Cyclones and climate change: Connecting the dots

graph_anatomy of a hurricane
Updated 27 August 2017

Cyclones and climate change: Connecting the dots

PARIS: Scientists freely acknowledge they do not know everything about how global warming affects hurricanes like the one pummeling southeast Texas.
But what they do know is enough to keep them up at night.
The amplifying impact of sea level rise, warming oceans, and hotter air — all incontrovertible consequences of climate change — is basic physics, they say.
Likewise accelerated shifts in intensity, such as the sudden strengthening that turned Harvey from a Category 2 to a Category 4 hurricane — on a scale of 5 — just as it made landfall Friday.
What is missing is a detailed track record of hurricanes past, the kind of decades-long log of measurements that climate scientists need to discern the fingerprint of human influence.
Starting in the 1970s, satellite data allowed for a better tally, but even that was not enough.
“It is awfully difficult to see climate change in historical data so far because hurricanes are fairly rare,” Kerry Emmanuel, a professor of atmospheric science at MIT in Boston, told AFP.
Experts, in other words, do not disagree on the potential of manmade global warming to magnify the destructive power of the tropical storms known variously around the world as cyclones, hurricanes and typhoons.
Rather, they are confounded — for now — by a lack of information.
“Just because the data don’t allow for unambiguous detection yet, doesn’t mean that the changes haven’t been occurring,” noted James Kossin, a scientist at the US National Oceanic and Atmospheric Administration’s Center for Weather and Climate in Madison, Wisconsin.
Kossin figured out that cyclones have drifted poleward in their respective hemispheres over the last three decades, a finding hailed by other hurricane gurus as the most unambiguous evidence so far that global warming has already had a direct impact.
When it comes to cyclones and climate change, there are many points of near “universal agreement,” said Emanuel.
One is the consequence of rising seas.
“The most lethal aspect of hurricanes — wherever they occur in the world — is storm surge,” he said in an interview.
“It is physically the same phenomenon as a tsunami, except that it is excited by wind rather than a sea floor shaken by an earthquake.”
If Hurricane Sandy — which caused $50 billion in damage — had happened a century earlier, it probably would not have flooded lower Manhattan because sea level was about 30 centimeters (a foot) lower, he pointed out.
Global warming is likely to add roughly a meter to the global watermark by century’s end, according to recently revised estimates.
“The surge from these storms will be more devastating — higher and more penetrating,” said James Elsner, an atmospheric scientists and hurricane expert at Florida State University.
A second point of consensus is that hurricanes will hold more water, raising the threat of lethal and destructive flooding.
“We calculate that 1 degree Celsius of warming translates into a 7 percent increase in humidity in the atmosphere,” said French scientist Valerie Masson-Delmotte, co-chair of the UN’s Intergovernmental Panel on Climate Change (IPCC).
The US National Hurricane Center predicts that Harvey could dump more than 40 inches by the time skies clear.
Hurricane Mitch — the second deadliest Atlantic hurricane on record — left some 19,000 dead in Central America, “all from fresh-water flooding,” noted Emanuel.
“The irony is that hurricanes are known for wind, yet wind is third on the list of lethal aspects,” after storm surges and flooding caused by rain.
Earlier this year, Emanuel published a study pointing to yet another worrying climate “signal” emerging from the noise of raw data.
Scientists have made great progress in anticipating the path a storm will follow, extending their predictive powers from a day or two to about a week.
At the same time they have made scant headway in forecasting hurricane strength.
“The thing that keeps forecasters up at night is the prospect that a storm will rapidly gain strength just before it hits land,” Emanuel said, citing Harvey as an example.
In 2015, Hurricane Patricia in the Pacific Ocean intensified more rapidly — “It just went ‘Boom!’” — than any storm on record.
“Global warming can accentuate that sudden acceleration in intensity,” Emanuel said.
A finding oft cited as evidence that the jury is still out on whether climate change will boost cyclones is that scientists do not know if there will be more or fewer such storms in the future.
But even if there are fewer, which seems likely, that misses the point, the experts interviewed agreed.
Since 1971, tropical cyclones have claimed about 470,000 lives and caused some $700 billion in damages globally, according to the Center for Research on the Epidemiology of Disasters.
But most of that death and destruction is attributable to a relative handful of storms. Just three, for example, have caused well over half of all storm-related deaths in the US since 1900.
So even if the number of mostly smaller storms diminishes, that’s not what counts.
“The idea of ‘fewer but stronger’ seems to be the fingerprint of climate change on tropical cyclones,” Elsner concluded.


