What makes 2017 Atlantic hurricane season unprecedented?

Flood of hurricanes

The series of hurricanes that ravaged the Atlantic in September are a dress rehearsal of a stormy future. Hurricane Harvey produced the second largest rainfall event in US history, dumping about 1,316 mm of rain on southeast Texas. This is more than 150 per cent of average rainfall the state gets in a year. It claimed over 70 lives and devastated large parts of Texas. Then Hurricane Irma created a new record by maintaining a maximum wind speed of 298 kmph for 37 hours and killing over 60 people. A dozen Caribbean island nations were also flattened by hurricane Irma. Hurricane Maria was the first category 4 storm to hit Puerto Rico in nearly 90 years. The island’s governor Ricardo Rossello said, “We have not experienced an event of this magnitude in our modern history.”

The warning came eight months ago. In December 2016, a climate science report by 13 US federal agencies observed, “There is some danger, in the form of evoking complacency, in placing too much emphasis on the recent absence of a specific subset of hurricanes.” They were referring to the fact that the country had not witnessed a major hurricane landfall for 11 years. Harvey and Irma signalled the end of “hurricane drought”.

Tropical cyclones are known as hurricanes in the Atlantic or Eastern Pacific; typhoons in the western North Pacific; and, simply cyclones in the South Pacific and Indian Ocean. They are part of the process through which the Earth’s atmospheric system maintains its heat balance, transferring it from the tropics towards the poles and into space. When the air above the sea surface warms up to about 27°C or more, it rises into the atmosphere and cold air from the surrounding areas takes its place. This creates a downward spiral of air into the centre and an upward wind due to pressure differences between the ocean surface and the outer atmosphere. The wind carries water vapour along with it and takes the form of a swirl. This water vapour then forms clouds, which make a circular formation, and suck up more warm air and moisture from the ocean below, adding to their size.

Such a formation can be several hundred kilometres wide with a depression, called an eye, at its centre. The eye remains at low pressure and calm, with strong winds from all around flowing into it. The eye wall, located just outside the eye, causes the most damaging winds. Depending on its intensity, the wall pushes water inland faster than it can drain off. This rapid rise of water—several metres in just a few minutes—is the storm surge. It is the this storm surge that was whipped up by Irma’s eye wall and damaged 90 per cent of homes in Florida Keys. On September 20, when hurricane Maria triggered a storm surge, Puerto Rico witnessed a torrent of water.

HAVE THEY BECOME FIERCE?

The US, however, was lucky not to experience storm surges of such intensity between 2006 and 2016 as it was not hit by a Category 3 or higher “major hurricane” during these years. On May 25, forecasters at the National Oceanic and Atmospheric Administration (NOAA) predicted an above-normal hurricane season with 70 per cent likelihood of 11 to 17 named storms (wind speed of 63 kmph or higher), out of which 5 to 9 could become hurricanes (winds speed of 119 kmph or higher), including two to four major hurricanes (see ‘Categories of carnage’). Half way into 2017 hurricane season that lasts from June to November, 13 named storms, seven hurricanes and four major hurricanes have already been recorded. What is unusual is the development of two Category 4 and two Category 5 hurricanes in a month, and three major hurricanes passing through the same region in three weeks, as Maria, Irma and Jose have in the Caribbean. And this hurricane season is far from over.

“The season has the potential to be extremely active, and could be the most active since 2010,” the NOAA said in an August 9 press release. It is difficult to predict how the second-half of the hurricane season will play out, but it is well poised to surpass 2005’s record of 15 hurricanes and most number of Category 5 storms (Emily, Katrina, Rita and Wilma). Gerry Bell, lead seasonal hurricane forecaster at NOAA, noted that one of the factors pointing to an above-normal season include much warmer waters across the tropical Atlantic than what climate models had previously predicted.

Bell’s claim is endorsed by Kerry Emanuel, professor of Atmospheric Science at the Massachusetts Institute of Technology (MIT), who says tropical Atlantic is exhibiting high “thermal potential”, which means water can rapidly evaporate into the atmosphere. The greater the speed, the more favourable conditions are for hurricanes to form, and the more powerful they can become, adds Emanuel.

This “thermal potential” due to abnormally warm waters in the Atlantic coincides with scientific concern over rising greenhouse gases in the atmosphere and elevated global temperature. The surface temperature of water in the Atlantic was above 28°C this September. But Irma gained strength when it came across more warm water—about 32°C—on its path to Florida. The same was the case with Hurricane Harvey. It intensified rapidly because the sea surface temperature in Gulf of Mexico was about 4°C above normal. In fact, in the last 35 years, the total rise in temperature is about 0.32°C.

