How People Change Earth's Climate

By the end of this lesson, you will be able to use scientific evidence to explain how human activities such as burning fuels, cutting down forests, and building cities can change Earth's climate.

Climate is the average pattern of temperature, rainfall, and wind in a place over many years, which is different from weather, the conditions outside on any single day. Scientists study climate using evidence like temperature records kept for more than a hundred years, air bubbles trapped in ancient ice, and measurements of gases in the atmosphere taken from towers and satellites. That evidence shows that Earth's average temperature has been rising, and the rise lines up closely with the growth of human industry.

One big reason is greenhouse gases, which are gases like carbon dioxide and methane that trap heat near Earth's surface the way a car's closed windows trap heat on a hot Houston afternoon. When we burn coal, oil, and natural gas to make electricity or run vehicles, we add carbon dioxide to the air. Measurements show carbon dioxide levels are much higher today than at any time in the ice core record, and more trapped heat means warmer air and oceans.

Deforestation, the large-scale removal of trees, adds to the problem because living trees pull carbon dioxide out of the air during photosynthesis. Fewer trees means more of that gas stays in the atmosphere. Urbanization, the growth of cities, also matters: concrete and asphalt in places like Dallas or San Antonio soak up sunlight and release heat, so cities often measure several degrees warmer than nearby ranchland.

Together this evidence helps scientists predict changes Texans may notice, such as hotter summers, stronger droughts, heavier rainstorms, and rising sea level along the Gulf Coast.

Try it: using what you learned, explain why a neighborhood with many shade trees might record cooler afternoon temperatures than a parking lot just one block away.