## Doc. 5.7

CLIVAR SSG-12, May 6-9 2003

Joint CLIVAR/CCl

Expert Team on Climate Change Detection, Monitoring and Indices (ET/CCD)

Prepared by F. Zwiers with contributions from the ET/CCD.

1.  IMPLEMENTATION HIGHLIGHTS: significant progress on implementation
    made during the past year, highlighting any new activities, major
    results and scientific milestones;

    a.  The newly minted ET/CCD is the successor to the joint WCRP/CCl
        Working Group on Climate Change Detection (WGCCD). The
        membership of the joint ET/CCD has only recently been finalized.
        The team now consists of four CCl representatives

        i.  A. Mokssit (Morocco, co-chair)

        ii. C. Folland (UK)

        iii. S. Sensoy (Turkey)

        iv. L. Molion (Brazil)

> and four CLIVAR representatives

v.  F. Zwiers (Canada, co-chair)

vi. N. Bindoff (Australia)

vii. P. Jones (UK)

viii. D. Karoly (USA).

> The ET/CCD is continuing in its efforts to enhance the availability of
> information that is required to detect climate change in data sparse
> regions. It is doing this by promoting regional workshops on the
> quality control of climate data and the use of that data for the
> calculation of climate indices for use in detection studies. To date,
> workshops have been held in the Caribbean (University of West Indies,
> Mona, Jamaica January 8-12, 2001, Taylor, 2001; Peterson et al., 2002)
> and in Africa (Direction de la Meteorologie Nationale, Casablanca,
> Morocco, February 18-23, 2001, Mokssit, 2003; Eastering et al., 2003).
> A lesson from the African workshop is that these meetings are most
> effective when they engage scientists from neighboring countries
> within a region, because these then work to strengthen regional
> collaborations that may already exist. Plans for additional workshops
> in South America and southern Africa will be described below.

b.  The team has reviewed its terms of reference. The current terms of
    reference are discussed in the Appendix below, and simplified terms
    of reference are proposed.

c.  The European Climate Assessment report (Klein-Tank, et al., 2002)
    provides a comprehensive assessment of observed daily and
    precipitation temperature extremes that is based on carefully
    homogenized data, and a range of indices describing both the mean
    climate and climate extremes.

d.  Papers that base their conclusions on indices of mean and extreme
    climate are beginning to appear with regularity in the literature
    (e.g., Folland and Anderson, 2002; Frich, et al., 2002; Braganza, et
    al., 2003; Karoly, 2003; Kiktev et al., 2003).

e.  The EU MICE Project ([M]{.underline}odelling the
    [I]{.underline}mpacts of [C]{.underline}limate
    [E]{.underline}xtremes) is making heavy use of indices of climate
    extremes that had previously been developed in coordination with the
    WGCCD. Their work includes the evaluation of indices computed from
    observations, global climate models, and regional climate models.
    Information about MICE is available at
    <http://www.cru.uea.ac.uk/projects/mice/index.html>.

f.  The EU STARDEX project ([ST]{.underline}atistical [A]{.underline}nd
    [R]{.underline}egional [D]{.underline}ynamical Downscaling of
    [EX]{.underline}tremes for Europe) is also making extensive use of a
    standard set of indices of climatic extremes. The STARDEX selection
    of indices builds upon previous US/WMO initiatives to develop
    climate indices. A software package is available to calculate nearly
    60 indices from daily temp/precip data is available from STARDEX.
    Further information, and the software, are available at
    <http://www.cru.uea.ac.uk/projects/stardex/>.

g.  The new EU EMULATE project ([E]{.underline}uropean and North
    Atlantic daily to [MUL]{.underline}tidecadal Clim[ATE]{.underline}
    variability) is creating indices of changing extremes for Europe
    since the mid nineteenth century and will relate extremes to
    regional atmospheric circulation anomalies. Information about
    EMULATE is available at
    http://www.cru.uea.ac.uk/cru/projects/emulate/.

h.  The USGCRP has recently renewed its funding of the "Ad Hoc"
    detection group that was formerly lead by Dr. T. Barnett. The newly
    reconstituted group, now lead by Dr. T. Crowley and Dr. G. Hegerl
    (both at Duke University), will meet in late April 2003. The group
    promotes the exchange of data between the major climate modelling
    centers and is working actively on the detection of anthropogenic
    change on regional scales and in climatic extremes. Some highlights
    of the work of this group include

    i.  Further synthesis of global detection results by using a
        multi-model approach (Gillett, et al., 2002). Greenhouse gas and
        sulphate aerosol signals derived from an ensemble of models are
        jointly detectable in 20^th^ century surface temperature
        observations, and virtually no scaling is required on the
        ensemble mean signals to achieve the best fit to observations.

