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CLIMATE SERVICE CENTER 2.0
How to read a Climate-Fact-Sheet
Instructions for reading and interpretation of the climate-fact-sheets
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Briefing paper
How to read a Climate-Fact-Sheet
Instructions for reading and interpretation of the
Climate-Fact-Sheets
Climate Service Center 2.0
Fischertwiete 1
D-20095 Hamburg
Telephone: +49-(0)40-226 338 424
Facsimile: +49-(0)40-226 338 163
www.climate-service-center.de
2nd Ed., Hamburg, July 2014
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Table of Contents
1. Concept and structure of the Climate-Fact-Sheets .............................................................. 3
2. Data underlying the Climate-Fact-Sheets ............................................................................ 3
2.1. Description of the multi-model-ensemble based on global climate projections ............ 4
2.2. Description of the multi-model-ensemble based on regional climate projections
available for Europe .................................................................................................... 5
3. The spectrum of climate projections ..................................................................................... 6
4. Geographical variations in climate projections ..................................................................... 7
5. Explanation of diagrams used in the Climate-Fact-Sheets .................................................. 8
5.1. Climate diagrams .......................................................................................................... 8
5.2. Explanation of the projection diagrams ......................................................................... 9
5.2.1. Projection diagrams for Climate-Fact-Sheets based on global climate projections ... 9
5.2.2. Projection diagrams for Climate-Fact-Sheets based on regional climate projections
..................................................................................................................................12
6. Explanation of the evaluation criteria for determining “resilience” and “signal strength” .... 15
7. Description of factors examined in the Climate-Fact-Sheets ............................................. 17
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1. Concept and structure of the Climate-Fact-Sheets
The Climate Service Center 2.0 compiles Climate-Fact-Sheets containing climactic
information relating to individual countries. For every country requested there is an
individually compiled Climate-Fact-Sheet. Depending upon the individual case in point (and
the nature of the assignment), cross-border Climate-Fact-Sheets are also available for
certain selected regions.
The Climate-Fact-Sheets have a three-part structure, comprising information on the current
climate, historical climate development and future climate projections. The sections relating
to current and historical climate development are the form of a concise overview. The main
focus of the Climate-Fact-Sheets is information relating to projected future climate
developments in the country requested and the main bulk of the Climate-Fact-Sheet
therefore relates to this.
Each Climate-Fact-Sheet delivers as standard information on six climate indices - (mean
annual temperature [maximum/minimum temperature], mean annual and monthly
precipitation level, periods with low precipitation [dry spells], intensity and frequency of heavy
rain events, difference between precipitation and evaporation, rise in sea-level). In addition
to this, supplementary indices may also be employed in the creation of each respective
Climate-Fact-Sheet.
Subregions
Where necessary, in a specific country’s available Climate-Fact-Sheet, the territory of that
country will be divided into separate climate zones. This is especially applicable to countries
with a large surface area, containing several climate zones. These will be analysed
individually with regard to future climatic developments. However, information on the current
climate, or on historical climate development respectively, apply for the country as a whole,
i.e. across the borders of any existent climate zones.
2. Data underlying the Climate-Fact-Sheets
As mentioned above, the Climate-Fact-Sheets provide a brief overview of the current climate
in the target country as well as climatic developments in the past, while also providing a
detailed synopsis of projected climatic change. Correspondingly, various sources of data
have been referred to.
In order to plot the current climate and past climatic conditions and, in addition to the values
from the literature as listed in the respective fact-sheet, globally available observation data
from the Climate Research Unit of the University of East Anglia in Norwich (UK) is referred
to. More commonly known as CRU, these data sets are often used as reference material in
climate research.
An estimation of future climate change is made on the basis of projections of global and/or
regional climate models. A so-called multi-model-ensemble always forms the basis of this.
This means that no single climate projection in any single model is analysed, but instead a
variety of projections from a variety of models. The intention is to increase the resilience of
projections regarding future climatic change, since one can generally assume that
conclusions suggested by any single model, given the necessary simplification of naturally
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occurring processes within that model, are only conditionally applicable. As these simplifying
methods are employed differently in the case of each model, one can assume that when
considering several models (i.e. a multi-model-ensemble), that the robustness of the results
will rise.
