``Baby Dima'' is a six-month-old mammoth now in a laboratory in Russia's Permafrost Institute - a dire reminder of the dangers of climatic change. His species became extinct more than 39,000 years ago when the Ice Age ended and Siberia warmed.

Now scientists are concerned that Yakutsk, the capital of Russia's semiautonomous Yakutia republic, and thousands of mining towns scattered across the frozen wastelands of Siberia, could also be endangered as global warming threatens to melt the frozen earth beneath them.

``We're sinking,'' says scientist Tatyana Botulo at the Permafrost Institute in Yakutsk. ``If the permafrost continues to melt, only the mountaintops will stay afloat. Our studies show that if temperatures continue to rise, Yakutsk may sink altogether by 2030.''

Permafrost - ice that stays permanently under the soil with a 40 percent water content mingled with sands and rock - is caused by freezing temperatures. In winter - nine months of the year in Siberia - permafrost grips the earth to a depth of 6-1/2 feet. In summer, its top layer dissolves into a swamp.

As the ice melts, the earth's surface moves. Roads, runways, and sidewalks crack. Railroads built on steel pylons bend out of shape and sink into the permafrost. In Yakutsk, crooked houses lean over frozen streets, their balconies twisted out of shape. Some have already sunk by one-third.

If the scientists' warnings are correct, the top layer of permafrost that freezes and melts every year will grow to more than 16-1/2 feet. This means that piles on which buildings are built must be hammered even deeper into the earth.

Urban pollution is accelerating the change in climate, Botulo says. Yakutsk is built in a river valley where there is no wind. ``Our city has no ventilation. All the smoke from car fumes, water-heating plants, and buildings sits in the valley,'' she says. ``This is speeding up the warming.''

The republic's ecology minister, Vasily Alekseyev, says a new town of single-story buildings will have to be built from scratch in a different location. ``Not a single apartment block built on cement pillars will survive. Our forefathers picked a very bad place to build Yakutsk. Come back in 100 years, and you won't find our city here,'' he says.

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