    ii. Further assessment of the presence of an anthropogenic change
        signal in global ocean heat content (Reichert et al., 2002).
        This work has ruled out changes in solar forcing and seafloor
        heating as the primary explanation of the observed increase in
        ocean heat content.

    iii. Evaluation of model predicted tropopause height signals in
         observational data (Santer et al, 2002) that links the observed
         decadal-scale increase in tropopause height to anthropogenic
         warming of the troposphere and ozone induced cooling of the
         stratosphere.

    iv. Evaluation of model predicted change in distribution of
        atmospheric mass (Gillett, et al., 2003). The model-simulated
        response in sea level pressure to anthropogenic forcing in the
        20^th^ century has been detected in several data sets, including
        gridded observations, analyses, and reanalyses. The models
        appear to under estimate the response.

    v.  The use of climate change detection formalisms to assess
        paleo-reconstructions of Northern Hemisphere temperature
        (Hegerl, et al., 2003a). Results indicate that effects of
        volcanic forcing and anthropogenic greenhouse gas forcing are
        detectable in these records. Solar forcing, on the other hand,
        appears to play a relatively modest role in the multi-decadal
        variability of hemispheric mean temperature.

    vi. Evaluation of approaches that may be suitable for the early
        detection of anthropogenic change in climate extremes (Hegerl,
        et al., 2003b). Results indicate that while signal to noise
        ratios are generally lower for extremes, changes in modest
        precipitation extremes are more robustly detectable than changes
        in means when fingerprints from one model are used to detect
        change in another model. This comes about because there is
        somewhat greater similarity between model fingerprints for
        extremes, than for precipitation means.

    vii. Several approaches to regional detection are under
         consideration. Some early results include those from Zwiers and
         Zhang (2003), who use a standard optimal detection formalism
         and are able to detect an anthropogenic signal in North
         American and Eurasian surface air temperature data, and Karoly,
         2003, who uses a combination of climate change indices for
         North America, and also concludes that there is strong evidence
         of an anthropogenic influence.

    viii. Additionally, using a general linear model approach and an
          appropriate experimental design, Sexton et al (2003) show the
          ability of an atmospheric general circulation model forced
          with observed sea surface temperature and a variety of
          anthropogenic focings to detect many regional anthropogenic
          signals down to the model grid scale.

    ix. The community is actively pursuing the use of Bayesian
        techniques, as a means for combining detection results from
        several indices or variables, and as a way to better quantify
        the effects of uncertainty on the analysis.

i.  New work examining the historical ocean profiles of temperature and
    salinity have been undertaken in individual ocean basins and
    globally to asses the observed changes in the ocean.  This work has
    also now been compared with and tested for confidence with the
    results of Coupled Ocean Atmosphere GCM\'s for the global change
    scenarios and natural variability.  These comparisons show strong
    similarity with anthropogenic change and week similarity with
    natural variability (Banks and Bindoff, 2003).

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2.  NEW ACTIVITIES: significant future plans and/or changes of plan,
    including proposals to hold major scientific
    conferences/workshops/etc;

    a.  *Workshops on climate change indices for data sparse regions.*
        The ET/CCD is developing plans for two additional regional
        workshops that are designed to enhance the capacity of
        developing world scientists to quality control their climate
        data and to contribute indices computed from that data to global
        and regional detection studies.

        i.  The main priority is to organize a workshop in South America
            that will help to fill the large data void that presently
            exists in that part of the world. Contact is being made with
            a number of regional scientists to explore possible venues
            and to establish potential participants.

        ii. As a second priority, the team also plans to exploit an
            opportunity in southern Africa to collocate a workshop with
            the 9^th^ International Meeting on Statistical Climatology
            that is will be held in Cape Town, South Africa, on 25-28
            May 2004. This venue provides an excellent opportunity to
            bring regional scientists in southern Africa and statistical
            climatologists from other parts of the world together, and
            to improve the reporting of climate change indices from
            southern Africa.

