Turn Down The Heat: Why a 4C Warmer World Must Be Avoided

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Information about Turn Down The Heat: Why a 4C Warmer World Must Be Avoided

Published on October 23, 2013

Author: theclimateinstitute



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.

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


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

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. 5

Consistent global warming in line with IPCC projections (Rahmstorf et al., 2012)

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 7

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 8

Ocean warming has continued over past 10-15 years Change in global average upper ocean heat content (1022 J) 9

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 10

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 11

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 12

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.

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

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

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

Reducing ocean acidification damages Mitigation

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

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

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.

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.

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.

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.

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

Results from World Bank Study of three regions 25

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

% 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).

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

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. 29

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 30

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. 31

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 32

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.

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

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

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” 36

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.

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.

Australian climate policy in context

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 40

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. 41

Additional slides 42

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