Hawaii has had some tough environmental luck lately, from ongoing problems like invasive species and declining fish stocks to more recent scourges like marine debris washing ashore and last week's 233,000-gallon molasses spill in Honolulu Harbor.

One of the state's most troubling environmental issues, however, can be harder to visualize. The trade winds normally breathe life into Hawaii, bringing light rain, soft breezes and mild temperatures while pushing out the stagnant humidity that often plagues tropical paradises. But the northeast trade winds have been fading in recent years, leaving Hawaiians to struggle with muggy weather and unfamiliar water shortages.

"People always try to ask me, 'Is this caused by global warming?' But I have no idea," University of Hawaii at Manoa meteorologist Pao-shin Chu told the Associated Press earlier this year. While the cause is unknown, Chu co-authored a study last year that at least helped quantify the problem. It found a broad decline in Hawaii's northeast trade winds since 1973, including a 28 percent drop at Honolulu International Airport.

Aside from creating unusually muggy conditions for Hawaii, this has already led to stubborn droughts, and could threaten rain-fed aquifers that supply water for drinking and irrigation. It's also letting more volcanic smog — aka "vog" — accumulate over land instead of blowing out to sea, aggravating asthma and other respiratory ailments.

If these changes are caused by global warming, Hawaii could be in for yet another manmade environmental catastrophe. But the culprit remains a mystery for now, and there's a chance this is all just part of a natural, poorly understood climate cycle. Either way, the trade winds aren't dead yet, as illustrated in a mesmerizing new time-lapse video, "Honolulu Clouds," by renowned photographer Gavin Heffernan:

Heffernan was in Honolulu last week for a business trip, and explains on Vimeo that he "managed to sneak out and pop some timelapses of the gorgeous Hawaiian surroundings." The video was shot during the height of the molasses spill, Heffernan tells MNN, but doesn't show the sludge since it was filmed a few miles east of the harbor. "I was there during the spill but I didn't see any effects with my own eyes," he says. "So sad, though."

The video instead focuses on flowing air and moisture pushed through Hawaii by the trade winds, creating a tranquil yet stirring tribute to the islands' world-famous weather.

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