text stringlengths 0 2.31k |
|---|
Lack of Finance as a Barrier to Climate Action
Insufficient financing, and a lack of political frameworks and
incentives for finance, are key causes of the implementation
gaps for both mitigation and adaptation (high confidence).
Financial flows remained heavily focused on mitigation, are
uneven, and have developed het... |
Challenges
remain for green bonds and similar products, in particular around
integrity and additionality, as well as the limited applicability of
these markets to many developing countries (high confidence).
{WGII SPM C.3.2, WGII SPM C.5.4; WGIII SPM B.5.4, WGIII SPM E.5.1}
Current global financial flows for adaptat... |
{WGII SPM C.1.2, WGII SPM C.3.2, WGII SPM C.5.4, WGII TS.D.1.6}
Without effective mitigation and adaptation, losses and damages will
continue to disproportionately affect the poorest and most vulnerable
populations. Accelerated financial support for developing countries
from developed countries and other sources is ... |
63
Current Status and Trends
Section 2
Cross-Section Box.2: Scenarios, Global Warming Levels, and Risks
Modelled scenarios and pathways102 are used to explore future emissions, climate change, related impacts and risks, and possible mitigation and
adaptation strategies and are based on a range of assumptions, includin... |
Depending on levels of GHG mitigation, modelled emissions scenarios based on the SSPs can be consistent with low or high warming levels104.
There are many different mitigation strategies that could be consistent with different levels of global warming in 2100 (see Figure 4.1).
{WGI Box SPM.1; WGII Box SPM.1; WGIII Bo... |
The very low and low GHG emissions scenarios (SSP1-1.9 and
SSP1-2.6) have CO2 emissions declining to net zero around 2050 and 2070, respectively, followed by varying levels of net negative CO2
emissions. In addition, Representative Concentration Pathways (RCPs)107 were used by WGI and WGII to assess regional climate ... |
WGI primarily used the term
scenarios and WGIII mostly used the term modelled emissions and mitigation pathways. The SYR primarily uses scenarios when referring to WGI and modelled emissions and
mitigation pathways when referring to WGIII. {WGI Box SPM.1; WGIII footnote 44}
103 Around half of all modelled global emis... |
{WGIII SPM C.1.4; SRCCL Box SPM.1}
105 SSP-based scenarios are referred to as SSPx-y, where ‘SSPx’ refers to the Shared Socio-economic Pathway describing the socioeconomic trends underlying the scenarios, and
‘y’ refers to the level of radiative forcing (in watts per square metre, or Wm–2) resulting from the scenario ... |
64
Section 2
Section 1
Section 2
Global Warming Levels (GWLs)
For many climate and risk variables, the geographical patterns of changes in climatic impact-drivers110 and climate impacts for a level of global
warming111 are common to all scenarios considered and independent of timing when that level is reached. This mo... |
65
Current Status and Trends
Section 2
which drives
that change
influence
Emissions
a) AR6 integrated assessment framework on future climate, impacts and mitigation
Climate
Impacts / Risks
Mitigation Policy
Adaptation Policy
Socio-economic changes
0
1
2
3
4
5
6
7
°C
b) Scenarios and pathways across AR6 Working Group rep... |
0
and SSP1-2.6
Category
in WGIII
Category description
GHG emissions scenarios
(SSPx-y*) in WGI & WGII
RCPy** in
WGI & WGII
C1
limit warming to 1.5°C (>50%)
with no or limited overshoot
Very low (SSP1-1.9)
Low (SSP1-2.6)
RCP2.6
C2
return warming to 1.5°C (>50%)
after a high overshoot
C3
limit warming to 2°C (>67%)
C... |
where ‘SSPx’ refers to the Shared Socio-economic Pathway or ‘SSP’ describing the socio-economic trends
underlying the scenario, and ‘y’ refers to the approximate level of radiative forcing (in watts per square metre, or Wm–2) resulting from the
scenario in the year 2100.
