The floating cap of sea ice on the Arctic Ocean shrank this summer to what is probably its smallest size in a century, continuing a trend toward less summer ice that is hard to explain without attributing it in part to human-caused global warming, various experts on the region said today.

The findings are consistent with recent computer simulations showing that a buildup of smokestack and tailpipe emissions of greenhouse gases could lead to a profoundly transformed Arctic later this century in which much of the once ice-locked ocean is routinely open water in summers.

It also appears that the change is becoming self sustaining, with the increased open water absorbing solar energy that would be reflected back into space by bright white ice, said Ted A. Scambos, a scientist at the National Snow and Ice Data Center in Boulder, Colo., which compiled the data along with NASA.

"Feedbacks in the system are starting to take hold," Dr. Scambos said. "The consecutive record-low extents make it pretty certain a long-term decline is underway."

On Tuesday, the California Budget Project, a public policy research group in Sacramento, estimated that it takes $51,177 a year for a two-parent California family with two children to afford rental housing, commuting costs, food and other basics. The figure is $71,377 if both parents work and $53,987 for a single parent with two kids.

And on Labor Day, the Budget Project reported that California's highest-paid workers -- those in the top 10 percent -- earned 5.1 times more than workers making wages in the lowest 10 percent, up from 3.8 times more in 1979.

In the Bay Area, where a family with two working parents needs $79,946 a year to eke a basic living -- no car, no vacations and no home ownership -- costs are higher than the state averages.

If the ships were at capacity, with 7,116 evacuees, for six months, the price per evacuee would total $1,275 a week, according to calculations by aides to Sen. Tom Coburn (R-Okla.). A seven-day western Caribbean cruise out of Galveston can be had for $599 a person -- and that would include entertainment and the cost of actually making the ship move.