Bill Hare, CEO of Climate Analytics, summarises the World Bank report Turn Down The Heat: Why a 4C Warmer World Must Be Avoided for The Climate Institute's Boardroom Lunch Conversation on 21 October 2013.

1. Turn Down The Heat: Why a 4oC
World Must Be Avoided
Bill Hare, CEO, Climate Analytics gGmbH, Berlin
The Climate Institute
Boardroom Lunch Conversation
Monday 21 October 2013

3. 3

4. 4°C – World Bank Report
• Observed
• Ten times more area experiences extreme heat
compared to 40 years ago
• Significant economic damages on the poorest countries
from high temperatures over last few decades
• Rate of sea level rise now well above range projected
in IPCC AR4 and TAR assessment reports
• Regional sea-level rise since 1950s higher than the
global mean in Pacific

5. IPCC AR5: Greater evidence of human
influence since IPCC AR4 in 2007
• Extremely likely that human influence has been
the dominant cause of the observed warming
since the mid-20th century.
• The evidence for human influence has grown
since AR4.
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6. Consistent global warming in line with IPCC
projections
(Rahmstorf et al., 2012)

7. IPCC AR5: Has the warming slowed
down?
• Observations show slower rate of warming over
the past 10-15 year, but…
– Past decade: warmest on record
– Last three decades each warmer than the other and warmer than
any since 1850.
• IPCC WGI findings repudiate claims of climate
science denialists that recent reduction in rate of
warming undermines climate science
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8. AR5: Recent warming ”slowdown” or “hiatus”
• Past decade: warmest
on record
• Periods of slowdowns
and accelerations
occur regularly
• These are related to
variations in forcing
(e.g. volcanic
eruptions, solar
activity) and to
internal redistribution
of heat in ocean,
causing natural
variations of surface
warming, and
Global Average surface temperature (°C)
compared to average over 1850-2012
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9. Ocean warming has continued over past
10-15 years
Change in global average upper
ocean heat content (1022 J)
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10. IPCC AR5: How warm will it get?
• Likely to exceed 1.5°C (and 2°C) for all new IPCC
scenarios except the lowest (called RCP2.6)
• Warming will continue beyond 2100 under all RCP scenarios
except RCP2.6
• Warming likely to exceed 4°C by 2100 for highest
of new IPCC scenarios (RCP8.5)
• If carbon cycle feedbacks include range of
warming is higher
• 2.5-5.6°C in 2081-2100 above 1986-2005 or 3.1-6.2°C above
pre-industrial
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11. Heading towards 4oC
• Recent greenhouse gas emission trends and
recent emission projections imply higher 21st
century emission levels
– International Energy Agency’s 2012 assessment
indicated that in the absence of further
mitigation action there is a 40% chance of
warming exceeding 4°C by 2100.
• a 10% chance of exceeding 5°C
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12. IPCC AR5: Sea level rise
• Global mean sea level will continue to rise during
the 21st century
– Under all RCP scenarios the rate of sea level rise will
very likely exceed that observed during 1971–2010
– 0.5 to 1m rise by 2100 projected for highest IPCC
scenario (RCP8.5)
• Rate of rise during 2081–2100 of 8 to 16 mm/yr
– 0.26 to 0.55m rise by 2100 projected for lowest IPCC
scenario (RCP2.6)
• Relative to 1986–2005
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13. Caution: Sea-level rise risk
• Uncertainty still considerable
• High end of uncertainty is hard to establish as
recognised in AR5:
– “… it has been concluded that there is currently insufficient
evidence to evaluate the probability of specific levels above the
assessed likely range. ” (IPCC AR5 WG1 SPM)
• Within a 2000 year timeframe about 2.3m of sea
level rise per oC of global warming can be
expected.

14. Observed sea level change at top of range
projected in IPCC assessment reports

15. 4°C – World Bank Report
• Projected (World Bank: 4°C report)
• Warming >3°C by 2100 and possibly >4°C by 2100
• One in five chance with present pledges of above 4°C
• One metre of sea level rise by 2100
• Further rise of several metres in following centuries
• Regional sea-level rise about 20% larger in tropical
oceans than global mean

16. 4°C – World Bank Report
• Warming more pronounced over land
• Regional projections >6°C in Africa, the Middle East,
& Amazon)
• Warming of 2+°C projected to lead to severe
and widespread droughts over many densely
populated areas
• e.g. Europe, eastern USA, South East Asia, and Brazil
• Ocean acidification rises to levels higher than
known from Earth history leading to major
damages to ocean food production