    b.  *Overview of climate change detection research.* The ET/CCD will
        maintain a liaison with the USGCRP "Ad Hoc Detection Group"
        through the direct participation of F. Zwiers and P. Jones. It
        will also maintain a liaison with the Working Group on Climate
        Modelling (WGCM), and will continue to evaluate and promote the
        use of indices for climate change detection. In addition, the
        team is planning to provide input to the IPCC 4^th^ Assessment
        Report scoping process.

    c.  *Links with other activities*.

        i.  The ET/CCD developed links with the GCOS Atmospheric
            Observations Panel for Climate in 2002. A GCOS and
            (hopefully) ET/CCD branded web site that updates indices of
            climate change and variability in near real time is planned
            for later in 2004. This may be jointly developed by the
            Hadley Centre and the Australian Bureau of Meteorology and
            have the needs of IPCC particularly in mind.

        ii. A new CLIVAR project, the Climate of the Twentieth Century
            (C20C), co-hosted by the Hadley Centre and the USA Center
            for Ocean Land Atmosphere Studies involving about 8
            atmospheric modelling groups, will be studying the causes of
            particular extreme seasons or sets of seasons in different
            regions of the world (Folland et al, 2002). The project is
            in two phases, 2002-4 and 2004-6. A Workshop is planned in
            April 2004 in Trieste.

3.  ISSUES and CHALLENGES: especially any concerns/problems, that need
    to be brought to the attention of the JSC and CHALLENGES, especially
    those requiring guidance, recommendations, decisions and actions at
    JSC level;

    a.  It was envisioned that the ET/CCD would do its work primarily by
        e-mail, and that it would not be necessary for the team to have
        face-to-face meetings. However it is our assessment that an
        early face-to-face meeting of the team would enhance progress
        towards the regional workshops. It would be best if such a
        meeting could be held within 6 months in South America so that
        it can be used to pave the way for a South American workshop. We
        therefore request JSC and WMO support for such a meeting.

    b.  We also seek JSC and WMO support for a South African workshop
        that would be collocated with the 9^th^ International Meeting on
        Statistical Climatology (scheduled for 25-28 May 2004).

    c.  The ET/CCD requests that teams, panels and working groups
        concerned with the improvement and extension back in time of
        global historical data sets including data archaeology, use of
        proxy data, and the homogeneous extension of such data sets into
        the future sometimes using new (e,g. satellite technology)
        report to the ET/CCD on developments in these areas. This is a
        key issue to climate change monitoring and detection. Some
        ET/CCD members are engaged in a range of such issues. One
        example is the new I-COADS initiative (Diaz et al, 2002). This,
        together with enhanced land data, will help improve many data
        sets including the IPCC global temperature series, pressure at
        mean sea level which urgently needs improvement, surface
        humidity and several others. An example of a specific data set
        is the new global HadSLP data set under construction by Dr
        Robert Allan in the Hadley Centre which is also benefiting from
        improved analysis methods.

4.  RELEVANCE TO APPLICATIONS: i.e. what aspects of each panel is
    relevant to or is involved in applications?

    a.  There are many aspects of the ET/CCD's work that are relevant to
        applications and policy. Contributions from the climate change
        detection community will be extremely important to the IPCC 4AR
        report, and the policy synthesis that derives from that
        assessment is hugely influential in setting government climate
        policy throughout the world. These contributions are broadly
        influential across a broad spectrum of the science, including
        monitoring climate change, impacts and adaptation research, the
        validation of climate models, the detection of anthropogenic
        change across a broad spectrum of climate indicators and
        regions, and the projection of future change.

    b.  Because the panel is joint with the CCl, its membership has
        direct involvement in many climate applications.

5.  BANNER: Feedback/comments on the WCRP Banner.

    a.  We support the notion of a WCRP banner project, and agree that
        its focus should be climate prediction on times scales from a
        season to a century. However, such a banner project should focus
        on more than a coordinated assessment of predictability. We feel
        that it would be wiser to headline the WCRP with a broad climate
        *prediction* project (as opposed to a predictability project).
        Focusing exclusively on predictability implicitly sends a
        message that the research on predictability and prediction to
        date has been ineffectual. This is a message that is contrary to
        the significant early progress that is already being made on
        short term climate prediction and the research some centres are
        already undertaking on prediction up to a decade or more ahead.
        Focusing instead on prediction would provide opportunities to
        leverage the work that is already underway, and to more sharply
        focus on real deliverables and applications (of which there are
        many).

