3. Reading Climate and Pollution Evidence

Environmental questions often give you graphs, tables, maps, or short passages. Start by reading the axes and units. CO2 may be measured in parts per million. Temperature might be shown as an anomaly, meaning difference from a baseline average. Dissolved oxygen may be measured in mg/L.

Evidence becomes stronger when several independent measurements point the same way. For climate change, thermometer records, ocean heat content, glacier mass, sea level, and biological timing all provide related evidence. For pollution, water samples, species counts, and oxygen measurements can tell the same story from different angles.

Be careful with cause and effect. A correlation alone is not enough. But when a correlation matches a tested physical mechanism, the claim becomes stronger. CO2 and temperature are not just two lines rising together; greenhouse gases absorb outgoing infrared radiation, which explains why more greenhouse gases can warm the planet.

On the GED®, choose conclusions that match the data's scope. If a study measured one river, do not claim all rivers. If a graph covers 1990-2020, do not claim what happened in 1800 unless the data includes it.