The copper market and related exchange traded funds are gaining momentum and trading back above their long-term trend lines after the red metal experienced its best week since 2011.

Over the past week, the iPath Dow Jones-UBS Copper Subindex Total Return ETN (NYSEArca: JJC), an exchange traded note, rose 7.3%, iPath Pure Beta Copper ETN (NYSEArca: CUPM) gained 6.6% and United States Copper Index ETF (NYSEArca: CPER) increased 8.1%. Additionally, the producers equities-backed First Trust ISE Global Copper Index Fund (NasdaqGM: CU) returned 7.7% and Global X Copper Miners ETF (NYSEArca: COPX) was up 7.0% over the past week. [Commodity ETFs Starting to Turn Around]

Both copper metal- and miner-related exchange traded products are now trading back above their 200-day simple moving averages. [Dr. Copper Could get Heathy This Year]

Supporting copper’s momentum, traders are growing less bearish about China, the world’s largest consumer of copper, reports Alex Rosenberg for CNBC. Specifically, China’s official purchasing manager’s index beat expectations, revealing mild growth in April.

The recent weakness in the U.S. dollar also bolstered hard assets, such as copper, which tend to have an inverse relationship with the greenback – a weaker USD means that it takes more to acquire the same amount of copper. The Dollar Index, which tracks a basket of major foreign currencies, was trading around 95.5 Monday.

Moreover, some argue that the recent strength in copper prices is also driving greater forward momentum through short-covering – previous short sellers are calling it quits and buying back into the asset to cover their short positions.

Nevertheless, some warned that the recent gains could be short-lived as the weakness in the U.S. dollar may not last.

“I’m looking for a pullback here, I think it’s going to settle in a little bit,” David Seaburg, head of equity sales trading at Cowen, said on CNBC. “I think this spike is really predicated mostly on dollar weakness and hedge-fund short-covering here.”

iPath Dow Jones-UBS Copper Subindex Total Return ETN

For more information on the red metal, visit our copper category.

Max Chen contributed to this article.