CVAS - Climate Variability Across Scales



The Climate Variability Across Scales (CVAS) working group examines climate variability in space and time, with the focus on Holocene decadal to millennial variability, and its implications for future climate evolution. Special focus is given to scaling as a means to compare paleo time series with observations and simulations.
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- Assess the time-scale dependent transfer functions from climate to the recorded proxy in order to implement and improve proxy system models, building on and integrating work by PAGES' former working group DAPS.
- Improve statistical and modeling tools for analyzing and comparing (paleoclimate) time series and spatial distributions and to bring these tools to other PAGES working groups.
- Create a synthesis of the spatio-temporal structure of climate variability based on the PAGES 2k Network and TEMP12k databases: “The CLIMAP of temperature variability” and compare this to current model simulations (CMIP/PMIP).
- Investigate the implication of the results for reconstruction and assimilation efforts and for constraining climate projections.
- Advance our understanding of the physical mechanisms of scaling constrained by our empirical findings.
- Explore the application of CVAS concepts beyond climate variability e.g. the possible interactions between 'physics' and 'life' at the centennial scale (with links to PAGES working group EcoRe3)


Heather Andres (ECR; climate modeling, attribution, model-data comparison)
Michel Crucifix (theoretical climate dynamics)
Christian Franzke (theoretical meteorology, methods)
Fabrice Lambert (data liaison officer; ice-core records)
Thomas Laepple (group leader; statistics, proxy recording systems)
Gerrit Lohmann (climate modeling, dynamical system theory)
Shaun Lovejoy (nonlinear geophysics)
Kira Rehfeld (statistics, climate modeling)
Cristian Proistosescu (ECR; statistics, conceptual climate models)
Anne de Vernal (marine records)


Phase 1
 Phase 2
 Dec 2022

While climate variability occurs over huge ranges, decadal to millennial variability is of special importance. Firstly, the natural variability at these scales dynamically interacts and overlaps with anthropogenic forcing, with implications for understanding both the industrial epoch and future climate projections.

Secondly, paleoclimate records suggest that variability at these scales is strong, yet it cannot be explained by the much lower frequency orbital forcing. Thirdly, existing climate models seem to strongly underestimate centennial to millennial climate variability, at least on regional scales, pointing to major deficiencies in either internal variability, the strength of responses to forcing, or erroneous paleoclimate-based variability estimates.

The origin, magnitude and scaling of environmental variability are linked to the stability of the Earth system, its sensitivity to external forcing, as well as the statistics of extremes and are thus a central topic in PAGES' holistic Earth system science approach.

Phase 1 of CVAS (2016-2019) brought together paleoclimate scientists across disciplines on the question of scaling in climate variability using tools and theory from nonlinear geophysics.

Phase 2 (2020-2022) will quantify climate variability across space and at decadal and longer time scales by combining advanced understanding of paleo-proxy data, proxy-system modeling, scaling analysis techniques, theory and climate models.

Creating links

In previous CVAS workshops, the two formerly very separated communities – nonlinear geophysics and paleoclimatology (data-producers, modelers and statisticians) – created strong links and an understanding for one other. This challenging cross-disciplinary thinking was advertised and brought to a wider audience via annual CVAS EGU sessions and CVAS EGU short courses.

Tools and review articles were developed, including a Past Global Changes Magazine issue. CVAS Phase 2 will build on this foundation by reinforcing partnerships and exchange with other PAGES groups (i.e. 2k Network, SISAL, VICS) to solve the outstanding problem of decadal to millennial variability in the climate system.

Moving from understanding each other to synergistic production of knowledge, specific topics will be selected for each workshop and teams will be formed. They will prepare their contribution to the workshop topic in advance and synthesize the results after the workshop, with the aim of producing publications which can be directly built upon in order to answer the objectives of Phase 2.

In the PAGES Science Structure, centered on climate, environment and humans, this group will focus on climate variability: however, this is so integral to the ability of ecosystems and human societies to adapt that climate variability could be situated quite centrally in the triangular conceptual diagram of the new PAGES structure.

The working group is very close to and will contribute to the Integrative Activity on Thresholds by investigating the links between variability and stability. It will further contribute to the Integrative Activity of Extremes, linking variability, intermittency and extremes, also from the perspective from nonlinear geophysics.

