In Kyushu, Japan on Friday, government officials urged 700,000 residents to evacuate as record heavy rains and severe flooding inundated the city for the fifth day in a row. Half a world away in West Virginia, another unpredicted record deluge dumped 8.2 inches of rain, washed out roads, cut off shopping malls, flushed burning homes down raging rivers, and left more than 14 people dead and hundreds more stranded.
Individually, these events would be odd. But taken together with what are now scores of other extreme flooding events happening around the world in the space of just a few months and the context begins to look a lot like what scientists expected to happen due to human-forced climate change.
700,000 Urged to Evacuate in Kyushu Deluge
(Heavy rains fall over Kyushu on Friday in the most recent wave of extreme storms to blanket the island. Image source: LANCE MODIS.)
In Kyushu, the skies opened up on Monday. An extension of a seasonal front draped across China and feeding on moisture bleeding off of record hot ocean surfaces edged out over Japan. Mountainous cloud banks unloaded. Record rains in the range of five inches an hour then began to inundate the southern Japanese island. This mass dumping of water eventually accumulated to half a meter (or 1.6 feet) over some sections of the island over the course of just one 24 hour period.
The rains set loose raging rivers of water through Kyushu streets and saturated hillsides already weakened by an April earthquake. The flooding and resulting landslides killed 6 people on Monday alone and resulted in calls for tens of thousands of people to evacuate the hardest hit areas. Over the week, hourly rainfall totals of 1-3 inches and daily rainfall rates of 4-8 inches continued as more and more of the region succumbed to flooding. By Friday, bridges and roads had been washed out, an elderly man, a university student, and a child had gone missing, trains had been blocked by mudslides and the evacuation calls extended to include 700,000 people.
Unexpected Record Floods Hit West Virginia
By early Wednesday in West Virginia the weather was starting to get a little rough. Strong storms had been running over the region since Tuesday as an unstable air mass funneled lines of thunderstorms into the Appalachian Mountain region. The forecast did indicate some potential for severe weather, but nothing near so extreme as what emerged.
NOAA QPC predictions called for peak rainfall amounts in the range of 3.24 inches from Wednesday through Friday. But the inundation that occurred on just Thursday alone resulted in rainfall totals of more than two and a half times that:
(In another instance that calls into question whether current forecast models are keeping up with the heavy rainfall potentials that are now made possible by a record hot global atmosphere NOAA’s predicted rainfall totals are again greatly exceeded by events — this time in West Virginia where 14 people have been reported dead due to flooding. An indication that weather prediction may not be fully taking into account the added threat posed by human-forced warming. And also an indication that endemic climate change denial in the US political system [in vast majority among republicans] — which has resulted in a dramatic failure to fund needed and necessary climate change monitoring — is having a harmful overall impact to public safety and disaster preparedness. Image source: NOAA QPC.)
Reports indicate that 8.17 inches of rain fell in just one 24 hour period in Sulfur Springs, West Virginia. But it was just the center mass of the worst flood in a century for parts of the state. One that has so far resulted in the deaths of more than fourteen people. Five hundred people are also currently stranded in a shopping mall that has now been cut off by the flood.
(A burning home floats down a West Virginia creek swollen to a raging torrent by the worst flood to hit the state in 100 years.)
Numerous homes and hundreds of cars have also been lost due to the flash floods that swept through West Virginia’s valleys. In one instance, a burning house was filmed floating down a river. As a result of the severe and unexpected rains, 44 of the state’s 55 counties have now been declared a disaster area.
Conditions in Context — Global Warming Fuels More Extreme Rainfall Events
These severe flooding events add to those this week occurring in China, Australia, Sri Lanka, Indonesia, and Great Britian over just the past seven days. In addition, extreme floods have swept through Texas, Canada, Central Asia, Europe, Ghana and Argentina over the past couple of months.
The floods occur at a time when global temperatures are just coming off of new record highs during the first part of 2016. Temperatures that, in February peaked near 1.5 degrees Celsius hotter than 1880s averages. For each 1 degree Celsius that you add to global temperature, you increase the atmospheric moisture loading by about 7 percent. This is a physical fact of the Earth’s climate system. If you heat the atmosphere, you increase evaporation and that results, in turn, in more moisture held up in the world’s airs.
It’s this well understood dynamic of atmospheric physics that scientists have long warned would result in more extreme droughts and downpours as a result a human-forced warming of the world. Chris Fields, a climate scientist cited by US News and World Report in an article covering the record Paris floods earlier this month also noted:
“One of the clearest signs of climate change, over much of the world, is the increase in the fraction of the rain that falls in the heaviest events.”
So not only does a loading up of the hydrological cycle with moisture result in heavier rainfall events generally, it also results in a greater fraction of overall rainfall coming in the form of heavy rain. In other words climate change causes heavier rain on top of heavier rain. The worst events, as a result do not just get worse, they get much, much worse. And this is due to the added convection — or updrafts — that keep moisture in the air longer. In other words, the rain in a hotter world needs to be heavier to fall out of clouds that are pushed higher and with greater force by heat rising up off the Earth’s surface.
(In a record-warm world, a transition from El Nino to La Nina can result in an unprecedented amount of moisture being wrung out into trough and storm zones. Extraordinarily heavy rainfall events like those experienced across the world over the past few months is the all-too-likely result. It’s a feature that has been added by global temperatures that are now about 1.2 C hotter than 1880s in the annual average. As global temperatures increase, heavy precipitation events will continue to grow more intense even as droughts in other regions worsen. Image source: Earth Nullschool.)
As for the timing of the most recent heavy rainfall events — the last element to the equation has been a transition from El Nino to La Nina. During the most recent El Nino, the Equatorial Pacific warmed and new record global temperatures were achieved. But as the Equatorial Pacific cooled, so did the atmosphere. And now, some of that record atmospheric moisture load isn’t recieving quite as much heat from beneath keeping it all aloft. So a greater portion of it tends to fall out in the post El Nino period.
And none of this is to say at all that El Nino is causing the increased rate of flooding. The El Nino to La Nina transiton is a natural variability based event that is instead being influenced by human-forced warming in such a way that is resulting in an increasingly extreme period of rainfall. And we’re experiencing that globally now.
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Hat tip to Greg
Hat tip to Colorado Bob
Hat tip to Climate Hawk