For evidence of just how ruthless this summer has been in the global markets, look no further than Harbinger Capital Partners.

This year, the hedge fund run by Philip Falcone has had nothing but stellar news to report to shareholders. Thanks to bets against subprime mortgages, returns for 2007 were 116 percent. Returns through the end of June were 40 percent after Harbinger cashed in on its short position in Bear Stearns.

But now Harbinger shareholders are being sorely reminded that what goes up must inevitably come down.

Nearly two-thirds of the hedge fund's gains in the first half of the year were erased in July and the first two weeks in August, reports James Mackintosh on the Financial Times' Alphaville blog. The fund was stung by the sudden reversal of the long-energy-short-financials trade that has hurt so many hedge funds this summer.

But before you shed a tear for Falcone's investors, it bears noting that the fund is still up 14 percent year-to-date. That's cause for envy among his peers. The global index of funds tracked by Hedge Fund Research is down 5.5 percent so far this year.

Harbinger's performance during the past six weeks underscores the tremendous turbulence in the global markets, and it doesn't bode well for those fund managers less fortunate than Falcone during the first half of this year.

Harbinger has had some high-profile hits and misses so far this year. It waged war with the New York Times Co. and successfully pushed Arthur Sulzberger to give it two seats on its expanded board. So far, though, any change Harbinger hoped to inspire has had little effect on shareholders. Shares in the New York Times Co. have steadily declined since the proxy war ended in March, and it's now being pressured to cut its dividend.

More recently, Harbinger took a 4.9 percent stake in Cablevision, the New York-area cable company controlled by the Dolan family. Since then, the company announced plans to explore strategic options for some of its divisions and plans to begin paying shareholders a regular dividend.

And earlier this week, Harbinger sought approval to double its 15.6 percent stake in the iron-ore company Cleveland-Cliffs in order to prevent its proposed $8.1 billion takeover of Alpha Natural Resources.