At present, climate projections from a multi-model-ensemble of global climate models are
available for all regions of the world, the spatial resolution of which, however, lies between
approximately 100 and 500 kilometres. An additional ensemble is available for Europe with a
spatial resolution of 25 to 50 kilometres. Depending upon the country in question, the climate
projections in the fact-sheets refer to either the global projection ensemble or, in the case of
a European country, to a combined regional and global climate projection ensemble. The
respective ensembles are described below in sections 2.1. and 2.2..
The Climate-Fact-Sheets only contain projected future changes. In the case of all values and
scenarios mentioned in the Climate-Fact-Sheets these changes always refer to the mean of
the climatic normal period between 1961 and 1990, selected to make up the reference
period. This period forms the generally applicable climatic normal period. This averaging over
thirty years ensures that short-term climate changes (e.g. annual or decadal fluctuations) do
not adulterate the long-term climate change signal. This is why, in the case of the projection
diagrams shown in section 5, a moving average is shown over thirty years. Climate values
calculated on a daily basis form an exception to this thirty-year averaging. In the case of the
global climate model ensemble, we only have available data for two twenty-year annual
periods (see Table 1). However, on the scale of regional climate projections, several annual
periods of thirty years can be referred to.
2.1. Description of the multi-model-ensemble based on global climate projections
These model simulations were created within the framework of the “Coupled Model
Intercomparision Project No. 3” (CMIP3) and form the data basis of climate projections for
the fourth assessment report of the IPCC (Intergovernmental Panel on Climate Change),
published in 2007. Model simulations are available from several different global climate
models for a low (B1); medium (A1B) and high (A2) emissions scenario 1, all of which find
consideration within the Climate-Fact-Sheets. This makes it possible to examine all of the
scenarios together, or specific scenarios individually. The examination of all of the scenarios
makes sense, since it is not possible at the current time to estimate which emissions
scenario is the most likely. Admittedly at present many factors point to a strong increase in
emissions, nevertheless, it is no more or less likely that this will ultimately occur than in the
case of the other less severe scenarios. Separate consideration of the scenarios makes it
easier to estimate which climatic changes are projected in the “best case scenario” (low
emission scenario – B1) or in the “worst case scenario” (high emission scenario – A2).
In order to ascertain the projected changes in averaged values (annual mean temperature
(maximum/minimum temperatures), mean annual and monthly precipitation values, mean
annual evaporation and runoff), it is sufficient to consult data of model simulations with a
temporal resolution of one month. For this data (with monthly temporal resolution),
simulations from a multitude of climate models exist for the complete period between 1900
1
The classifications low, moderate and high refer to an increase in greenhouse-gas concentrations in
the future atmosphere. The projected development of the CO2 concentration is here used as an
appropriate example. The current level is approximately 385 ppm (level as of 2010). Up to the year
2100, the following atmospheric CO2 concentrations are projected, depending on the scenario: B1->
540ppm; A1B-> 700ppm; A2-> 825ppm. For more information on emissions scenarios visit
http://www.ipcc.ch/ipccreports/sres/emission/index.htm.
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and 2100 and for each of the three scenarios (see table below). In order to estimate any
changes in the duration of heat waves, cold spells and dry spells, or to evaluate changes in
the intensity and frequency of heavy rainfall events, however, we need to refer to the daily
output provided by the climate models. Daily data of climate models, however, requires a
huge storage capacity. Therefore this data is only available for shorter time periods in the
IPCC archives: for the reference period between 1960 and 1990 and for two twenty-year
periods in the future (2046 to 2065 and 2081 to 2100). All values represented in the ClimateFact-Sheets – including their derivations - are described in more detail in the glossary.
