Highlights from Dr. Mary Lou Zeeman’s Online Q&A (April 2018)

What do lakes, fisheries, coral reefs, moods, kayaks, social media posts, the spread of disease, and the Earth’s energy balance all have in common? Tipping points: when a system changes abruptly from one alternative steady state to another. How can mathematical modeling help support decision making in the face of these alternative possibilities? What makes for resilience? What causes change?

On April 19, 2018, mathematician Dr. Mary Lou Zeeman (Bowdoin College) answered your questions about these exciting and accessible dynamics, which can inform your own choices and those of our global society. She was joined by environmental scientist Dr. Ross Lieblappen (Vermont Technical College). Read more below to learn about the Q&A, and you’ll also find a list of resources recommended by both scientists!

Dr. Zeeman is a professor of mathematics at Bowdoin College in Maine. She is also the co-director of the Mathematics and Climate Research Network, and on the executive council of the Computational Sustainability Network, working with other researchers to build understanding of how mathematics can help us make decisions for sustainability and resilience in the face of a changing planet.

Dr. Lieblappen is an assistant professor at Vermont Technical College who teaches physics and environmental biology. Ross is a specialist in polar research, especially what we can learn from the microstructure of snow and ice. Here’s a photo of him sharing ice core samples with visitors to the 2017 National Math Festival!

Online Q&A Highlights

Tipping points apply across many different kinds of systems. Not only coral reefs, ponds, and other natural environments, but your mood, social media, and many other phenomena are all subject to the choices we make. You can find a short video from Dr. Zeeman’s talk at the National Math Festival last year if you want an example of some tipping points!

Highlights: Tipping Points and Planet Earth” with Dr. Mary Lou Zeeman from MSRI / National Math Festival on Vimeo.


Q: What do the ice cores have to do with the mathematics you research?

Answer (Dr. Lieblappen): Ice cores are a fascinating material with many different research questions they can help answer. Different types of ice cores can help answer different questions. The first distinction to make is whether the ice is glacial ice (meaning it is from a glacier/ice sheet and over land) or sea ice (frozen ocean). Glacial ice cores from Antarctica or Greenland can help us answer questions about the climate of Earth hundreds of thousands of years ago. The Antarctica Ice sheet has places where the ice is 2 miles thick and about 800,000 years old. Sea ice does not get much thicker than 10 feet and is usually only 1-10 years old. Thus, the scientific questions it can help answer are generally more geared to recent climate.

My personal research is primarily on sea ice cores. I am interested in understanding the structure of the ice. Sea ice has a complex network of salt water (brine) channels that remain liquid even at very cold temperatures. These channels provide a pathway for chemical compounds such as salts to travel between the ocean and the atmosphere, where they can play a role in atmospheric chemistry.

Answer (Dr. Zeeman): Good question! Check out the graph of Earth’s global temperature history over the last 800,000 years here. It shows temperature and CO2, and their really tightly linked behavior. The data to build those graphs came from the ice cores. Math modeling of climate processes is then used to help understand which processes could be responsible for the observations we see, and how the processes interact with each other.


Q: I’m looking for some hope in terms of how close we are to a tipping point (or past one) for correcting climate change. Is there any modeling or research done on course correcting the changes we’ve made to the atmosphere/environment, or are we only looking at ways to now deal with the new (an possibly inhospitable) global climate we’ve created?

Answer (Dr. Lieblappen): One of the exciting things about the time we currently live is that we still have lots of control over our future impact on the climate. I might point you to NASA Earth Observatory that gives potential future global surface temperatures. The decisions we make on emissions in the next few years can help determine which of the many possible climate scenarios the future of our planet takes.

Answer (Dr. Zeeman): I think there’s plenty of room for hope. As you say there’s certainly plenty of research being done about how cities and food systems (for example) can adapt to the changing climate they face. But there’s also lots of continuing research about carbon sinks for example (both natural and man-made) that may help course correct for the existing atmospheric carbon. And – altho progress sometimes seems slow – the transition to renewable energies is happening.

Another thing I find hopeful is that the concept of tipping point is not so scary when we consider having more than one “control variable”. For an explanation of what I mean, I recommend you watch a lecture by my father, Sir Christopher Zeeman, on Catastrophe and Psychology. (Sir Christopher Zeeman Christmas Lectures). There is a nice explanation of the idea of tipping from a math modeling point of view, but there is also so much more that the model can show us, including – in some situations – smooth routes back from a state/situation we don’t like to a state/situation we prefer.


Q: Are tipping points usually singular or do they vary depending on the direction of state transition (your observation in multiple cases)?

Answer (Dr. Zeeman): Oh, interesting question. About direction of state transition, if you mean going “backwards” across a tipping point you just crossed, there is often a return, but it’s sometimes “further back” than the original. That idea is called “hysteresis”. If you mean a totally different direction of state transition, then the tip can completely disappear and become gradual smooth change. Beautiful math to study!


Q: Why was the Boston Marathon day so cold if there is global warming?

Answer (Dr. Lieblappen): Couple of answers. First, whatever it is like one day is not indicative of what the long-term trends are. Weather refers to the conditions on a short time and they can vary widely even if the long-term trend is in a particular direction. One can think about the stock market and how much it varies day to day versus long term trends. Climate refers to these long-term trends (often at least 30 years).

Second, although the global average temperature of the Earth has been increasing, this does not mean that every part of the Earth is increasing at that same rate. We know the Earth’s climate is changing. This may mean some areas get warmer, some wetter, some drier, some windier, and even perhaps some get colder. For New England, we expect storms to generally be more intense and overall wetter. Further, we have begun to see larger fluctuations in the jet stream. As the Arctic warms (at a faster rate than the rest of the world), it weakens the large cold block of air generally located over the Arctic ocean. As this breaks up, it allows the northern air block to mix more with lower latitudes. Cities like Boston can then experience really extreme cold events (or really extreme hot events) on what is typically a nice mild spring day.


Further Explorations

Dr. Zeeman: I’ve found that pretty much everybody I talk to cares about the sustainability of some aspect of the planet. There are some great educational resources out there. e.g. at NASA and at the Mathematics of Planet Earth site and the Mathematics and Climate Research Network site.

Here are more links you can explore, recommended by Dr. Zeeman and Dr. Lieblappen!

RESOURCE: Mathematics and Climate Research Network

RESOURCE: Computational Sustainability Network

This website has news, videos, publications from CompSustNet, where interdisciplinary research teams focus on cross-cutting computational topics such as optimization, dynamical models, big data, machine learning, and citizen science; applying them to sustainability challenges including conservation, poverty mitigation and renewable energy.

RESOURCE: National Center for Environmental Informations (NCEI) website for paleoclimate records

These paleoclimatology datasets provide access to descriptive information and explanatory notes, maps, searches, visualizations, and more. The data cover the globe, and while most span the last few millennia, some datasets extend back in time 100 million years. Most of the data are time series of geophysical or biological measurements and some include reconstructed climate variables such as temperature and precipitation.

RESOURCE: Intergovernmental Panel on Climate Change (IPCC) 

This site contains assessments of climate change by the IPCC, drawing on the work of hundreds of scientists from all over the world. The purpose is to enable policymakers at all levels of government to make sound, evidence-based decisions.

RESOURCE: CO2 Measurements at Mauna Loa Observatory

This site features graphs of the recent monthly mean carbon dioxide measured at Mauna Loa Observatory, Hawaii. The last four complete years of the Mauna Loa CO2 record plus the current year are shown. The data is collected by the National Oceanic and Atmospheric Administration (NOAA) as part of the Earth System Research Laboratory’s Global Monitoring Division.