The biblical flooding in South Carolina is at least the sixth so-called 1-in-1,000 year rain event in the U.S. since 2010, a trend that may be linked to factors ranging from the natural, such as a strong El Niño, to the man-made, namely climate change.
So many "1-in-1,000 year" rainfalls is unprecedented, said meteorologist Steve Bowen of Aon Benfield, a global reinsurance firm. "We have certainly had our fair share in the United States in recent years, and any increasing trend in these type of rainfall events is highly concerning," Bowen said.
A "1-in-1,000 year event" means that there's a 1 in 1,000 (or 0.1% chance) of it happening in any given year in a given location, the National Oceanic and Atmospheric Administration (NOAA) said.
In addition to this weekend's floods in South Carolina, which killed at least nine people, the other 1-in-1,000-year rain events include the Tennessee floods in May 2010, the Mid-Atlantic, Northeast and New England drenching during Hurricane Irene in 2011, the Colorado floods in 2013, the deluge in Baltimore in August 2014, and the flooding earlier this year in Nebraska, according to Bowen.
Scientists say there could be a connection between these floods and man-made climate change.
Research has confirmed that our warming climate is making intense short-term rains even heavier in many parts of the U.S. and the world, as warmer temperatures allow more moisture to evaporate from oceans and flow into rain-making storm systems, according to Weather Underground meteorologist Bob Henson.
A study earlier this year from Climate Central reported that 40 of the 48 contiguous states have recorded an uptick in heavy rain events in the past several decades (though South Carolina was not one of the 40).
The National Climate Assessment, a federal report from 2014, also found that a warming atmosphere would bring about more extreme rainfall events. (continued)
In 2013, after some controversy, South Carolina's Department of Natural Resources released a report on risks the state could face due to climate change. One of those risks? "A predicted result of climate change is the increase in intense storm events causing greater water inputs in shorter periods of time, affecting flood frequency and duration," the report noted.
Now, with an unfathomable amount of flooding hitting the state, it's easy to wonder if this is precisely the sort of event that South Carolina's scientists had in mind. After all, as our very own Capital Weather Gang has noted, this isn't merely a 1 in 1,000 year event for rainfall totals - in some locations the amount of rainfall "blows NOAA's 1,000-year events scale out of the water." And some have already suggested a "probable" climate change connection.
That said, climate scientists debate constantly about how and when to link extreme events to climate change, and the questions involved are anything but simple. Indeed, a recent essay in the journal Science issued a warning about such connections, noting that "even if it is certain that anthropogenic climate change has caused the frequency of European heat waves to double...the odds that this summer's European heat wave was caused by anthropogenic climate change are only even."
In the long term, climate scientists perform statistical studies to calculate whether they can say that a given event was made more likely to occur in a warming climate than in a climate that was not influenced by greenhouse gas emissions. This takes time to perform and requires large numbers of computer model simulations. So we can't consult such a source yet.
In the absence of such studies, then, what can we say about the South Carolina floods in a climate context? At least three things:
1. In general, more extreme rainfall events are a predicted consequence of a warming climate.
A warmer atmosphere is capable of holding more water vapor - and thus, more rain (or snow, for that matter) is expected in the most extreme precipitation events. And indeed, that's just what has been happening in the United States, according to the 2014 National Climate Assessment:
Thus, you can certainly say for the South Carolina floods - as you can for the 2013 Boulder, Colo., floods, and the Texas and Oklahoma floods earlier this year - that they are consistent with what we would expect in a warming world.
"As the world warms, more water evaporates from the ocean, as well as lakes and rivers," says Katharine Hayhoe, a climate scientist from Texas Tech University. "That means that, when a hurricane or a storm system comes along, there is on average more water vapor available for it to pick up and dump on us than there would have been 50 or 100 years ago."
However, some scientists are cautious about going beyond this relatively basic point and engaging in actual, causal attribution of the event.
"The peer review literature certainly suggests changes in the top 1 percent intense rain events, but I think that it would be speculative to conclude this event is caused by climate change, though I am open to the possibility there could be a link," says J. Marshall Shepherd, director of the program in atmospheric sciences at the University of Georgia.
"We do know that storm water management systems may not be engineered for this century's rainstorms," Shepherd adds.
2. The complicated connection to Hurricane Joaquin.
The reason things get complicated is that the rains over South Carolina are a very complex meteorological event with multiple causes, including Hurricane Joaquin (the rains tapped some of its tropical moisture) but also numerous other factors. "At least eight key elements conspired to create a highly efficient, small-scale rain machine centered on South Carolina," writes Jeff Halverson at Capital Weather Gang.