A 2013 study by the researchers at the Niels Bohr Institute in Copenhagen predicted a 10-fold increase in frequency of high-intensity hurricanes if the climate becomes 2°C warmer. “We find that 0.4°C warming of the climate corresponds to doubling of the frequency of extreme storm. If the temperature rises an additional degree, the frequency will increase by 3-4 times and if the global climate becomes 2°C warmer, there will be about 10 times as many extreme storm surges,” explains Aslak Grinsted, climate scientist at Niels Bohr Institute.

“Our analysis of historical data on hurricanes in the last five decades suggests that we are already on track to see intense hurricanes more frequently,” he says. Not only has the number of hurricanes increased from 49 during 1970-79 to 75 in 2000-09, the share of major hurricanes has also seen a jump. Category 4 and 5 hurricanes consisted about 32 per cent of the total number of hurricanes in 1970-79. After two decades, the share of major hurricanes increased to 47 per cent. With almost two-and-a-half hurricane seasons still left in the current decade, the total number of hurricanes has already crossed 54, with 40 per cent of them being major hurricanes.

The jump in the number of hurricanes that we have seen in 2017 is partly attributed to the absence of wind shear: the change in the speed and direction of winds according to altitude. Wind shear distorts the shape of a hurricane, causing it to dissipate. It renders the system incapable of drawing in warm and moist air from the ocean, and thus, it fails to intensify. But in the case of Irma, there was no wind shear, which allowed the hurricane to grow to its enormous size and intensity.

This absence of wind shear could be due to the Atlantic Multi-Decadal Oscillation (AMO), a natural cycle of warming and cooling observed in the North Atlantic over the last 1,000 years. The warm phase of the cycle decreases the wind shear, leading to the intensification of hurricanes.

To make matters worse, even El Niño is stuck in neutral mode this year, thus improving prospects of Atlantic hurricanes. When El Niño is active, ocean surface temperatures in the equatorial Pacific become warmer than normal. This warming leads to more wind shear. The delay in the onset of El Niño, and the resulting absence of wind shear is likely to increase the chances of these cyclones forming right up to the end of hurricane season.

As if these reasons were not enough, rising sea level due to global warming is also exacerbating the impact of these storms. According to NASA, the global average sea level has increased by 10 to 20 cm since 1870. However, the annual rate of increase over the past 20 years has been roughly 0.3 cm. The Intergovernmental Panel on Climate Change (IPCC), in its 2013 report, claimed that the oceans could rise between 28 and 98 cm by 2100, which is enough to inundate several cities along the US East Coast. Vertical increase in sea level leads to increased horizontal reach of the storm surge. Hurricane Sandy in 2005 is an example where sea-level rise extended the reach of the storm by 70 sqkm, affecting 83,000 additional individuals living in New Jersey and New York.

FORECASTS AND PREPAREDNESS

This correlation between rising sea level and increasing storm surge does not augur well for the coastal communities around the world. Take the case of the US. The already crowded US coast will see population growth from 123 million to nearly 134 million by 2020, if current population trends continue, claimed a report by NOAA.

More than 39 per cent of the US population is concentrated in counties directly on the shoreline, the report revealed. “Population density in shore-line counties is more than six times greater than the corresponding inland counties. And the projected growth in coastal areas will increase population density at a faster rate than the country as a whole,” says Kristen Crossett of NOAA’s National Ocean Service.

As many as 13.1 million people along the US coasts could be displaced by the end of this century. By then, nearly 70 per cent of them will be residing in southeastern US, with half of that concentrated in Florida alone. These findings emerge from a 2016 joint study by researchers at the University of Georgia and Stetson University in Florida. According to NOAA’s National Ocean Service, more than 1,540 single-family housing units are permitted for construction every day in coastal counties. In fact, coastal counties are home to 53 per cent of the nation’s population, yet they account for only 17 per cent of US land area, excluding Alaska.

Apart from the projected increase in coastal population, it is the “risk of an increased frequency of poorly anticipated” high-intensity hurricane landfalls that could lead to higher rate of injuries and casualties. Emanuel, in his paper published in August 2016, observed that as number of storms that intensify rapidly just before landfall could increase substantially by the end of this century, forecasting this rapid intensification is problematic.

