In 2007, the Supreme Court, in Massachusetts v. EPA, decided that the EPA must fulfill its authority. It must regulate tailpipe emissions of greenhouse gases. These gases cause, or contribute to, air pollution. The Clean Air Act authorizes the Environmental Protection Agency to regulate greenhouse gases because they qualify as air pollutants. Before, the EPA did not consider greenhouse gases as air pollutants. Now, the Court ordered the EPA to regulate carbon dioxide and other greenhouse gases. This was a landmark victory.
Finally, the U.S. government agreed with the reality of climate change and its risks. But you must also understand that the Supreme Court narrowly reached a majority decision, 5-4. In a future post, I’ll discuss Richard J. Lazarus’s book, The Rule of Five. It’s a gripping story of a coalition of state and environmental advocates that took on the George W. Bush administration’s EPA – and won.
Why is this important to bring up at this time? Simple answer. Trump’s EPA. In July 2025, Lee Zeldin, administrator of the EPA, announced plans to revoke the Obama 2009 “endangerment finding.” This finding is the cornerstone of U.S. climate regulations. I have followed climate policy for years. I think about Lazarus’s story of hard-won progress. I consider what it means in the face of this unprecedented rollback.
So, let’s start with a history of greenhouse gases and global warming.
Greenhouse Gases and Global Warming are not new ideas
19th Century Origins
Scientists knew hundreds of years ago that greenhouse gases trap heat. Here are a few examples.
- 1824 – Joseph Fourier was a French mathematician and physicist. He is generally credited with discovering the “greenhouse effect,” which is the atmospheric mechanism that traps heat.
- 1859 – John Tyndall demonstrates that gases like CO? and water vapor trap heat. Tyndall was an Irish physicist. One of his areas of study led him to study air. In particular, the connection between atmospheric CO2, and what is known as the greenhouse effect in 1859 is proven.
- 1896—Svante Arrhenius was a Swedish scientist who calculated that burning fossil fuels will raise Earth’s temperature over time. Arrhenius was awarded a Nobel Prize in Chemistry in 1903.
20th Century Developments
Temperatures increased dramatically in the 20th century. The science of climatology originated with Hippocrates around 400 BCE. Yet, serious study of climate change emerged in the 20th century.
- 1958 – Charles David Keeling begins measuring atmospheric CO? at Mauna Loa Observatory, revealing an upward trend known as the “Keeling Curve.” The Keeling Curve, named for Charles David Keeling, is a graph of atmospheric carbon dioxide (CO?) concentrations measured in parts per million (ppm). From 1958 to the current day, it is the longest continuous record of atmospheric CO?. CO? measurements are taken at the Mauna Loa Observatory in Hawaii, and the data are representative of the global atmospheric CO? concentration due to the pristine nature of the sampling location. The Keeling Curve is considered the most critical environmental data set in the 20th century. The Trump administration’s proposed funding cuts to NOAA climate programs, including global CO? and data collection, threaten decades of science.
- 1970s–1980s As CO? levels increase, scientists start publicly warning about the risks of global warming and its link to fossil fuels.
- 1988 – NASA scientist James Hansen testifies before the U.S. Senate that global warming is real and already underway. He said, “The greenhouse effect has been detected, and it is changing our climate now.” Hansen is now director of the Columbia Climate School: Climate Science, Awareness and Solutions
21st Century Turning Points
- 2007 – In Massachusetts v. EPA, the U.S. Supreme Court rules that greenhouse gases are air pollutants under the Clean Air Act. The EPA has the authority to regulate them.
- 2009 – The Obama-era EPA issues the Endangerment Finding. It officially recognizes that greenhouse gases pose a threat to public health. It also acknowledges their impact on welfare. It took ten years. The EPA finally acknowledged that greenhouse gases are a danger to humans (see the endangerment timeline). They are gases that are to be regulated according to the Clean Air Act.
- 2025—The Trump EPA now seeks to revoke this landmark finding. This action threatens to dismantle nearly two decades of environmental regulation rooted in climate science. Note: Since 2009, Republicans have actively attempted to influence the EPA. They aimed to get the agency to reconsider the Endangerment and Cause Finding for Greenhouse Gases. Their efforts began instantly after it was approved. See here, here, & here.
