Zan Stine

Alexander (Zan) Stine

Associate Professor of Climate Sciences
At SF STATE since 2013
Phone: 415-338-1209
Location: TH 610

Sc. B Geology/Physics-Mathematics - Brown University
Sc. M Climate Physics and Chemistry - Massachusetts Institute of Technology
Ph.D. Earth & Planetary Science – UC Berkeley

Research and/or Teaching Area: Climate change, reconstructions of past climates (particularly from tree rings), interactions of human societies and climate over the last ~4000 years, response of the global rain patterns to global warming, the annual cycle of climate variability.

My research focuses on how to separate natural climate variability from human-induced climate change in the observational record. Because we have been routinely measuring surface temperature over most of the world's land surface for less than 150 years, indirect methods of inferring temperature must be employed if we are to build the long records necessary to fully understand the scale of human influence on global climate. Currently much of my work focuses on problems in the interpretation of tree rings as a proxy for past climate variability, and on how our reconstructions of past climates can be improved by incorporating ecological laws into our reconstruction methodologies. I also use early documentary records from the last 4000 years as proxies for climate variability and to understand how preindustrial societies were affected by climate variability. This work is typically done in collaboration with historians. I am also interested in understanding how global rain patterns change in response to changing surface temperatures, and how we can better use historical records to understand this response.

I encourage students interested in working with me to contact me via email. Most students who work with me take on projects which use tree-rings to reconstruct the climate history of California. This work typically involves a combination of field work, laboratory work, and quantitative analysis. I also sometimes take students interested in working on more purely quantitative problems involving the use of large datasets to test hypotheses as to the response of Earth to greenhouse gasses. And I have some interesting projects for students who like archival research in the library.

Tree Rings

  • Because tree-ring growth is correlated with local climate at many locations, long tree-ring records have been used to infer the climate history of the Earth before the instrumental period. Work in my group focuses on understanding how tree-rings store climate information and how we can increase the fidelity with which we reconstruct past climate variability from these records.

    We seek to identify ways to use ecological principles to more fully separate various climate signals from the influence of non-climate stresses and from low frequency variability associated with competition and aging of the tree. For example, if the stress regime differs between trees at a site, then Liebig's Law of the Minimum implies that climate information is concentrated in the least-stressed trees in any year. Based on this insight, I introduced a reconstruction method which isolates the least-stressed trees within a site, and which leads to recovery of more climate signal than standard methods.

    Field work in the Sierra Nevada focuses on separating multiple distinct climate signals from within a single set of trees, either by measuring multiple climate proxies (tree-ring width and blue intensity), or by taking advantage of spatial variability in the stress regime.

Climate and Civilizations

  • Large organized civilizations began to form shortly after global climate began to stabilize following the last ice age. It is tempting, therefore, to speculate that climate variability continued to play a major role in the history of human civilization. However testing such a hypothesis is often difficult. Global scale volcanic eruptions provide a unique opportunity to identify the climate vulnerability of pre-industrial civilization because they represent large repeated climate forcings, which occur essentially at random. This work, done in collaboration with historians, asks (1) how did ancient human civilizations respond to climate change? and (2) how can we use ancient historical documents to test physical hypotheses about the response of climate to forcing?

The Global Hydrological Cycle

  • My group's work on the global hydrological cycle seeks to understand and quantify how precipitation and evaporation patterns will change in response to warming. As global temperatures warm, the amount of water that can by carried by the atmosphere increases rapidly. This will tend to amplify existing patterns, making wet regions of the world wetter and dry regions dryer. But warming may also change patterns of atmospheric circulation, which may have less easily predictable effects on how water is moved by the atmosphere. Our research seeks to identify the relative importance of each of these mechanisms for controlling the hydrological response to warming as a function of timescale.

Annual Cycle of Surface Temperature

  • The vast majority of the variability observed in the instrumental surface temperature record is at annual frequencies. Systematic changes have occurred in the amplitude and phase of the annual cycle of surface temperature over the past half century, which appear to be related to seasonal changes in atmospheric circulation over the same period. My work seeks to understand natural and anthropogenic influences on variability in seasonality, and how we can distinguish them from one another.


In Review

  • C Gao, F Ludlow, A Matthews, AR Stine, A Robock, Y Pan, R Breen, B Nolan, and M Sigl, Volcanic Climate Impacts Act as Ultimate and Proximate Causes of Chinese Dynastic Collapse , Nature Communications, in review  
  • A Izdebski, K Bloomfield, WJ Eastwood, R Fernandes, D Fleitmann, P Guzowski, J Haldon, F Ludlow, J Luterbacher, J Manning, A Masi, L Mordechai, T Newfield, AR Stine, C Senkul, E Xoplaki The emergence of interdisciplinary environmental history: bridging the gap between the humanistic and scientific approaches to the Late Holocene , Annales. Histoire, Sciences Socialess in review  
  • L Ma**, AR Stine, and K Simonin, Directional competition at treeline and implications for climate reconstructions , Trees: Structure and Function, in review  

   **Graduate student-led paper