** The AR5 scenarios (RCPy), which partly info... |
66
Section 2
Section 1
Section 2
Cross-Section Box.2 Figure 1: Schematic of the AR6 framework for assessing future greenhouse gas emissions, climate change,
risks, impacts and mitigation. Panel (a) The integrated framework encompasses socio-economic development and policy, emissions pathways
and global surface temper... |
67
Section 3
Long-Term Climate and
Development Futures |
68
Section 3
Section 1
Section 3
Section 3: Long-Term Climate and Development Futures
3.1 Long-Term Climate Change, Impacts and Related Risks
Future warming will be driven by future emissions and will affect all major climate system components, with
every region experiencing multiple and co-occurring changes. Many cli... |
Long-term Climate Change
The uncertainty range on assessed future changes in global
surface temperature is narrower than in the AR5. For the first
time in an IPCC assessment cycle, multi-model projections of global
surface temperature, ocean warming and sea level are constrained
using observations and the assessed c... |
{WGI SPM B.1.1, WGI Table SPM.1, WGI Figure
SPM.4} (Cross-Section Box.2 Figure 1)
Modelled pathways consistent with the continuation of policies
implemented by the end of 2020 lead to global warming of
3.2 [2.2 to 3.5]°C (5–95% range) by 2100 (medium confidence)
(see also Section 2.3.1). Pathways of >4°C (≥50%) by 2... |
{WGIII SPM C.1.3}
112 Understanding of climate processes, the instrumental record, paleoclimates and model-based emergent constraints (see Annex I: Glossary). {WGI SPM footnote 21}
113 The best estimates [and very likely ranges] for the different scenarios are: 1.4 [1.0 to 1.8]°C (SSP1-1.9); 1.8 [1.3 to 2.4]°C (SSP1-2... |
In all scenarios considered by WGI except the very high emissions scenario, the midpoint of the
first 20-year running average period during which the assessed global warming reaches 1.5°C lies in the first half of the 2030s. In the very high GHG emissions scenario, this
mid-point is in the late 2020s. The median five-ye... |
The best estimate of reaching 1.5°C of global
warming lies in the first half of the 2030s in most of the considered
scenarios and modelled pathways114. In the very low GHG emissions
scenario (SSP1-1.9), CO2 emissions reach net zero around 2050 and the
best-estimate end-of-century warming is 1.4°C, after a temporary ... |
69
Long-Term Climate and Development Futures
Section 3
policies limit this additional warming and lead to strong benefits
for air quality (high confidence). In high and very high GHG
emissions scenarios (SSP3-7.0 and SSP5-8.5), combined changes
in SLCF emissions, such as CH4, aerosol and ozone precursors, lead to a
n... |
{WGI SPM D.1.7, WGI Box TS.7} (Cross-Section Box.2)
Continued GHG emissions will further affect all major climate
system components, and many changes will be irreversible on
centennial to millennial time scales. Many changes in the climate
system become larger in direct relation to increasing global warming.
With e... |
The portion
of global land experiencing detectable changes in seasonal mean
precipitation is projected to increase (medium confidence) with more
variable precipitation and surface water flows over most land regions
within seasons (high confidence) and from year to year (medium
confidence). Many changes due to past and... |
Increases in hot and decreases in
cold climatic impact-drivers, such as temperature extremes, are
projected in all regions (high confidence). At 1.5°C global warming,
heavy precipitation and flooding events are projected to intensify
and become more frequent in most regions in Africa, Asia (high
confidence), North Am... |
70
Section 3
Section 1
Section 3
2011-2020 was
around 1.1°C warmer
than 1850-1900
the last time global surface temperature was sustained
at or above 2.5°C was over 3 million years ago
4°C
The world at
2°C
The world at
1.5°C
+
+
1
0
The world at
3°C
The world at
small absolute
changes may
appear large as
% or σ ch... |
change (%)
-40 -30 -20 -10
0 10 20 30 40
+
+
change (°C)
0
1
2
3
4
5
6
7
-1.5
-1.0
-0.5
0
0.5
1.0
1.5
change (σ)
With every increment of global warming, regional changes in mean
climate and extremes become more widespread and pronounced
Figure 3.1: Projected changes of annual maximum daily temperature, ann... |
71
Long-Term Climate and Development Futures
Section 3
3.1.2 Impacts and Related Risks
For a given level of warming, many climate-related risks are
assessed to be higher than in AR5 (high confidence). Levels of
risk120 for all Reasons for Concern121 (RFCs) are assessed to become high
to very high at lower global warm... |
Climate-related risks to health,
livelihoods, food security, water supply, human security, and economic
growth are projected to increase with global warming of 1.5°C. In
terrestrial ecosystems, 3 to 14% of the tens of thousands of species
assessed will likely face a very high risk of extinction at a GWL of 1.5°C.
