Dust concentrations were used as an indication of dryness or wetness in the region. The presence of different chemicals such as chlorides, sulphates and nitrates were taken to be suggestive of volcanic activity, fossil fuel burning and desertification. The researchers write in the journal Science that their analysis shows that both the last decade and the last 50 years were the warmest in 1,000 years. A dome protected the ice core drilling and processing operations from the elements They say the layers covering the last century reveal a four-fold increase in dust and a doubling of chloride concentrations, suggesting an increase in dryness and desertification. Professor Thompson said he was sure there was a clear signature of human activity in the ice layers.
Some researchers still doubt human activities are inducing global warming.
They also point to the inconsistencies in the various temperature records. Although surface data gathered at weather stations show a rapid warming over the last century, the atmospheric data produced in the last few decades by satellite and balloon studies show little or no warming. The researchers believe these inconsistencies must be adequately explained before humans are blamed for climate change. For the last 25 years, Professor Thompson and his colleagues have drilled cores from glaciers and ice caps in some of the most remote parts of the planet in an effort to recover records of ancient climate. Most current predictions of global climate change suggest that early signs of warming will be seen at high elevations where these ice caps exist.