Still, some scientists think the tropical moisture - partly linked to Joaquin - was key, and moreover, that its presence is tied to warm sea temperatures that, in turn, may have a climate connection.
Here's how climate scientist Michael Mann of Penn State University puts it:
This is yet another example, like Sandy, or Irene, of weather on "steroids," another case where climate change worsened the effects of an already extreme meteorological event. In this case, we're seeing once-in-a-thousand year flooding along the South Carolina coastline as a consequence of the extreme supply of moisture streaming in from hurricane Joaquin. Joaquin intensified over record warm sea surface temperatures in the tropical Atlantic, which both allowed it to intensify rapidly despite adverse wind shear, and which provided it with unusually high levels of moisture - moisture which is now being turned into record rainfall.
Indeed, Mann adds: "There is an exponential relationship between sea surface temperature and the amount of moisture in the atmosphere above it. So record warm temperatures means record amounts of moisture."
Adds Jennifer Francis, a climate scientist at Rutgers University who has argued that the melting of the Arctic is changing the nature of the northern hemisphere jet stream, which shapes weather patterns:
Recent heavy rains in the Carolinas over the weekend resulted from a deep, slow-moving front that tapped into a wealth of tropical moisture from the Atlantic Ocean. Sea-surface temperatures across the tropical Atlantic and along the U.S. eastern seaboard have been running well above normal....which provided extra evaporation and energy to fuel the frontal system. The entire weather pattern was slow-moving because of blocking high pressure over the N. Atlantic. Is there a connection to climate change? Very possibly, as heavy precipitation events like this one have increased in frequency, particularly in eastern North America. Warming oceans contribute to globally increasing water vapor content in the atmosphere. There is also evidence that very large waves in the jet stream, like the one that caused the slow frontal motion, are also occurring more frequently, perhaps in response to the rapidly warming Arctic. While these topics are still a focus of active research, this flooding event in the Carolinas bears all the hallmarks of expectations for a warming - and moistening - atmosphere.
3. In the end, it's about how much you stress the thermodynamics.
In a recent paper, the much cited climate researcher Kevin Trenberth of the National Center for Atmospheric Research tried to change the paradigm for how we think about the link between climate change and individual weather events - in effect, shifting the burden of proof more onto those who deny such a connection (and away from those who assert one).
Writing with his colleague John Fasullo and Theodore Shepherd, Trenberth argued that while it's hard to blame a changing climate for particular atmospheric dynamics - the atmospheric "steering" currents that first held Joaquin in in the Bahamas for an extended period, and then sent it out to sea, say - it is clear that the thermodynamic environment has changed for all storm events, because there is more available heat and moisture.
Or as the authors put it:
The climate is changing: we have a new normal. The environment in which all weather events occur is not what it used to be. All storms, without exception, are different. Even if most of them look just like the ones we used to have, they are not the same....We argue that under such conditions it is better for event attribution to focus not on the synoptic event, but rather on the influences of the changed large-scale thermodynamic environment on the extremes and temperatures and moisture associated with the event.
Trenberth therefore argued that events like Superstorm Sandy, 2013's Hurricane Haiyan and the devastating Boulder floods all had a climate change component to them. It seems reasonable to assume that the same argument would apply here. But on the other hand, that doesn't mean Trenberth has won over all of his colleagues yet.
So in sum: The floods were not "caused" by climate change, and the exact meteorological circumstances that caused them to occur are complex. However, the idea that extreme rains are worsening due to climate change is well established - and the rain in this particular event was likely worsened by thermodynamic factors that are tough to separate from a changing climate.
And several scientists are willing to say precisely that.
Catastrophic flooding in South Carolina since last week shattered state rainfall records and shocked longtime residents and officials, who said they've never seen rain so powerful. But it's hardly the first extreme, record-breaking weather event in the U.S. this year.
Floods, hurricanes, wildfires and other extreme events are becoming more frequent and more intense because of climate change, experts warn, and that's never been more apparent than in 2015.
Here's a look at some of the record-breaking weather-related events that have hit the U.S. this year.