For example, in 2015, hurricane Patricia intensified from category 1 (139 kmph) to category 5 (333 kmph) within 24 hours. During this same period, the National Hurricane Center had predicted intensification by only 56 kmph. While it takes 2-3 days on an average for a category 1 hurricane to reach category 5, hurricane Maria took just 15 hours. “We used a modelling approach to simulate many US landfall events in the climate of the late 20th and late 21st centuries. We find a large increase in the incidence of rapid intensification before landfall that is caused by global warming,” says Emanuel.

In fact, over the past 30 years (1984 to 2014), storm speeds have increased on average by 1.3 metres per second—or 3 miles per hour— according to a joint study by James Elsner at Florida State University and Namyoung Kang, deputy director of the National Typhoon Center in South Korea. Elsner believes that higher wind speed is perhaps not related only to higher sea surface temperature as upper-level air temperatures might also be playing a role.

“Higher sea surface temperature doesn’t come alone. It is likely to be accompanied by higher pressure anomaly capping over the thermo-dynamically unstable tropical troposphere. It results in a blasting effect that could be added on to the sea surface temperature’s direct contribution,” says Kang.

Scientists are also faced with another important question: why did Hurricane Harvey linger on Texas longer than it should have? “It just sat, and it sat close enough to the Gulf of Mexico that it could just keep pulling in all this moisture, and then it dropped all that rain in Houston,” says Phil Klotzbach of Colorado State University in an interview with the Pacific Standard. They are now trying to understand whether this slowness had something to do with the “episodes in which the jet-stream—the high-flying river of air that meanders around the higher-to-mid latitudes—gets locked into one place for an extended period”, perhaps making the storm system lazy.

These tropical cyclones are not just lingering, but they are also migrating towards the poles. James Kossin, a scientist at the US National Oceanic and Atmospheric Administration’s Center for Weather and Climate in Madison, Wisconsin says that in the last three decades, tropical cyclones, except hurricanes, have moved towards the poles in both hemispheres. What prevented hurricanes from north/south migration is the large decadal variation in the Atlantic. “The greatest poleward shifts have been observed in the western North Pacific, which has increased the hazard exposure across a large region, including Taiwan and Japan. Regions in the subtropics are the ones that would see their exposure increase,” says Kossin.

But the Trump administration has resisted talking about climate change. “To have any kind of focus on the cause and effect of the storm; versus helping people, or actually facing the effect of the storm, is misplaced,” says Scott Pruitt, an administrator with the US Environmental Protection Agency (EPA). Besides skirting questions from media on the link between hurricanes and global warming, White House officials have been suggesting that “hurricane systems are cyclical and not tied to global warming”. Their scepticism may suffer a quake as NOAA predicts sea-level rise in south Florida by as much as 86 cm by 2050 (see ‘Learning from Harvey’).

Research released by NOAA in August 2017 predicts that anthropogenic warming by the end of the 21st century is likely to increase intensity of tropical cyclones globally by 2 to 11 per cent on an average. It will likely cause tropical cyclones to bring substantially higher volume (about 10-15 per cent) of rainfall than current ones. Under such circumstances, coastal communities need support to mitigate climate disasters and deal with the aftermath.

However, the Trump administration is gearing up to vote on bills that would cripple the ability of the EPA to address health and environmental impacts due to climate disasters (see ‘Unsafe cuts’). If Trump’s proposals find support in the Congress, the EPA would face the biggest cut of any federal agency in the 2018 budget. Several programmes, aimed at helping communities deal with climate-related challenges, may soon cease to exist.

CALAMITY IN THE CARIBBEAN

The 2017 hurricane season has been the worst for Caribbean countries. Hurricane Irma, alone, affected more than 10 Caribbean countries and it came with a record-breaking price tag—about $13 billion. On September 20, Puerto Rico was hit by Hurricane Maria. For a country in a dire financial condition, rebuilding the decimated power infrastructure and rehabilitating dozens of communities would plunge it deeper into a fiscal crisis. Dominica, one of the poorest countries in the Caribbean, saw about 95 per cent of roofs damaged or destroyed by Maria.

Earlier, hurricane Irma had completely flat-tened Antigua and Barbuda, and for the first time in 300 years, there’s not a single person living on the island. “We’re a US $1 billion economy facing a US $250 million problem,” Ronald Sanders, the Antigua and Barbuda ambassador to the United States, said while referring to the cost of rebuilding the island that has been reduced to rubble. While back-to-back hurricanes are not uncommon in the Caribbean, the intensity of hurricanes such as Maria and Irma was not seen for decades.

