BEIJING, March 24 (Xinhuanet) -- Global warming appears to be pushing Earth's vast polar ice sheets toward a significant meltdown and could lead to a long and irreversible rise in sea levels within the next 100 years, according to new studies. One study found that warming temperatures are causing glaciers the size of Manhattan to trigger quakes, and computer models of climate and ice indicate that by about 2100, average temperatures could be 2.3 degrees Celsius warmer than today and that over the coming centuries, the world's oceans could rise 3.9 to 6 meters -- conditions last seen 129,000 years ago, between the last two ice...