California snowpack at all-time recorded low
In April, drought-stricken California witnessed a snowpack with virtually no snow and set an all-time recorded low in the Sierra Nevada mountains. At just 6 percent of the long-term average for that time of year, the snowpack measure shattered the previous low of 25 percent set in 1977 and again in 2014. Gov. Jerry Brown, pictured above with Frank Gehrke, chief of snow surveys for the California Department of Water Resources, announced that same day that there would be mandatory, statewide water cutbacks for the first time in history.
Record-breaking Boston snow didn't melt until July.
Boston recorded its all-time snowiest year, with 110.6 inches between July 1, 2014, and June 30, 2015. In what grew to be an ominous reminder of how miserable the winter was, the once 75-foot-high, trash-covered "snow farm," where plows corralled the ice, didn't melt until July 14. You could even follow the snow pile on Twitter.
Record-breaking heat scorches the U.S.
Multiple states have broken heat records as 2015 shapes up to be the hottest year on record. Florida recorded its hottest March to May, while California -- seen above with tourists in Death Valley this summer -- Idaho, Oregon, Utah and Washington all logged their hottest Junes.
Wettest month ever recorded leads to extreme flooding
May was the all-time wettest month ever recorded in the contiguous United States in 121 years of NOAA's record-keeping. The total rainfall of 4.36 inches was 1.45 inches above average. Nowhere was the wet weather more extreme than in Texas and Oklahoma, where precipitation totaled more than twice the long-term average. Flooding claimed 23 lives and forced people like the above Houston couple to navigate roadways by boat.
In September, extreme flash floods along the Utah and Arizona border claimed 20 lives, making it the deadliest flood in Utah state history and one of the deadliest weather events of the year.
The U.S. gets its earliest tropical storm in 60 years.
Tropical Storm Ana became the second-earliest tropical or subtropical storm to make landfall in the U.S. when it hit South Carolina on May 10. The only tropical storm to make a landfall earlier than that was in Florida in February 1952. While Ana didn't break the record, meteorologists at The Weather Channel noted that there has been an increasing frequency of tropical storms hitting before June 1 in the last decade.
California wildfires break spending records
The catastrophic Butte Fire and Valley Fire that started in Northern California last month were so intense that the U.S. Forest Service broke its record for spending in a single week, $243 million. The high cost of fighting the simultaneous wildfires prompted the Obama administration to direct $250 million toward the efforts.
ANCHORAGE - One of the most eroded Native Alaskan villages on the state's coast is being considered as a possible national model for moving entire communities whose futures are threatened by natural disasters escalated by climate change.
The state is hoping to kick-start an exodus from the village of Newtok, about 500 miles west of Anchorage, through a national competition for states and local governments vying for a slice of nearly $1 billion in grants to be awarded by the federal Department of Housing and Urban Development. The agency's National Disaster Resilience Competition is being promoted as an effort to address climate change and extreme weather.
If successful, Alaska officials are proposing that $62.6 million of the money be used for relocation costs, including money for infrastructure and to allow 62 families from Newtok to establish new homes at a site on higher ground nine miles away. In the draft proposal publicly released Friday, state officials are also seeking a total of $162.4 million for three other vulnerable villages - Emmonak, Galena and Teller - that storms have extensively damaged in recent years.
But officials acknowledge that competing for the funding, which went unused by victims of Hurricane Sandy, will not be easy. Alaska is among 40 finalists for the money, including New Orleans. But Alaska officials are hopeful.
"We think we have a very compelling story to tell," said Sally Russell Cox, a state planner who worked on the competition entry.
The release of Alaska's proposal opened a public comment period before the final contest submission is due to the department on Oct. 27.
President Obama, in a recent three-day visit to the state, focused almost entirely on climate change and how temperatures are rising faster in Alaska than anywhere else, already threatening entire communities.
Newtok is the only one of Alaska's several threatened communities that has begun a physical move. The Yup'ik Eskimo community of about 380 shepherded various multiagency projects, including the construction of several homes and the beginning of an evacuation community center, which would be completed with nearly $5.5 million sought through the competition.
The raging Ninglick River is taking over as much as 75 feet of riverbank a year, and is steadily inching toward homes. Melting permafrost is sinking, knocking homes and village boardwalks out of alignment.
Villagers say they are living on borrowed time, and they are lobbying for funding wherever they can find it. Newtok's relocation coordinator, Romy Cadiente, was in Washington last month to meet with officials, including members of Alaska's congressional delegation or their representatives.
The village is also trying to obtain money for some homes for the new site through the Federal Emergency Management Agency.
