Carbon Emissions: Why They Matter, What to Do

Carbon emissions resulting from human activities have increased so much over the past century, they are changing the earth's climate. Likely effects include rising sea levels, dying habitats, and extreme weather events.

The good news: Reducing your home's energy use contributes to the solution.

What is global climate change?

Carbon emissions—or more specifically, greenhouse gases such as carbon dioxide, methane, nitrous oxide, and ozone—act like a blanket around the planet, trapping energy to create a greenhouse effect. Like a greenhouse's glass, they let in the sun's warmth but don't let it dissipate. The natural greenhouse effect allows life on the planet, but now we have too much of it: Human activities are intensifying the greenhouse effect, pushing our system out of balance. A warmer planet threatens the delicate systems on which all of life depends.

The greenhouse effect. Graphic: U.S. Environmental Protection Agency

Recent climate changes

Climate changes have already occurred, according to leading climate scientists working with the Intergovernmental Panel on Climate Change (IPCC). Increased global average air and ocean temperatures, widespread melting of snow and ice, reduced plant and animal populations, and rising sea levels were documented in the IPCC's "2007 Synthesis Report."

Earth has warmed about 1ºF over the last 100 years, and it's heating up faster all the time. Eleven of the last 12 years (1995 to 2006) rank among the 12 warmest years on record (since 1850).

The results are showing up all over the planet: sea level rise, more extreme weather, and changes in the timing of seasons. One visible example is the melting of glaciers. Since 1850, larger glaciers in Montana's Glacier National Park have melted to one third of their previous size. A computer model shows that all glaciers in the park will be gone by 2030 if global temperatures continue to rise as forecast.

The disappearing glacier: 1932 to 1988

Boulder Glacier, Glacier National Park, Montana, July 1932

The same view of Boulder Glacier in July 1988, 56 years later. Photos courtesy of USGS.

What could happen if we don't act

If greenhouse gas emissions continue to increase, the average temperature at the Earth's surface could increase another 3.2 to 7.2ºF above 1990 levels by the end of this century, the IPCC predicts. While folks in Minnesota might welcome some warmer winter days, most of the effects of global climate change are not good news. Exactly where and when the changes will happen is hard to predict, just as meteorologists can't predict tomorrow's weather with 100% certainty. But scientists can say with confidence this is the current direction.

Unless we pull the plug on carbon emissions, we are likely to experience:

• Loss of water resources: Warming is projected to exacerbate competition for over-allocated water resources. In the western U.S, warming in the mountains will likely decrease snowpack, and cause more winter flooding and reduced summer flows.
• Sea level rise: Over the next century, sea level is expected to rise up to 3 feet, causing coastal flooding and loss of oceanfront property and loss of drinking water in coastal regions as saltwater infiltrates wells.
• Endangered crops and food supply: Climate change will impact food supplies around the world through effects on plant growth, altered rainfall patterns, and pest problems. In some parts of the world, people might not be able to grow the food they need.
• More fires: Increased temperatures and changes in rainfall increase fire danger. For instance, the California Regional Assessment notes an increase in the number and extent of areas burned by wildfires in recent years. Fire modeling results show that climate change will make fires hotter, faster moving, and more difficult to contain.
• Worsening air quality: Higher temperatures increase the formation of air pollutants, such as ground-level ozone and particulate matter. These pollutants are a concern for people with respiratory illnesses such as asthma. Poor air quality also affects ecosystems and agricultural crop yields.
• Extinctions: As the timing of seasons, rainfall patterns, and temperatures change, many plants and animals will be lost forever. The IPCC reports that if sea ice declines according to some projections, polar bears will face a high risk of extinction.
• Infectious diseases: Diseases now constrained geographically by climate will range farther, resulting in a higher likelihood of Lyme disease in more areas of the U.S. and malaria epidemics throughout Africa.

Main sources of carbon emissions

The main source of carbon emissions is the burning fossil fuels such as coal, natural gas, and oil. How much do we contribute with our home energy use? According to the U.S. Environmental Protection Agency's 2009 Greenhouse Gas Inventory Report, residential energy use is the second largest source of carbon emissions.

The vehicles we drive are also a big source, since every gallon of gasoline burned puts 20 pounds of carbon dioxide into the air. So it's no surprise that the passenger cars, SUVs, and trucks we drive are the third largest greenhouse gas source.

Top 5 U.S. Greenhouse Gas Sources

1. Industry
2. Residential energy use
3. Passenger cars and trucks
4. Commericial energy use
5. Diesel trucks

The greenhouse effect. Graphic: US EPA

Carbon emissions from home energy use

What in our homes produces the most carbon emissions? According to the 2008 U.S. Department of Energy's Buildings Energy Data Book, space heating is number one, followed by space cooling, and water heating. But other functions, especially lighting and use of electronics, refrigerators, and clothes and dish washers are significant.

In fact, unless your home is powered entirely by renewable energy, everything you do that uses energy contributes to global warming. The average American home's energy use is responsible for 62 pounds of carbon per day, according to the U.S. Department of Energy's Buildings Energy Data Book. To stabilize the earth's climate, scientists tell us we must reduce carbon emissions 80% by 2050. If we look at this at the level of an individual household, this means reducing each American home's carbon footprint to 12 pounds. Local, state, and federal government are starting to implement policies to cut carbon—but we all need to be part of the solution. Where can you make a cut today?

What you can do

• Save energy:  Whenever we use electricity produced by fossil fuels, we help put greenhouse gases into the atmosphere. Your home is filled with opportunities to save energy. Check our Activity Center for your best opportunities.
• Use renewable energy: Consider installing solar-generated electricity (photovoltaic) and solar-heated hot water (solar thermal). Home wind generators are even possible, as are passive solar home designs that use the sun's energy to heat the home directly. Another option is to purchase "green" energy, produced by renewable sources, from your utility.
• Buy carbon offsets: You can support carbon reduction projects by purchasing "carbon offsets" that compensate for your carbon emissions by funding practices that reduce emissions.
• Save transportation energy: Consider walking, riding a bike, or taking a bus or train. If you do drive, try carpooling or check fueleconomy.gov for the most efficient vehicle when you are ready to buy a new one.
• Reduce waste: Recycle cans, bottles, plastic bags, and paper to help save natural resources such as trees, oil, and aluminum that require a lot of energy to harvest and mine.
• Compost: Kitchen scraps sent to landfills decompose anaerobically, resulting in methane, a greenhouse gas 20 times more potent than carbon dioxide. Composting is aerobic and binds up, or "sequesters," the carbon in compost for use by plants.

Visit the Activity Center to learn more.