Yale Experts Explain Climate Change

June 25, 2021
Experts Dan Esty and Miranda Massie break down one of the most pressing environmental and social challenges of our time. 

How do we define climate change?

Climate change is the long-term change in the average weather patterns of Earth’s local, regional, and global climates.
“For about the last ten thousand years, the Holocene period in geological terms, humanity has occupied a fairly stable climate,” explains Miranda Massie (GSAS M.A. ‘92), Director and Founder of The Climate Museum. “While there have been changes from time to time, they are slight in the context of planetary history, and overall, weather systems have been predictable and coastlines have remained in place. Those conditions of relative stability are what allowed agriculture and then civilization to flourish. In other words, the Holocene climate is a basic precondition for what we understand about ourselves and our society. What we are seeing now is the fundamental disruption of that stability.”

What are some of the main causes of climate change?

“The fundamental changes to the stability of our climate are primarily due to the burning of fossil fuels like oil, coal, and natural gas, which started at a mass scale during the Industrial Revolution,” Massie says. 
Dan Esty, Hillhouse Professor of Environmental Law and Policy at the Yale School of the Environment and Yale Law School, explains that when we burn fossil fuels to do things like power our homes and vehicles and engage in most agricultural and manufacturing processes, we emit greenhouse gases. Often referred to as “GHGs”, these gases act like a heat-trapping blanket over the planet and prevent the heat that comes from sunlight from leaving the atmosphere. Some of the more common greenhouse gases are carbon dioxide, methane, and chlorofluorocarbons, and all have different heat-trapping capacities. 
“In addition to emitting greenhouse gases, another contributor to climate change is our destruction of carbon sinks, or places that would naturally store this carbon for us and keep it out of the atmosphere,” Esty says. “Plants and trees, for example, are natural carbon sinks. When we have a forest that is cut or burned down, we lose a sink, and we therefore lose some of the ability of the earth to absorb carbon dioxide. Widespread deforestation and changes in land use patterns, therefore, are significant drivers of the climate crisis.”
Massie also points out that while burning fossil fuels and eliminating carbon sinks is the clear physical cause of the climate crisis, this fossil fuel-based economy does not exist independently from our culture. 
“The cultural and social context for the climate crisis is critical.  Inevitably, the burning of fossil fuels as our primary source of energy both comes from and reinforces basic social understandings and practices developed over time: how human beings have come to relate to the rest of the natural world and to each other. At the heart of this lies a culture of exploitation–the sense that the rest of nature exists, inexhaustibly, for human use alone–and that some human beings similarly exist as resources for others with more social power. Colonization, rigid racial hierarchies, and the simultaneous fetishization and abuse of coal miners are examples of exploitation and dehumanization in our history and culture. These dynamics are deeply bound up with the fossil fuel economy,” Massie says. “Therefore, the entire organization of society and culture can also be usefully understood as the cause of climate change.”

What evidence tells us that climate change is happening?

“There is copious and irrefutable evidence that climate change is happening, but a lot of it is not immediately apparent to the average person,” Massie says. “For example, the concentration of carbon dioxide and other heat trapping gases in the atmosphere is not something that you and I can directly perceive. It’s something that scientists have measured.”
Esty explains that there is an entire science dedicated to extrapolating and tracking global temperatures and carbon dioxide levels across human history. Scientists can reconstruct human history by carving out polar ice cores or sediment from the ocean floor and examining their physical and chemical makeup to understand how the environment has changed over centuries.
“As a result of this science, we know very clearly that the level of carbon dioxide in the atmosphere has risen from a couple of 100 parts per million (ppm) in pre-industrial times to over 400ppm now,” Esty says. “That is a signal that we’ve dramatically increased the level of greenhouse gases in our atmosphere.”
Massie adds the example of the oceans becoming more acidic as they absorb higher levels of carbon dioxide, both of which can be measured by scientists and further proven by things such as the bleaching of coral reefs. 
However, for some communities around the world, climate change is already quite tangible.
“In recent years, we have seen growing evidence of increased intensity of windstorms, hurricanes, flooding, and more devastating forest fires,” Esty says, giving examples from the last decade including Hurricane Sandy and the Australian wildfires. “We have also seen glaciers and ice sheets crack and melt, causing measurable sea level rise. All of that gives us a signal that we’ve got a real problem that needs to be addressed.”