... |
{WGII SPM B.3, WGII SPM B.4.1, WGII TS.C.4.2; SR1.5 SPM A.3,
SR1.5 SPM B.4.2, SR1.5 SPM B.5, SR1.5 SPM B.5.1} (Figure 3.3)
At 2°C of global warming, overall risk levels associated with the unequal
distribution of impacts (RFC3), global aggregate impacts (RFC4) and
large-scale singular events (RFC5) would be transiti... |
{WGII Figure SPM.3}
121 The Reasons for Concern (RFC) framework communicates scientific understanding about accrual of risk for five broad categories (WGII Figure SPM.3). RFC1: Unique and
threatened systems: ecological and human systems that have restricted geographic ranges constrained by climate-related conditions and... |
For further explanations of global
risk levels and Reasons for Concern, see WGII TS.AII. {WGII Figure SPM.3}
changes in food availability and diet quality are estimated to increase
nutrition-related diseases and the number of undernourished people,
affecting tens (under low vulnerability and low warming) to hundreds... |
For example, very high extinction risk for endemic
species in biodiversity hotspots is projected to increase at least tenfold
if warming rises from 1.5°C to 3°C (medium confidence). Projected
increases in direct flood damages are higher by 1.4 to 2 times at 2°C
and 2.5 to 3.9 times at 3°C, compared to 1.5°C global wa... |
72
Section 3
Section 1
Section 3
Projected adverse impacts and related losses and damages from
climate change escalate with every increment of global warming
(very high confidence), but they will also strongly depend on
socio-economic development trajectories and adaptation actions
to reduce vulnerability and exposu... |
Many regions are projected to experience an increase in
the probability of compound events with higher global warming, such
as concurrent heatwaves and droughts, compound flooding and fire
weather. In addition, multiple climatic and non-climatic risk drivers
such as biodiversity loss or violent conflict will interact,... |
SRM has the potential to offset warming within one or two decades
and ameliorate some climate hazards but would not restore climate to
a previous state, and substantial residual or overcompensating climate
change would occur at regional and seasonal scales (high confidence).
Effects of SRM would depend on the specifi... |
73
Long-Term Climate and Development Futures
Section 3
c1) Maize yield4
c2) Fisheries yield5
Changes (%) in
maximum catch
potential
Changes (%) in yield
-20
-10
-3
-30
-25
-15
-35%
+20
+30
+35%
+10
+3
+25
+15
1
0 days
300
100
200
10
150
250
50
365 days
0.1
0%
80
10
40
1
20
60
5
100%
Areas with model disagreement
... |
Models do not represent changes in fishing activities and some extreme climatic
conditions. Projected changes in the Arctic regions have low confidence due to uncertainties associated with modelling multiple interacting
drivers and ecosystem responses.
4Projected regional impacts reflect biophysical responses to changin... |
74
Section 3
Section 1
Section 3
Figure 3.2: Projected risks and impacts of climate change on natural and human systems at different global warming levels (GWLs) relative to 1850-1900 levels.
