By Shihoko Goto -Exclusive to Copper Investing NewsRekindled worries about stalling growth prospects are putting a damper on commodities across the board this week including copper. In fact, the red metal hit a three month low amid concerns about a slowdown in China's growth prospects and Europe's inability to scramble out of its quagmire. Thursday, copper for December delivery ended 6 percent lower, down 20.05 cents to $3.057 a pound. Bearish macroeconomic news put a damper on the bulls, not least due to continued worries about the debt situation in the Eurozone. The fact that Moody's downgraded Spain's credit rating yet again didn't help matters, marking the third time that the county's ratings have been cut by the agency since June 2010. The country has the highest unemployment rate among the 27 nations that make up the European Union. Investors are keeping a close eye on ongoing negotiations between France and Germany to reach an agreement at the upcoming summit meeting this weekend about just how much money should be put in the European Financial Stability Facility. While the sum is currently set at 440 billion euros, speculation is growing that the figure could balloon to 2 trillion euros, which would significantly increase the effectiveness of financial intervention. That in turn could be enough to reignite global confidence in the financial future of Europe and lead to a rise in demand for industrial materials including copper. Perhaps more worrisome to copper investors though was news this week that China's third quarter GDP rose at its slowest pace since 2009. With China's once red-hot economy now seemingly sputtering and signs of robust growth being few and far between worldwide, industrial production is seen to be facing challenges, and demand for copper is projected to fall by many as a result.