Table 1: Overview of the availability of data in the global multi-model-ensemble
Emissions
scenarios
Low (B1)
scenario
Medium (A1B)
scenario
High (A2)
scenario
All scenarios
together
Monthly data
Daily data
(available for time period 1900 to 2100)
(available for time slices: 1961-90; 2046-65;
2081-00)
20 simulations
16 simulations
23 simulations
17 simulations
19 simulations
14 simulations
62 simulations
47 simulations
2.2. Description of the multi-model-ensemble based on regional climate projections
available for Europe
The regional climate projections were created within the framework of the EU project
ENSEMBLES. The data is freely accessible and has been elucidated in, among others, the
ENSEMBLES Final Report (report is freely available for download at http://ensembleseu.metoffice.com/docs/Ensembles_final_report_Nov09.pdf). For more information on the
ENSEMBLES project visit www.ensembles-eu.org.
Using the Climate-Fact-Sheets for European countries, one can refer to twenty climate
projections, based on a medium (A1B) emissions scenario. These climate projections were
created using 9 different climate models. The spatial resolution of this data is 25 or 50 km
and therefore much higher than that of the global climate projections. All simulations cover
the time period between at least 1961 and 2099, inclusive, so that both a continuous
evaluation of the whole century (2000 until 2100) and separate analyses of the concrete time
periods between 2006 to 2035; 2036 to 2065 and 2071 to 2100 can be made. Since regional
climate projections are available for the medium A1B scenario only, the global climate
simulations, as described in section 2.1., are also fed into the analysis to ensure that the
complete spectrum of available scenarios is considered.
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3. The bandwidth of climate projections
It is not possible on the basis of climate projections from several models to state a concrete
value for future climate change in a specific region. However, it is possible to indicate a
range of possible developments. In addition to the natural variability of a complex climatic
system, the reason for this is to be found in certain assumptions about the future
development of greenhouse gas emissions, whereby we are at present only minimally able to
assess, for example, how technical or political processes will operate in the future. In addition
to this, real meteorological processes are simplified for inclusion in the climate models and in
some cases also incorrectly depicted, which in turn generates a further range.
Using the specifications provided by the IPCC, the range of projected changes in the
Climate-Fact-Sheets is divided into two categories. According to the IPCC, an area of
change is to be categorized as “likely” when 66 percent of all changes projected through the
various models lie within this range. However, should the area contain 90 percent of all
projected changes, then it can, according to the IPCC, be categorized as “very likely”. In the
Climate-Fact-Sheets these areas have in each case been defined around the median (50
percent value) of the projected changes. This means that 33 percent of the projected
changes in an area categorized as “likely” lie above and 33 percent below the median of all
changes. In the case of the “very likely” category, we resultantly find 45 percent of the
changes above and 45 percent below the median (see figure 1).
For Climate-Fact-Sheets based on regional climate simulations with a smaller number of
model projections available (20 regional model simulations, as opposed to 62 global model
simulations), the complete range (the area between minimal and maximal change) of the
projected changes will be shown instead of the “very likely” area.
Variable
Max
45%
33%
Median
-33%
-45%
Min
Value of
today
Today
Figure1: Theoretical scheme to highlight the bandwidth of climate projections
Future
“likely”
“very likely”
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4. Geographical variations in climate projections
Both observed and projected climate changes are geographically variable. In the ClimateFact-Sheets we attempt to cover at least part of this variability by dividing the selected
country into separate climate zones. However, doing this allows only a small part of any
geographic variation to be quantified explicitly, since the climate change signal will not be
uniformly pronounced, e.g. in countries and regions merely extending across the climate
zone. Where it became necessary to introduce such information, the Climate-Fact-Sheets
necessarily contained qualitative evidence of geographical variations in the climate change
signal, an example of which is the statement that a rise in temperature inland tends to be
greater than that on the coast. Furthermore, by considering the level of significance in the
Climate-Fact-Sheets, we can rudimentarily trace the geographical variation. This means that
only that percentage of an individual country or region delivering a significant change signal
is examined. In any given Climate-Fact-Sheet, a pronouncedly heterogeneous distribution of
climate change signals for a chosen region tends to lead to weaker geographical significance
and, for example, to many regions displaying minimal (non-significant) change levels.
For more on the subject of geographic significance, see section 6.
Due to the brevity of the Climate-Fact-Sheets, it is unfortunately not possible to reach more
detailed conclusions on geographic variability. Because conclusions reached using different
projections from different climate models or emissions scenarios can prove to be just as
variegated, very detailed studies need to be carried out. The very rough spatial resolution of
the climate models also often impedes any further statements on the geographic variability of
the climate change signal.
