Including, we can only hope, President Bush, who has consistently refused to take any significant action to limit U.S. production of carbon emissions, the primary cause of global warming.

The disintegration of the 160-square-mile piece of the Wilkins ice shelf on the Antarctic Peninsula is the latest and one of the most startling pieces of evidence showing how fast global warming is changing the Earth's climate. The ice shelf has been breaking apart for the past decade, and scientists attribute the collapse to a temperature increase in Antarctica of 3 degrees over the past half-century.

A 600-square-mile chunk broke off of the same ice shelf in 1998, and nearly 2,000 square miles of the Larsen B ice shelf in western Antarctica dropped off in 2002.

The melting of the enormous Wilkins ice shelf, about 5,000 square miles in total size, would not raise the world's sea levels, because this ice is already floating on the ocean. However, if other Antarctic ice shelves, which are the edges of land-based glaciers, were to follow this one, sea levels would rise substantially.

Climate scientists and Antarctica researchers see the Wilkins breakoff as a sign of worsening global warming.

It is ''more indicative of a tipping point or trigger in the climate system,'' said Sarah Das, a scientist at the Woods Hole Oceanographic Institute. ''These are things that are not re-forming. So once they're gone, they're gone.''

Some parts of the Antarctic continent are cooling and others are not experiencing the same warming as the western peninsula that juts out into the ocean and is heating up even faster - as the latest breakoff indicates - than scientists have previously predicted.

This vulnerable west side of the continent could be the first to fall. If the rest were to follow, scientists warn, the resultant rising sea level could be disastrous for islands and coastlines.

The question is: How many "canaries" must die in the coal mine that is our Earth before America's leaders take decisive action to reduce emissions?