Environmental effects: It's our doing"Because the rates of emissions are growing, it looks like we could burn through the other half in the next 25 years" under one of the more dire scenarios outlined in the report. Other scenarios show that the threshold will be reached later this century. The finding constitutes a warning to governments to cut emissions of carbon dioxide, the main greenhouse gas, which is generated by the burning of fossil fuels, industrial activity and deforestation. Calling climate change "the greatest challenge of our time," panel co-chair Thomas Stocker said humankind's fate in the next 100 years "depends crucially on how much carbon dioxide will be emitted in the future". In the report, the panel said it is 95% certain that human activity is the dominant cause of the global warming observed since the 1950s. That is up from 90% six years ago. "Human influence has been detected in warming of the atmosphere and the ocean, in changes in the global water cycle, in reductions in snow and ice, in global mean sea level rise, and in changes in some climate extremes," the report said. The report is the panel's fifth major assessment since 1990. It reaffirms many of the conclusions of past reports, but with greater confidence. "The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen and the concentrations of greenhouse gases have increased," the panel wrote in a 36-page summary of its findings.