ClimateBiz: Growing numbers of U.S. financial firms have started to play on the European Climate Exchange (ECX) as they seek to gain experience of how carbon markets operate ahead of the launch of a U.S. cap-and-trade scheme. Sara Stahl, business development director for the ECX, said the second half of the year had seen an influx of U.S. firms joining the exchange, helping to drive traded volumes of carbon credits up to record levels. “A lot of new players have joined the market this year …