by the multi-year process of the 2013-2015 Review
including a structured expert science-policy dialogue (SED). The SED concluded its work in
2015 and published a comprehensive summary report that in particularly also assessed the
impacts at different levels of global mean temperature (GMT) increase such as 1.5°C and 2°C.
The report found that a ''concept in which up to 2°C of warming is considered safe, is
inadequate and would therefore be better seen as an upper limit''. On the other hand, it also
recognized substantial science-gaps in differentiation in impacts between a 1.5°C and a 2°C
warming limit (UNFCCC, 2015b). Such impact differentiation has not been at the focus of
scientific community in the IPCC AR5 and there is an expectation that the special report of
the IPCC will also address these issues.
In the following, the current state of the literature on the differences in climate impact
projections between 1.5°C and 2°C will be presented. In particular, results for different
impact and region specific findings will be outlined. This is followed by an analysis of risks at
multi-century time scales including abrupt shifts and large-scale so-called tipping elements in
the earth system. Implications for sustainable development will be analyzed. Finally, some
elements that require further research will be outlined including questions of scenario
dependence of impacts at 1.5°C and current research activities aiming at addressing these in
time for the 1.5°C special report.
2. Climate Impact Projections at 1.5°C
For the first time, an IPCC report focusses on a warming level rather than using a scenario
approach. Such GMT targets do not stand for themselves but rather serve as ‘focal points’ to
operationalise the ultimate objective of the United Nations Framework Convention on Climate
Change (UNFCCC) ‘avoiding dangerous interference’ with the climate system. They are
therefore primarily rooted in political risk assessments (Jaeger and Jaeger, 2011; Knutti et
al., 2015), which also means that the information on projected impacts of a greenhouse gas
(GHG) induced GMT increase (such as 1.5°C and 2°C above pre-industrial levels) provided the
basis for the adoption of different temperature limits.
To best assess the impacts at different levels of warming, translating global limits into
regional- and impact-related consequences as also requested in the respective UNFCCC
decisions is required. Feil! Fant ikke referansekilden. provides an overview of key
differences in climate impacts between 1.5°C and 2°C based on a recent literature
assessment.
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Figure 1 Projected impacts at 1.5 °C and 2 °C GMT increase above pre-industrial levels for a selection of indicators
and regions. a, Increase in global occurrence probability of pre-industrial 1-in-a-1000 day extreme temperature
events (Fischer and Knutti, 2015). b, Increase in extreme precipitation intensity (RX5Day) for the global land area
below 66° N/S and South Asia (Schleussner et al., 2016a). c, Reduction in annual water availability in the
Mediterranean (Schleussner et al., 2016a). d, Share of global tropical coral reefs at risk of long-term degradation
(Frieler et al., 2012). e, Global sea-level rise commitment for persistent warming of 1.5 °C and 2 °C over 2000 years
(Levermann et al., 2013). f, Changes in local crop yields for present-day tropical agricultural areas (Schleussner et
al., 2016a) (below 30° N/S, model dependent implementation of present day management). Dashed boxes: no
increase in CO2 fertilization (No CO2). Panels b, c and f display median changes that are exceeded for over 50% of the
respective land areas. From (Schleussner et al., 2016b), Copyright with Nature Climate Change.
Extreme Weather Events
Extreme weather events are among the most impact relevant climate hazards. Regional
assessments for extreme weather events including extreme temperatures and precipitation
are key to understand differences in the climate signals and to assess the differences
between different warming levels (Seneviratne et al., 2016). In the following, assessments for
different types of extreme weather events as well as large scale circulation systems affecting
the occurrence of such events are provided.
