Final answer:
Based on the conclusions of the two groups of scientists, it can be concluded that there is only one true cause of the rise in sea level. The true statement is that `Sea levels have risen because of both global warming and the melting of polar ice caps.`
The answer is option ⇒3
Step-by-step explanation:
The rise in sea level is indeed attributed to both global warming and the melting of polar ice caps.
Here are the key details supporting this answer:
- 1. Global warming and thermal expansion: As global temperatures increase due to the accumulation of greenhouse gases in the atmosphere, the oceans also warm up. Warmer water has a lower density, causing it to expand and take up more space. This thermal expansion contributes to the rise in sea level.
- 2. Melting of polar ice caps: The melting of land ice, such as glaciers and ice sheets in polar regions like Antarctica and Greenland, adds more water to the oceans. As these ice masses melt, the resulting water flows into the ocean, increasing sea levels.
- 3. Glacial retreat: Glaciers are also retreating worldwide due to global warming. The meltwater from glaciers contributes to sea level rise, although to a lesser extent compared to the melting of polar ice caps.
- 4. Other factors: In addition to global warming and ice melting, other factors can influence regional variations in sea level rise. These include changes in ocean currents, tectonic activity, and natural climate cycles.
The answer is option ⇒3) Sea levels have risen because of both global warming and the melting of polar ice caps.