Spring Sun Brings Massive Melt

LODGEPOLE, Calif., May 18, 2006 — -- The snow pack under the towering giant sequoias in the Sierra Nevada Mountains is melting fast now under the hot spring sun.

 It does so every year, of course, but virtually all climate scientists say it will melt faster and faster on average over the next several decades as a direct result of the invisible carbon dioxide that human machinery keeps pouring into the air.

  There is far more carbon dioxide in Earth's atmosphere now than there has been at any time during the entire 2,000-year lifetimes of the more mature of these powerful, massive trees.

 Far more carbon is now in the atmosphere than at any time in at least the past 650,000 years.

 Human civilization is only about 10,000 years old -- born in the retreat of the last ice age -- and made possible in part by the relatively stable global climate since that ice age ended.

 The oldest of these trees were already taking youthful gulps of air at the same time Jesus and Caesar drew breath. One tree is so big you can walk inside the folds of its huge twisted trunk -- into a little room -- and step out again into the dappled sunlight to feel the soft dry bark with your palm.

 On snowshoes, we walked out into Round Meadow with Sequoia National Park rangers Chris Waldschmidt and Kyle Nelson on one of their regular treks to measure the snow pack for the California State Water Board.

 The rangers were in short sleeves under the blue spring sky in this football-field-size forest meadow ringed by great trees, and sunglasses guarded against the lingering glare of the snow pack where marsh flowers will soon bloom amid fresh rivulets.

   In the San Joaquin Valley below -- some 20 miles to the west -- an agricultural miracle unfolds that would simply not be possible without the irrigation water that melts down from the mountains during spring and summer.

 That icy water gets distributed among orchards and fields by one of the most complex and sophisticated water management systems on the planet.