UNFCCC, Paris November 2015 The 2°C goal is not safe and 1 ... › ... › DegreeLimitTalk.pdf ·...
Transcript of UNFCCC, Paris November 2015 The 2°C goal is not safe and 1 ... › ... › DegreeLimitTalk.pdf ·...
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Holm Tiessen, 2017
UNFCCC, ParisNovember 2015
The 2°C goal is not safe and 1.5°C has many benefits
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Holm Tiessen, 2017
Key Messages from the UNFCCC Structured Expert Dialogue
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Holm Tiessen, 2017
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
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Holm Tiessen, 2017
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
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Holm Tiessen, 2017
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
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Holm Tiessen, 2017
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 benefitsin reduced damages, risks and adaptation needs
www.climateanalytics.org, 2015
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Holm Tiessen, 2017
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
www.climateanalytics.org, 2015
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Holm Tiessen, 2017
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 warmingis a political question
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Rising temperatures are not only an in situ phenomenonbut shift transitional zones and increase affected territory in- islands- mountains- high latitudes
Regional, national and international concerns needunderstanding of climate science in a societal context
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Holm Tiessen, 2017
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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Holm Tiessen, 2017
To assess CC impacts and "desirable" limits
climate phenomena and their effectsmust be identified and quantified
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Holm Tiessen, 2017
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
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Holm Tiessen, 2017
There are direct effects of mean temperature change
zone of maximum freeze-thaw cycles shifts pole-ward and up-slopeaffecting:
- plants (trees)- cropping systems - soil C and N- technical structures (concrete)
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Holm Tiessen, 2017
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 CO2 increases frost sensitivity
Frost damage is an important issue as temperatures rise
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Holm Tiessen, 2017Gu
Increased Cold Damage in a Warming World
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Holm Tiessen, 2017Gu
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Holm Tiessen, 2017
The University of Illinois warns that field working days are changing
the typical planting window for maize will be reduced and shifted bywarmer, 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) orshorter season (harvested before the drought, sacrificing yield)
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Holm Tiessen, 2017
IPCC models and scenarios
fewer cold, and more warm days and nights arevery likely at the global scalelikely in North America, Europe, and Australia
for warming daily extremes there ismedium confidence for much of Asialow 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
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Holm Tiessen, 2017
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
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Holm Tiessen, 2017
Current disaster impacts vary between regions:
Economic losses are higher in developed countriesFatalities 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
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Holm Tiessen, 2017
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
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Holm Tiessen, 2017
discussion:
measurements, predictions, experiences,social perceptions and vulnerabilities
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Types of change
IPCC
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Holm Tiessen, 2017
average summer temperatures around the 1900-2006 meanblue: observed 1900-2006red: projected 2090
The hottest summer on record in France (2003) was 3.6° above the meanThe average for 2090 is projected to be 3.7° above the meanThere is a small probability of summers 9.8° above the mean
Battisti et al
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Holm Tiessen, 2017
How to quantify extremes?
count the number of record-breaking events and examine the count for any trenddistinguish 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 independentindex such as insurance payout
rarer, extremer events are naturally most difficult to quantify
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Holm Tiessen, 2017
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 precipitationoften as extreme rainfall
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Holm Tiessen, 2017
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 barleyof 40 Mt or US$ 5 billion per year.
Lobell and Fields
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Holm Tiessen, 2017
reduction in yield increases
wheat
maize
rice
temperature increase population increase
temperature increaseproductivity change food security risk
Global
Regional
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Holm Tiessen, 2017
CO2 fertilization vs. CC
1 ppm of CO2 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 CO2 and climate have cancelled each other
CO2 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
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Holm Tiessen, 2017
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
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Holm Tiessen, 2017
What are the mechanisms of CC effects on plants?
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Holm Tiessen, 2017
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
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Holm Tiessen, 2017
In the thermal kinetic windowthe Michaelis-Menten constant for CO2 (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
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Temperature dependence of biochemical reaction rate
30°C is a critical zone
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Holm Tiessen, 2017
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 senescenceabscission of reproductive organs in crops and fruit trees(even tropical trees)
heat stress reduces not only seed weight but also vigour andgermination, carrying the damage into future seasons
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Holm Tiessen, 2017
All phenological stages are temperature sensitive:
development accelerates linarly with degree days,this reduces time for grain fillingabove 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
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Holm Tiessen, 2017Teixeira
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Holm Tiessen, 2017Lobell
Effect of changed temperature and rain on yields
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Holm Tiessen, 2017
Effect of changed temperature and rain on yields (2)
Lobell
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Holm Tiessen, 2017
In summary
Heat stress is determined by canopy temperature >30°Cwhich depends on weather, canopy properties, soil moisture
>34°C, both development and senescence acceleratereducing 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 variationsmall increases in mean temperatures can markedly increasethe frequency of high temperature injury
canopy temperature can be reduced by 10 - 15°C under irrigation
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Holm Tiessen, 2017
maxima do not behave like means:
in Europe, mean summer (growing period)maximum temperature change between 1880 - 2005 was+1.6 ± 0.4°C
models predict scaling factors of 2 in 90th percentile T maxfor Southern Europe: i.e. 4°C for 2°C mean change
The 2003 heat wave accelerated crop ripening by 2 weeks, reducedItalian maize yields by 36%, European fruit harvest by 25% andwheat harvests by 22% (mostly harvested before the peak heat)
markets compensated because it was only one season and onecontinent
Della-Marta et al.Battisti
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Effects of Extreme Events
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Average percentage share of damage by type of hazard
cropsforestry
livestock
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Holm Tiessen, 2017
climate related disasters and deaths
WMO - Atlas of Losses
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Holm Tiessen, 2017
North America & CaribbeanSouth America
Number of reported disasters by decade and hazard type (1971-2010)
WMO - Atlas of Losses
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Holm Tiessen, 2017
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
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Holm Tiessen, 2017
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"
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Holm Tiessen, 2017
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 vulnerabilitieskept 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)
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Holm Tiessen, 2017
Lempert and Groves, 2010
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
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Holm Tiessen, 2017
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Holm Tiessen, 2017
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 responsesat all delta T
is it posible to work towards a consensus to invest in a low delta T?