2.1.1 Extreme Temperatures
Changes in temperature extremes are found to be particularly pronounced (Figure 1a). Recent
assessments of the difference in the occurrence of heat extremes between 1.5°C and 2°C
found a robust difference between the warming levels indicating that the probability of
occurrence of a hot extreme almost doubles between 1.5°C and 2°C (Fischer and Knutti,
2015). Relative to a comparably smaller natural variability, a warming of 2°C would imply a
new climate regime in terms of heat extremes in tropical regions (Schleussner et al., 2016a)
and currently unusual heat waves are projected to become the new normal in Africa (Russo et
al., 2015). The world’s poorest people, that are dominantly located at low latitudes, will be
exposed to substantially more frequent daily temperature extremes at much lower levels of
warming then their wealthier counterparts (Harrington et al., 2016), with substantial
implications for human health as well as labor productivity (Dunne et al., 2013) or even
habitability of certain areas (Pal and Eltahir, 2015)
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2.1.2 Extreme Precipitation
Unlike trends in extreme temperature, patterns for precipitation related changes are
considerably more uncertain, although robust changes in the water cycle may be experienced
by half of the world's population under a 2°C warming (Sedláček and Knutti, 2014). A robust
increase in the intensity of heavy precipitation events (Absolute annual maximum of
consecutive 5-day precipitation, RX5Day, see Figure 1 b) of about 5% (66% uncertainty range:
[4,6%]) relative to the 1986-2005 reference period for 50% of the global land-area under a
1.5°C warming and 7% [5,7%] under a 2°C warming is projected globally (Schleussner et al.,
2016a). These changes are particularly pronounced in high northern latitudes and South Asia,
where an intensification of about 10% is projected under 2°C (Schleussner et al., 2016a).
However, extreme precipitation may also increase over the world’s dry regions, which
indicates that even regions experience an overall drying trend may at the same time see an
increase in extreme precipitation risk highly relevant for flooding (Donat et al., 2016). The
fraction of extreme precipitation events attributable to anthropogenic influence is estimated
as about 30% [20,40%] under 1.5°C and to increase to about 40% [30,50%] under 2°C (Fischer
and Knutti, 2015).
2.1.3 Droughts
With regard to dry extremes, the majority of the global land area may experience only minor
changes in dry spell length (Consecutive Dry Days, CDD) under a 1.5°C or 2°C warming
relative to the reference period. Robust changes are projected for about 25% of global land
area (Schleussner et al., 2016a) such as the subtropical regions and in particular in the
Mediterranean, where an extension of dry spell length of about 7% [4,10%] and 11% [6,15%]
for 1.5°C and 2°C is projected, respectively. It is, however, important to highlight that these
changes only relate to meteorological drought (precipitation induced only), rather than
including effects of temperature increase on evapotranspiration and soil moisture, which are
of key relevance to assess hydrological droughts. As increasing temperatures increase
evapotranspiration, drought conditions can also be elevated without necessarily decreasing
precipitation. If such effects are included, robust increases in drought occurrences are
projected for large areas globally (Dai, 2013; Prudhomme et al., 2013). In addition, also local
anthropogenic activity will interfere with the hydrological signal (Van Loon et al., 2016).
2.1.4 Tropical Cyclones
Studying the difference in storm activity such as tropical cyclones for 1.5°C and 2°C is
hampered so far by limited statistics of such events based on the current climate model
designs. However, with warming sea-surface temperatures and atmospheric adjustments, a
continuation of the poleward migration (Kossin et al., 2014) of such cyclones as well as
increases in intensity (Wing et al., 2015) are expected to increase with increasing warming
(Emanuel, 2013).
2.1.5 Quasi-resonant amplified mid-latitude planetary waves
Projections of extreme events are subject to substantial uncertainties related to the model
capabilities adequately reproducing such events, but also related to large-scale circulation
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adjustments related to climate change. One such phenomenon that present generation
climate models do not capture in full is related to quasi-resonant amplified mid-latitude
planetary waves (Coumou et al., 2014), which has been shown to increase probabilities of
specific norther latitude extreme weather events such as heat waves in western North
America and central Asia, cold outbreaks in eastern North America, droughts in central North
America, Europe and central Asia, and wet spells in western Asia (Screen and Simmonds,
2014). Although the processes driving these amplifications are not yet fully understood and
may differ between summer and winter events, sea-ice concentrations appear to be an
important driver at least of winter extremes (Kretschmer et al., 2016). As northern
hemisphere sea-ice is highly sensitive to levels of warming around 1.5°C, our understanding of
the atmospheric impacts of vanishing sea ice needs to be advanced to better assess the risks
posed by such wave amplifications for the mid-latitudes.
2.1.6 El Niño Southern Oscillation
Extreme event occurrences with multi-annual re-occurrence times will be strongly affected
by the El Niño Southern Oscillation (ENSO) in particular over tropical regions (Seneviratne et
al., 2012). Post-AR5 studies have shown that ongoing warming will lead to more extreme El
Niño as well as La Niña conditions (Cai et al., 2015a, 2015b; Latif et al., 2015). Enso related
extreme weather events such as extreme precipitation in South America or drying in Southern
Africa may thereby become more frequent. Changes in ENSO at 1.5°C, however, have not yet
been assessed and given substantial uncertainties in present generation models and the lack
of targeted 1.5°C and 2°C scenarios, it will hardly be possible to distinguish changes at 1.5°C
and 2°C warming in the near future.