**References:**

Banks, H. T. and N.L. Bindoff, 2003: Comparison of observed temperature
and salinity changes in the Indo-Pacific with results from the coupled
climate model HadCM3: processes and mechanisms, *Journal of Climate*, in
press.

Braganza, K., D.J. Karoly, A.C. Hirst, M.E. Mann, P. Stott, R.J.
Stouffer, and S.F.B. Tett, 2003: Simple indices of global climate
variability and change: Part I - Variability and correlation structure.
*Climate Dynamics,* DOI 10.1007/s00382-002-0286-0, in press.

Diaz, H. Folland, C.K., Manabe, T., Parker, D. Reynolds, R. and
Woodruff, S., 2002: Workshop on Advances in the Use of Historical Marine
Climate Data. *CLIVAR Exchanges,* **25**, 71-73

Easterling, D.R., Alexander, L.V., Mokssit, A. and Detemmerman, V.,
2003: Workshop Summary: CCl/CLIVAR Workshop to develop Priority Climate
Indices for Africa, *Bull Amer. Met. Soc.,* submitted.

Folland C.K. and C.W.Anderson, 2002: Estimating changing extremes using
empirical ranking methods. *J. Climate.,***15,** 2954-2960.

Folland, C.K., Shukla J., Kinter J., and M. J. Rodwell, 2002: C20C: The
Climate of the Twentieth Century Project. *CLIVAR Exchanges,* **23**,
37-39.

Frich, P., L.V. Alexander, P. Della-Marta, B. Gleason, M. Haylock,
A.M.G. Klein-Tank, and T. Peterson, 2002: Observed coherent changes in
climatic extremes during the second half of the twentieth century.
*Climate Research*, **19*, ***193-212.

Gillett, N.P., F.W. Zwiers, A.J. Weaver, G.C. Hegerl, M.R. Allen and
P.A. Stott, 2002: Detecting anthropogenic influence with a multi-model
ensemble. *Geophys. Res. Lett.*, **29**, 31-1-31-4

Gillett, N.P., F.W. Zwiers, A.J. Weaver, and P.A. Stott, 2003: Detection
of human influence on sea level pressure, *Nature*, accepted.

Hegerl, G.G., T.J. Crowley, S.K. Baum, K.-W. Kim, and W.T. Hyde, 2003a:
Detection of volcanic, solar and greenhouse gas signals in
paleo-reconstructions of Northern Hemisphere temperature. *Geophys. Res.
Lett.*, accepted.

Hegerl, G.C., F.W. Zwiers, V.V. Kharin, and P.A. Stott, 2003:
Detectability of anthropogenic changes in temperature and precipitation
extremes. To be submitted.

Karoly, D.J., 2003: Detection of anthropogenic climate change in the
North American region. AMS 14^th^ Global Change Symposium, Long Beach,
California, 9-13 Feb. 2003.

Klein-Tank, A., J. Wijngaard, and A. van Engelen, 2002: *Climate of
Europe -- Assessment of observed daily temperature and precipitation
extremes.* Published by KNMI, De Bilt, the Netherlands. 36pp. Available
in electronic form from http://www.knmi.nl/samenw/eca/index.html.

Kiktev, D., D. Sexton, L. Alexander and C. Folland, 2003: Comparison of
modeled and observed trends in indices of daily climate extremes.
*Journal of Climate*, submitted.

Peterson, T.C., Taylor, M.A., Demeritte, R. Duncombe, D.L. Burton, S.,
Thompson, F., Porter, A. Mercedes, M., Villegas, E., Fils, R.S., Klein
Tank A., Warner, R., Joyette, A., Mills, W., Alexander, L. and Gleason,
B., 2002: Recent Changes in Climate Extremes in the Caribbean Region\".
*J. Geophys. Res. - Atmospheres*, **107**, No. D21, 4601.

Mokssit, A., 2003: Development of priority climate indices for Africa: A
CCl/CLIVAR Workshop of the World Meteorological Organization.  In: 
Bolle, Hans-Jurgen, Ed., *Mediterranean Climate Variability and Trends*,
Springer, Berlin. pp 115-123.

Reichert, K.B., R. Schnur and L. Bengtsson, 2002: Global ocean warming
tied to anthropogenic forcing. *Geophys. Res. Lett.*, **29** (11), DOI
0.1029/2001GL013954.

