The earth’s climate changes over time. Some of these changes appear to be natural, some seem to be caused by human action. The greenhouse effect and urban heat islands are two examples of climate change caused by man.

Urban Heat Islands Look at the isolines on the drawing above. What do those isolines tell us?

Why do you think the temperature is so much warmer in a big a city than it is in nearby suburbs or rural areas?

Does this visual help explain what scientists call the “Urban Heat Island Effect?”

Here are some other ways that urban areas influence the climate.

Discussion questions: 1. How does the “urban heat island effect” impact the people who live in large cities? 2. Is the “urban heat island effect” something local and state governments should be aware of for planning purposes? Why or why not?

The Greenhouse Effect Some scientists compare the Greenhouse Effect to what happens inside your car on a hot day. Describe that process. Pretend you have gone to the mall. Your car was nice and cool when you parked outside. When you get back two hours later, you can barely touch the steering wheel or the seat belt buckle. Why?

Many gardeners, especially those who live in colder climates, build greenhouses to protect their delicate plants and flowers during the winter. Examine the drawing below to see how the greenhouse keeps the fragile plants nice and toasty even during cold weather.

The sunlight passes through the clear windows of the greenhouse, but the heat energy can’t get back out. Essentially the air pollution created by humans acts like the walls of a greenhouse, trapping heat energy from the sun and raising the temperature of the earth.

Can the greenhouse effect be controlled by people? How?

One fear about the Greenhouse Effect is that as the earth’s temperature rises, the ice at the poles might start to melt. Although a change like this would be gradual, what kind of impact do you think it could have on humans who live in areas near sea level?

What do you think the cartoonist is trying to say here?

What about this cartoonist?