As the heat continued to build in the Caribbean this northern summer fishermen and ocean old-timers knew there was a dark side to the hot days and calm conditions where turquoise waters sparkle to the horizon.
“We are worried about what this means for hurricanes,” said Puerto Morelos guide Carlos as he loaded day trippers to snorkel on the northern tip of the world’s second-largest barrier reef.
As tourists frolicked in Mexico, the first hints of catastrophe were coming to life half a world away in Ethiopia.
Wisps of wind that started in the cradle of civilisation were nourished by warmer waters and favourable conditions in the Atlantic Ocean to become meteorological monsters.
Cyclone Harvey made a chaotic path as a tropical depression, going past Belize and into the Gulf of Mexico where it sucked up the hot waters to become a rain-heavy hurricane that swamped Texas.
After making landfall near Port Aransas on the Gulf Coast on August 26, Harvey was held in place for days by two high-pressure systems to dump record rains on Houston.
Since Harvey, the Atlantic Ocean has been a launch pad for super-strength hurricanes that have barrelled through the Caribbean islands like a bowling alley of carnage.
The end of the range is Florida where millions of people have been evacuated in anticipation of Irma making landfall late last night (AEST).
Around-the-clock media coverage followed Hurricane Irma as it left a trail of catastrophic damage through an area best known as a tropical playground for the rich and famous.
Tabloid newspapers have been able to measure the hurricane season through the eyes of celebrity property.
Virgin boss Richard Branson has embellished his reputation for having an adventurous spirit by hunkering down with staff in the concrete wine cellar of his luxury resort on Necker Island in the British Virgin Islands.
After a direct hit from Irma last week, Branson emerged from the cellar to declare the island devastated.
“I have never seen anything like this hurricane,” he said. “We are still assessing the damage, but whole houses and trees have disappeared.”
Branson’s son Sam said boats throughout the Virgin Islands had been “piled up like matchsticks in the harbour”.
“Huge cargo ships were thrown out of the water and into rocks. Resorts have been decimated,” Branson Jr said. “The houses have their roofs blown off; even some churches where people sheltered have lost roofs,’’ he said.
US President Donald Trump’s two-hectare Le Chateau des Palmiers estate on Saint Martin was hit, with 95 per cent of the island’s buildings and infrastructure destroyed.
Mick Jagger and Oprah Winfrey reportedly had dodged the worst of Irma’s fury. But Robert De Niro vowed to push ahead with development of a $250 million luxury resort he is building with James Packer on the eastern Caribbean island of Barbuda.
Barbuda was smashed by Irma and still faces a direct hit by Hurricane Jose, which is following immediately behind.
“Barbuda now is literally rubble,” Antigua and Barbuda Prime Minister Gaston Browne said in the wake of Irma.
Celebrities aside, the stark reality is that hundreds of thousands of people have been left homeless across the Caribbean.
Many will be without electricity for months. Recovery costs will probably run to more than $US100 billion ($125bn) and reconstruction efforts will continue for years.
The final bill will depend greatly on how badly Florida is hit, the path the hurricanes follow and how many more hurricanes develop in a furious year that has broken a more than decade-long drought for the US.
September 11 marks the peak of the northern hemisphere cyclone season that will run to the end of October.
But even before the 2017 season has ended and the damage bill has been tallied, debate has started about whether human activity has made the fierce hurricane conditions even more extreme.
Some commentators, including The Sydney Morning Herald, were quick to claim Harvey was effectively “karma” for Texas because of its history of oil and gas production.
Oscar-winning actor Jennifer Lawrence said Harvey and Irma were signs of “Mother Nature’s rage and wrath” at the US for electing Trump to the presidency and not believing in man-made climate change.
The Tim Flannery-backed Climate Council declared: “Fingerprints of climate change all over Tropical Storm Harvey.”
Council chief executive Amanda McKenzie issued a statement to claim climate change was driving and influencing extreme weather events around the globe.
“Climate change is now supercharging extreme weather events including storms, bushfires, heavy rainfall and floods,” she said.
“This is occurring in a more energetic climate system, that’s warmer and loaded up with more moisture than ever before.”
McKenzie said Harvey was a “window into our future”.