What makes it worse is that many Caribbean countries have an impoverished economy. Haiti is a classic example. In 2016, Hurricane Matthew hit US, Canada, Haiti and its neighbouring nations in the Caribbean. But despite hitting each of the nations hard, Haiti faced the greatest destruction with more than 470 deaths. Even hours before landfall, many Haitians were unaware of the impending disaster because the poorest country in the Americas, with 2.5 million people living in extreme poverty, does not have disaster pre-paredness mechanisms.

One of the markers of lack of preparedness in the Caribbean islands is their electricity grids. They are exposed, centralised and powered by fossil fuels. When an island is hit by storms and power plants are shut down, the entire island goes dark. Damage to vulnerable seaports also cuts off access to neighbouring nations. For these low-lying countries, which are already heavily indebted, the risk of losing wealth in climate disasters is ultimately the last nail in the coffin.

In the upcoming UN climate talks, the Caribbean nations are planning to urge the richer countries to play a bigger role in helping region bolster its defense mechanism. There is a need to speed up access to capital, especially the $10-billion Green Climate Fund, set up to help developing countries to tackle climate change. “It takes too long for these resources to move, given the urgency of the need,” says William Warren Smith, President of Caribbean Development Bank. After the Atlantic hurricane season ends, the focus must shift to addressing this growing resilience gap.

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Learning from Harvey

USA and the world are paying a high price for Donald Trump's ideology

JOSEPH E STIGLITZ

Hurricane harvey has left in its wake upended lives and enormous property damage, estimated by some at US $150-180 billion. But the storm that pummeled the Texas coast for the better part of a week also raises deep questions about the United States’ economic system and politics.

It is ironic, of course, that an event so related to climate change would occur in a state that is home to so many climate-change deniers—and where the economy depends so heavily on the fossil fuels that drive global warming. Of course, no particular climate event can be directly related to the increase in greenhouse gases in the atmosphere. But scientists have long predicted that such increases would boost not only average temperatures, but also weather variability—and especially the occurrence of extreme events such as Hurricane Harvey. As the Intergovernmental Panel on Climate Change concluded several years ago, “There is evidence that some extremes have changed as a result of anthropogenic influences, including increases in atmospheric concentrations of greenhouse gases.” Astrophysicist Adam Frank succinctly explained: “Greater warmth means more moisture in the air which means stronger precipitation.”

To be sure, Houston and Texas could not have done much by themselves about the increase in greenhouse gases, though they could have taken a more active role in pushing for strong climate policies. But local and state authorities could have done a far better job preparing for such events, which hit the area with some frequency.

In responding to the hurricane ? and in funding some of the repair?everyone turns to government, just as they did in the aftermath of the 2008 economic crisis. Again, it is ironic that this is now occurring in a part of the country where government and collective action are so frequently rebuked. It was no less ironic when the titans of US banking, having preached the neoliberal gospel of downsising government and eliminating regulations that proscribed some of their most dangerous and anti-social activities, turned to government in their moment of need.

There is an obvious lesson to be learned from such episodes: markets on their own are incapable of providing the protection that societies need. When markets fail, as they often do, collective action becomes imperative.

And, as with financial crises, there is a need for preventive collective action to mitigate the impact of climate change. That means ensuring that buildings and infrastructure are constructed to withstand extreme events, and are not located in areas that are most vulnerable to severe damage. It also means protecting environmental systems, particularly wetlands, which can play an important role in absorbing the impact of storms. It means eliminating the risk that a natural disaster could lead to the discharge of dangerous chemicals, as happened in Houston. And it means having in place adequate response plans, including for evacuation.

Effective government investments and strong regulations are needed to ensure each of these outcomes, regardless of the prevailing political culture in Texas and elsewhere. Without adequate regulations, individuals and firms have no incentive to take adequate precautions, because they know that much of the cost of extreme events will be borne by others. Without adequate public planning and regulation, including of the environment, flooding will be worse. Without disaster planning and adequate funding, any city can be caught in the dilemma in which Houston found itself: if it does not order an evacuation, many will die; but if it does order an evacuation, people will die in the ensuing chaos, and snarled traffic will prevent people from getting out.