"We're trying to really focus on how to get this village out of there," Ms. Cadiente said in an interview Wednesday. "That shore is not going to grow back."
As the East Coast prepares for a possible Hurricane Joaquin landfall, experts warn that its intensity and potential for destruction are exacerbated by climate change.
Joaquin, which strengthened into a dangerous Category 4 hurricane on Thursday and battered sparsely populated Bahamian islands, will strengthen in the next 12 to 24 hours, the National Hurricane Center reported. Its current path has it nearing North Carolina and Virginia on Sunday or Monday, but mid-Atlantic and Northeast states will experience minor to moderate flooding over the weekend regardless of whether the hurricane makes landfall.
Joaquin's quickly progressing strength can be tied to unprecedented sea surface temperatures in the hurricane's vicinity, Michael Mann, director of the Earth System Science Center at Pennsylvania State University, told The Huffington Post.
"Joaquin has been traveling over a record-warm ocean surface and undoubtedly that has contributed to its rapid intensification," he said. "In a very basic sense, warmer ocean surface temperatures mean there is more energy available to strengthen these storms. So we expect more intense hurricanes in general in a warmer world."
A map from the National Oceanic and Atmospheric Administration shows the temperatures in Joaquin's path at a "record warmest."
Climate Nexus, an organization dedicated to clean energy solutions, warned that because oceans expand as they absorb heat, that gives Joaquin "a higher platform from which to run up onto land" and increases the threat of severe flooding. The sea level in the New York Harbor, it noted, has risen nearly a foot over the last century.
"There is not uncertainty about sea level rise," RAND researcher Jordan Fischbach told Time in August. "As we get more sea level rise, these large storm events will with certainty damage ... assets and people."
Because a warmer atmosphere holds more moisture in the air, Climate Nexus noted, hurricanes are loaded with more potential for destructive rainfall.
Kevin Trenberth, a senior scientist with the National Center for Atmospheric Research, explained the phenomenon last month while discussing recent flooding in Utah and Arizona.
"When the right weather system comes along," he told HuffPost, "that weather system can be thought of as a device for reaching out -- quite a ways at times -- and grabbing the available moisture and bringing it in and dumping it down."
Mann warned it's likely we'll be seeing more hurricanes of Joaquin's strength.
"Based on our work, climate change is already leading to both more intense and larger hurricanes than before," he said. "That translates to more frequent Sandy-like storm surges for New York and elsewhere."
The Marshall Islands, a network of small islands in the South Pacific, is one of the countries most at risk of the dangers of climate change. The roughly 50,000 people who call the Marshalls home are facing rising sea levels, increasingly violent storms, drought and flooding.
an especially high tide inundated several of the islands, including Majuro, the largest and most populous. Parts of the island were under water. Hundreds of people had to flee their houses. The president said later that his people "stand to lose everything."
In November, world leaders will meet in Paris for a conference on climate change. This week, in a joint interview with The WorldPost and Al Jazeera America, Tony de Brum, the foreign minister of the Marshall Islands, discussed global warming and his goals for the Paris talks.
Christiana Figueres, the U.N. climate chief, recently said that no matter what countries pledge in Paris, we'll still be on track for a 3-degree rise in global temperatures. What is your reaction to that?
We want to keep everything under 2 degrees -- under 1.5 degrees, if possible. We want the world to keep that as a goal. For us, anything more than that is not an option. It means that the islands will go under. For the Marshalls, for 39 atolls in the Federated States of Micronesia, for three atolls in Palau, for Maldives, for Tokelau -- anything over 2 degrees is catastrophic.
That is why we've been insisting that the language be kept -- the language we agreed to many years ago -- of 1.5 to 2 degrees of global warming. And that there be a five year cycle of negotiations so that people can ratchet up their commitments and respond to science and technology on a much quicker basis.
If you wait too long and, for example, set a ten-year plan in 2020, we'd return to the negotiating table in 15 years. That's too much time -- too long for small vulnerable islands. It would reach a point where there are more irreversible consequences of climate change than there are solvable ones. Adaptation and dealing with the impacts of climate change become a lot more expensive. We need to do something about it now.
And we're also insisting that the Green Climate Fund be fully funded ($100 billion in place) so that vulnerable countries have assurances and confidence that there is a way out of this.
As ice caps melt into the oceans, climate change might leave many low-ground metropolises submerged.
But it's not just rising seas that could put New York City underwater. The Big Apple could face a repeat of hurricane Sandy flooding, according to researchers at Pennsylvania State University.
