In an interview with the German news publication Der Spiegel, meteorologist Hans von Storch said that scientists are so puzzled by the 15-year standstill in global warming that if the trend continues their models could be “fundamentally wrong.”

“If things continue as they have been, in five years, at the latest, we will need to acknowledge that something is fundamentally wrong with our climate models,” Storch told Der Spiegel. “A 20-year pause in global warming does not occur in a single modeled scenario. But even today, we are finding it very difficult to reconcile actual temperature trends with our expectations.”

Environmentalists have been increasingly calling on President Obama to address global warming before it becomes irreversible. The World Bank reported that global temperatures could rise by 4 degrees Celsius over the next century if greenhouse gas emissions aren’t brought under control. Many world leaders are committed to limit the increase to 2 degrees Celsius.