Projected risks and impacts shown on the maps are based on outputs from different subsets of Earth system models that were used... |
Interquartile ranges of WGLs by 2081–2100
under RCP2.6, RCP4.5 and RCP8.5. The presented index is consistent with common features found in many indices included within WGI and WGII assessments. (c) Impacts
on food production: (c1) Changes in maize yield at projected GWLs of 1.6°C to 2.4°C (2.0°C), 3.3°C to 4.8°C (4.1... |
Hatching indicates areas where <70% of the climate-crop model
combinations agree on the sign of impact. (c2) Changes in maximum fisheries catch potential by 2081–2099 relative to 1986-2005 at projected GWLs of 0.9°C to 2.0°C (1.5°C)
and 3.4°C to 5.2°C (4.3°C). GWLs by 2081–2100 under RCP2.6 and RCP8.5. Hatching indica... |
75
Long-Term Climate and Development Futures
Section 3
Salt
marshes
Rocky
shores
Seagrass
meadows
Epipelagic
Warm-water
corals
Kelp
forests
AR5 AR6
AR5 AR6
AR5 AR6
AR5 AR6
AR5 AR6
Global surface temperature change
relative to 1850–1900
Global Reasons for Concern (RFCs)
in AR5 (2014) vs. AR6 (2022)
°C
0
1
1.5
2
3
4
5
0... |
increase in the
length of fire season
e.g. over 100 million
additional people
exposed
0
–1
1950
2000 2015
2050
1
2
3
4
50
100
0
75
25
Resource-rich
coastal cities
Large tropical
agricultural
deltas
Arctic
communities
Urban
atoll islands
r
R
Maximum potential
response
No-to-moderate
response
r
R
r
R
r
R
r
R
Global mea... |
coral
reefs decline
>99%
e.g. coral
reefs decline
by 70–90%
Land-based systems
Ocean/coastal ecosystems
Food insecurity
(availability, access)
a) High risks are now assessed to occur at lower global warming levels
The SSP1 pathway illustrates
a world with low population
growth, high income, and
reduced inequalit... |
76
Section 3
Section 1
Section 3
0
1
1.5
2
3
4
0
1
1.5
2
3
4
°C
°C
0
1
1.5
2
3
4
0
1
1.5
2
3
4
°C
°C
Europe -Risks to people, economies and infrastructures due to coastal and inland flooding
-Stress and mortality to people due to increasing temperatures and heat extremes
-Marine and terrestrial ecosystems disruptions
-W... |
risk to food security and economic disruption due to
destruction of settlements and infrastructure
-Economic decline and livelihood failure of fisheries, agriculture, tourism and from
biodiversity loss from traditional agroecosystems
-Reduced habitability of reef and non-reef islands leading to increased displacement... |
especially in coastal cities and settlements
-Biodiversity loss and habitat shifts as well as associated disruptions in dependent
human systems across freshwater, land, and ocean ecosystems
-More frequent, extensive coral bleaching and subsequent coral mortality induced by
ocean warming and acidification, sea level ri... |
and degraded water quality
-Risk to food and nutritional security through changes in agriculture, livestock, hunting,
fisheries, and aquaculture productivity and access
-Risks to well-being, livelihoods and economic activities from cascading and
compounding climate hazards, including risks to coastal cities, settleme... |
The development of synthetic diagrams for Small
Islands, Asia and Central and South America was limited due to the paucity of adequately downscaled climate projections, with
uncertainty in the direction of change, the diversity of climatologies and socioeconomic contexts across countries within a region, and
the res... |
77
Long-Term Climate and Development Futures
Section 3
Figure 3.3: Synthetic risk diagrams of global and sectoral assessments and examples of regional key risks. The burning embers result from a literature based
expert elicitation. Panel (a): Left - Global surface temperature changes in °C relative to 1850–1900. These... |
Lines connect the midpoints of the transition from moderate to high risk across AR5 and AR6. Panel (b): Risks for
land-based systems and ocean/coastal ecosystems. Diagrams shown for each risk assume low to no adaptation. Text bubbles indicate examples of impacts at a given warming level.
Panel (c): Left - Global mean... |
“No-to-moderate response” describes efforts as of today (i.e., no further significant action or new types of actions).
