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Climate archivists, continued

Ice age ecologist

Much of Jack Williams’ research also has direct implications for conservation biologists and land managers. 

Jack Williams collects core samples
Jack Williams collects and analyzes
lake sediment cores to study natural
communities’ response to change.

“When the world is changing to a condition that may be very different than what we’re used to and what our management process is based on, that’s a fundamental challenge for practitioners and for ecologists,” he explains. 

“The past gives us actual data about species’ responses to climate change,” he says. 

His work focuses on the environmental changes of the last 20,000 years. “This is the last big period of climate change, when you’ve gone from an ice age – a glacial era – to the Holocene interglacial period,” he explains. 

This time period serves as a model system for understanding how ecosystems respond to large or rapid climate change, periods of drought and increases in carbon dioxide (the greenhouse gas most associated with global warming). “These are all things that happened over this time period that are similar in magnitude to what’s happening now,” Williams says. 

Using networks of pollen data, Williams has helped build databases that enable him and other scientists to examine environmental changes not only at a specific location, but across the continent, mapping how a species’ range has shifted because of climate change. Through his findings, he has advanced the concept of “no-analog” communities, or communities of species remixed into combinations not seen today. 

“The records show very clearly that species were not all heading at the same rate, in the same direction, as climates changed in the past,” he says. “As a result, we had this reshuffling of species into new communities.”

From past to present

Williams believes no-analog communities formed in response to no-analog climates – mixtures of climatic conditions that happened in the past but don’t happen today. A similar situation could soon emerge, he says, exacerbated by rapid climate change, invasive species and changing land use patterns. 

“When the world is changing
to a condition that may be
very different than what
we’re used to and what our
management process is
based on, that’s a fundamental
challenge for practitioners
and for ecologists.”

“All these things are creating a novel world,” he says. “Just as some of the late glacial climates were outside the bounds of what we see today, and as we saw species reshuffling in response to these past climates, we may expect a similar response in the 21st century.” 

For example, some arctic and alpine climates – those at the coldest end of the spectrum of today’s climates – are at risk of being lost in the 21st century, he says, placing species that are endemic or uniquely adapted to these climates at a heightened risk of extinction. 

But how do you prepare for environmental scenarios in a future climate very different from the present? Again, the past comes into play, using the geological record as a testing ground. 

By asking climate models to predict past species distributions during past periods of no-analog climates, Williams explains, researchers can assess a model’s robustness and predictability.

One of Williams’ colleagues, Zhengyu Liu, has undertaken a major effort to improve the predictive power of climate models. 

Liu, a past director of CCR and a professor of atmospheric and oceanic sciences and environmental studies, is leading a team of scientists producing a state-of-the-art continuous simulation of the past 21,000 years of global climate change. Eventually, the simulation will run through the present and extend 2,000 years into the future.

Zhengyu Liu
Zhegnyu Liu

This National Science Foundation-funded project explores a new paradigm of model-data comparison, coupling the detailed results of the continuous simulation with physical evidence of past climate conditions, such as from fossils and the Greenland and Antarctic ice cores. Matches between the simulated past climate and actual past data help to validate and refine the model and improve its credibility in predicting future climates.

“If the model can reproduce the past with sufficient and credible value, then the future prediction might be true,” Liu explains. “When you have the best model and the best data to verify a model, then you sync it and use the model to make predictions.”

Interdisciplinary collaborations like this are commonplace at the Center for Climatic Research. 

“What’s great about CCR is that everyone is working on an important different piece; it’s a nexus,” says Williams, explaining that each member of the diverse research team brings a different expertise. 

Hotchkiss agrees. “My lab does some of the simplest kinds of reconstructing of climate ourselves, but it’s critical for me to interact with climate modelers and the people who really understand the physics of climate to make sure I’m not diving into a complicated ecosystem response based on a spurious notion,” she says. “CCR is one of the only places in the world where you can do that, and they’ve been doing it for long enough that it’s part of the culture.” 


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