CVAS Phase 2 will integrate and continue the proxy system modeling part of DAPS, with a special focus on the transfer function between climate variability and proxy variability. The outcomes of this research are relevant for all reconstruction efforts in PAGES situated in different research groups.

We further envision a collaboration with VICS on the relative role of volcanic versus internal climate variability in shaping the variability in warm climates as the Holocene. We would like to engage with SISAL to constrain and reconstruct terrestrial hydroclimate variability and with the 2k Network group concerning the use, interpretation and the variability perspective on the 2k datasets.

Finally, we would like to discuss/explore the application of the CVAS concepts beyond climate variability, e.g. the possible interactions between 'physics' and 'life' at the centennial scale with PAGES groups such as EcoRe3.

Scientific goals

Find out more about the group's scientific goals here.

Learn more and participate

Find out more about the people involved in CVAS here.

Subscribe to the CVAS mailing list here.

Seminar series - announcement June 2020

Group leaders are planning an online seminar series to start Phase 2 discussions. The series aims to provide an overview of the current state of the research relevant to the CVAS community in order to identify starting points for collaborative projects.

To keep the format nice and enjoyable, they suggest to have a bi-weekly meeting, lasting one hour (but the webinar room will be open for those who would like more time for discussion), and aim to have only two people presenting for 10 to 15 minutes to leave plenty of time to discuss.

Call for contributions

Contributions do not need to be traditional conference talks, and organizers encourage contributions that would be mainly a discussion around a central problem that you think is relevant for the CVAS community. The number of online seminars will depend ultimately on the number of talks.

We aim to have topic unity for a single seminar, starting with general talks across the interests of CVAS and going into more specific topics as the seminar progresses.

The CVAS subgroups identified in the structure so far include:

(A) transfer of climate to proxy variability (building on the DAPS PSM work)
(B) methods for variability and scaling analysis
(C) theory and mechanisms of (climate) variability
(D) variability synthesis product.

Of course, any contribution that doesn't fall in any of these topics, or covers more than one, is more than welcome.

For now, we only request short statements of interest of one to two lines that describe your contribution, from a title to a topic, or a short description. We will then sort these contributions into blocks and sessions.

Some examples from the organizing team

- How much climate variability is recorded in ice core records at resolution below centennial ? (Talk - Mathieu Casado)
- Holocene climate variability from a large database of pollen-based reconstructions in the Northern Hemisphere were evaluated. Discussion of mechanisms leading to a scaling break from instrumental data to the reconstructions. (Short Talk+Discussion - Raphaël Hébert)
- Glacial variability recorded in pollen (Talk - Nils Weitzel)
- Precipitation vs. temperature variability changes under changing mean state (Short talk + Discussion - Kira Rehfeld)
- Forcing variability vs. proxy/model variability (Talk - Beatrice Ellerhoff)
- Budyko-Sellers version 2.0: the 2D Fractional Energy Balance Equation and climate modelling. (Talk - Shaun Lovejoy)
- Why do we always see power law scaling in proxy data? (Discussion - Thomas Laepple)

If you are interested, please contact Raphaël Hébert (This email address is being protected from spambots. You need JavaScript enabled to view it.) with your short statement by 24 June 2020. If you think you have colleagues that could provide relevant contributions, please share this with them.

Planned Phase 2 timeline

January 2020: Start of CVAS Phase 2

Formation of subgroups on the:
(A) transfer of climate to proxy variability (incorporating the DAPS PSM work)
(B) methods for variability and scaling analysis
(C) theory and mechanisms of (climate)variability; and
(D) variability synthesis product.

May 2020: Splinter Meeting at EGU, CVAS EGU session and a CVAS EGU short course

All details here.

December 2020: First CVAS-II Meeting: Beyond Palaeoclimate Ping Pong

All details here.

This meeting (as well as the other upcoming meetings) will be openly advertised and used to focus on one specific theme (in this case consistent data-model comparison) with external experts and participants from the other PAGES groups. The meetings will further be used to work in and across CVAS subgroups in the plenum as well as in parallel working sessions.

July 2020: Setup of a website/repository (or continuation of the DAPS website) on tools, data and models

May 2021: Splinter Meeting at EGU, CVAS EGU session and a CVAS EGU short course

Autumn 2021: Second CVAS general meeting

May 2022: Splinter Meeting at EGU, CVAS EGU session and a CVAS EGU short course

Autumn 2022: CVAS Synthesis meeting