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5. Explanation of diagrams used in the Climate-Fact-Sheets
5.1. Climate diagrams
In order to adequately represent the current climate in the various countries and regions in
fact-sheet form, Walter-Lieth climate diagrams (figure 2) are used, showing observed values
for temperature and precipitation. These are included as a 30-year mean value (normal
climatic period) and offer a useful overview of the annual cycles of temperature and
precipitation as well as annual mean temperature and annual total precipitation.
In extremely simplified form a dependence of evapotranspiration on air temperature is
assumed. Meaning that when the precipitation curve runs above the temperature curve,
conditions will be humid and in the opposite case scenario, arid. The boundary between arid
and humid conditions runs through the point where the precipitation value [mm] is double that
of the mean temperature [°C]. The temperature and precipitation scales are therefore plotted
in a ratio of 1:2.
In this illustration, for example, we can see that the period from mid-March to mid-November
is humid (blue areas), while in the other months arid conditions (bright red areas)
predominate. The months from April until October show high rainfall (a change in rainfall
level of a factor of 10 – dark blue area). The mean annual temperature is 24.7°C, the annual
total precipitation is 1564 mm.
annual mean temperature
in °C
annual total precipitation
in mm per year
threshold above which
precipitation scales by factor 10
red line: Annual cycle of monthly
mean temperature in °C
blue-coloured area: humid
conditions above threshold
light-red coloured area: arid
conditions
blue-colored area: humid
conditions below threshold
blue line: annual cycle of monthly
precipitation in mm/month
Months from January to December
Figure 2: Climate diagram after Walter-Lieth. Temperature and precipitation scaled to 100mm in ratio 1:2. This serves to mark
months with arid (bright red) and humid (blue) conditions. Monthly precipitation values above 100mm are shown in compressed
form.
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5.2. Explanation of the projection diagrams
5.2.1. Projection diagrams for Climate-Fact-Sheets based on global climate projections
Time series:
The projection diagram in figure 3 shows the mean change in a parameter (in this case the
temperature in °C): to the left in the time series from 2011 to 2100 (compared to the mean of
the reference period 1961 to 1990) and to the right in the 30-year periods 2006-35, 2036-65
and 2071-00 (here also compared to the mean of the reference time period from 1961 until
1990).
This time series shows the median of the model simulations (light blue lines), as well as two
other ranges: the dark grey area contains 66 percent of all projected values and is here
denoted as “likely”, meaning that a climate change where the values fall within this range will
probably occur. 90 percent of all projected values lie within the light grey are and are denoted
here as “very likely”, meaning that a climate change where the values lie within this range
has a high probability of occurring. For instance, in this illustration we can see that between
now and 2100, the median projection of change in annual mean temperature of all available
projections is for an increase by 3.6°C compared to the reference period. This change is
likely to be in the range of 2.5 to 4.8°C and very likely to be somewhere between 1.8 and
5.2°C.
The time periods on the right-hand side of the illustration show not only the span of values
within all of the model simulations, but also the ranges of the change signals following the
scenarios B1, A1B and A2. The structure of the bars corresponds to the time series (lefthand detail): The median lies within both probability ranges. For instance, from the illustration
we can see that the median projection of change in annual mean temperature is for an
increase by 2.6°C for the time period 2036-2065 according to the scenario A1B. This
increase is likely to be in the range of 1.9 to 3.2°C and to very likely to be somewhere
between 1.7 and 3.3°C.
Unit of
displayed
variable
dark-coloured area - likely:
66% of all projected changes
fall within this range
light-blue line: Median of
all model projections
red: bandwidth of all
projected changes according
to the high scenario (A2)
orange: bandwidth of all
projected changes according
to the medium scenario (A1B)
yellow: bandwidth of all
projected changes according
to the low scenario (B1)
grey: bandwidth of all projected
changes for all scenarios
Time-series of 30-year running
mean data from2011 to 2100
Time-slice: mean over 30 years
light-coloured area - very likely:
90% of all projected changes fall
within this range
Figure 3: Example for the standard diagram used to present time series of projected changes of global climate models in the
Climate-Fact-Sheets.