America and the world are paying a high price for devotion to the extreme anti-government ideology embraced by President Donald Trump and his Republican Party. The world is paying, because cumulative US greenhouse-gas emissions are greater than those from any other country; even today, the US is one of the world’s leaders in per capita greenhouse-gas emissions. But America is paying a high price as well: other countries, even poor developing countries, like Haiti and Ecuador, seem to have learned (often at great expense and only after some huge calamities) how to manage natural disasters better.

After the destruction of New Orleans by Hurricane Katrina in 2005, the shutdown of much of New York City by Sandy in 2012, and now the devastation wrought on Texas by Harvey, the US can and should do better. It has the resources and skills to analyse these complex events and their consequences, and to formulate and implement regulations and investment programmes that mitigate the adverse effects on lives and property.

What America doesn’t have is a coherent view of government by those on the right, who, working with special interests that benefit from their extreme policies, continue to speak out of both sides of their mouth. Before a crisis, they resist regulations and oppose government investment and planning; afterwards, they demand ?and receive?billions of dollars to compensate them for their losses, even those that could easily have been prevented.

One can only hope that USA, and other countries, will not need more natural persuasion before taking to heart the lessons of Hurricane Harvey.

Joseph E Stiglitz, a Nobel laureate in economics, is University Professor at Columbia University and Chief Economist at the Roosevelt Institute.

With special arrangement with Project Syndicate

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Meanwhile, the monsoon anomaly

Instead of quantum of rainfall, we must analyse the distribution of rainfall to understand the changing nature of the monsoon

India was not left out by the global disruptions in weather events. The monsoon ended its June-September annual cycle even though a few weather forecasters said it would continue till mid-October. Down To Earth had earlier reported that this year’s monsoon has left behind contrasting trails of devastation caused by floods and drought-like spells. This is the third consecutive year when the monsoon has behaved in a similar way: extreme rain events pushing up the cumulative rainfall tally, while leaving behind a significant portion of the country with deficit rainfall.

A case in point is Chandigarh. The city’s rain deficit reduced from 24 per cent to 8 per cent in a single day. On August 21, it received 15 per cent of its annual average rainfall in just 12 hours. For the sake of record, the India Meteorological Department (IMD) released its weekly bulletin on progress of the monsoon on September 21, the last of the season. It says the country has received 5 per cent less than the normal rainfall. As IMD defines a normal monsoon year as up to 19 per cent deficit rainfall, India is on its way to a normal monsoon year. But as one tracks the progress across four months, it brings out a scary scenario.

This year, many cities were devastated by torrents of sudden record-breaking rainfall. On September 19, Mumbai experienced 304 mm of rainfall, the highest-ever recorded in September in the last 10 years. On August 29, the city had recorded 331.4 mm of rain—the highest 24-hour rain in August in the last two decades.

While Bengaluru was brought to its knees on August 15, when it received its highest single-day rainfall in the last 127 years, residents in Chandigarh struggled to keep their heads above water with the city experiencing 120.8 mm of rain on July 28— the highest single-day rainfall in 10 years in the month of July. The only hill station in the dry state of Rajasthan, Mount Abu, received a record 770 mm of rain in 24 hours on July 23, when its annual average is 1,600 mm.

It is not just the cities which bore the brunt of the floods. One-third of the country’s total districts—265—were devastated, 2,000 people killed and over 4.6 million hectares of farmland were affected, according to the Flood Situation Report of the Union Ministry of Home Affairs.

And then there was unprecedented rainfall deficiency. As per IMD, about 37 per cent districts received deficient rainfall till September 21. Drought-like conditions loom over 235 districts, according to the National Agriculture and Drought Assessment System.

However, the Union Agriculture Ministry has downplayed the situation saying there is deficit rainfall in only 95 districts. Despite food bowl states such as Punjab, Haryana and Madhya Pradesh recording rainfall deficit of 19 per cent, 30 per cent and 21 per cent respectively, the government claims that “the yield is expected to be same as of last year”.

Latest government data further confirms this oscillation between floods and droughts. Though the National Disaster Management Authority says that 12 states experienced floods, IMD data shows that only two states, Gujarat and Rajasthan, experienced excess rainfall. The rains battered these states for short durations and caused floods, but overall, these states received less than average rain. The rest of the states show a deficit or a neutral trend. The anomalies are striking. The most flooded districts in the eastern Uttar Pradesh are also rain-deficient. For example, Kushinagar district, which faced heavy flooding, still has a deficit of 63 per cent. It is time authorities recalibrate the mapping of the monsoon.