Impacts on Ecosystems
Climate change has been recognized as one of the major threats to ecosystems (Oppenheimer
et al., 2014) and the velocity of climate change exceeds the mobility of many terrestrial
species for a warming exceeding 1.5°C (IPCC, 2014). In addition, ocean ecosystems appear to
be particularly threatened by climate change due to warming, deoxygenation as well as ocean
acidification (Gattuso et al., 2015). Risks for several coastal and marine organisms are found
to be high already for a warming around 1.5°C, which also comes with detrimental
consequences for ecosystem services such fisheries or coastal protection. In particular, global
coral reef systems are projected to be threatened by ocean acidification and thermal stress
(Frieler et al., 2012; Meissner et al., 2012). Projections accounting for warming as well as
ocean acidification indicate that virtually all global warm water coral reef systems will be at
risk of long-term degradation under a warming of 2°C and only under 1.5°C some of these
systems may survive (compare Figure 1 d). Similarly, polar ecosystems and traditional
livelihoods are under immense pressure as sea-ice vanishes and only a long-term warming of
well below 2°C may ensure significant summer sea-ice coverage in the Arctic (Hezel et al.,
2014). Taken together, these findings give additional justification to the assessment of
attributing high to very high risks for unique and threatened systems, one of the five key
reasons for concern in the IPCC AR5 (Oppenheimer et al., 2014).
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Water Availability and Crop Yields
Patterns of change in water availability emerge similarly to changes in water cycle extremes
(Schewe et al., 2014). While global changes are not yet significant, an increase in water
availability exceeding 5% and 10% is projected for high-latitudes regions, as well as the SouthAsian monsoon regions for a 1.5°C and 2°C warming (Schleussner et al., 2016a). At the same
time, water availability is projected to decrease in subtropical regions and most prominently
in the Mediterranean (see Figure 2 c). Total annual water availability in this region is
projected to reduce by about 9% at 1.5°C and by about 17 % at 2°C compared to the 19862005 reference period. Risks also emerge for other, particularly subtropical regions such as
Central America, South Africa or Australia.
Crop yield projections are highly uncertain and differ substantially on the regional level.
While being sensitive to uncertainties arising from climate projections (in particular related
to changes in the water cycle), the dominant uncertainty arises from crop models that differ
substantially in the represented processes (Nelson et al., 2014). Most prominent processes
include CO2 fertilization (McGrath and Lobell, 2013), effects of other pollutants such as ozone
concentrations (Tai et al., 2014), or the impact of heat extremes (Deryng et al., 2014). In
addition, assumption about management changes and autonomous adaptation in agriculture
models differ considerably (Nelson et al., 2014).
Among these, CO2-fertilization also affecting the water use efficiency of the plants features
particularly prominent, as it would lead to increasing yields and thereby counterbalancing or
even overcompensating for detrimental effects of climate change. However, effects of CO 2fertilization play out very differently between regions, with much higher gains in temperate
and higher latitudes than in tropical regions (Deryng et al., 2016). At the same time, it is
unclear to what extend such projected gains due to fertilization are realistic, as the
observational record indicates increased impacts of climate change on crop yields already in
the observational record mainly related to climate-related natural disasters (Moore and
Lobell, 2015). In an assessment of cereal production losses across the globe resulting from
extreme weather disasters during 1964–2007 it has been found that droughts and extreme
heat significantly reduced national cereal production by 9–10% (Lesk et al., 2016).
Figure 1 f shows projections of median yield changes at 1.5°C and 2°C warming for tropical
regions and different crop types based on (Schleussner et al., 2016a). Even when accounting
in full for the effects of CO2-fertilization, median tropical maize and wheat local yields are
projected to decrease at 1.5°C and this decrease is projected to double under 2°C.
Projections for soy and rice indicate a median increase in yields under 1.5°C, but little
additional gain for a warming of 2°C, indicating that positive effects of increased CO 2 are
increasingly counterbalanced by detrimental climate effects.
