Final answer:
Scientists can determine if carbon dioxide comes from burning fossil fuels by analyzing isotopic signatures and tracking the increase in atmospheric carbon dioxide levels.
Step-by-step explanation:
Scientists can tell if carbon dioxide comes from the burning of fossil fuels through various methods. One method is by measuring the isotopic signatures of the added carbon dioxide in the atmosphere. When fossil fuels are burned, they release carbon dioxide with a distinctive isotopic composition. By analyzing the isotopic ratios, scientists can determine if the carbon dioxide is from fossil fuel combustion. Another method involves tracking the increase in atmospheric carbon dioxide levels over time. The burning of fossil fuels has caused a significant rise in carbon dioxide levels in the atmosphere, which can be attributed to human activities.