Hong Kong police warn of ‘live fire’ if they face deadly weapons from protesters

Updated 17 November 2019

Hong Kong police warn of ‘live fire’ if they face deadly weapons from protesters

  • Protests have tremored through the global financial hub since June
  • China has repeatedly warned that it will not tolerate the dissent

HONG KONG: Hong Kong police Monday warned for the first time that they may use “live rounds” after pro-democracy protesters fired arrows and threw petrol bombs at officers at a beseiged university campus, as the crisis engulfing the city veered deeper into danger.
Protests have tremored through the global financial hub since June, with many in the city of 7.5 million people venting fury at eroding freedoms under Chinese rule.
China has repeatedly warned that it will not tolerate the dissent, and there have been concerns that Beijing could send in troops to put an end to the spiralling unrest.
Three protesters have been shot by armed police in the unrelenting months of protests. But all in scuffles as chaotic street clashes played out — and without such warnings being given.
A day of intense clashes, which saw a police officer struck in the leg by an arrow and protesters meet police tear gas with volleys of petrol bombs, intensified as night fell.
Clashes rolled across Kowloon, with the epicenter around the Hong Kong Polytechnic University (PolyU), where scores of defiant demonstrators set large fires to prevent police from conducting a threatened raid on the campus.
They hunkered down under umbrellas from occasional fire from water cannon and hurled molotov cocktails at an armored police vehicle, leaving it ablaze on a flyover near the campus.
Police declared the campus a “riot” scene — a rioting conviction carries up to 10 years in jail — and blocked exits as spokesman Louis Lau issued a stark warning in a Facebook live broadcast.
“I hereby warn rioters not to use petrol bombs, arrows, cars or any deadly weapons to attack police officers,” he said.
“If they continue such dangerous actions, we would have no choice but to use the minimum force necessary, including live rounds, to fire back.”
Police said they fired at a car late Sunday that had driven at a line of officers near the campus — but the vehicle reversed and escaped.
Protesters at the campus appeared resolute — a twist in tactics by a leaderless movement so far defined by its fluid, unpredictable nature.
“I feel scared. There’s no way out, all I can do is fight to the end,” said one protester joining the barricade in front of the university building.
“We need a base to keep our gear and have some rest at night before another fight in the morning,” another called Kason, 23, told AFP.
On Sunday, activists parried attempts by police to break through into the PolyU campus, firing rocks from a homemade catapult from the university roof, while an AFP reporter saw a team of masked archers — several carrying sports bows — patrolling the campus.
Violence has worsened in recent days, with two men killed in separate incidents linked to the protests this month.
Chinese President Xi Jinping this week issued his most strident comments on the crisis, saying it threatened the “one country, two systems” model under which Hong Kong has been ruled since the 1997 handover from Britain.
Demonstrators last week engineered a “Blossom Everywhere” campaign of blockades and vandalism, which forced the police to draft in prison officers as reinforcements, shut down large chunks of Hong Kong’s train network and close schools and shopping malls.
The movement, characterised by its fluidity and unpredictability, has started to coagulate in fixed locations, showing the protesters’ ability to switch tactics.
The protests started against a now-shelved bill to allow extradition to China but have billowed to encompass wider issues such as perceived police brutality and calls for universal suffrage in the former British colony.
The financial hub has been nudged into a recession by the unrelenting turmoil.
A poster circulating on social media called for the “dawn action” to continue on Monday.
“Get up early, directly target the regime, squeeze the economy to increase pressure,” it said.
The education bureau said schools will remain closed again on Monday.
Earlier on Sunday, dozens of government supporters gathered to clear barricades near the university campus — a sign of the divisions slicing through the city.
Many residents are wearied by the sapping protests. Others support the Chinese-backed city government.
Some applauded a Saturday clean-up by Chinese troops from a garrison of the People’s Liberation Army in Kowloon.
The garrison is usually confined to the barracks under Hong Kong’s mini-constitution, although it can be deployed at the request of the city’s government to help with public order breakdown or natural disasters.
Hong Kong’s government, which presides over a city that enjoys greater freedoms than the mainland, said it did not ask the PLA for help on Saturday.
The choreographed troop movement “has only compounded the impression that Beijing has simply ignored” Hong Kong’s unique political system, said analyst Dixon Sing.