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Time slices:
The projection diagram in figure 4 shows the change in a parameter (in this case changes in
the duration of long-lasting cold spells in days) as averaged over two periods of twenty years:
2046-2065 and 2081-2100 (compared to the mean of the reference period 1961 to 1990). As
with the previous illustration, we can also see the median of the model projections, as well as
the ranges denoted as “likely” and “very likely”. The time periods show the change signal with
a span covering the value of all available model simulations (grey bars) and according to
scenarios B1 (yellow bar), A1B (orange bar) and A2 (red bar). The median (light blue line)
lies within both ranges. For instance, we can see from the illustration that for the period
2081-2100, the median projection of change in the duration of long-lasting cold spells is for a
decrease by 2 days according to scenario A1B. The projected change is likely to be in the
range of -4 to -1 days and very likely to be between -5 and +8 days.
dark-coloured area - likely:
66% of all projected changes
fall within this range
Unit of
displayed
variable
light-blue line: Median of
all model projections
red: bandwidth of all
projected changes according
to the high scenario (A2)
orange: bandwidth of all
projected changes according
to the medium scenario (A1B)
yellow: bandwidth of all
projected changes according
to the low scenario (B1)
light-coloured area - very likely:
90% of all projected changes fall
within this range
grey: bandwidth of all
projected changes for all
scenarios
Averaged over period
2046 to 2065
Averaged over period
2081 to 2100
Figure 4: Example for the standard diagram used to present time slices of projected changes of global climate models in the
Climate-Fact-Sheets.
Annual cycle:
The projection diagram in figure 5 shows the changes within the annual cycle of a parameter
(in this case precipitation amounts in percent). The change refers to a thirty-year average at
the end of the century (2071 to 2100), as compared to the reference period 1961-1990. As in
the previous illustrations, two ranges are indicated around the median of all model
simulations (light blue line): the dark grey area contains 66 percent of all projected values. It
is denoted here as “likely”, meaning that a climatic change, which has values within this area,
will probably occur. The light grey area contains 90 percent of all projected values. In
keeping with the previous diagram, this area is denoted as “very likely”, meaning that a
projected climatic change, which has values within this range has a high probability of
occurring.
Another piece of information that we can extract from the illustration is the difference in the
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annual cycle of the parameter separated according to the individual scenarios. To facilitate
ease of overview, only the median of projected changes will be represented in the case of
each of the scenarios B1 (yellow curve), A1B (orange curve) and A2 (red curve).
For instance for the A2 scenario, we can see from this illustration that the median projection
of change in monthly precipitation is for a decrease during the summer season (maximum
decrease in August by -21 percent) and for an increase during the winter and spring seasons
(maximum increase in April by 11 percent).
Unit of
displayed
variable
dark-coloured area - likely:
66% of all projected changes
fall within this range
light-coloured area - very likely:
90% of all projected changes fall
within this range
red: median of all
projected changes according
to the high scenario (A2)
orange: median of all
projected changes according
to the medium scenario (A1B)
light-blue line: Median of
all model projections
Months from January to December
yellow: median of all
projected changes according
to the low scenario (B1)
grey: bandwidth of all
projected changes for all
scenarios
Figure 5: Example for the standard diagram used to present projected changes in the annual cycle of parameters simulated by
global climate models in the Climate-Fact-Sheets.
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5.2.2. Projection diagrams for Climate-Fact-Sheets based on regional climate
projections
Time series:
The projection diagram in figure 6 shows the average change in a parameter (in this case,
temperature in °C): to the left in the time series from 2006 to 2100 (in comparison to the
mean of the reference time period 1961 to 1990) and on the right in the 30-year time periods
2006-35, 2036-65 and 2071-00 (here also in comparison to the mean from the reference time
period 1961 to 1990).
This time series shows the median of the model simulations (light blue line) as well as two
ranges of change: the dark area contains 66 percent of all projected values from regional
climate simulations. It is denoted as “likely”, meaning that a climate change where the values
fall within this range will probably occur. The lighter (turquoise) area extends between the
minimum and maximum of all projected changes of the regional climate models. For
instance, we can see from the illustration that towards 2100 the median projection of change
(based on regional climate projections) in annual mean temperature is for an increase by
3.3°C compared to the reference time period. This change is likely to be in the range of 2.7 to
5°C. The range for all projected changes by the regional climate models is between 1.9 and
6.1°C.
