Making Sense of Climate Change

Earlier this year, I had an opportunity to attend a virtual talk presented by leading climate scientist and communicator Dr. Katharine Hayhoe. She began by asking the audience to send in one word that describes how they feel when thinking about climate change. The responses popped up live in a word cloud on Hayhoe’s shared screen:




Those words also describe how I felt when I realized the conclusion to my series of blogs on the 2021 Nobel Prizes would address the topic of climate change.

I join the majority of Americans who agree that global warming is happening (72%) and that it is mostly caused by human activities (57%). I’m also in the 64% of people who rarely or never talk about climate change. This is my first time writing about it.

Though I care deeply about the effects of climate change, I wasn’t excited to write about a problem that mostly leaves me feeling overwhelmed and ineffective. As a person who tends to bend towards hopefulness, the last thing I wanted was to communicate hopelessness to readers.

Because of this, I decided to read Dr. Hayhoe’s recent book, Saving Us. In the book (on which her conference talk was based), Dr. Hayhoe describes why hopefulness—not fear or anxiety—is what we need to start implementing solutions. And that this hopefulness starts by being willing to talk about climate change, say why it matters to you and learn about the incredible work already happening to help solve the problem.

So, in light of that advice, let me take this chance to tell you a bit more about how three physicists helped us understand the complexities of Earth’s climate and how human activity is changing it.

Modelling Carbon Dioxide’s Warming Effects

Scientists have known of the ability of CO2 to trap heat and cause warming effects since the 1850s. Based on a knowledge of thermodynamics and of the physical properties of carbon dioxide (CO2), scientist Svante Arrhenius determined in 1896 that a doubling of CO2 levels in Earth’s atmosphere could lead to a 6 °C increase in ground temperature.

Over fifty years later, atmospheric physicist Syukuro Manabe took a more nuanced approach to understand the relationship between atmospheric CO2 levels and global temperature. Manabe created a model that incorporated the way air moves vertically through the atmosphere—hot air rises and cool air sinks. It was among the first climate models to incorporate dynamic behavior of atmospheric systems. Though his more precise model did not estimate as much warming as Arrhenius’s earlier calculations, Manabe’s model confirmed that increased CO2 in the atmosphere results in higher global temperatures.

Fingerprinting the Causes of Warming

We all know weather is chaotic, complex and challenging to predict more than a few days in advance. But if that’s the case for weather, then why are scientists able to make long-term predictions about how our climate will behave?

Klaus Hasselmann, a physicist who began his career by studying the fluid dynamics of ocean waves and currents, provided the answer. Hasselmann developed a climate model that incorporated weather data as rapidly changing noise. The model was able to show how noisy, chaotic weather could result in changes to the climate.

This idea of finding ways to describe and interpret a complex system is related to the work of Georgio Parisi, the third recipient of the 2021 Nobel Prize in Physics. Parisi’s work, though not directly addressing climate, examined how seemingly disordered systems have underlying rules for their behavior. From initial theories based on a class of strange materials called spin glasses, Parisi’s findings have influenced research on systems in biology, neuroscience, mathematics and climate modelling.  

Through the 1970s to 1990s, Hasselmann also used his climate model in combination with physical data to show how different factors—human and natural—contributed to increasing global temperatures. This “fingerprinting” approach made clear that Earth’s warming temperatures cannot be explained by natural causes like volcanic eruptions or variations in solar activity. The observed increase in global temperatures over the past 170 years is caused by humans. Hasselmann’s work laid a foundation for further studies that have corroborated that same conclusion—climate change is caused by the greenhouse gases our industries, activities and lifestyles emit.

The Capacity for Change

This year’s Nobel Prize in Physics recognized work that allowed researchers to tease out the rules and patterns that govern complex, interconnected and disordered systems. Manabe, Hasselmann and Parisi’s work has helped us understand the why and how of the physical, observable data that tells us the temperature of the earth is increasing.

The debate of climate change is not whether it is happening, nor if it is caused by humans. The data and the models tell us that it is happening and that we have caused it. And we’re starting to see the impacts of that change

The question now is what are we going to do about it? What can I do about it?

There’s an image in Saving Us that provides an encouraging response to that question:

“We often picture the challenge of solving climate change as a giant boulder at the bottom of a huge hill. Only a few people are straining their backs to roll it up, and it hasn’t budged an inch. But in reality…that giant boulder is already at the top of the hill. It’s starting to gradually roll downhill in the right direction. There are many millions of hands on it, pushing. Each one we add speeds it up a little more.”

“In this fight for our future, though, we are not alone. My hand is on the boulder, pushing it down the hill. So, too, are the hands of millions of others: countries, corporations, and organizations big and small. There are individuals, too…We just need to get that boulder rolling faster.”

(Katharine Hayhoe. Saving Us, pgs. 185, 191)

Learn more about our goal to reduce emissions by 50% by 2030 and our other sustainability goals by visiting Planet Aware.  

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