What are the impacts of climate change, both to the environment and to humans? 

Climate change has and will continue to increase local, regional, and global temperatures and alter weather patterns. As Esty points out, these changes will lead to more severe weather events and natural disasters, ultimately disrupting communities and infrastructure around the world. 
“We also know that there will be devastating impacts to species and ecosystems that humans don’t directly connect to or rely on,” Esty adds. “The stress of increased temperatures and ocean acidification may prove too much for certain species, causing them to collapse.”
Increasing temperatures will also melt glaciers at the Earth’s poles, which will not only affect the species that live there, but will also cause global sea level rise. This will impact coastal communities and ecosystems by eroding or engulfing the land and heightening the risk of severe flooding. 
“Because of the historically stable climate, we’ve developed a robust civilizational infrastructure that is geographically anchored,” Massie explains. “You can’t just take farmland that’s been developed over the course of hundreds of years and move it north every three to five years. As Climate Scientist Katharine Hayhoe says, if it were five thousand years ago, as the sea levels rise, we would just pick up our coastal encampments and move them further inland. But that’s hard to do, if your coastal encampment is modern New York City or Hong Kong.”
A change in weather patterns will also have serious consequences for our global food system.
“Changes in rainfall patterns and new periods of drought are particularly concerning, as they may alter the lands that are suitable for food production as well as the types and amounts of crops that can successfully grow and feed our global population,” Esty says. 
Massie points out that these disruptions to our homes, infrastructure and food systems will challenge the equitable access to the necessities of life and put great stress on the social fabric of humanity.
“The climate crisis has a number of cascading and interacting effects that are already disrupting the foundations of our civilization and causing massive public health problems–including 8.7 million deaths annually from the fossil fuel particulate matter alone. Very importantly, climate impacts intensify existing inequalities rather than reducing them–while also creating new ones,” Massie says. 
Massie goes on to explain that many communities around the world who will experience the most devastating effects of climate change have often contributed the least to the crisis and/or are least equipped to protect themselves. 
“Island Nations, for example, have contributed virtually nothing to climate change, and yet they may have the physical home for their sense of belonging, their national identity and culture completely wiped out by sea level rise,” Massie explains. “In Miami, the Haitian community is under pressure to leave Little Haiti, which sits on elevated ground, as real estate developers look to make way for wealthier, mostly white new residents fleeing the beachfront flood zone as sea levels rise.
There are examples everywhere. The fossil fuel economy requires sacrifice zones, and sacrifice zones require racism and other hierarchies … It’s important to include in the definition of the climate crisis that it is a crisis of social inequality.”

What is being done to prevent and prepare for climate change?

