Which two lines of evidence support recent anthropogenic climate change?

• A. Decreasing CO2 concentrations and cooling temperatures
• B. Stable Arctic ice and unchanged precipitation patterns
• C. Decreasing sea levels and reduced wind speeds
• D. Rising CO2 concentrations and warming global temperatures

Answer: (D)

Human-caused climate change is supported by two strong lines of evidence: rising carbon dioxide in the atmosphere and a clear warming trend in global temperatures. CO2 levels have climbed from about 280 ppm before industrialization to well over 400 ppm today, a rise linked to burning fossil fuels and deforestation. This extra CO2 traps more infrared radiation, boosting the planet’s energy balance. At the same time, global average temperatures have increased over the modern era, with warmth intensifying in recent decades and the oceans absorbing much of that heat. The close timing between the rapid rise in CO2 and the observed warming, along with supporting clues like isotopic evidence pointing to fossil fuel sources and climate models that reproduce the warming only when human greenhouse gases are included, makes these two lines of evidence the strongest indicators of anthropogenic influence. Other options describe cooling, stable ice, or falling sea levels, which do not match the observed global warming pattern.