The time periods on the right-hand side of the illustration show not only the span of values in
the regional model simulations (turquoise), but also the projected change signal of the global
model ensemble (IPCC-AR4), according to scenario A1B (yellow) and all available scenarios
(B1, A1B and A2) combined (red). The bars thereby define the span between respective
minimum and maximum of the projected changes. For example, in the illustration we can see
that for the global model projections according to the A1B scenario (yellow bar) and the
period 2006-2035, the median projection of change in the annual mean temperature is for an
increase 1.4°C. The total range of projected changes extends from 0.4 to 2.4°C.
Unit of
displayed
variable
dark-coloured area - likely: 66% of
all projected changes of the regional
models fall within this range
light-blue line: median of all
regional/global model projections
red: bandwidth (Min/Max) of all
projected changes of the global
models
yellow: bandwidth (Min/Max) of
projected changes of the global models
according to the medium scenario (A1B)
Time-series of 30-year running
mean data from2011 to 2100
light-coloured area – Min/Max: all
projected changes of the regional
models fall within this range
Time-slice: mean over 30 years
turquois: bandwidth (Min/Max) of all
projected changes of the regional models
according to the medium scenario (A1B)
Figure 6: Example for the standard diagram used to present time series of projected changes of regional climate models in the
Climate-Fact-Sheets.
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Time slices:
The projection diagram in figure 7 shows the changes in a parameter (in this case changes in
the duration of long-lasting heat waves in days) as averaged over thirty-year time periods:
2006-2035, 2036-2065 and 2071-2100 (compared with the mean of reference period 1961 to
1990). Here, however, we must also consider that, in the case of the global climate
projections (yellow and red bars), we only have access to data for two twenty-year periods
(2046-2065 and 2081-2100). As with the previous illustration, we are also presented with the
median of the projected changes (light blue line) as well as two ranges of change: the dark
“likely” area contains 66 percent of all projected values from regional climate simulations and
the complete range of projected changes. The colours of the bars represent the range of
regional climate projections (turquoise) as well as the range of global climate projections
according to scenario A1B (yellow bar) and all available scenarios combined (red).
Unit of
displayed
variable
dark-coloured area - likely: 66% of
all projected changes of the regional
models fall within this range
light-coloured area – Min/Max: all
projected changes of the regional
models fall within this range
turquois: bandwidth (Min/Max) of all
projected changes of the regional
models according to the medium
scenario (A1B)
light-blue line: median
of all regional/global
model projections
red: bandwidth (Min/Max) of all
projected changes of the global
models
yellow: bandwidth (Min/Max) of
projected changes of the global
models according to the medium
scenario (A1B)
Time-slice: mean over 30 years
Figure 7: Example for the standard diagram used to present time slices of projected changes of regional climate models in the
Climate-Fact-Sheets.
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Annual cycle:
The projection diagram in figure 8 shows the projected changes in the annual cycle of a
parameter (in this case monthly precipitation amounts in percent). This change refers to a
thirty-year average for the end of the century (2071 to 2100), compared to the reference
period 1961-1990. As in the previous illustration, the two ranges of change are shown
together with the median of all regional model simulations (light blue line): the darker area
contains 66 percent of all projected values for the regional climate models. This is here also
denoted as “likely”, meaning that any climatic change with values lying within this range, will
probably occur. The lighter area extents between the minimum and maximum of all projected
changes in the regional climate models.
One further piece of information that we can extract from the illustration is in what way the
change in the annual cycle of a parameter towards the end of the century is represented
within the global models. In each case, and in order to facilitate ease of overview, only the
median of changes for scenario A1B (yellow curve) and all available scenarios combined
(red curve) is represented.
