One thing I've noticed over the years as I've written about climate change is that the actual predicted effects of a warmer world often aren't well known. People understand that the planet is getting hotter, a change that is both easy to understand and directly familiar to almost everyone.
But the effects of the increased heat are much broader than simply higher temperatures. In an effort to delineate what scientists expect to see as the world warms, I spoke with Alex Halliday, director of the Earth Institute at Columbia University.
Here are the negative repercussions scientists expect to see in a warmer world:
--Increased health risks
--Shifts in growing areas for crops
--Broader spread of some diseases
--Big precipitation events with even more rain and snow
--Rising sea levels
--Warmer ocean water
--Shifts in sea habitats
--Thawing permafrost, releasing more greenhouse gases
"I think we need to be very worried about these things that we're not very certain about at the moment," Halliday said. As we learn more, he added, we learn more about the "potential that actually it could be far worse than we've actually considered before. And that has important implications for everything: for what will happen to the economics of the world, what will happen to populations, what will happen to food security, etc."
That, in essence, is the most precise summary of the effects of climate change. All of the factors above, yes, but more broadly that the effects will be bad, they will be substantial - and they may very well be worse than we expect.
A stretch of desolate Alaskan shoreline is eroding more than twice as fast as it used to, fueled by Earth's warming temperatures.
A satellite-based study of the retreating permafrost coastline at Drew Point, in Alaska's North Slope region, shows that from 1955 to 1979, the rate of loss was about 23 feet per year. From 2007 through 2016, it was about 56 feet per year.
In the most extreme year, 2016, the coast retreated by an average of 72 feet. Most strikingly, all of this is occurring during a relatively narrow window of roughly 90 days, or the open-water season, when the coast is beset by waves. The length of the open-water season has also doubled in recent decades.
Calculating the consequences over a 5½-mile stretch of coastline, lead study author Benjamin Jones said that means about 30 football fields are being lost annually and that about 300 were lost in total between 2007 and 2016.
Few other stretches of Arctic coastline are being watched in the same way. Jones estimates that only 1 to 2 percent of Arctic coastlines have been surveyed to study how much they are eroding, and few to the extent that Drew Point has been.
Yet vulnerable permafrost - the reason for what's happening at Drew Point - is present across the Arctic.
Research shows that temperatures not much warmer than the planet is experiencing now were sufficient to melt a major part of the East Antarctic ice sheet in Earth's past, including during one era about 125,000 years ago when sea levels were as much as 20 to 30 feet higher than they are now.
"It doesn't need to be a very big warming. As long as it stays 2 degrees warmer for a sufficient time, this is the end game," said David Wilson, a geologist at Imperial College London and one of the authors of the new research, which was published in Nature.
The research concerns a little-studied region called the Wilkes Subglacial Basin, which is roughly the size of California and Texas combined, and contains more than 10 feet of potential sea-level rise. Fronted by three enormous glaciers named Cook, Mertz and Ninnis, the Wilkes is known to be vulnerable to fast retreat because the ice there is not standing on land and instead is rising up from a deep depression in the ocean floor.
Moreover, that depression grows deeper as you move from the current icy coastline of the Wilkes farther inland toward the South Pole, a downhill slope that could facilitate rapid ice loss.
What the new science adds is that during past warm periods in Earth's history, some or all of the ice in the Wilkes Subglacial Basin seems to have gone away. That's an inference researchers made by studying the record of sediments in the seafloor just off the coast of the current ice front.
Montana has warmed 2.7 degrees Fahrenheit since 1950, considerably more than the United States as a whole. That added heat is contributing to raging forest fires and bark beetle outbreaks, a combination that has devastated the state's forests. Montana's forests had historically been large carbon sinks, pulling carbon dioxide from the air. In recent years, disease and other disturbances have caused forests to die, emitting carbon dioxide instead as they rot.
Montana is one of six states in the West where trees have been emitting carbon in the past decade or so, according to an analysis by David Cleaves, former climate change adviser to the chief of the U.S. Forest Service. In the 1990s, Montana's forests were pulling some 20 million tons of carbon dioxide out of the air each year. But by the 2010s, they had reversed course and were putting a few million tons per year back again. The net result is that Montana is sending an extra 20 million tons of carbon dioxide into the atmosphere each year. One reason is that an epidemic of bark beetles has been decimating forests. While beetle outbreaks have happened before, scientists think rising temperatures have made them worse. In western Montana, there have been fewer of the frigid days - around minus-40 degrees Fahrenheit - that would kill off insect larvae.
