Question

this graph of ice age cycles shows that the earth has gone through several cycles of global warming and cooling, and that these temperature changes correlate with carbon dioxide levels. modern humans evolved about 200,000 years ago. some scientists believe that the current increase in global temperature has been made worse by human activity. why might some scientists disagree?
options:

• human activity does not affect carbon dioxide levels, so it cannot affect global temperatures.
• carbon dioxide levels and global temperatures have shown significant increases before modern humans existed.
• modern humans evolved about 200,000 years ago and the carbon dioxide level and global temperature decreased from 200,000 to 150,000 years ago.
• carbon dioxide levels and global temperatures show the same amount of fluctuation that occurred before modern humans existed.

(chart: comparison chart of sea level, global temperature and co₂ pollution (in the last four cycles of ice ages))

Explanation:

To determine why some scientists disagree, we analyze each option:

• Option 1: Incorrect. Human activities (like burning fossil fuels) do affect CO₂ levels and global temperatures.
• Option 2: Incorrect. The graph shows cycles of warming/cooling, but significant modern CO₂ increase is due to human activity, not just pre - human fluctuations.
• Option 3: Incorrect. The timeline of human evolution (200,000 years ago) and CO₂/temperature trends don't support this as a reason for disagreement about current human - caused warming.
• Option 4: Correct. The graph of ice - age cycles shows that CO₂ levels and global temperatures had fluctuations (warming/cooling cycles) before modern humans existed. Some scientists use this to argue that current warming might be part of a natural cycle, disagreeing with the idea that human activity is the main cause.

Answer:

1. Carbon dioxide levels and global temperatures show the same amount of fluctuation that occurred before modern humans existed.