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3. Climate Impacts Byond 2100 and
Abrupt Shifts in the Climate System
Many impacts of climate change will not materialize fully in this century, but rather over
centuries and millennia to come. This is particularly the case for the impacts on the ocean
and the cryosphere such as ocean acidification (Mathesius et al., 2015), glacier melt and sealevel rise (Clark et al., 2016), and loss of permafrost (Schneider von Deimling et al., 2012).
Long-term Sea-level Rise
Even after temperatures stabilize or decline, sea-levels will continue to rise for centuries to
come with contributions from thermal expansion of the ocean, as well as glaciers and in
particular the Antarctic and Greenland ice-sheet. A peak warming within the range of current
iNDCs with a Carbon Budget of 1,250 GtC (after the year 2000) could be sufficient to trigger
substantially losses of the Greenland and Antarctic ice sheets eventually leading to about 20m
sea-level rise over 10, 000 years (Clark et al., 2016; Winkelmann et al., 2015). As displayed in
Figure 1 e, a persistent warming of 1.5°C over 2000 years would lead to a sea-level rise of
about 3 m, compared with nearly 5 m for 2°C. On average, 2000-year sea-level rise is
projected to increase by 2.3m per °C warming (Levermann et al., 2013), that could be
substantially higher on even longer time scales. However, the regional distributions of such
sea-level rise would differ decisively. As for future warming above pre-industrial levels, the
dominant contributions to sea-level rise would come from the polar ice-sheets, equatorial
sea-levels would rise above the global average.
Figure 2 An overview of selected tipping elements of the earth system and future temperature
trajectories. The exact location when such tipping points would be triggered is uncertain, and the ranges
indicated comprise data-driven assessments as well as expert elicitations. WAIS: West Antarctic icesheet, THC: Atlantic thermohaline circulation, ENSO: El Nino Southern Oscillation. From (Schellnhuber,
H. J. Rahmstorf and Winkelmann, 2016), Copyright with Nature Climate Change .
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Tipping elements and abrupt shifts in the
Earth System
Key contributions of long-term future sea-level rise come from Greenland and parts of the
Antarctic ice sheet that are classified among the tipping elements of the earth system, which
means that they are projected to exhibit self-amplifying and strongly non-linear behavior
above a critical threshold. Once such dynamics are triggered, these ice-sheets would be in
unstable, irreversible retreat. For the Greenland ice sheet, the best estimate of such a
threshold is around 1.6°C GMT increase above pre-industrial levels (Robinson et al., 2012).
Recent findings from West Antarctica suggesting that an irreversible marine ice-sheet
instability might have already been triggered there for several basins (Favier et al., 2014;
Joughin et al., 2014), although a direct attribution of this tipping to an anthropogenic origin
cannot be made with sufficient confidence. At the same time, other potentially unstable
basins have been identified in East Antarctica (Mengel and Levermann, 2014). For the West
Antarctic ice sheet, some findings suggest that a full destabilization of the ice sheet, implying
at least 3 m of global sea-level rise, could be triggered following just another 60 years of
currently observed melt rates (Feldmann and Levermann, 2015). Although the underlying
time-scales of such a disintegration may reach up to several millennia, a thorough assessment
of a long-term global temperature limit requires to factor in such long-term effects. Evidence
from earth history indicates, that sea-levels during past warming periods not exceeding 2°C
above pre-industrial levels have been 6-13m higher than today (Dutton et al., 2015).
Figure 2 depicts a range of such tipping elements and an assessment of their respective
‘tipping points’. Several of these elements, including the West Antarctic and the Greenland
ice-sheet, Alpine Glaciers, Arctic summer sea-ice, but also tropical coral reefs fall within the
range of 1.5-2°C GMT increase above pre-industrial levels or even below.
These large scale identified tipping elements may, however, not be the only parts of the
climate system exhibiting abrupt or highly non-linear change with respect to increasing global
mean temperature. Recently, (Drijfhout et al., 2015) provide a catalogue of such abrupt
shifts in current generation climate models for warming scenarios exceeding 10°C. They
identified 37 such shifts including in in ocean circulation, sea ice, snow cover, permafrost,
and terrestrial biosphere and found that about 50% of all abrupt shifts identified already
occur at 2°C above pre-industrial levels, and only about 20% at a warming level of 1.5°C.
Their assessment, however, is based on occurrences of such abrupt shifts in individual climate
models, rather than ensembles, and from transient climate scenarios with contiguously
increasing temperatures. Thereby, abrupt shifts that occur with a certain time lag after the
forcing may not be adequately attributed.
