The leading edge of a vast oil slick started to come ashore in Louisiana on Thursday night, a shroud of devastation falling on America's coastline even as the blown-out BP oil well that produced it continues to belch millions of gallons of thick crude into the Gulf of Mexico for a third straight week.
At moments like this, it's hard to see any silver lining here at all. But it's possible there is one. Many environmentalists say that the wrenching and omnipresent images of filth and death are at last providing Americans with visible, visceral and possibly mobilizing evidence of the effects that fossil fuels are having on our environment every day.
Rick Steiner is horrified at the damage. A University of Alaska marine specialist, he's watched cleanup efforts ever since the Exxon Valdez spill in 1989, and has learned some bitter lessons.
"Government and industry will habitually understate the volume of the spill and the impact, and they will overstate the effectiveness of the cleanup and their response," he said. "There's never been an effective response -- ever -- where more than 10 or 20 percent of the oil is ever recovered from the water. Once the oil is in the water, the damage is done."
And most of the damage remains invisible deep below the surface, including the wide-scale destruction of essential plankton in the area and the wiping out of an entire generation of fish larvae. "This is real toxic stuff," Steiner said.
But the damage that is visible -- the vast and foul oil slick, the dolphins swimming through sludge, the birds coated in oil, the dead fish and sharks and turtles -- is enough to thoroughly disgust anyone paying attention.
And that, Steiner said, makes it a "teachable moment" that "will hopefully serve as a wake-up call that we need to turn to sustainable energy."
After all, that carbon we're seeing poison the Gulf was headed into the planetary ecosystem anyway, through tailpipe emissions.
"That's part of the irony of all this, is it just took a shortcut," Steiner said. "This carbon took a shortcut into the environment from what it normally does, and it's obvious to people what the problem is here."
A much smaller oil spill in Santa Barbara 40 years ago helped mobilize the Earth Day movement, which in turn led to most of the major environmental legislation of the 20th century. The Exxon Valdez disaster, 20 years later, led to tougher (but evidently not tough enough) rules about oil spills.
And now Steiner and fellow environmentalists think this spill provides an opportunity not just to revisit offshore oil drilling, but the whole carbon dynamic.
"This just reminds us, in a powerful way, how dirty the energy we rely on is," said environmental writer Bill McKibben. "If anything good is going to come out of this, it'll be because it focuses our attention -- but more palpably, focuses the president's attention -- on questions of dirty energy,"
McKibben is the founder of the global grassroots climate-change Web site 350.org and his latest book, Eaarth: Making a Life on a Tough New Planet is about adjusting to a changed world.
"Our problem is not primarily that there's a stuck valve in the bottom of the Gulf of Mexico. That's a terrible problem," McKibben told HuffPost. "The bigger problem is that there's a stuck economy based on fossil fuels that the president hasn't really done anything major yet to fix.... The problem is that the whole system is dirty from beginning to end."
The Senate has been cobbling together tepid climate-change bills while President Obama sits on the sidelines, McKibben said. "Now is the moment when he could galvanize the nation. He could say: 'Let's really learn from what's happened in the Gulf. Let's think about the way that we're turning all the oceans of the world acid at a rapid rate by pouring carbon into the atmosphere. Let's think not only about those coal miners in West Virginia, but also about what burning coal is doing to people all over the world.' "
This would, McKibben acknowledges, require a bit of a turnaround. "In this case, Obama three weeks ago told us he wanted a lot more offshore oil drilling, and told us it was safe. He should get up and say 'I was wrong. And in a deeper sense, I was wrong not to be taking on whole hog, as the centerpiece of my presidency, the fight to finally get us really moving off coal and gas and oil.'"
It's a moment of reckoning, McKibben said.
"We'll find out in the next couple of weeks whether he's serious about an energy transformation, or whether he's as corporatist and cautious on this as he appears to be on other things."
Wesley Warren, director of programs at the Natural Resources Defense Council, calls the Gulf spill "a watershed moment" much like Santa Barbara 40 years ago or the Exxon Valdez 20 years ago -- events that "really defined energy and environmental policy for a generation," he said.
"Washington needs a response that is as large as this spill is, to deal with our dependence on oil," he told HuffPost. "This is just a symptom of a system that's gone on too long, unchecked, when a change is needed."
It's not just the imagery, it's also the economic toll on fisherman and coastal communities that will make this spill so affecting, he said. "That makes it dramatic in a way that two weeks ago, there was no way to show the American people what was at stake. This is vivid and direct and is the consequence of an overdependence on oil that we could have rid ourselves of 40 years ago or 20 years ago," he said.
"The best thing to do with carbon is to keep it underground where it belongs."
Despite the White House's considerable effort to demonstrate that the administration is responding aggressively to the Gulf spill, there are, as of yet at least, no signs that Obama will seize the moment to advance an anti-carbon agenda.
Indeed, last week, he promised better safeguards for oil drilling going forward, but recommitted himself to domestic oil production.
Is there any chance there will be enough public outrage that Members of Congress will be pressured into voting for legislation that puts a stiff price on carbon going forward? So far there are no overt signs of that, either.
But Damon Moglen, global warming campaign director for Greenpeace USA, told HuffPost that the dynamics of the debate have already changed.
"I think objectively, number one, the proposal that we are going to offer new offshore drilling is dead. It's dead on delivery. I think in addition that there is a tremendous likelihood that we will have a ban or a return to the moratorium on drilling," Moglen said.
"And more broadly, I think this is going to break open the debate on both the climate and energy bills... I think we are going to have the opportunity to talk about a much more ambitious and visionary commitment to clean renewables and efficiency technologies, instead of continued hand-outs and support for the fossil fuels industry.
"The details of that? That'll be played out in the weeks to come."
Dan Froomkin is senior Washington correspondent for the Huffington Post. You can send him an e-mail, bookmark his page; subscribe to RSS feed, follow him on Twitter, friend him on Facebook, and/or become a fan and get e-mail alerts when he writes.