News•November 11, 2013

Typhoon Haiyan's Deadly Surge Noted in Warsaw Talks

The devastation and mounting humanitarian crisis in the Philippines in the wake of Super Typhoon Haiyan is becoming more apparent with each passing hour, with the final death toll possibly climbing as high as 20,000 or more, making it the deadliest and most expensive natural disaster in that storm-prone country’s history.

Storm surge-related damage near Tacloban, Philippines.
Credit: British Red Cross.

While Haiyan’s winds have garnered most of the headlines, reports from the hardest-hit areas now indicate that it was likely the massive storm surge that caused the most damage and greatest loss of life, particularly in Tacloban City, a city of 220,000. Tacloban City and the community of Guiuan on the south shore of Samar Island, where the storm’s fiercest winds and waves first made landfall, now resemble areas struck by the 2004 Indian Ocean Tsunami, with ships tossed inland, coastal infrastructure flattened, and the horrific sight of bodies lying in the streets.

The typhoon has added an emotional charge to the latest round of the typically staid U.N. climate negotiations that began Monday in Warsaw, Poland, where countries are working to set a course toward a new climate treaty in 2015. In a speech on Monday, the delegate from the Philippines, Yeb Saño, pleaded for the world to act to reduce greenhouse gas emissions, using Haiyan as an example of the devastating consequences of global warming.

“Typhoons such as Haiyan and its impacts represent a sobering reminder to the international community that we cannot afford to procrastinate on climate action,” Sano said. “What my country is going through as a result of this extreme climate event is madness. The climate crisis is madness. We can stop this madness. Right here in Warsaw.”

Based on the scientific literature, though, Haiyan's intensity was not a clear cut sign of manmade global warming. Studies still show a high amount of uncertainty about how global warming is affecting the frequency and intensity of West Pacific typhoons, although there are signals emerging in other ocean basins, such as the Atlantic.

As that debate plays out, global warming is already making any coastal storm that occurs more damaging by raising global sea levels, a point that Haiyan drove home all too vividly.

Storm surge refers to the the bulge of seawater pushed ashore by a tropical cyclone’s winds, forward speed, and low atmospheric pressure. Super Typhoon Haiyan possessed all the necessary tools for building a deadly surge. When it made landfall, the storm was moving at a rapid pace — about 20 mph — and combined with surface wind speeds gusting more than 200 mph and a nearly historically low atmospheric pressure reading, helped push a powerful surge of water onshore along and to the north of the storm’s path.

It will take some time before it becomes clear exactly how high the storm surge reached but news reports indicate it may have been somewhere between 15 to 20 feet in Tacloban City and that the water swept inland by at least a half mile. The New York Times reported that the storm surge was “the highest in the country’s modern history.”

Other reports spoke of people in coastal villages who seem to have simply “vanished” into the sea after the surge swept through and retreated.

Map of regional patterns of observed sea level (in mm/year), showing a regional hot spot in the Western Pacific and Indian Oceans.
Click image to enlarge. Credit: CLS/Cnes/Legos.

Josh Morgerman, a storm chaser with the iCyclone team who rode out the storm in Tacloban City, described the scene in vivid and disturbing detail in a Facebook post: “At the height of the storm, as the wind rose to a scream, as windows exploded and as our solid-concrete downtown hotel trembled from the impact of flying debris, as pictures blew off the walls and as children became hysterical, a tremendous storm surge swept the entire downtown. Waterfront blocks were reduced to heaps of rubble.”

Storm surges are natural events that have historically been tropical cyclone’s biggest killers. However, there is increasing evidence that manmade global warming is making the impacts of storm surges worse by raising the sea levels that they build up on top of.

The most recent report from the U.N. Intergovernmental Panel on Climate Change found that during the 1901-2010 period, global averaged sea level rise was 0.07 inches per year, which accelerated to .13 inches per year between 1993 and 2010. The IPCC’s four scenarios of the amount of greenhouse gases in the atmosphere through 2100 all show faster rates of sea level rise compared to that observed during 1971-2010. The new report projected that global mean sea level rise for 2081-2100 will likely be in the range of 10.2 to 32 inches, depending on greenhouse gas emissions and the rate of melting of polar ice sheets. The scenario with the highest amounts of greenhouse gases in the atmosphere showed a mean sea level rise range between 21 and 38.2 inches, which would be devastating for many highly populated coastal cities at or near current sea levels.

The IPCC report found that as sea level increases, the chances of extreme sea level events, such as inundation due to storm surges from typhoons and other storms, increases sharply.

“Higher mean sea levels can significantly decrease the return period for exceeding given threshold levels,” the report said. For example, the IPCC cited a study that found that for a global network of 198 tide gauges, a 1.6 foot mean sea level rise “would result in the frequency of sea level extremes increasing by an order of magnitude or more in some regions.”

Research done by Climate Central scientists has also shown that even relatively small increases in sea level can dramatically escalate the risks of storm surge-related flooding in the U.S. For example, the 1-foot rise in sea level in Lower Manhattan during the past century resulted in greater coastal flooding than would otherwise have occurred when Hurricane Sandy struck in 2012.

Sea level is rising at different rates in various regions of the world, with particularly rapid rises observed in the Western Pacific, including in the Philippines. In fact, the West Pacific has been a hotspot of sea level rise in recent years, but that may be at least partly related to natural climate variability that has favored warmer-than-average sea surface temperatures in the Western Pacific, while the eastern Pacific has remained generally cooler than average.

Projections of global mean sea level rise over the 21st century relative to 1986–2005. The assessed likely range is shown as a shaded band. The assessed likely ranges for the mean over the period 2081–2100 for all scenarios are given as colored vertical bars, with the corresponding median value given as a horizontal line.
Credit: IPCC Working Group I.

Other dynamics can be at play, too. In the Philippines’ capital of Manila, a city of 12 million people that Haiyan spared, tide gauge measurements indicate that the mean sea level is increasing quickly, at a rate of about a half an inch per year based on data from 1969-2010. That's an equivalent to an increase of 4.39 feet in 100 years, according to data from the U.S. National Oceanic and Atmospheric Administration (NOAA). The IPCC attributed that to the increased depletion of groundwater, which is causing the land to sink.

Other gauges in the Philippines show smaller, although still consequential, amounts of sea level rise in recent decades, as do satellite-derived estimates of sea level rise in that area.

In addition to the connection between storm surge severity and sea level rise, Super Typhoon Haiyan, also raises the issue of climate adaptation, which is on the negotiating table at the Warsaw summit.

Developing countries are seeking funds from industrialized nations to help them fund adaptation efforts aimed at making themselves more resilient to extreme events and sea level rise, and therefore better able to withstand events like Haiyan. At the 2009 U.N. climate summit in Copenhagen, industrialized countries pledged $100 billion annually in climate financing starting in 2020, but the U.S., for one, has recently signaled that most of this money will come from the private sector rather than publicly-financed foreign aid, disappointing developing nations.