The Global Thinking Project: Citizen Science Before It Was Cool
In the 1990s and early 2000s, students from the U.S. were already engaging with the science of global warming. They engaged not through abstract lectures, but through hands-on inquiry and international collaboration.
Global Thinking Projects:
- Air Quality Monitoring: Students used ozone badges and handheld sensors. They measured ground-level ozone, which is a greenhouse gas. It contributes to respiratory illness. They logged readings, analyzed data, and compared results across continents.
- Project River Watch: Participants tested rivers, lakes, and ponds for pH, turbidity, temperature, nitrates, and dissolved oxygen. These are key indicators of environmental health. They are influenced by climate change.
- Climate and Ecology Dialogues: Students used email, video conferences, and shared digital workspace. They explored the causes and consequences of global warming in a cross-cultural context. Often, they reached conclusions long before policymakers did.
“We learned that the air I breathe in Georgia is connected to the winds of Siberia. Our rivers speak the same language as Australian streams.”
— Student participant, Global Thinking Project
Why It Mattered Then—and Matters Now
Students were **doing science and diplomacy**–a model of **democratic, inquiry-based education**.
Long before the EPA recognized the legal basis for regulating CO2, young people in GTP were already measuring the science. They were also modeling and acting on it. This was science for the sake of the planet, not politics—a model of democratic, inquiry-based environmental education.
The Legal Legacy:
*Massachusetts v. EPA* vs. Trump’s Undoing
| Arguments in favor of Mass vs EPA | Trump Era Endangerment Reversal |
| Green House Gases (GHG) are pollutants under the Clean Air Act | Trump EPA claims CO2 and other GHG don’t endanger public health. They have no evidence. |
| EPA must regulate pollutants that harm humans. Air pollution causes more humans to die than other climate effects like fires, flooding, wind. | Trump seeks to revoke Endangerment Finding |
| Climate change is causing real harm. | Trump appointees deny the science, without evidence. |
| Read The Rule of Five,: Making Climate History at the Supreme Court by Richard Lazarus. It tells the full story of how the EPA lost. Now, the EPA must regulate greenhouse. | Noting to report to support the current EPA |
In The Rule of Five, Lazarus tells the gripping inside story. An unlikely coalition of states and environmental advocates challenged the George W. Bush administration’s EPA. They emerged victorious. The title refers to the fact that it takes five votes on the Supreme Court to secure a majority decision. In April 2007, that magic number was reached: by a narrow 5–4 margin, the Court ruled in Massachusetts v. EPA. The ruling stated that greenhouse gases are “air pollutants” under the Clean Air Act. The EPA can and must regulate them if they are found to endanger public health or welfare.
This was a watershed moment for environmental law. Justice John Paul Stevens’s opinion has been called the most important environmental decision of our time. It was the first time the U.S. government was legally compelled to acknowledge the reality of climate change and its risks.
In fact, the decision led to the first legally consequential acknowledgment by the United States government. It recognized that greenhouse gases emitted as a result of human activity are endangering human health and welfare. Environmentalists often compare Massachusetts v. EPA to Brown v. Board of Education.
It was a case that “changed everything” for climate policy. It established a precedent that the federal government could not ignore the science of climate change. Source: The Rule of Five.
Record Heat and Regulatory Retreat
As heat domes, wildfires, and superstorms sweep across the U.S. and the globe, the Trump administration is using regulatory tools not to protect us—but to protect fossil fuel interests. Today, as I write this, cities and towns in the USA and Canada experience high levels of air pollution. The pollution comes from fires. Air pollution slips beneath the radar except during these times. But more than 7 million people world wide dies from diseases caused by air pollution. And Trump wants people to die
Revoking the Endangerment Finding would:
- Shut down future EPA climate regulations
- Undo limits on vehicle emissions
- Weaken clean air standards tied to CO? and methane
- Ignore decades of citizen science, public education, and legal precedent
This is not just a political reversal—it is a war on science and a betrayal of public health.
GTP’s Legacy and the Path Ahead
What we built through the Global Thinking Project was a vision of global citizenship grounded in science and empathy. We taught students to watch their world, to speak across borders, and to act on evidence. That legacy is more vital than ever.
As politicians try to erase climate science from the law, we must remind the world.
“The atmosphere doesn’t recognize borders–and neither should truth.”
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