Has potential global warming been detected in the Earth’s vegetation?
One possible indicator of a warming planet is the finding that forests and grasslands in the Northern Hemisphere are greening a full week earlier in spring than they did in the mid 1970s. This has been determined by very careful monitoring of planetary car bon dioxide levels. The normal spring decline in CO is indicative of uptake by green plants awakening from the winter sleep. This effect has been noted earlier and earlier in the season, suggesting that milder winters are lengthening the growing seasons. If this trend continues it may be one of the better pieces of evidence available to confirm that a true global warming is taking place (though the cause is not necessarily pinned down).
Where might evidence of global warming first be detected?
Computer models suggest that one of the first signs of global warming may be a warming near the surface, especially in south polar regions, and, ironically, a cooling in the upper atmosphere, again particularly in the Southern Hemisphere. Recent analyses of 25 years of balloon soundings do indeed suggest a cooling stratosphere, especially in more southern latitudes. At the surface, Antarctica also appears to be get ting warmer. Over the last 50 years the average temperature on parts of the ice continent has increased by 2.5°C. Some of the milder coastal regions are seeing 25-fold increases in the amount of vegetation. And in 1995, a gigantic iceberg some 23 by 48 miles in size broke loose and floated out to sea. The 600-foot-thick iceberg was the size of the country of Luxembourg. None of these findings are conclusive, but they do strengthen the case of those scientists who believe human activities are warming our planet. These effects are rather good evidence that at least some anthropogenic-caused global warming may be kicking in.