“Maximum potential response” represents a combination of responses implemented to their full extent and thus significant additional efforts compared to today, assuming minimal
financial, social and poli... |
Right - Risks associated with food security due to climate change and patterns of socio-economic development. Risks to food security include availability and
access to food, including population at risk of hunger, food price increases and increases in disability adjusted life years attributable to childhood underweigh... |
As warming levels increase, so do the risks of species extinction or
irreversible loss of biodiversity in ecosystems such as forests (medium
confidence), coral reefs (very high confidence) and in Arctic regions
(high confidence). Risks associated with large-scale singular events
or tipping points, such as ice sheet in... |
Global mean sea level rise will continue in the 21st
century (virtually certain), with projected regional relative sea level rise
within 20% of the global mean along two-thirds of the global coastline
(medium confidence). The magnitude, the rate, the timing of threshold
exceedances, and the long-term commitment of s... |
Over the next 2000 years, global mean sea level will rise by about
2 to 3 m if warming is limited to 1.5°C and 2 to 6 m if limited to 2°C
(low confidence). Projections of multi-millennial global mean sea level
rise are consistent with reconstructed levels during past warm climate
periods: global mean sea level was v... |
78
Section 3
Section 1
Section 3
impacts on populations in low elevation coastal zones. If global
warming increases, some compound extreme events124 will
become more frequent, with higher likelihood of unprecedented
intensities, durations or spatial extent (high confidence). The
Atlantic Meridional Overturning Circ... |
At higher levels
of warming, losses and damages will increase, and additional human and natural systems will reach adaptation
limits. Integrated, cross-cutting multi-sectoral solutions increase the effectiveness of adaptation. Maladaptation
can create lock-ins of vulnerability, exposure and risks but can be avoided ... |
Globally, adaptation options related
to agroforestry and forestry have a sharp decline in effectiveness at 3°C,
with a substantial increase in residual risk (medium confidence).
{WGII SPM C.2, WGII SPM C.2.1, WGII SPM C.2.5, WGII SPM C.2.10,
WGII Figure TS.6 Panel (e), 4.7.2}
With increasing global warming, more li... |
Above 1.5°C global
warming level, limited freshwater resources pose potential hard limits
for small islands and for regions dependent on glacier and snow melt
124 See Annex I: Glossary. Examples of compound extreme events are concurrent heatwaves and droughts or compound flooding. {WGI SPM Footnote 18}
125 There are ... |
For example, inclusive, integrated
and long-term planning at local, municipal, sub-national and national
scales, together with effective regulation and monitoring systems
and financial and technological resources and capabilities foster
urban and rural system transition. There are a range of cross-cutting
adaptatio... |
79
Long-Term Climate and Development Futures
Section 3
long-term planning and implementation of adaptation actions with
benefits to many sectors and systems. (high confidence) {WGII SPM C.4,
WGII SPM.C.4.1, WGII SPM C.4.2, WGII SPM C.4.3}
Sea level rise poses a distinctive and severe adaptation challenge
as it implies... |
80
Section 3
Section 1
Section 3
2020
2100
2050
2150
Ecosystem-based adaptation
Sediment-based protection
Elevating houses
Protect levees
Protect barriers
Planned relocation
≈30 years
≈50 years
≥100 years
≈100 years
≈15 years
≈15 years
Indicative time for planning and implementation
Typical intended lifetime of measure... |
Losses of coastal
ecosystems and
ecosystem services
Groundwater
salinisation
Flooding and damages
to coastal infrastructure
Global sea level rise
in meters relative to 1900
sea level
rise by 2100
depends on
the emissions
scenario
this can be chronic high
tide flooding and extreme
flooding during storms
lik... |
81
Long-Term Climate and Development Futures
Section 3
Figure 3.4: Observed and projected global mean sea level change and its impacts, and time scales of coastal risk management. Panel (a): Global mean sea
level change in metres relative to 1900. The historical changes (black) are observed by tide gauges before 1992 ... |
Changes relative to 1900 are calculated by adding 0.158
m (observed global mean sea level rise from 1900 to 1995-2014) to simulated changes relative to 1995-2014. The future changes to 2300 (bars) are based on literature assessment,
representing the 17th–83rd percentile range for SSP1-2.6 (0.3 to 3.1 m) and SSP5-8.5 ... |
82
Section 3
Section 1
Section 3
3.3 Mitigation Pathways
Limiting human-caused global warming requires net zero anthropogenic CO2 emissions. Pathways consistent
with 1.5°C and 2°C carbon budgets imply rapid, deep, and in most cases immediate GHG emission reductions in
all sectors (high confidence). Exceeding a warming... |
The stronger the reductions in non-CO2 emissions the lower the
resulting temperatures are for a given RCB or the larger RCB for the
same level of temperature change. For instance, the RCB for limiting
warming to 1.5°C with a 50% likelihood could vary between 300 to
600 GtCO2 depending on non-CO2 warming129. Limitin... |
Most countries report their anthropogenic
land CO2 fluxes including fluxes due to human-caused environmental change (e.g., CO2 fertilisation) on ‘managed’ land in their National GHG inventories. Using emissions
estimates based on these inventories, the remaining carbon budgets must be correspondingly reduced. {WGIII SP... |
