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

PAGES SSC liaison

Paul Valdes (University of Bristol, UK)


 Phase 1
 Phase 2

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 (2020-2023) 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

This group is open to anyone who is interested, and early-career researchers are encouraged to be involved.

Find out more about the people involved in CVAS here.

Subscribe to the CVAS mailing list here.

Seminar series 2 - November 2020 to March 2021

The second seminar series is called "Climate variability across scales: from the butterfly's wings to the age of the Earth."

> Access the list of speakers and dates on the official website

You must email group leader This email address is being protected from spambots. You need JavaScript enabled to view it. to receive the Zoom link information.

Some of the presentations will be recorded and saved on the CVAS Seminar series playlist on PAGES YouTube channel.

Seminar series 1 - July to October 2020

Group leaders have organized 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.

The workshops will be held every second Thursday at 13:00-14:00 UTC, starting 16 July and finishing 22 October.

> Access the schedule here (pdf, 44KB).

Information for presenters: If you are unable to present at the date that you were assigned or wish to make modifications to your description, please contact Raphaël Hébert: This email address is being protected from spambots. You need JavaScript enabled to view it.

Instructions to join

The WebEx videoconference tool is used. The meeting will be open 30 minutes in advance in order for participants to test and resolve potential connectivity issues prior to the start.

There are several ways to join the meeting. Choose one that fits you best.

A. Computer based
Automatic: (simple but no choice… and installs an app)

1. Open
2. Enter meeting number and password Meeting number (access code): 168 947 043 Meeting password: NJkPRkaj543
3. The little arrow next to "Join Meeting'' allows you to choose between the browser based web-app and desktop app (installation necessary). If the button is inactive then the room is not ,"open'' yet.
4. Join the meeting. Test your mic (and if you want your cam) and enter the room

B. You can also dial in directly by phone
For Germany: +49-619-6781-9736
Other international dial in numbers can be found in this list (let us know if you need a global call-in number)

C. Join by using Microsoft Lync/Skype for Business
Dial This email address is being protected from spambots. You need JavaScript enabled to view it.

D. Using the Cisco Webex Meetings Mobile App for your smartphone

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