17. Reducing ocean acidification damages
Mitigation

18. 4°C – World Bank Report
• Dramatic increase in intensity and frequency of
high-temperature extremes
• All tropical islands in the Pacific, tropical South
America, central Africa likely to regularly experience
heat waves of unprecedented magnitude and
duration.
• Coolest summer months in 2080–2100 in most
continental regions substantially hotter than the
warmest experience today

19. 4°C – World Bank Report
Societal and ecosystem impacts: Poor affected most
• Sea-level rise potentially severe for small island states
and cities highly vulnerable to extreme flooding
• Water scarcity substantially amplified
– (particularly Northern & Eastern Africa, Middle East, & South Asia)
• Significant risk for global food security:
• large negative crop yield impacts anticipated in India, Africa, but
also United States & Australia

20. 4°C – World Bank Report
• Societal and ecosystem impacts:
– Ocean acidification and warming leads to regional
extinction of entire coral reef ecosystems:
• impacts on coastal and fishing communities and
tourism
– Likely large-scale biodiversity loss: dramatic
reduction in ecosystem services.

21. Rapidly emerging risks
• Disruption of ocean and ecosystems due to
warming and ocean acidification
– Interfering with global ocean production and damaging marine
ecosystems.
• By 2100 surface waters of the ocean could be nearly 150 percent more acidic,
resulting in a pH that the oceans haven’t experienced for more than 20 million
years.
– Already being observed
• Observed reduction in the habitat for tropical pelagic fishes (e.g tuna).
– Reductions in oceanic food production could have very negative
consequences for food security.

22. Rapidly emerging risks
• Collapse of coral reef systems in the next several
decades.
– Combined effects of ocean warming and acidification
– Limiting warming to 1.5oC may not be sufficient to protect majority of
reefs
– Substantial losses of coral reefs for 1.5-2°C from both heat and ocean
acidification effects, with a majority coral systems no longer viable at
current locations
• Most coral reefs appear unlikely to survive by the time 4°C warming is reached.

23. Probability of severe bleaching during
a given year increase rapidly with
warming
1.6oC and ca 450 ppm
CO2
2.3oC and ca 550 ppm
CO2
Meissner, K. J., T. Lippmann and A. Sen Gupta (2012). "Large-scale stress factors
affecting coral reefs: open ocean sea surface temperature and surface seawater
aragonite saturation over the next 400 years." Coral Reefs 31: 309-319.

24. Small Island States
• Combined effects of sea level rise and other climate changes
likely to have far ranging adverse consequences with
increasing loss and damages
– Loss of shoreline, saltwater intrusion and inundation of
settled and agricultural areas and impacts on
infrastructure.
– Increased vulnerability to diseases
– Economic decline due to loss of tourism assets, population
displacement and decreased agricultural productivity

25. Results from World Bank Study of
three regions
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26. Key Findings Across the Regions
• Unusual and unprecedented heat extremes projected
to increase substantially, with adverse effects on
humans and ecosystems
• Water availability expected to decline by 20% for many
regions under a 2°C warming and 50% under a 4°C
warming
• Agricultural yield and nutritional quality projected to
decrease in the three regions studied under a 1.5-2°C
world, with negative influences on economic growth
and poverty eradication

27. % of GLOBAL land area
with
heat extremes in the
summer months
Rapid rise between
2030s (around 1.5°C)
and 2040s (around 2°C)
but large further
increase towards 4°C
Multi-model mean (thick line),
individual models (thin lines)
above (JJA) RCP2.6 (left) and
RCP8.5 (right).

28. Key Findings Across the Regions
• Terrestrial ecosystems: warming to shift systems, alter species
composition leading to extinction
– Savanna ecosystems particularly exposed as early as the 2030s
• Sea-level rise: more rapid than previously projected
– 50 cm by the 2050s may be unavoidable (results of past emissions).
– Limiting warming to 2°C may limit global rise to about 70-100cm by
2100.
– Higher Sea-level rise near Equator in combination with storm surges
and tropical cyclones will increase risks