{WGI SPM D.1.3}
131 Uncertainties for total carbon budgets have not been assessed and could affect the specific calculated fractions.
132 See footnote 131.
133 These projected adjustments of carbon sinks to stabilisation or decline of atmospheric CO2 concentrations are accounted for in calculations of remaining carbon... |
While
natural land and ocean carbon sinks are projected to take up, in absolute
terms, a progressively larger amount of CO2 under higher compared to
lower CO2 emissions scenarios, they become less effective, that is, the
proportion of emissions taken up by land and ocean decreases with
increasing cumulative net CO... |
83
Long-Term Climate and Development Futures
Section 3
0
1000
500
1500
2000
2020
a) Carbon budgets and emissions
Lifetime emissions from fossil fuel
infrastructure without additional abatement,
if historical operating patterns are maintained
2020–2030 CO2 emissions
assuming constant at 2019 level
1.5°C (>50% chance)... |
Panel (a) Assessed remaining carbon budgets to limit
warming more likely than not to 1.5°C, to 2°C with a 83% and 67% likelihood, compared to cumulative emissions corresponding to constant 2019 emissions until 2030, existing and
planned fossil fuel infrastructures (in GtCO2). For remaining carbon budgets, thin lines ... |
84
Section 3
Section 1
Section 3
2030
43
[34-60]
41
[31-59]
48
[35-61]
23
[0-44]
21
[1-42]
27
[13-45]
5
[0-14]
10
[0-27]
2040
2050
84
[73-98]
85
[72-100]
84
[76-93]
75
[62-91]
64
[53-77]
63
[52-76]
68
[56-83]
49
[35-65]
29
[11-48]
5
[-2 to 18]
Net ze... |
..]
2065-2070
(97%)
[2055-2090]
2080-2085
(86%)
[2065-...]
Net zero
GHGs
(5)
(% net zero
pathways)
2095-2100
(52%)
[2050-...]
2070-2075
(100%)
[2050-2090]
...-...
(0%)
[...-...]
2070-2075
(87%)
[2055-...]
...-...
(30%)
[2075-...]
...-...
(24%)
[2080-...]
...-...
(41%)
[2075-...]
...-...
(31%)
[2075-... |
6
1.6
1.6
1.7
1.7
1.7
1.8
1.9
2100
1.3
1.2
1.4
1.4
1.6
1.6
1.6
1.8
<1.5°C
38
[33-58]
38
[34-60]
37
[33-56]
24
[15-42]
20
[13-41]
21
[14-42]
17
[12-35]
11
[7-22]
<2.0°C
90
[86-97]
90
[85-97]
89
[87-96]
82
[71-93]
76
[68-91]
78
[69-91]
73
[67-87]
59
[50-77]
<3.0°C
100
[99-100]
100
[99-... |
with the 5th-95th percentile
interval in square brackets.
Percentage of net zero
pathways is denoted in
round brackets.
Three dots (…) denotes net
zero not reached for that
percentile.
Median cumulative net CO2
emissions across the
projected scenarios in this
category until reaching
net-zero or until 2100, w... |
Detailed
likelihood definitions are
provided in SPM Box1.
