A Planet Under Pressure: Global Emissions in 2025

As 2025 wraps up (even though it feels like it just started!), here’s a quick update on global greenhouse gas emissions. Sadly, the news isn’t great—our three biggest heat-trapping gases are still risi

Carbon Dioxide (CO2) Emissions

CO₂ is one of the main greenhouse gases. Greenhouse gases act like a blanket around Earth, trapping heat. We need some of them to keep the planet warm enough for life, but too much makes Earth heat up too fast.

CO₂ comes from burning fossil fuels like coal, oil, and natural gas. It also comes from wildfires and volcanoes. Scientists have been measuring CO₂ since 1958 at the Mauna Loa Observatory in Hawaii. Back in 1988, levels were around 350 parts per million (ppm). By April 2014, they hit 400 ppm, and today they’re even higher.

“Parts per million” simply means how many CO₂ molecules there are out of one million molecules of air.

Scientists also study CO₂ trapped in tiny air bubbles inside Antarctic ice cores. These give us a long-term record going back hundreds of thousands of years. When we combine the ice core data with modern measurements, we can see how sharply CO₂ has climbed in the last few decades.

CO₂ has now increased more than 50% compared to the 1700s, when the industrial era began. That rise is happening much faster than anything seen at the end of the last ice age, when CO₂ increased slowly over thousands of years. Worse yet, once it’s added to the air, it hangs around for a long time: between 300 to 1,000 years. 

Satellites also track CO₂ from high in the atmosphere. Maps show CO₂ climbing from about 365 ppm in 2002 to over 420 ppm in 2022.

Why CO₂ Goes Up and Down Each Year

Even though CO₂ keeps rising overall, it naturally goes up and down during the year. This is mostly because of plants:

• Spring and summer (Northern Hemisphere): Plants grow and pull CO₂ out of the air.
• Fall and winter: Plants die back and release CO₂ as they decompose.

The Southern Hemisphere shows the opposite pattern, but because there’s far more land and vegetation in the north, the global cycle follows northern seasons.

Methane (CH₄) Emissions

Methane is another important greenhouse gas, and its levels have been rising quickly in recent decades. About 60% of the methane in the atmosphere today comes from human activities.

Methane traps a lot more heat than carbon dioxide (CO₂) molecule for molecule, but it doesn’t stay in the air as long. Methane lasts only 7 to 12 years, while CO₂ can remain for hundreds of years. Even so, methane is the second-biggest driver of global warming after CO₂.

Methane comes from both natural and human-made sources. The largest human sources are:

• Agriculture, especially livestock like cows
• Fossil fuels, such as coal, oil, and natural gas
• Landfills, where trash breaks down and releases methane

Nature produces the other 40%, mostly from wetlands. As plants and organic matter break down in wet, low-oxygen environments, they naturally release methane into the air.

Are you itching to know how NASA tracks methane? Here’s the place for you to learn more!

Nitrous Oxide (N₂O) Emissions

Nitrous oxide is another greenhouse gas that we hear very little about. In 2022, it made up about 6% of all U.S. greenhouse gas emissions from human activities. Globally, about 40% of N₂O emissions come from humans.

N₂O is naturally part of Earth’s nitrogen cycle, but human activities are increasing how much ends up in the atmosphere. The main sources are:

Agriculture: mostly from making fertilizer

Burning fossil fuels

Wastewater treatment: tiny microbes help break down the nitrogen in the water. But as they do this, they also produce nitrous oxide (N₂O).

Nitrous oxide is extremely potent. One pound of N₂O warms the atmosphere 265 times more than one pound of CO₂. It also lasts much longer—N₂O stays in the atmosphere for about 121 years before it breaks down.

Even though N₂O makes up a smaller share of total emissions, its strength and long lifetime make it a major part of the global warming puzzle.

What Can We Do About Greenhouse Gas Emissions?

We’ve talked a lot about reducing carbon dioxide emissions but not about methane and nitrous oxide. The EPA has a great list of ways to reduce methane emissions.

Reducing N₂O starts with tackling the biggest human-made sources. In agriculture, using smarter fertilizer practices—like applying only the amount plants actually need, using slow-release formulas, and planting cover crops—can cut down on extra nitrogen that turns into N₂O. Improving wastewater treatment systems also helps by keeping oxygen levels stable and upgrading old equipment so bacteria don’t produce as much N₂O during the cleaning process. Cutting back on fossil fuel use, improving industrial systems, and preventing leaks in chemical manufacturing can also make a big difference. By taking action in each of these areas, we can lower N₂O emissions and help slow global warming.

For a technical reference on methods to lower N₂O emissions, this is a good summary.

Folks, we can do this. Share this information with your family and friends, and let your elected officials know that we need real action to protect our kids and grandkids!