Santer, B.D., R. Sausen, T.M.L. Wigley, J.S. Boyle, K. AchutaRao, C.
Doutriaux, J.E. Hansen, G.A. Meehl, E. Roeckner, R. Ruedy, G. Schmidt,
and K.E. Taylor, 2002: Behavior of tropopause height and atmospheric
temperature in models, reanalyses, and observations. Part I: Decadal
changes. *Journal of Geophys. Res.*, in press.

Sexton, D.M.H., Grubb, H., Shine, K.P. and C.K. Folland, 2002: Design
and analysis of climate model experiments for the efficient estimation
of anthropogenic signals. *J. Climate (in press).*

Taylor, M.A., 2001: The Caribbean Climate Data Workshop -- "A worhshop
on enhancing Caribbean climate data collection and processing capability
and the dissemination of derived global climate change information for
the region.". *CLIVAR Exchanges*, **6**, 34-35.

Zwiers, F.W. and X. Zhang, 2003: Toward regional-scale climate change
detection. *Journal of Climate*, **16*, ***793-797.

**Appendix --Terms of Reference**

This appendix lists the current terms of teference of the ET/CCD and
discusses proposed changes to these terms. This will be followed below
by a listing, without commentary, of the proposed revised terms of
reference.

1.  To further develop and publicize indices and indicators of climate
    change and variability, with particular emphasis on the creation of
    indices of daily to seasonal extremes covering the global land
    surface using standardised software packages.

\[**No change** from current TOR\].

2.  To further develop other indices of value to the IPCC, related to
    changes in mean climate and its variability from the sub-surface of
    the oceans to the stratosphere.

\[**No change** from current TOR\].

3.  To provide input on indices to WMO publications such as the Annual
    Statement on the Status *of* the Global Climate.

> \[**No change** from current TOR, except a typographical error has
> been corrected is indicated in italics\].

4.  To compare modeled and observed indices, and report on the
    comparisons, with some emphasis on changing extremes.

\[**No change** from current TOR\].

5.  To assist in the specification and implementation of observing
    system experiments with models used for global and regional climate
    change detection, with emphasis on the GUAN and GSN networks.

> \[**Propose to remove** this statement from the TOR. Note however that
> the team may be expected to work in this area as appropriate under the
> terms of the simplified Item 8 below\].

6.  To arrange for or make assessments that identify and quantify the
    magnitude of biases introduced by automated means of measurement and
    their consequences for detection and monitoring.

> \[**Propose to remove** this statement from the TOR as this is
> inherent in many activities of the ET/CCD\].

7.  To consider other issues of homogeneity as deemed appropriate.

> \[**Propose to remove** this statement from the TOR as this is also
> inherent in many activities of the ET/CCD\].

8.  To collaborate with and provide inputs to other groups, especially
    those set up under IPCC auspices, regarding the adequacy of the
    global observing system for the purposes of supplying advice to
    Conferences of the Parties to the Rio Greenhouse Gas Convention, and
    regarding the development of indices.

> \[**Propose to simplify** as follows:
>
> To collaborate with and provide inputs to other groups, especially
> those set up under IPCC auspices, regarding the adequacy of the global
> observing system and the development of indices.\]

9.  To maintain plans for capacity building in developing countries in
    the above activities, particularly through Workshops. In particular,
    to work closely with START on capacity building through its
    Monitoring Extreme Climate Events (START-MECE) group.

> \[**Propose to remove** this statement from the TOR. Information about
> this activity is not available on the START website. It is expected,
> however, that the team will maintain contact with MECE if it proceeds
> under the terms of the simplified version of Item 8\].

10. To submit reports in accordance with timetables established by the
    COPAG and/or Management Board, and agreed with CLIVAR participants.

> \[**Propose to remove** this statement from the TOR. It is implicit
> that all working groups, expert teams, etc., will report as
> required\].

*[Proposed revised Terms of Reference for the joint CCl/CLIVAR
ET/CCD.]{.underline}*

1.  To further develop and publicize indices and indicators of climate
    change and variability, with particular emphasis on the creation of
    indices of daily to seasonal extremes covering the global land
    surface using standardised software packages.

2.  To further develop other indices of value to the IPCC, related to
    changes in mean climate and its variability from the sub-surface of
    the oceans to the stratosphere.

3.  To provide input on indices to WMO publications such as the Annual
    Statement on the Status of the Global Climate.

4.  To compare modeled and observed indices, and report on the
    comparisons, with some emphasis on changing extremes.

5.  To collaborate with and provide inputs to other groups, especially
    those set up under IPCC auspices, regarding the adequacy of the
    global observing system and the development of indices.