Our experts explain that there are two key approaches to prevent and prepare for climate change: mitigation and adaptation.
“Mitigation is the attempt to reduce the amount of greenhouse gas emissions going into the atmosphere,” Esty explains. “It also includes efforts to increase and protect the sinks that are absorbing carbon dioxide.”
There are a wide range of mitigation efforts happening at the local, regional, country, and international scales. A key area of focus is moving towards energy efficiency and a transition to a clean energy grid, which is one that relies on renewable energy sources like solar, wind, and hydro power that do not emit greenhouse gases. This shift has implications for transportation and shipping, industry and manufacturing, agriculture, construction, and our material consumption as we know it. For decades, countries around the world have collaboratively committed to reducing global emissions through international treaties like the Paris Climate Agreement, and individual regions, states, and cities have put forth policies and plans to reduce emissions domestically. 
Esty mentions a new component of climate change mitigation currently being researched by scientists that is meant to deal with the GHGs we have already emitted. This area of research is called “geoengineering”, which is the deliberate large-scale manipulation of an environmental process that affects the Earth’s climate, in an attempt to counteract the effects of global warming. Esty explains that this strategy involves everything from designing technologies to reflect solar radiation back into space to developing man-made ways to capture or ‘sequester’ carbon and store it in the ground. 
Importantly, while geoengineering may help to reduce some of the severe impacts of climate change as we transition our energy grid, the human alteration of natural global processes comes with its own set of ethical concerns.
The second key approach to preparing for climate change is called adaptation. 
“Adaptation is simply figuring out how we as a society can live with at least some of the impacts of climate change,” Esty says. “Sometimes this is described as resilience, or hardening ourselves to the changes in weather, temperature, and systems that will undoubtedly come.”
This might involve moving or retrofitting coastal homes, roads, rail lines, and power plants that are under increased risks of flood due to sea level rise, or adding additional green spaces to cool down urban areas that will experience extreme heat as temperatures rise. 
Massie explains that the inequities of climate change are also apparent within access to mitigation and adaptation resources. For example, while adaptation efforts are expected to save money down the line, they take a large amount of upfront investment, which is something that not all communities have. 
Truly mitigating and equitably adapting to climate change, Massie believes, will require a shifting of individual mindsets and social policies. 
“You cannot imagine getting to a resilient, zero-carbon economy and society without major interventions toward equality and toward a different set of relationships among humans and with nature,” Massie says. “Our entire mode of being has developed as a complex, interconnected system, and our energy source can’t be simply severed from that.”

What role do individuals play in mitigating and/or adapting to climate change?

“To meaningfully take on climate change, we need to be hugely ambitious,” Massie says. “It is not just the responsibility of government, but also all of society and all of culture. Scientists have agreed that the worst impacts can almost certainly be avoided, but to do that we need the broadest possible public engagement.”
When it comes to mitigating climate change, Esty adds that in the near future, we should expect incentives to switch to more sustainable forms of transportation, like electric vehicles or biking, as well as renewable energy. The impact associated with one’s food choices will likely also become a public concern.
“People should be prepared to pay for the harms they are in effect causing when they consume high greenhouse gas emitting products, with meat consumption being a particularly notable example,” Esty says.
In terms of adaptation, Esty says that it is imperative for individuals to think about their risk to climate impacts like severe weather and to prepare themselves, their property, and their community accordingly.
Massie points out that we will also need individuals to stand up for their communities in an activist capacity to demand that their elected officials move away from the interests of and reliance on fossil fuel companies and take ambitious climate action.
“These are huge challenges that we as a society can meet, if we establish the correct social, political and cultural context in which decisions get made,” Massie says. “To get started properly, we have the technology we need–what we don’t have yet is the will to implement it at the required scale and speed.
We need intensely ambitious and community-minded action by government at all levels and across the private sector, sustained for a long time. In turn that requires a broad cultural shift toward civic engagement and action–the mobilization of people coming together to push that forward–both activists who are already deeply involved with the climate justice struggle and, critically, the broader public as well.”            

What is Yale Doing?

In 2020, Yale met its greenhouse gas emissions goal of reducing emissions by 43% below 2005 levels, despite a 21% growth in the campus footprint. This achievement was made possible by countless individuals and academic and operational departments on campus.
Some notable contributions to this goal include:
  • Significant investments in our energy supply. We updated our power plants and increased our reliance on renewables like solar and geothermal energy.
  • Retrofits of older campus buildings to become more energy efficient.
  • Employment of new design guidelines to ensure for the highest standards of efficiency in new construction and renovations while improving the usage of existing campus space.
  • Personal energy reductions through participation in initiatives like the Yale Carbon Charge Recess Checklist.
In summer 2021, Yale announced a new emissions reductions target that includes achieving zero actual carbon emissions — in other words, reducing carbon emissions to zero without having to purchase carbon offsets — by 2050, and reaching net zero emissions by 2035, or “zero” emissions after offsets and other campus reductions in emissions are factored in.
More information can be found in the full announcement from Peter Salovey and Scott Strobel.