Close your eyes and picture waves lapping at the first-floor facades of high-rise hotels. The golden sands along Waikiki have long been submerged by the surging Pacific Ocean, as has the nearby Kalakaua Avenue.

A few late-returning tourists in this future Honolulu plod through the low tide and past the partially submerged check-in desk of their hotel, before climbing up several flights of stairs to their electricity-less rooms.

They cannot fly home because, in this storm-tide future, commercial planes remain idle on the runway at the low-lying Honolulu International Airport, their landing gear deep in a dark pond of water and their lighting and navigation systems in need of repairs.

Call it Waikiki’s Venetian nightmare. (Italy has long struggled to slow the legendary city’s descent into the waters that surround it, to little avail.)

And there is more. Storm water systems along the coastline, unable to handle the influx of seawater, spew sewage around homes.

Reefs that once teemed with brilliant colored coral and bright speckled fish are largely barren, except for thick patches of algae. Ahi and ono, deep-water protein staples, are increasingly scarce.

Beyond the destruction to a way of life, the hit to the economy of Hawaii is enormous.

The Ghost of Christmas Future could tell you that such visions are not what will come to pass, they are the things that could come to pass, if we don’t change. In this case, that means, if humans don’t find a way to curtail global carbon emissions — at least if a recently released federal report proves correct.

The third National Climate Assessment aims to help federal, state and local officials to adapt to mounting environmental challenges likely to result from warming waters, higher average temperatures, more extreme weather, and rising sea levels.

“This is a wakeup call,” said Jo-Ann Leong, one of the lead authors of the study and a scientists at the Hawaii Institute of Marine Biology. “If we could get everyone to pay attention and start doing these long-term plans, that is what I would like to see from this report.”

The document reflects sophisticated new data that scientists now have on climate change, she explained.

Even if carbon emissions are slashed, the report indicates that the effects of climate change may be very dangerous this century. But on the current trajectory, without major reductions, the situation will be much worse.

Some Don’t Like It Hot

Throughout the United States, humans are already grappling with more frequent and severe heat waves, stronger storms and extreme droughts. Coastal ecosystems like Hawaii are particularly at risk, according to the report, which warns that some of the changes may be irreversible.

Nationally, the average temperature has risen by 1.5 degrees fahrenheit since 1895 — more than 80 percent of that increase has occurred in the last 30 years. This past decade is the hottest on record. A brutal 2011 drought in Texas caused $7.6 billion in agricultural losses. There have been others.

By the end of the century, even with major reductions in carbon dioxide emissions, the temperature is expected to rise an average of another 3 degrees to 5 degrees. If emissions aren’t curtailed, the temperature could rise by as much as 10 degrees.

Meanwhile, the rate of sea level rise has doubled in the last two decades. In the past century the sea rose by 8 inches; it’s expected to rise an average of between one to four feet by the start of the next century.

The effects of climate change are, of course, playing out differently throughout the country. Scientists have a hard time making accurate long-term predictions about the impacts that major weather changes will have on the environment. Complex climate systems include what scientists call feedback loops — factors that can both accelerate or slow warming trends, depending on what part of the world they are looking at.

“Sometimes you can interpret things as signaling there is a trend here and if you just extrapolate to the end of the century things look really dire,” said Jeffrey Polovina, an oceanographer at the National Oceanic and Atmospheric Administration who contributed to the report. “But we know that systems are a lot more complicated than just extrapolating a suggestion or a possible trend.”

“But that’s not to downplay the severity of it.”

The Struggling Silversword of Haleakala

Along the slopes of Halekala National Park, a plant with dozens of sword-like leaves and that is covered with silver hairs, juts out of the dry ground. The leaves are hardy enough to withstand the mountain’s gusting winds, frigid nighttime temperatures and dry daytime heat. From the plant’s cylindrical base, a stalk of hundreds of maroon flowers grows to human heights.

The only place that the plant, which is aptly named the silversword, exists on earth is in Haleakala. And scientists say it’s critical to the alpine ecosystem. But the plant’s numbers have declined dramatically in the past two decades.

The silversword is one of the native plants in Hawaii that is considered most vulnerable to the changing climate and its peripheral effects. High-elevation ecosystems on Maui and the Big Island are already showing clear signs of increased drought and higher temperatures.

Native birds are also at risk, particularly those that have evolved along high-elevation forests to escape disease and predators. Mosquitoes now migrate further upslope as temperatures warm, which threatens bird species with diseases such as avian malaria.

Invasive species have better resistance to such dangers, but Hawaii’s native plants are particularly at risk.

Some of the state’s freshwater resources are expected to become more dry, limiting the availability of drinking water and the ability of farmers to irrigate their fields.

As more drought-like conditions threaten the upper slopes, less rainfall descends into the islands’ watersheds. And warming temperatures and decreased rainfall throughout the islands are expected to lead to further declines in aquifers and surface catchments.

On the Big Island, rainfall and water flows have already diminished, threatening freshwater fish’s ability to make their way to the ocean to spawn before swimming back upstream.

Underwater

Honolulu International Airport sits just 7.7 feet above sea level, making it one of the top 10 most vulnerable airports in the country to flooding.

The risk to such crucial infrastructure from sea-level rise was highlighted in 2012 by Hurricane Sandy, which left runways at Laguardia Airport in New York City under several feet of water.

The risks aren’t just to tourism and travel. If Hawaii’s airports and harbors are damaged or destroyed it could lead to dangerous disruptions of critical imports “because Pacific Islands are almost entirely dependent upon imported food, fuel, and material.” As a result, the report adds, “the vulnerability of ports and airports to extreme events, sea level rise, and increasing wave heights is of great concern.”

And then there are the more obvious dangers to coastal roads, waterfront homes and businesses — especially hotels — from flooding and erosion. Hawaii’s tourism industry could face heavy losses. The report estimates that the state would lose $2 billion annually in visitor spending just from the loss of Waikiki beach.

About the Author