The five illustrative scenarios
(SSPx-yy) considered by AR6
WGI and the Illustrative
(Mitigation) Pathways
assessed in WGIII are
aligned with the tempera-
ture categories and are
indicated in a separate
column. Global emission
pathways contain region... |
1-1.5]
[1.1-1.4]
[1.3-1.5]
[1.2-1.5]
[1.5-1.8]
[1.5-1.8]
[1.5-1.7]
[1.5-2.0]
[1.9-2.5]
[2.4-2.9]
2.2
2.1
2.7
4
[0-10]
37
[18-59]
[83-98]
71
0
[0-0]
8
[2-18]
[53-88]
Category/
subset
label
limit
warming
to 1.5°C
(>50%)
with no
or
limited
overshoot
…
with
net zero
GHGs
…
without
net zero
GHGs
return
warmi... |
5°C
(>50%)
limit
warming
to 3°C
(>50%)
[212]
Category
(2)
[# pathways]
C1
[97]
C1a
[50]
C1b
[47]
C2
[133]
C3
[311]
C3a
[204]
C3b
[97]
C4
[159]
C5
C6
[97]
Table 3.1: Key characteristics of the modelled global emissions pathways. Summary of projected CO2 and GHG emissions, projected net zero timings and the resulting ... |
Values in the table refer to the 50th and [5–95th] percentile values across the pathways falling within a given category as defined in WGIII Box SPM.1.
The three dots (…) sign denotes that the value cannot be given (as the value is after 2100 or, for net zero, net zero is not reached). Based on the assessment of climat... |
85
Long-Term Climate and Development Futures
Section 3
3.3.2 Net Zero Emissions: Timing and Implications
From a physical science perspective, limiting human-caused
global warming to a specific level requires limiting cumulative
CO2 emissions, reaching net zero or net negative CO2 emissions,
along with strong reductio... |
This is different from achieving net zero GHG
emissions, where metric-weighted anthropogenic GHG emissions (see
Cross-Section Box.1) equal CO2 removal (high confidence). Emissions
pathways that reach and sustain net zero GHG emissions defined by the
100-year global warming potential imply net negative CO2 emissions
... |
Global net zero
CO2 emissions are reached in the early 2050s in pathways that limit
warming to 1.5°C (>50%) with no or limited overshoot, and around
the early 2070s in pathways that limit warming to 2°C (>67%). While
non-CO2 GHG emissions are strongly reduced in all pathways that limit
warming to 2°C (>67%) or low... |
Negative values (e.g., in C5, C6) represent
an increase in emissions. The modelled GHG emissions in 2019 are 55 [53–58] GtCO2-eq, thus within the uncertainty ranges of estimates for 2019 emissions [53-66] GtCO2-eq
(see 2.1.1).
