- Stocks look to Jackson Hole summit for a boost- Draghi hints at action ahead of ECB meeting- Glencore leads fallers on growing opposition to mergerGlobal stock markets were mostly trading in the red on Wednesday afternoon in spite an upwards revision to US economic growth as investors showed caution ahead of a meeting of central bankers this Friday.Investors are hoping that the Jackson Hole summit this week will see the US Federal Reserve hint at further stimulus measures like it has done in the past. However, in spite of an upwards revision to US gross domestic product (GDP) growth figures for the second quarter today - adjusted to an annual rate of 1.7% from 1.5% - US benchmarks slipped after the opening bell.Analyst Craig Erlam from Alpari said: "While [the data] in itself is unlikely to cause too much of a stir, the fact that the number has been revised higher since the last meeting is not going to work in the favour of those hoping the Fed loosen monetary policy next month."European Central Bank (ECB) President Mario Draghi is being forced to miss the Jackson Hole conference due to "a heavy workload", increasing speculation that he could be putting the finishes touches to plans for strong action ahead of an ECB meeting next week. Draghi hit back at German criticism of his bond-buying proposal today, sparking rumours that something big is on the horizon in Europe. The ECB "will always act within the limits of its mandate," Draghi said in German newspaper Die Zeit. "Yet it should be understood that fulfilling our mandate sometimes requires us to go beyond standard monetary policy tools."Alpari's Erlam said this afternoon: "I don't think there's any doubt any more than Draghi will announce their bond buying programme at the ECB press conference in September."In other news, German Chancellor Angela Merkel reiterated her opposition to the European Stability Mechanism being granted a banking licence, saying that the idea is "not compatible with the treaties". However, Italian Prime Minister Mario Monti argued that "modifications to the treaties can be asked for".FTSE 100: Glencore provides a drag on merger riskCommodities marketer and producer Glencore was leading the decline on the Footsie today, not only because it went ex-dividend today but as a result of reports that its proposed merger with mining giant Xstrata could be at risk. Xstrata shareholder Norges Bank Investment Management has raised its stake in the miner in the last few weeks, fuelling concerns that the Norwegian fund could join forces with Qatari Holdings to vote to block the merger.Miners on the whole were out of favour today as risk appetite waned. Rio Tinto, Kazakhmys, Anglo American and Vedanta Resources were registering moderate losses by the close. Copper producer Antofagasta was also lower despite beating earnings estimates in the first half as a decrease in copper prices was offset by higher levels of production. Outsourcing group Serco was higher after saying that it expects good growth in full-year organic revenues in 2012 despite a 2.1% fall in the first half. Utilities giant SSE was among the risers after Bank of America Merrill Lynch lifted its recommendation from 'neutral' to 'buy', explaining that the company's tariff increase announced last week has erased a downside risk to earnings. "The move underpins the profitability of the supply division and gives us greater confidence in the medium-term outlook for EPS and DPS progression," the broker said. Shares in Marks and Spencer were in red once again as takeover speculation continues to fade. The stock jumped on Friday after Bloomberg reported that private equity firm CVC was considering making an offer. However, analysts at Investec have said this morning that a successful bid is unlikely and the "bid spec bubble" is expected to burst. FTSE 250: RusPetro drops after swinging into the red West Siberia-focused oil and gas firm RusPetro was a heavy faller after reporting a pre-tax loss of $26.4m, compared with a profit of $0.6m in the first half of last year. Revenues, however, tripled as production ramps up. A host of second-tier stocks went ex-dividend today and were trading in the red, such as African Barrick Gold, Devro, Ferrexpo, Henderson, Hikma, Lancashire Holdings, Wood Group, Micro Focus, Rank Group and Stagecoach. FTSE 100 - RisersReed Elsevier (REL) 589.00p +1.90%Admiral Group (ADM) 1,196.00p +1.61%Babcock International Group (BAB) 914.00p +1.50%Whitbread (WTB) 2,133.00p +1.38%Compass Group (CPG) 717.00p +1.20%SSE (SSE) 1,372.00p +1.11%Aberdeen Asset Management (ADN) 277.50p +1.06%Bunzl (BNZL) 1,115.00p +1.00%Next (NXT) 3,625.00p +0.95%Sage Group (SGE) 298.70p +0.88%FTSE 100 - FallersGlencore International (GLEN) 368.50p -4.04%Rio Tinto (RIO) 2,773.50p -3.09%Weir Group (WEIR) 1,635.00p -2.79%Kazakhmys (KAZ) 617.00p -2.68%Anglo American (AAL) 1,816.00p -2.65%Vedanta Resources (VED) 889.00p -1.66%Lloyds Banking Group (LLOY) 33.49p -1.64%Xstrata (XTA) 924.10p -1.61%International Consolidated Airlines Group SA (CDI) (IAG) 142.70p -1.52%BHP Billiton (BLT) 1,904.00p -1.47%FTSE 250 - RisersCarpetright (CPR) 670.00p +4.69%Yule Catto & Co (YULC) 165.00p +4.43%Dialight (DIA) 1,140.00p +3.92%Homeserve (HSV) 220.60p +3.81%Ophir Energy (OPHR) 550.00p +3.58%Brewin Dolphin Holdings (BRW) 149.10p +3.11%SVG Capital (SVI) 279.10p +2.84%Afren (AFR) 128.20p +2.81%Cape (CIU) 192.60p +2.61%Euromoney Institutional Investor (ERM) 768.00p +2.26%FTSE 250 - FallersRuspetro (RPO) 125.50p -11.31%New World Resources A Shares (NWR) 276.00p -6.76%Bumi (BUMI) 321.30p -5.50%Ferrexpo (FXPO) 172.60p -4.11%Centamin (DI) (CEY) 76.15p -3.73%Talvivaara Mining Company (TALV) 130.00p -3.56%Lonmin (LMI) 608.00p -3.49%Rank Group (RNK) 135.70p -3.42%Henderson Group (HGG) 104.80p -2.69%Micro Focus International (MCRO) 545.00p -2.68%