Unit of
displayed
variable
dark-coloured area - likely: 66% of
all projected changes of the regional
models fall within this range
light-coloured area – Min/Max: all
projected changes of the regional
models fall within this range
red: median of all
projected changes of the
global models
light-blue line: median
of all regional model
projections
yellow: median of
projected changes of
the global models
according to the
medium scenario (A1B)
Months from January to December
Figure 8: Example for the standard diagram used to present projected changes in the annual cycle of parameters simulated by
regional climate models in the Climate-Fact-Sheets.
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6. Explanation of the evaluation criteria for determining “confidence” in projected
changes and the “signal strength”
In addition to a representation of projected climate changes, the Climate-Fact-Sheets also
present an evaluation of the projected climate changes in terms of the confidence in the
changes and the signal strength. Not every parameter described in the Climate-Fact-Sheets
can be extracted from climate models to the same. Assertions made for the one parameter
will therefore necessarily be more resilient than those of another parameter. Furthermore,
there are regional differences in the resilience of climate change projections, which are
appropriately marked and identifiable in the Climate-Fact-Sheets. In order to determine the
confidence in the projected changes presented in the Climate-Fact-Sheets, definitions have
been set; as summarised in table 2.
Table 2: Overview of criteria for estimating the confidence in projected changes.
Criterium
Representation of
observed data by
the model
(validation)
Sub-criterium (if
required)
Premise
Evaluation of
confidence
when both sub-criteria are not realistically
represented in the models
low
when only one of the two sub-criteria is realistically
represented in the models
medium
when seasonality and amount are realistically
represented in the models
high
when the median of the change signal is clearly
lower than the spread for “likely”
low
when spread for “very likely” corresponds to at least
twice the value of the spread for ”likely”, or the
median of the change signal is lower or equal to the
spread for “likely”
medium
when the spread for “very likely” is lower than twice
the value of the spreads for “likely” and the median
of the change signal is higher than the spread for
“likely”
high
when less than 66 percent of all model simulations
agree in the direction of change (in- or decrease).
low (not robust)
when at least 66 percent of all model simulations
agree in the direction of change (in- or decrease).
high
(robust)
Seasonality
and
amount/height
Change signal
Direction/trend in
the model
projections
and
spread
Strength of the
change signal
Robustness
and
significance
All criteria are included in equal measure in a 3-tier (high, medium, low) total evaluation; no
weights are given to the individual criteria.
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Those criteria that contribute to the determination of the “signal strength”, refer to the level of
the median of projected changes towards the end of the 21st century (time period 2071 to
2100), as well as to the geographical significance of the projected changes (however, with a
slightly increased emphasis on the magnitude of the climate change signal). This means that,
in order to evaluate the signal strength also the geographic distribution of the climate change
signal is included. The criteria for designating signal strength are defined in table 3 below:
Table 3: Overview of evaluations criteria for estimating signal strength of the projected changes.
Criterium
Sub-criterium (if
required)
Level of change
Geographic
variability
Fraction of area
showing statistically
significant climate
change signals (on
the 95th confidence
level)
Premise
Evaluation of
signal strength
Change <15 percent / change in temperature <1°C
weak
Change 15 - 40 percent / change in temperature 13°C
moderate
Change >40 percent / change in temperature >3°C
strong
< 33 percent of projected changes are significant
weak
Between 33 percent and 66 percent of projected
changes are significant
moderate
> 66 percent of projected changes are significant
strong
The representations of the confidence in the projected changes and the respective signal
strength appear in a combined diagram in the Climate-Fact-Sheets: a example of a case of
medium confidence in the projected changes and a moderate signal strength is shown in
figure 9 below. In cases with higher (lower) confidence in the projected changes, there is a
swing upwards on the confidence scale (or downwards). If the signal strength is estimated to
be stronger (weaker), then the red colouration of the thermometer rises (falls).
Figure 9: Graphic representation of confidence in the projected changes and the respective signal strength of the projected
climate change signal using an example of medium confidence and moderate signal strength.
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7. Description of parameters examined in the Climate-Fact-Sheets
Temperature:
Those temperatures examined in the Climate-Fact-Sheets refer to the air temperature at the
surface of the earth. We distinguish between annual mean temperature and maximum and
minimum temperatures. The annual mean temperature is the average of daily mean
temperatures throughout the year. The maximum and minimum temperatures are gleaned
from daily data which are then averaged for each month, with the respective highest/lowest
mean temperatures being selected. The maximum (minimum) temperature provides the
highest (lowest) monthly averaged daily maximum (minimum) temperature for a specific
year.
