UNFCCC, Paris November The 2 C goal is not safe and 1.5 C has many benefits

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1 UNFCCC, Paris November 2015 The 2 C goal is not safe and 1.5 C has many benefits

2 Key Messages from the UNFCCC Structured Expert Dialogue

3 A long-term global goal defined by a temperature limit serves its purpose well The guardrail concept that a warming limit of 2 or 1.5 guarantees protection from dangerous anthropogenic interference no longer works UNFCCC SED

4 Assessing the adequacy of the long-term global CC goal implies risk assessments and value judgments not only at the global but also at regional and local levels (Risk = probability x consequence) We need benchmarks for sound climate policy in the light of national circumstances UNFCCC SED

5 We know how to measure progress on mitigation but challenges still exist in measuring progress on adaptation The science on 1.5 C warming is less robust than for 2 C or more: is the difference really only a gradual increase in risks or does it include non-linear and threshold effects? UNFCCC SED

6 2 C warming should be a strict upper defence line That defence line should be pushed as low as possible The present 0.8 C warming already challenges the adaptive capacity of societies and ecosystems Limiting warming to 1.5 C provides large benefits in reduced damages, risks and adaptation needs

7 Countering the counter-argument: mitigating for 1.5 C rather than 2 C does not pose greater risks to food security from biofuel competition limiting warming to 1.5 C avoids large risks to food security

8 Recent science - policy discourse: moved from 1.5 to significantly below 2 assumes an overshoot is inevitable wants to return to 1.5 by the end of the Century whether to limit peak, end-of-century or long-term warming is a political question

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10 Rising temperatures are not only an in situ phenomenon but shift transitional zones and increase affected territory in - islands - mountains - high latitudes Regional, national and international concerns need understanding of climate science in a societal context

11 Questions on Mitigation and Adaptation what is the relationship between changing means and extremes? is CC reversible within "human" time scales (buffering)? at what level of CC do irreversible changes occur? what effects of CC are irreversible?

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13 To assess CC impacts and "desirable" limits climate phenomena and their effects must be identified and quantified

14 Drought types: Meteorological drought is measured as the size and duration of a precipitation shortfall Agricultural drought links meteorological drought to plant water demand, soil moisture deficits and agricultural impacts Hydrological drought are effects of meteorological drought on water supply. they lag meteorological drought Irrigation links agricultural and hydrological drought Socio-economic drought are effects on the supply and demand of goods and services American Meteorological Society

15 There are direct effects of mean temperature change zone of maximum freeze-thaw cycles shifts pole-ward and up-slope affecting: - plants (trees) - cropping systems - soil C and N - technical structures (concrete)

16 Alternating warm and freezing weather endangers vegetation, as early plant development may be cut by subsequent frosts - freeze-thaw cycles reduce frost hardening and cause tree dieback - for winter crops this is agravated by lower snow pack - elevated CO 2 increases frost sensitivity Frost damage is an important issue as temperatures rise

17 Increased Cold Damage in a Warming World Gu

18 Gu

19 The University of Illinois warns that field working days are changing the typical planting window for maize will be reduced and shifted by warmer, wetter springs, and drier, hotter summers April and May will be far too wet to work the fields, but a later planting window is risky because of summer droughts new maize cultivars may be needed in the future: longer season (hoping for pollination before the drought) or shorter season (harvested before the drought, sacrificing yield)

20 IPCC models and scenarios fewer cold, and more warm days and nights are very likely at the global scale likely in North America, Europe, and Australia for warming daily extremes there is medium confidence for much of Asia low to medium confidence for Africa and South America - depending on the region low confidence in predictions of El Niño or Monsoon regime changes - even in sign! low confidence for the attribution of changes in tropical cyclone activity - because of incomplete understanding of the physical mechanisms

21 Compare these model predictions to actual events: From 2000 to 2008, Asia had the highest number of climate-related disasters the Americas suffered the highest proportion (54.6%) economic losses, followed by Asia (27.5%) and Europe (15.9%) Africa accounted for only 0.6% of global economic losses - there are clearly problems with predicting but also with measuring climate events and impacts

22 Current disaster impacts vary between regions: Economic losses are higher in developed countries Fatalities and % GDP loss are higher in developing countries but such statistics depend on highly variable data and are affected by few extreme extremes impacts depend on the size of extremes and on return periods

23 What is seen as extreme events depends on vulnerabilities: location - heat wave in Sweden, rainfall on semiarid soils adaptation - agriculture, disease control, urban design, infrastructure extreme impact can be caused by less extreme events: for instance, at the geographical freeze-thaw boundary, freezing rain has brought down power grids

24 discussion: measurements, predictions, experiences, social perceptions and vulnerabilities

25 Types of change IPCC

26 average summer temperatures around the mean blue: observed red: projected 2090 The hottest summer on record in France (2003) was 3.6 above the mean The average for 2090 is projected to be 3.7 above the mean There is a small probability of summers 9.8 above the mean Battisti et al

27 How to quantify extremes? count the number of record-breaking events and examine the count for any trend distinguish hot extremes from cold extremes combine indicators into a single Climate Extremes Index and measure the fraction of a region with high CEI measure economic effects of extremes by an independent index such as insurance payout rarer, extremer events are naturally most difficult to quantify

28 Predicting the incidence of extreme rainfall: absolute humidity increases 7% per 1 C increase absolute (but not relative) humidity increases are significant between 1973 and 2003 globally increased atmospheric moisture content leads to increased precipitation often as extreme rainfall

29 Impacts of CC on agriculture a negative yield response to increased growing season temperatures explains one third of variations in global average yields of the six most widely grown crops. between 1981 and 2002, high temperatures have resulted in annual combined losses for wheat, maize and barley of 40 Mt or US$ 5 billion per year. Lobell and Fields

