Along the coast in Western Australia, a cliffside reveals a long-dead coral reef frozen in time. Geochemist and paleoclimatologist Andrea Dutton (M.S. ‘00, Ph.D. ‘03) collects samples from field sites like this fossilized wall of rock in Western Australia to analyze and date them. To accomplish that, Dutton uses a radiometric dating technique to determine the fossils’ age by measuring trace amounts of uranium that get incorporated into the coral over time from seawater.
Once that uranium gets locked into the skeleton, it starts to decay as it ages and turns into thorium. “Like a ticking clock,” Dutton says. By dissolving the coral, she can measure how much uranium and thorium are in the skeleton and, thus, how old the sample is.
There’s a lot of information trapped in those samples. Because coral grows at the sea surface, determining when the coral grew indicates how high the sea level was at a given point in time. And by understanding how high the sea levels were during past warm periods, for example, Dutton can demonstrate how sensitive ice sheets were, and still are, to warming.
125,000 years ago, during a period known as the Last Interglacial, the climate resembled today’s global temperature. Because of this similarity, the fossilized coral reefs from that period provide a reasonable analogue to understand how the earth might respond to the current rise in temperature. Dutton says the results are sobering.
The last time the earth was at the same global temperature it is today, Dutton and her colleagues estimate that sea levels were six to nine meters, or 20 to 30 feet, higher than they currently are today—meaning a lot of places on coasts around the world could soon be underwater.
Small Degrees, Big Effects
Climate change discussions tend to overlook the drastic effects that a one-degree (Celsius) rise in global average temperature have on the planet, and on us. “When we talk about the need to limit global warming to two degrees, sometimes people don’t understand because they think, ‘But it changed by 20 degrees outside from yesterday to today,’” says Dutton. “But the global average temperature changing by one or two degrees makes for huge planetary change everywhere.”
Some perspective? During the last ice age, when ice sheets more than a mile thick covered North America and mastodons and mammoths roamed the planet, Earth was just four degrees Celsius colder than it is today.
Even though Earth has experienced warm periods in its past, Dutton explains that the current acceleration in the rate of sea level rise is a direct response to the warming of our atmosphere and oceans, which is driven by human-caused global warming. “Scientists have demonstrated that the warming we see today cannot be explained by natural causes,” she says. “One hundred percent of the current warming is caused by humans. In fact, looking at natural causes alone, the Earth should be slightly cooling right now.”
If all carbon emissions were to stop today, a certain amount of warming would continue because of what has already been set in motion, Dutton says, and some impacts are permanent on human timescales. “Human behavior and industry have warmed the climate so much faster than what’s seen in the geologic record that the ice sheets are now catching up to that change,” she says.
“It’s like taking two ice cubes and throwing them in a hot room—the ice cubes being Greenland and Antarctica,” she says. “Now we’re sitting back and watching them melt.”
All Hands on Deck
In graduate school, Dutton was drawn to the social relevance of paleoclimatology, and the bridge between her research and its global impact has only gotten stronger. “I’ve stuck with this work because it’s so urgent and important,” Dutton says. “As much as I still enjoy the science behind it, that motivation is really what drives me.”
Dutton was named a MacArthur “Genius” Fellow in 2019, and she’s currently in New Zealand as a Fulbright U.S. Scholar based at the Antarctic Research Centre (ARC) at Victoria University of Wellington. There, she’ll pair her knowledge of the rising sea levels with the research the ARC field geologists have gathered from the ice sheets directly, which will provide a more thorough understanding of what might happen to future sea level rise. “When we look at projections of sea-level rise, the largest uncertainty is how the Antarctic ice sheet specifically is going to respond to sustained global warming.”
Dutton also spends a lot of time doing something outside of her usual job description: talking with audiences around the world about how to combat the climate crisis. And although some impacts of the climate crisis are already locked in, Dutton explains that responding urgently and honestly is the only way forward. “The reality is that it’s not always going to be okay. We’re dealing with huge fires, massive flooding, intense hurricanes. This is going to carry into the future and get worse.”
But climate change is not black and white; it is not a choice between no change and complete doomism. There is a lot of gray space in between. “We can all be part of the solution using our own skillset,” continues Dutton. “We need bankers who are thinking creatively, architects thinking creatively, filmmakers reaching audiences who think creatively. We’re going to need every contribution to move us forward.”
“It’s quite clear we can control the climate because that’s what we’ve been doing, just in the wrong direction,” Dutton says. “Now if we put our minds to it, we can control it in the way we want. One degree of warming is already bad enough.”