4 Emissions milestones are provided for 5-year intervals in order to be consistent with th... |
86
Section 3
Section 1
Section 3
2000
2020
2040
2060
2080
2100
0
20
40
60
2000
2020
2040
2060
2080
2100
0
20
40
60
2000
2020
2040
2060
2080
2100
2000
2020
2040
2060
2080
2100
Gigatons of CO2 equivalent per year (GtCO2-eq/yr)
CO2
GHG
CO2
GHG
CH4
CO2
GHG
CH4
a) While keeping warming to 1.5°C
(>50%) with no or limite... |
Top row: GHG, CO2 and CH4 emissions over time (in
GtCO2eq) with historical emissions, projected emissions in line with policies implemented until the end of 2020 (grey), and pathways consistent with temperature goals in colour
(blue, purple, and brown, respectively). Panel (a) (left) shows pathways that limit warming... |
Reductions
in GHG emissions in industry, transport, buildings, and urban areas
can be achieved through a combination of energy efficiency and
conservation and a transition to low-GHG technologies and energy
carriers (see also 4.5, Figure 4.4). Socio-cultural options and behavioural
change can reduce global GHG emis... |
The technical geological storage capacity is estimated to be on the order of 1000 GtCO2, which is more than the CO2 storage requirements through
2100 to limit global warming to 1.5°C, although the regional availability of geological storage could be a limiting factor. If the geological storage site is appropriately se... |
87
Long-Term Climate and Development Futures
Section 3
from zero or low-carbon sources in 2050, such as renewables or
fossil fuels with CO2 capture and storage, combined with increased
electrification of energy demand. Such pathways meet energy service
demand with relatively low energy use, through e.g., enhanced ene... |
All assessed modelled pathways
that limit warming to 2°C (>67%) or lower by 2100 include land-based
mitigation and land-use change, with most including different
combinations of reforestation, afforestation, reduced deforestation, and
bioenergy. However, accumulated carbon in vegetation and soils is at
risk from f... |
CDR methods vary in terms
of their maturity, removal process, time scale of carbon storage, storage
medium, mitigation potential, cost, co-benefits, impacts and risks, and
governance requirements (high confidence). Specifically, maturity
ranges from lower maturity (e.g., ocean alkalinisation) to higher
maturity (e.g.... |
Methods and levels of CDR
deployment in global modelled mitigation pathways vary depending on
assumptions about costs, availability and constraints (high confidence).
{WGIII SPM C.3.5, WGIII SPM C.11.1, WGIII SPM C.11.4}
137 Limited overshoot refers to exceeding 1.5°C global warming by up to about 0.1°C, high oversho... |
Compared to pathways without overshoot, societies and ecosystems
would be exposed to greater and more widespread changes in climatic
impact-drivers, such as extreme heat and extreme precipitation, with
increasing risks to infrastructure, low-lying coastal settlements, and
associated livelihoods (high confidence). Ov... |
{WGI SPM C.2, WGI SPM C.2.1,
WGI SPM C.2.3; WGII SPM B.6, WGII SPM B.6.1, WGII SPM B.6.2; SR1.5 3.6}
The larger the overshoot, the more net negative CO2 emissions needed
to return to a given warming level (high confidence). Reducing global
temperature by removing CO2 would require net negative emissions of
220 GtCO2... |
88
Section 3
Section 1
Section 3
3.4.1 Synergies and trade-offs, costs and benefits
Mitigation and adaptation options can lead to synergies and
trade-offs with other aspects of sustainable development
(see also Section 4.6, Figure 4.4). Synergies and trade-offs depend
on the pace and magnitude of changes and the deve... |
There are potential synergies between sustainable development and,
for instance, energy efficiency and renewable energy. (high confidence)
{WGIII SPM C.4.2, WGIII SPM D.1.3}
For agriculture, land, and food systems, many land management
options and demand-side response options (e.g., dietary choices,
reduced post-harv... |
(high confidence) {WGII SPM B.5.4, WGII SPM C.2.4;
WGIII SPM C.11.2; SR1.5 SPM C.3.4, SR1.5 SPM C.3.5; SRCCL SPM B.3,
SRCCL SPM B.7.3, SRCCL Figure SPM.3}
139 The impacts, risks, and co-benefits of CDR deployment for ecosystems, biodiversity and people will be highly variable depending on the method, site-specific conte... |
The aggregate effects of climate change
mitigation on global GDP (excluding damages from climate change and
adaptation costs) are small compared to global projected GDP growth.
Projected estimates of global aggregate net economic damages and
the costs of adaptation generally increase with global warming level.
(hi... |
{WGII SPM B.4, WGII
SPM B.6; WGIII SPM C.12, WGIII SPM C.12.2, WGIII SPM C.12.3 WGIII Box TS.7;
SR1.5 SPM B.3, SR1.5 SPM B.5, SR1.5 SPM B.6}
Considering other sustainable development dimensions, such as the
potentially strong economic benefits on human health from air quality
improvement, may enhance the estimated b... |
Accelerated and equitable mitigation and adaptation bring benefits from avoiding damages from climate
change and are critical to achieving sustainable development (high confidence). Climate resilient development138
pathways are progressively constrained by every increment of further warming (very high confidence). There... |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.