Warming temperatures are causing a steady rise in copper, zinc and sulfate in the waters of Colorado mountain streams affected by acid rock drainage. Concentrations of these metals have roughly doubled in these alpine streams over the past 30 years, presenting a concern for ecosystems, downstream water quality and mining remediation, according to a new study. Natural chemical weathering of bedrock is the source of the rising acidity and metals, but the ultimate driver of the trend is climate change, the report found, and the results point to lower stream volumes and exposure of rock once sealed away by ice as the likely causes.