By the time today’s ten-year-olds are in their 50s, Bermuda will be experiencing rising sea levels, bigger and more frequent hurricanes and warmer waters if climate change trends continue.

Climate Change and Bermuda Part 1: The Science and Physical Hazards, released this week, considered years of research and observations globally and locally to gauge how climate change will affect the island.

Mark Guishard, the primary author of the report, said climate change will have a number of effects of varying complexity.

“Weather events have always been a fact of life, but the changes in the behaviour of the most impactful conditions are increasingly linked to the background changes in the climate,” he said in the report.

“If we think of climate as the backdrop for weather, then it is clear that as the background conditions change, the extreme events linked to those conditions should also change.

“Near Bermuda, for example, the changes in hurricane activity over the last two decades have been remarkable, and documented.

“One does not need to be a climate scientist, oceanographer or meteorologist to note that, with a detected trend in warmer surface ocean waters, the likelihood of stronger hurricanes becomes greater over time. This is what we’re seeing near Bermuda.”

These are some of the most likely changes:

Hurricanes

Models have suggested that a growing number of tropical cyclones will travel through the western North Atlantic, with one more major storm per decade.

The report said: “Warmer surface ocean waters and decreases in wind shear mean the conditions will continue to become more and more conducive to hurricane formation and intensification, with higher wind speed categories likely being attained through the decades to come.

“Tropical cyclones’ lifetime maximum intensities have moved closer to our latitude by 0.5 degrees latitude per decade on average. Less certainty exists about whether this represents an ongoing future trend.”

Dr Guishard said that a few computer models do suggest an increase in the number of storms approaching the island in future scenarios.

He said: “Some conditions that support hurricane development — warm water and low atmospheric wind shear — are projected to become more conducive to more storm activity.

“This does not mean that more storm activity is definite, but we have seen increases in Bermuda hurricanes and their intensity in the last 20 years, which supports this finding.”

Sea levels

The report warned that sea levels around Bermuda have risen and are expected to continue to rise in the coming century.

The report said: “Mean sea level in Bermuda has been rising, as measured by monthly average sea levels at a tide gauge in St George’s from 1932 to 2018. This is the only extensive tide gauge record for Bermuda.

“Mean sea level in Bermuda is projected to continue to rise at an accelerating pace through the end of this century.”

The issue is worsened by incidents of storm surge along with spring tides and warm eddies, which cause temporary increases of sea levels.

The report noted: “October 2017 saw the development of a large-scale warm eddy moving through the Bermuda area, raising mean sea levels above the normal tide.

“Water levels over one foot above the predicted tides were experienced for 29 days during October and November 2017. Tide gauge measurements reaching just over 1.5ft above the predicted tide level were observed during this period.

“This event was coincident with a spring tide and the combined effect was localised seawater flooding in low-lying coastal areas, such as King’s Square and areas of Ordnance Island in St George’s.”

Air temperature

The report said that average monthly air temperatures have risen by about 1C over the past 70 years, more significantly in the summer, as has humidity.

"Due to an inconsistent surface temperature record in Bermuda, and the fact that the ocean has a moderating effect, the surface air temperature trends are less obvious than one might imagine under global warming,“ Dr Guishard wrote.

“Moisture in the air, as measured by specific humidity, also shows an upward trend.”

While no specific projections have been established for Bermuda, the report said the consensus is that temperatures in the North Atlantic will continue to rise.

Water temperature

Surface ocean temperatures have risen by more than 1C in the 2010s and are expected to rise further under current projections.

“Recent publications show very clearly the accelerating trend of upper ocean temperature near Bermuda,” Dr Guishard wrote. “There are some periods of cooling and warming that offset one another, resulting in an overall warming trend of approximately 0.85C of the surface waters from the 1980s through 2019.

“This trend has been dominated by a 1.18C increase in surface temperature through the 2010s.”

In addition to fuelling hurricanes, warmer waters could threaten coral reefs around the island, although Dr Guishard said there was some “room for optimism” as studies suggested that the deeper and cooler waters around the Bermuda platform may provide a “refuge” for corals.

Other phenomena

Projections for how climate change will impact other weather phenomena such as rainfall, winds and ocean swells were uncertain in the report.

While the report noted that there had been an increase in average wind speeds over the past 40 years, the change was not statistically significant.

“There is a high degree of uncertainty and complexity about the projections of average surface winds in the North Atlantic,” Dr Guishard wrote.

“This uncertainty may stem from disagreement between multiple climate-resolving models, themselves with their own varying sources of inputs and resolutions.”

Average rainfall and days with recorded rainfall have also increased in Bermuda, but the report had low confidence that the trend would continue.

The report said that warmer weather would make heavy downpours of rain more likely and noted a trend of increased days in which thunder is reported, as tracked by LF Wade International Airport.

“This trend can be treated with a reasonable confidence — thunderstorms have significant impacts to aviation operations, so their observations are critical to record,” the report said.

“This trend in thunderstorm occurrence aligns with our physical understanding that a warmer environment should support heavier short-duration rainfall events.

“As the surface ocean and air warms, the energy available for thunderstorm development and heavier rainfall rates increases.”