A storm surge like the one that forced its way past the barricades in its path, swamping roadways and flooding subway tunnels during the 2012 superstorm could happen again, the researchers say.
"In the pre-anthropogenic era, the return period for a storm producing a surge of 2.81 meters (9 feet) or greater like Sandy at the Battery would have been about 3,000 years," Andra Reed, study author and graduate student in meteorology at Penn State, said in a university release. "We found that, in the anthropogenic era, the return period for this same storm surge height has been reduced to about 130 years."
Storm surges occur when winds and atmospheric pressure from a large storm churn seas up higher than normal resulting in inland flooding. But the storm's power isn't the most influential factor in storm surges. The size of the storm, the tide, and sea level all contribute.
"Sea level is rising because of climate change," said Michael Mann, meteorologist at Penn State. "But climate change also appears to be leading to larger and more intense tropical storms."
There were seawalls in place to hold back such a storm surge off Manhattan, but the water flooded over the barrier into Battery Park on the southern tip of the island.
The Federal Emergency Management Agency (FEMA) issued a revised floodplain map following the 2012 storm. This new map is a fresh look, as the last one was made in 1983 by the agency.
This new map generously expands the flood zone of the region, perhaps too generously according to some.
Almost doubling the number of buildings contained in the floodplain, the map also increases the number of potentially affected residents by 83 percent. This brings the marked area to 400,000 residents and 71,500 structures.
The city has called FEMA's map is overcautious, according to an August article in the Wall Street Journal. Officials had their own study done, showing a significantly smaller floodplain.
It may be devastating to live through flooding like many did in 2012, but for the city it comes down to economics.
When an area is dubbed a floodplain, certain protective measures must be put in place. However, some of those fall on the homeowners in the form of higher insurance costs.
New York is appealing FEMA's map with those costs in mind, but officials are still wary of the risks.
"It was necessary for the city to do it, to try to keep that affordability for homeowners," Donovan Richards, a City Council member who represents parts of Queens, told the Journal. "But we also have to be cautious, and not shrink the map to the extent that if another storm comes, these homeowners would not have been in the flood zone."
As if on cue, a king tide powered by a supermoon flooded parts of South Florida Sunday and Monday, setting a soggy stage for international forums aimed at drawing attention to the perils of climate change.
In downtown Miami, about 1,200 people gathered to train for a climate corps led by former Vice President Al Gore, who drew mainstream attention to the issue in his 2006 Academy Award-winning documentary An Inconvenient Truth. For nearly three hours, Gore walked a crowd that included participants from 80 countries through his now-famous slide show, rebooted with a decade's worth of new science and data supporting the dire consequences of a warming planet.
Across Biscayne Bay, where climate change has made Miami Beach ground zero for rising seas, the French Embassy hosted another panel in advance of a U.N. summit in Paris in November.
"The scientists have long since told us we have to change," Gore told the packed room at the Hyatt Regency overlooking the Miami River. "But now Mother Nature is saying it with water in the streets in this city."
Though Gore largely avoided politics, he accused the state's power companies of standing in the way of solar power and took a subtle jab at Gov. Rick Scott, whose environmental regulatory agency has tended to avoid using the term "climate change" in official documents. Scott has denied reports that he banned the phrase.
"Miami has an enormous amount at risk," Gore said as he showed pictures of sunny-day flooding in South Florida during a 2013 king tide. "I just wonder how the governor watches this and says, 'I don't notice anything. Do you notice anything?' Not to make an ad hominem comment, but I'm genuinely curious."
This year's king tide coincided with a Sunday supermoon that put the moon closest to the earth in its oblong orbit, fueling higher than expected tides. A second king tide was forecast for about 9 p.m. Monday, followed by a second round just after 10 a.m. and 10 p.m. Tuesday and 11 a.m. and 11 p.m. Wednesday.
The seasonal high tides, which scientists say have been inching up with rising sea levels, put Indian Creek Drive underwater for part of the day. Flooding was also reported in Fort Lauderdale, Hollywood and farther north in the Hillsboro and Deerfield Beach areas, said Jennifer Jurado, director of Broward County's division of Environmental Planning and Community Resilience.
Around Miami Beach in areas where new pumps kicked on as part of a $200 million plan to keep the city dry, no flooding occurred, the city reported. The city has touted its approach as a model for other coastal communities that will inevitably be dealing with increased flooding. (continued)