30 reduction in yield increases Global temperature increase population increase wheat rice maize Regional productivity change temperature increase food security risk

31 CO 2 fertilization vs. CC 1 ppm of CO 2 increase => 0.1% yield increase for C3 crops 35 ppm increase since 1981 should result in 3.5% yield increase but there is a 3% decrease in wheat yield due to climate trends effects of CO 2 and climate have cancelled each other CO 2 benefits do not exceed temperature related losses - even below 2 warming foregone global production of wheat (19 Mt yr -1 ), maize (12 Mt yr -1 ) and (barley 8 Mt yr -1 ) Lobell and Fields

32 Reanalysis of African maize trials: each degree day above 30 C reduced the yield by 1% under optimal rain-fed conditions, and by 1.7% under drought conditions Drought cannot be predicted with confidence under warming, but it will be more severe under higher temperatures these are largely linear effects that have already started - confirming that there is no "guard rail" of 2 or 1.5 C Lobell

33 What are the mechanisms of CC effects on plants?

34 growing degree days "mean daily C above a threshold that permits growth" with its new variant: "the time that foliage is inside the thermal kinetic window" (TKW) Above the TKW ( 35 C), plant growth is reduced because - membrane phase changes (more saturated lipids produced) - RuBisCO enzyme kinetic are rates reduced - starch synthesis is reduced - heat shock proteins (HSP) are produced - heat stress increases N concentration, and quality - reproduction is curtailed

35 In the thermal kinetic window the Michaelis-Menten constant for CO 2 (Km) is minimal and stable RuBisCO (Ribulose-1,5-bisphosphate carboxylase/oxygenase) and other enzyme systems follow this relationship Enzyme kinetics translate temperature effects into non-linear functions of reduced production

36 Temperature dependence of biochemical reaction rate 30 C is a critical zone

37 In addition to inhibition of photosynthesis, heat stress affects phytohormone levels - increases abscisic acid, salicylic acid, and ethylene - decreases cytokinin, auxin and gibberellic acids enzymatic changes cause premature plant senescence abscission of reproductive organs in crops and fruit trees (even tropical trees) heat stress reduces not only seed weight but also vigour and germination, carrying the damage into future seasons

38 All phenological stages are temperature sensitive: development accelerates linarly with degree days, this reduces time for grain filling above 30 degrees the effect becomes non-linear in addition, spikelet formation is most sensitive - damage at this stage reduces grain number above the TKW, a 1 C rise depresses grain yield by 8 to 10% with 3 to 4% less grain weight and 5 to 6% fewer grains

39 Teixeira

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41 Effect of changed temperature and rain on yields Lobell

42 Effect of changed temperature and rain on yields (2) Lobell

43 In summary Heat stress is determined by canopy temperature >30 C which depends on weather, canopy properties, soil moisture >34 C, both development and senescence accelerate reducing grain yields Some responses are linear but at higher temperature (nearer 40 C) non linear and direct threshold effects occur In agro-ecological zones whith wide diurnal temperature variation small increases in mean temperatures can markedly increase the frequency of high temperature injury canopy temperature can be reduced by C under irrigation

44 maxima do not behave like means: in Europe, mean summer (growing period) maximum temperature change between was +1.6 ± 0.4 C models predict scaling factors of 2 in 90th percentile T max for Southern Europe: i.e. 4 C for 2 C mean change The 2003 heat wave accelerated crop ripening by 2 weeks, reduced Italian maize yields by 36%, European fruit harvest by 25% and wheat harvests by 22% (mostly harvested before the peak heat) markets compensated because it was only one season and one continent Della-Marta et al. Battisti

45 Effects of Extreme Events

46 Average percentage share of damage by type of hazard forestry crops livestock

47 climate related disasters and deaths WMO - Atlas of Losses

48 Number of reported disasters by decade and hazard type ( ) South America North America & Caribbean WMO - Atlas of Losses

49 Climate extremes occur even without anthropogenic climate change In addition, there is high confidence that heat waves, heavy precipitation, glacial retreat, permafrost degradation, mountain slope instabilities, mass movements, and glacial lake outbursts, will increase small islands will suffer rising sea levels, inundation, shoreline change, and saltwater intrusion into groundwater

50 Extreme events have greatest impact in sectors with close links to climate: water, agriculture and food, forestry, health, transport, tourism Settlement patterns, coastal development, urbanization, socioeconomic changes influence exposure and vulnerability to climate extremes (high confidence) Ageing societies are vulnerable to climate extremes (heat waves) Several Latin American countries score low in adaptation preparedness because of lack of "innovation" "social inequality" and "deficits in governance"

51 Coping vs. adaptation In post-hurricane Mitch Nicaragua, poor households coped successfully, regaining most assets and avoiding extreme poverty but their environmental, social, economic, and political vulnerabilities kept them in a poverty trap missing development gains too much coping will drain coping capacity adaptation will reduce the need to cope in the future adaption requires knowledge, learning and resources Jakobsen (2009)

52 No regrets strategies Risk management for climate change can benefit from the robustness of no regrets adaptation. A robust strategy prepares for both expected and surprising changes and may provide for broad stakeholder acceptance. Low-regrets strategies should produce co-benefits: improve livelihoods, and ecosystem conservation aim at sustainable pathways towards climate change mitigation, adaptation, disaster risk management, and sustainable development Lempert and Groves, 2010

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54 Summary there are physical-atmospherical reasons for non-linear changes in conditions and events, particularly at higher delta T there are bio-physical reasons for linear responses at lower delta T, and non-linear responses and threshold effects at higher delta T there are social and governance reasons for highly variable responses at all delta T is it posible to work towards a consensus to invest in a low delta T?