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Figure 3 Poverty projections for 2030 for different policy choices and climate change scenarios. From (Hallegatte et
al., 2015).
4. Vulnerability, livelihoods and
sustainable development
The 1.5°C special report also speaks to requirements of poverty eradication and sustainable
development. Chapter 13 of the IPCC AR5 Working Group 2 report, assessed impacts on
livelihoods and poverty (Olsson et al., 2014). They found that:
“Climate change will create new poor between now and 2100, in developing and
developed countries, and jeopardize sustainable development. The majority of severe
impacts are projected for urban areas and some rural regions in sub-Saharan Africa and
Southeast Asia (medium confidence, based on medium evidence, medium agreement).
Future impacts of climate change, extending from the near term to the long term,
mostly expecting 2°C scenarios, will slow down economic growth and poverty reduction,
further erode food security, and trigger new poverty traps, the latter particularly in
urban areas and emerging hotspots of hunger. “
Similarly, the regional chapter on Africa (Niang et al., 2014) assesses that:
“Of nine climate-related key regional risks identified for Africa, eight pose medium or
higher risk even with highly adapted systems, while only one key risk assessed can be
potentially reduced with high adaptation to below a medium risk level, for the end of
the 21st century under 2°C global mean temperature increase above preindustrial levels
(medium confidence)”.
To what extent limiting warming to 1.5°C would reduce such risks remains an open question,
in particular as these impacts are to a large extent driven by vulnerabilities and exposure and
not just by an increase in climate hazards. The impacts of the 2015-2016 extreme El Nino
event in Africa underscore the vulnerability of these countries to climate hazards already at
current levels of warming.
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A recent comprehensive report of the World Bank addressed the impacts of impacts of
climate change on poverty (Hallegatte et al., 2015) and found clear evidence that climate
change is a threat to poverty eradication. In this report, different scenarios of climate change
impacts and socio-economic development until 2030 have been assessed (see Feil! Fant ikke
referansekilden.). Although socio-economic development clearly dominates, a high impact
climate change scenario is found to increase 2030 poverty levels by around 10% regardless of
the development scenario assumed. Under a low impact scenario, this increase will be
reduced to about 3%. Such findings are of great relevance for assessing near-term benefits of
stringent mitigation, as small differences in the climate hazard may be substantially amplified
by the extreme vulnerability of the global poor in the near term. The importance of this nearterm perspective is also underscored by assessments of risks for agricultural production. As
the bulk of growing food demand is expected in the next decades, impacts of smaller
magnitude in the near-term can be at least as consequential for food prices or food security
as larger magnitude impacts in the future (Lobell and Tebaldi, 2014). Such risks may be
further amplified by food supply shocks that arise from remote climate impacts in food
importing countries. It has been found that export bans in major producing regions, as a
result of for example climate disasters hitting such regions, would put up to 200 million
people below the poverty line at risk, 90% of which live in Sub-Saharan Africa (Bren d’Amour
et al., 2016).
Impacts on health and labour productivity
Health impacts of climate change may arise through a variety of factors also and in particular
also related to air quality and fossil fuel emissions. A direct health impact of climate change
is related to human mortality during extreme temperatures and a recent global cross-country
panel assessment (N=75 million deaths) showed that around 8% of observed mortality over the
1985 to 2012 was attributable to non-optimum temperatures, with the effect of cold
temperatures dominating the overall response (Gasparrini et al., 2015). Extreme hot and cold
events have been found to be responsible for about 1% of observed mortality in this panel.
Recently, first attempts to attribute excess deaths during heat waves have revealed that a
share of the fatalities during the 2003 heat wave in London and Paris can already be
attributed to anthropogenic climate change (Mitchell et al., 2016a). As projections of
extreme heat differ considerably between 1.5°C and 2°C, so may the effects on human
health.
Similarly, rising temperatures are projected to have detrimental consequences on labor
productivity (Zander et al., 2015). A global assessment of labor productivity indicated that a
warming of 2°C around 2050 could reduce global labor productivity by about 10% compared to
present day (Dunne et al., 2013).
As 1.5°C GMT increase above pre-industrial levels may already be reached in the 2030s,
establishing a direct connection between impacts at 1.5°C and the UN sustainable
development goals (SDGs) seems appropriate. In any case, integrated perspectives of SDGs
and warming targets should go beyond focusing on mitigation aspects only (Stechow et al.,
2016).
