It started in the Marshall Islands, at sunrise. Divers descended into the blue waters above the Majuro Atoll, their cameras capturing fragile coral ecosystems at risk from rising temperatures and acidifying oceans. A banner unfurled in front of the camera's lens read "Connect our dots: Your carbon emissions kill our coral."

A world away, a group of young Afghan men gathered in the shoals of the Kabul River, a vital waterway fed by runoff from dwindling glaciers. They, too, held signs, this time reading "Too much drought already at 392 [parts per million]."

For 24 hours on Saturday, May 5, activists around the world trained the eyes of their cameras on flooded streets, dry lake beds, fire-torn forests and devastated houses, snapshots that together formed a global map of extreme weather and its aftershocks. The pictures all carried a single message, spelled out in signs and banners in half a dozen languages: Climate change is real, and here is your evidence.

The planetwide day of action, entitled "Connecting the Dots Between Climate Change and Extreme Weather," was organized by the group 350.org, an American nonprofit dedicated to raising awareness and expediting political action on global warming. The group's name derives from the level of atmospheric carbon -- 350 parts per million -- that most scientists say is necessary for life on Earth to continue without serious impact. Already the world is well above that mark, at 394 parts per million, and the carbon count continues to rise.

"[The day of action] is in fact a sort of global ritual -- a blessing for the hundreds of events across more than 100 countries taking place ... for Climate Impacts Day," wrote Aaron Packard, a 350.org organizer in the Marshall Islands. "The dots are especially important -- at each of those hundreds of events, people will be holding dots up to in a bid to help the world 'connect the dots' between the recent deluge of extreme weather events and climate change."

Too big to see?

In March of this year alone, 15,000 temperature records were broken across the United States. Oklahoma experienced its hottest summer on record -- including the hottest day recorded in the United States -- contributing to an already severe drought. The National Oceanic and Atmospheric Administration documented 14 weather and climate disasters in 2011 -- another record -- each causing more than $1 billion in damages and the loss of human life.

Scientists and the Intergovernmental Panel on Climate Change say that there is a strong probability that these extreme weather events have been exacerbated by rising concentrations of atmospheric carbon. Saturday's day of action attempted to hammer home that message.

"As long as [climate change] remains one abstract problem in the long list of problems, we will never get to it," wrote 350.org founder and environmentalist Bill McKibben, in a pre-event editorial published in The Guardian. "In reality, climate change is actually the biggest thing that is going on every single day."

"If we could only see that pattern, we would have a fighting chance," he wrote. "It is like one of those trompe l'oeil puzzles where you can only catch sight of the real picture by holding it a certain way."

Climatologists say that the Earth's climate is far too large a system to be "observed" in any kind of empirical sense. Weather patterns, hurricanes and heat waves are products of the larger whole, the way flowers might be said to be products of spring, or a cold sweat the product of a fever.

While scientists cannot identify any one particular weather event and say, with total certainty, that it is the product of global warming, the amalgamation of many such events can indicate a shifting climate, said Kevin Trenberth of the National Center for Atmospheric Research.

"All storms are affected by global warming. They can't not be," he said. "Sea temperatures have risen 1 degree Fahrenheit since the 1970s. There's 4 percent more water vapor in the atmosphere since the 20th century. What is the magnitude of that effect? That's all contributing to the environment in which weather forms."

A global problem with local impacts

"The question is, what's the magnitude of that change?" he added. Ninety to 95 percent of the time, weather looks like it did before, he said. But 5 to 10 percent of time, the weather exceeds even the extreme limits of the past.

"Those are the places where you're going to see climate change contributing to the intensification of weather patterns," Trenberth added.

The photographs uploaded to the 350.org website throughout the day Saturday take those numbers out of the realm of the abstract and give them concrete form.

In one, a group of Buddhist monks in mustard-yellow robes stands in front of a temple -- much of it shrouded in scaffolding -- that was damaged by floods last year. In the Andes of South America, three children holding a green dot stand before the mountains where the snowcaps are receding and glaciers are vanishing.

"The evidence of climate change is all around us," wrote Crissy Fields, an activist who participated in the day's events from San Francisco. "Every day, new scientific studies document impacts we're already experiencing."