29. Agricultural and Nutritional Quality
• Crop production systems under increasing
pressure to meet growing global demand.
• Significant crop yield impacts already being felt at +0.8 °C
warming.
• Higher atmospheric levels of CO2 could result in lower
protein levels of some grain crops.
• Warming above 1.5-2°C increases risk of reduced
crop yields and production losses in Sub-Saharan
Africa and South Asia.
• Likely strong, adverse repercussions on food security and
negative influence on economic growth and poverty
reduction in impacted regions.
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30. Food security threatened:
Severe decrease in per capita calories availability
3,000
-21,4%
Production in 000,000 tons
Per capita calories availability
2,500
2,000
2010
1,500
2050 (no climate change)
2050 (with climate change)
1,000
500
Only -8.5%
Total production (000,000 tons)
Per capita availability (kcal/cap/year) for 2050 projected
population
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31. Development Implications
• Sub-Saharan Africa´s food production systems are increasingly at
risk
– Significant yield reductions under 2°C warming, strong adverse
repercussions on food security
• South East Asian rural livelihoods are faced with mounting
pressures as sea levels rise and important marine ecosystem
services lost.
• South Asian populations exposed to increasing risks
– Disturbances to the monsoon system and rising peak temperatures
put water and food resources at severe risk.
– In deltaic areas, populations exposed to multiple threats of increasing
tropical cyclone intensity, sea-level rise, heat extremes and extreme
precipitation.
– Multiple impacts can have severe negative implications for poverty
eradication in the region.
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32. Climate shocks roll back development
• Climate shocks (for example droughts or
cyclones) have the potential to drive poor
households into poverty traps
– Wealthy households - with higher coping capacity (access to
funding, education, or networks) - projected to recover faster
• Climate shocks could potentially increase social
inequalities and roll back development progress
• Assessing socioeconomic and climate
vulnerabilities is crucial for successful adaptation
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33. 4°C – World Bank Report
Conclusions:
• No certainty that adaptation to a 4°C
world is possible
• Warming of 4°C can still be avoided:
studies show technically and
economically feasible pathways to hold
warming likely below 2°C.

34. Urgency of mitigation
• UNEP 2012:
– Current pledges when projected into the future
lead to 3 to 5°C warming
• World Energy Outlook 2012:
– Full lock-in of CO2 emitting infrastructure allowed
for 2°C (450ppm) pathway by 2017

35. Is below 2°C feasible?
• Emissions reductions in 2020 for a 2°C and
1.5°C pathway are similar but diverge rapidly
afterwards.
• Closing the 2020 emissions gap entirely
remains technically and economically feasible
– Can only be achieved by increasing ambition and
action beyond the current pledges

36. Can warming be limited below 1.5oC?
• Lowest of the WGI scenarios (RCP2.6) indicates
global warming can be limited below 1.5°C above
pre-industrial levels
– Emission reduction by 2050 of average 50% (range 14–
96%) relative to 1990 levels needed (RCP2.6)
• Negative emissions may be required after 2050
– “As likely as not that sustained globally negative
emissions will be required to achieve the reductions in
atmospheric CO2 in RCP2.6”
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37. Why are 2020 emission levels important?
UNEP Emissions Gap Report 2012
• Gap between emissions pledges and pathways
towards 1.5 and 2°C increased since last year
by 2 GtCO2e,
• Emissions need to be reduced by about 15% from
present levels by 2020 to be in line with 1.5 or 2°C.
• If emissions too high in 2020 it becomes very
costly and possibly infeasible to meet the
warming goals.

38. Delay possible?
All "later action" pathways indicate urgency
• Studies looking at returning below 1.5°C do not
indicate the luxury of delay
• “Later action" comes at the expense of
– Higher overall costs
– Higher technological dependency
– Pressure on future policy requirements and societal
choices
– Higher climatic risks
• For 1.5°C, immediate action and energy efficiency
are key.

39. Australian climate policy in context
http://www.climateactiontracker.org/

40. Conclusions
• Science shows that failure to reduce CO2
emissions leads into very high-risk territory:
– High potential for societal disruptions
– Rapidly increasing risk of crossing tipping points in
physical, biological and human syste,s
– Will lead us to climate regimes not experienced in
human history
– Knowledge about the precise impacts and risks at
high levels of warming is very incomplete
– Risks rise rapidly with warming
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41. Climate Analytics
Science based policy
to prevent dangerous climate change
Mission: Synthesize and advance scientific knowledge in the
area of climate change and on this basis provide support and
capacity building to stakeholders. By linking scientific and
policy analysis, we provide state-of-the art solutions to global
and national climate change policy challenges.
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42. Additional slides
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