Global copper smelting activity rebounded in September as higher treatment charges spurred many smelters to increase output, data from satellite surveillance showed on Monday. Copper processing rose worldwide despite declines in top producer China and in the United States, satellite service SAVANT and broker Marex said in a statement. Spot treatment and refining charges (TC/RCs) in top copper consumer China AM-CN-CUCONC have surged some 45% over the last three months and are set for their biggest quarterly gain since the first quarter of 2011. Benchmark copper prices CMCU3 on the London Metal Exchange are up nearly 20% so far this year, having hit a record in May. Under SAVANT's dispersion index, 50 points indicate smelters are operating at the average level of the last 12 months. It also has a second index showing the percentage of active smelters. Its global dispersion index for copper rose to an average of 49.3 in September from 45.9 a month earlier. In nickel, global smelting activity showed a significant fall, led by China due to government power curbs, the statement said. The dispersion index fell to 41.1 in September from 48.1 in August and is likely to be further constrained as the monsoon season in the Philippines reduces nickel ore shipments, it added.