Long-lasting heatwaves:
Heatwaves are defined as a number of consecutive days with a daily mean temperature
above a given temperature threshold. For heatwaves the threshold has been set at the 95th
percentile of the daily mean temperatures (on 95 percent of all days the daily mean
temperature is lower than this value) within the control period 1961 to 1990. Since especially
long heatwaves are of importance, only the 95th percentile (95 percent of all heatwaves are
shorter) of the duration of heatwaves are examined and described as long-lasting
heatwaves.
Long-lasting cold spells:
Cold spells are defined as a number of consecutive days with a mean daily temperature
below a given temperature threshold. For cold spells the threshold has been set at the 5th
percentile of the daily mean temperature (on 95 percent of all days the daily mean
temperature is higher than this value) for the control period 1961 to 1990. Since especially
long cold spells are of importance, only the 95th percentile (95 percent of all cold spells are
shorter) of cold spells are examined and described as long-lasting cold spells.
Precipitation:
Both the annual total precipitation and monthly total precipitation amounts are represented in
the Climate-Fact-Sheets. Both amounts are reached by adding together daily precipitation
values over the corresponding time periods.
Actual evaporation:
In the Climate-Fact-Sheets the actual evaporation is derived from the latent heat flux by a
functional relation from the Food and Agriculture Organisation of the UN (FAO). The units are
mm. As distinct from the potential evaporation, this value also relates to the available water
reserves. The values for the actual evaporation are therefore low for arid regions, despite
their high energy potential.
Climatic water balance:
The climatic water balance is the difference between the annual total precipitation and the
annual total actual evaporation. Its unit is mm and it provides information about the amount
of water theoretically available on the earth’s surface. In scientific language this is often
referred to as runoff, whereby this should not be confused with the river runoff.
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Long-lasting dry spells:
Dry spells are defined as a number of consecutive days with total precipitation below a given
precipitation threshold. For dry spells the threshold value was set at the 5th percentile of daily
precipitation (on 95 percent of all days the total daily precipitation is higher than this value)
within the control period 1961 to 1990. Since long dry spells are especially important, the 95th
percentile of the duration of dry spells (95 percent of all dry spells are shorter) is defined as a
long-lasting dry spells.
Intensity of heavy rainfall events:
The heavy rainfall intensity is defined as the 95th percentile of total daily precipitation values.
This is the precipitation value which is not reached on 95 percent of all days (only rainy days
with 1 mm precipitation are considered).
Frequency of heavy rainfall events:
The heavy rainfall frequency is defined as the number days upon which total daily
precipitation exceeds the above defined heavy rainfall intensity.
Solar irradiation:
Solar irradiation refers to the solar radiation that reaches the earth’s surface. In the ClimateFact-Sheets it is presented in kWh/m2 per year.
Wind speed:
Mean wind speed is defined in the models as being at a height of 10 m above ground
surface. As a result of the rough horizontal resolution of global climate models, confidence in
this parameter is limited.
Intensity of storm events:
Storm intensity is defined as the 95th percentile of peak daily wind speeds (gusts). This is
therefore the gust that is not reached on 95 percent of all days. This rate is calculated on the
basis of the regional climate model data only and is not very resilient.
Frequency of storm events:
Storm frequency is defined as the number of days upon which the above defined storm
intensity was exceeded. This value is calculated on the basis of the regional climate model
data only and is not very resilient.
Sea level:
Projected changes in sea level are the only value in the Climate-Fact-Sheets not extracted
from primary data, but instead compiled from the literature. At present only limited
conclusions can be drawn from model projections for a change in sea level and those are
linked with high uncertainty. In the Climate-Fact-Sheets we therefore avoid making any
detailed statements concerning regional rises in sea level. Concerning an observed rise in
sea level it must also be taken into consideration that the accuracy of measurement using
state-of-the-art, satellite-supported measuring methods is to within 1mm/year, whereas that
of tide-gauge measurements is even less accurate.