Biological Energy - What's in the News?

Humans' Effect on the Environment
Inference vs. Evidence

Imagine that you were visiting your great-grandma's house. While exploring it, you found an old black and white photograph like the one here. Notice that it appears to be an old home that collapsed with a large tree sticking out of the window. How do you think it happened?

  1. What might have caused the home to look this way?
  2. Could a natural disaster have occurred?
  3. Could this have been caused by a tornado, a hurricane, a landslide or was it due to some other event?

You might only have the information in the photo to help you decide. In making your decision you are using a process called inference. To infer is come to a conclusion using only the information that is available. You may use some life experience to help you. In this example, the color of the photo and the debris in the picture are clues.

Later, you discover the truth about the photograph! The picture of the home in your grandma’s house was actually taken in 1889 when a dam burst and destroyed the home with debris from a nearby forest. When the dam collapsed, a wall of water full of debris, including the tree that pierced the home, flooded the town. Did you infer that this is what had happened? You may not have thought of this, although your guess may have been close. Having direct evidence would have made your decision much easier. Evidence is something that furnishes direct proof of an event. Witnessing the event yourself would even be better.

Because we are not witnesses to every event that happens, we must rely on the recollection and observations of others. Often this comes from written reports. When reading a written event such as a newspaper or magazine article you should think about the accuracy of the report. This is important. Generally the more inference it takes to reach a conclusion the less likely the conclusion will be accurate. The more direct evidence a person has the more likely a conclusion is to be true.

When reading a newspaper or magazine article about science events think about how much direct evidence there is. If the author actually witnessed the event their account is more likely to be accurate. Remember, the more inference required to reach a conclusion the less likely the inference is true.

Read the following fictitious newspaper article about the environment and look for direct evidence that supports the statements that are made.

Humans are Altering Earth’s Environment
by John Newsworthy

WASHINGTON — Today, climatologists raised the public’s awareness of the greenhouse effect by saying that we depend on the greenhouse effect to keep our world temperatures at normal levels. The greenhouse effect is explained as Earth’s atmosphere trapping heat energy from moving out of the atmosphere. This keeps Earth’s surface warm.

Climatologists demonstrated this using a plant greenhouse to model the process. Our atmosphere acts like a plant greenhouse. Light comes into the greenhouse, but much of the resulting heat is trapped. Without the greenhouse effect the temperature of planet Earth would be much colder.

Some scientists fear that the greenhouse effect could cause temperatures to rise too high as certain gases in the environment increase. One reason that this happens is that we are burning more and more fossil fuels, like gasoline. Carbon dioxide is the main atmospheric gas that has scientists worried. Carbon dioxide is released as fossil fuels are burned.

During this century, the amount of carbon dioxide in Earth’s atmosphere has increased by 20%. Our industrial society has also increased the release of methane and nitrous oxide. These are also greenhouse gases. If these gases continue to increase at their current rate, the planet could warm by 5 degrees Celsius over the next twenty years.

An increase in the greenhouse effect results in a process called global warming. Global warming could cause severe damage to Earth’s environment. The effects of global warming include ice melting in polar climates, hotter days and loss of crops and plants. Disease could thrive in a warmer environment. Human death rates may increase due to disease. People may be forced to move to different climates. Animals may not be able to survive. Some animals require a certain temperature for eggs to hatch or water temperatures that are more moderate to ensure their survival.

Most scientists agree that we should try to reduce greenhouse gases. Doing this could minimize the problems of global warming. Reducing carbon dioxide from cars and factories and conserving energy would help. We should conduct more research to provide scientists and citizens' better answers.


  1. What statements in the article are inference only?
    • List five examples of inferences in the article
  2. Which statements in the article are supported by evidence?
    • List five statements in the article that are backed by evidence.

Find a newspaper or magazine articles about the effects of humans on the environment. Bring one article that relies heavily on inference for conclusions and one article that provides more actual evidence. Share your article with friends, family, or your science teacher.