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5. Scenario dependence of impacts at
1.5°C scenarios
The preliminary findings of climate impacts at 1.5°C presented above are generally extracted
from existing scenario runs via approaches of pattern scaling or sub-selecting warming time
slices. A generalization of these findings is thereby based on the assumption of scenario
independence. While this assumption largely holds for temperature related signals, impacts
related to changes in the hydrological cycle as well as impacts including a socio-economic
component will show a clear scenario dependency. This is illustrated in Feil! Fant ikke
eferansekilden.Feil! Fant ikke referansekilden. that depicts the response of the global
annual precipitation for different RCP scenarios.
Figure 4 Illustration of scenario dependent changes in the global
precipitation response to different RCPs from (Mitchell et al., 2016b)
Displayed are changes in global mean precipitation annual-mean multimodel-mean data from CMIP5 over the 2006-2100 period for RCP2.6 (blue)
and RCP8.5 (red). All anomalies are relative to pre-industrial levels.
Copyright with Nature Climate Change.
While precipitation changes under the continuous warming scenario RCP8.5 scale nearly linear
with GMT increase, the assessment of the RCP2.6 scenario reveals ongoing changes in the
hydrological cycle after GMT stabilization (Mitchell et al., 2016b). Such changes may be
related to dynamics of time lagged elements of the climate system, in particular the oceanic
response, (Herger et al., 2015) or regionally related to adjustments in large scale circulation
patterns such as the Atlantic Meridional Overturning Circulation (Schleussner et al., 2014).
Circulation related changes as e.g. the expansion of the Hadley Cell or movement of the
Intertropical Convergence Zone (ITCZ) may lead to highly non-linear regional changes or even
trend reversals under high emission scenarios (Hawkins et al., 2014).
Furthermore, most presently available emissions pathways that hold warming below 1.5°C in
2100 are characterized by a temporary overshoot above this warming level (Schleussner et
al., 2016b). Whether or not the impacts under such a 1.5°C scenario will be similar to nonovershoot scenarios remains an open question.
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6. Key research questions and planned
scientific activities for the 1.5°C
Special Report
Following the state of the current literature outlined above, a (non-exhaustive) list of key
research questions on the impacts of 1.5°C can be identified:
1. The consequences of peak warming and the duration of potential overshoot above 1.5°C
for associated climate impacts need to be assessed, as well as the longer term (multicentury and millennial) consequences of limiting warming to 1.5°C. This should include
the assessment of tipping points and abrupt shifts.
2. Improved understanding of the consequences of ocean acidification and deoxygenation
under 1.5°C pathways compared to higher levels of warming, and their implications for
natural systems, livelihoods and marine living resources and related economic activities
3. The understanding of the potentials and limits of differentiating between different
levels of warming in the light of model uncertainty and natural variability needs to be
advanced.
4. The interlinkages between near-term warming and sustainable development
trajectories need to be explored further. Given the substantial vulnerability to climate
hazards in particular of the global poor over the next decades, near-term mitigation
benefits arising from avoided impacts and the co-benefits of mitigation need to be
reassessed.
5. Understanding the relationship between 1.5°C warming and achievement of the 17
recently adopted SDGs, in relation to high levels of warming and different socioeconomic pathways.
A range of ongoing community research efforts are aiming at addressing impacts of 1.5°C
warming and to produce results in time for the 2018 special report. The following table
provides a (non-exhaustive) list of such activities and their main research aims.
Table 1 Ongoing research activities on 1.5°C impacts.
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E-mail: [email protected]
Web: www.environmentagency.no
Postal address: Postboks 5672 Sluppen, N-7485 Trondheim
Visiting address Trondheim: Brattørkaia 15, 7010 Trondheim
Visiting address Oslo: Grensesvingen 7, 0661 Oslo
The Norwegian Environment Agency is working for
a clean and diverse environment. Our primary
tasks are to reduce greenhouse gas emissions,
manage Norwegian nature, and prevent pollution.
We are a government agency under the Ministry
of Climate and Environment and have 700
employees at our two offices in Trondheim and
Oslo and at the Norwegian Nature Inspectorate’s
more than sixty local offices.
We implement and give advice on the
development of climate and environmental
policy. We are professionally independent. This
means that we act independently in the individual
cases that we decide and when we communicate
knowledge and information or give advice.
Our principal functions include collating and
communicating environmental information,
exercising regulatory authority, supervising and
guiding regional and local government level,
giving professional and technical advice, and
participating in international environmental
activities.