One problem with the Climate Council analysis is that Irma developed into a major hurricane over relatively cool waters in the Atlantic. Surface temperatures where the hurricane formed were 26.5C, about two degrees below what is considered necessary to build a major hurricane, climate scientist Judith Curry said.
“So why did Irma develop into a major hurricane?” Curry asked. “We can’t blame 26.5C temperatures in the mid-Atlantic on global warming.”
Other weather factors may explain the development. In particular, a weak wind shear and favourable circulation field allowed the circular formation to generate quickly.Nonetheless, McKenzie said the answer was a rapid transition “to clean, affordable and reliable renewable energy and storage technologies”.
Serious weather authorities say it is too early to properly understand the impact of human activity on hurricanes.
The National Oceanic and Atmospheric Administration has published a detailed evaluation of the impact of climate change on hurricane strength and prevalence. NOAA’s Geophysical Fluid Dynamics Laboratory said it was premature to conclude that human activities — and particularly greenhouse gas emissions that cause global warming — have already had a detectable impact on Atlantic hurricane or global tropical cyclone activity.
NOAA said records of past Atlantic tropical storm or hurricane numbers from 1878 to the present show a pronounced upward trend, which is also correlated with rising sea surface temperatures.
“However, the density of reporting ship traffic over the Atlantic was relatively sparse during the early decades of this record, such that if storms from the modern era (post 1965) had hypothetically occurred during those earlier decades, a substantial number would likely not have been directly observed by the ship-based ‘observing network of opportunity’ ”, NOAA said.
“We find that, after adjusting for such an estimated number of missing storms, there is a small nominally positive upward trend in tropical storm occurrence from 1878-2006,” NOAA said.
“But statistical tests reveal that this trend is so small, relative to the variability in the series, that it is not significantly distinguishable from zero,” it said.
It found the rising trend in Atlantic tropical storm counts was almost entirely because of increases in storms of less than two days, which were particularly likely to have been overlooked in the earlier part of the record.
NOAA said the evidence for an upward trend was even weaker for hurricanes that made landfall in the US, which showed a slight negative trend beginning from 1900 or from the late 1800s.
“While major hurricanes show more evidence of a rising trend from the late 1800s, the major hurricane data are considered” unreliable, NOAA said.
“In short, the historical Atlantic hurricane record does not provide compelling evidence for a substantial greenhouse warming-induced long-term increase.”
NOAA said human activities might have already caused changes that were not yet detectable because of the small magnitude of the changes or observational limitations, or are not yet confidently modelled. But it said any impacts were more likely to be felt in decades to come.
NOAA said there were better than even odds that anthropogenic warming over the next century would lead to an increase in the occurrence of very intense tropical cyclones in some basins.
This increase in intense storm occurrence was projected despite a likely decrease (or little change) in the global numbers of all tropical cyclones, it said.
NOAA said anthropogenic warming by the end of the 21st century would probably cause tropical cyclones to have substantially higher rainfall rates than present-day ones, with a model-projected increase of about 10-15 per cent for rainfall rates averaged within about 100km of the storm centre.
“In summary, neither our model projections for the 21st century nor our analyses of trends in Atlantic hurricane and tropical storm counts over the past 120-plus years support the notion that greenhouse gas-induced warming leads to large increases in either tropical storm or overall hurricane numbers in the Atlantic,” NOAA said.
“One modelling study projects a large increase in Atlantic category 4-5 hurricanes over the 21st century, but we estimate that this increase may not be detectable until the latter half of the century,” it said.
“Therefore, we conclude that despite statistical correlations between SST (sea surface temperatures) and Atlantic hurricane activity in recent decades, it is premature to conclude that human activity — and particularly greenhouse warming — has already caused a detectable change in Atlantic hurricane activity.”
NOAA did say it was likely that climate warming would cause hurricanes in the coming century to be more intense globally and to have higher rainfall rates.
“In our view, there are better than even odds that the numbers of very intense (category 4 and 5) hurricanes will increase by a substantial fraction in some basins, while it is likely that the annual number of tropical storms globally will either decrease or remain essentially unchanged.”
It said the relatively conservative confidence levels attached to hurricane projections, and the lack of a claim of detectable anthropogenic influence at this time contrasted with the situation for other climate metrics, such as global mean temperature.
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