Rising temperatures also are shrinking the mountain snowpack, weakening the forests. The snowpack, which has been declining since the 1930s, has been melting more quickly in the past four decades. Trees stressed by drought struggle to resist beetle attacks, and the drier ground makes forests more susceptible to fires.
Fish don't follow international boundaries or understand economic trade agreements. Different species live in regions all over the globe. If that wasn't complicated enough, they also migrate as they age.
And in response to climate change, vital fishery stocks such as salmon and mackerel are migrating without paperwork. According to a study in Science magazine, coastal countries need to collaborate even more on international fishing regulations to prevent misuse of resources. Food, environmental and economic securities are at stake, it warns.
"This isn't some imaginary future threat," said Malin Pinsky, an assistant professor at Rutgers University who helped lead researchers at six universities in a half-dozen countries as part of the Nippon Foundation-University of British Columbia Nereus Program.
Fisheries are critical to food security, jobs and economic stability. As far back as the 1600s, Great Britain and Iceland faced off over rights to the Atlantic cod; they negotiated their claims to the meaty half of fish and chips over the next several centuries. And after World War II, fishery disputes prompted militarized action in democratic countries. Navies were deployed. Protests were staged.
Today, according to Angee Doerr, a research scientist who specializes in fisheries at the Stanford Center for Ocean Solutions, developing countries in tropical areas are particularly at risk. "Equatorial countries are highly dependent on fish as a protein source," she said. As water temperatures increase, "fish are moving to stay within their comfortable range." This means they may be leaving their traditional waters altogether.
The study, which reflects an unusual combination of expertise from law, policy, economics, oceanography and ecology, suggests multi-species movement across dozens of countries' waters. Challenges will only increase, according to the researchers. One reason is that policymakers often move more slowly than the fish. The study identifies gaps in international regulations for global fisheries, with the researchers expressing concern that limited attention is being paid to the cascading effect on the food chain.
Six years after it was stricken by a wasting disease off the northern California coast, the sunflower sea star - one of the most colorful starfish in the ocean - has all but vanished, and the domino effect threatens to unravel an entire marine ecosystem.
The cause of the sunflower sea star's demise is a mystery, but it coincided with a warming event in the Pacific Ocean, possibly tied to the climate, that lasted for two years, ending in 2015. It heated vast stretches of water in patches and probably exacerbated a wasting disease that had earlier struck the creature.
"I've never seen a decline of this magnitude of a species so important," said Drew Harvell, the lead author of a study published in the journal Science Advances that documented the sunflower sea star's retreat into possible extinction off California and Oregon.
Their disappearance could not have come at a worse time. Sunflower sea stars started dying off around the time that the population of their favorite prey, purple sea urchins, exploded. The voracious urchins feed on vegetation that is key to the ecosystem in that area of the Pacific - bull kelp forests that support young fish, snails, crabs, birds and a range of other animals.
Over the last few years, California's fifth largest fishery, red sea urchins harvested for sushi, has cratered. A once teeming population of decorative snails called abalone, which drew tourists and professional divers, has also crashed. Both animals rely on kelp to survive, and their combined loss has cost the state tens of millions of dollars, according to economists.
Coral reefs are bleaching four to five times as frequently as they did around 1980, according to a study that suggests climate change may be happening too rapidly for some reefs to withstand. Coral bleaching occurs when corals lose their color after the symbiotic algae that live in coral cells and provide them with nutrients are expelled due to heat stress. The longer this state of stress lasts, the longer the estranged algae stay away and the less likely that corals will recover. So scientists tend to distinguish between moderate bleaching, which can be managed, and severe bleaching, which can kill corals and also leave surviving corals more vulnerable to disease and other threats.
"With a fourfold increase over the last 35 years, if you take that forward, it's unfortunately in complete agreement with what the climate models have been saying," said Mark Eakin, one of the study's authors and head of the National Oceanic and Atmospheric Administration's Coral Reef Watch. "[We're] looking at 90 percent of reefs seeing the heat stress that causes severe bleaching on an annual basis by mid-century."
The study comes after the unprecedented 2014-2017 global bleaching event that produced devastating consequences to the Great Barrier Reef off Australia and many other global reefs.
The new survey of 100 major coral reefs, from 1980 through 2016, found only a handful that had not suffered severe bleachings during that period. More striking, it found that the rate of severe bleaching is increasing over time. The average reef in the group bleached severely once every 25 or 30 years at the beginning of the 1980s, but by 2016 the recurrence time for severe bleaching was just 5.9 years. The study said that as ocean waters have grown steadily warmer, global bleaching events are now triggered not only in warm-water El Niño years, but potentially in any year, including cooler La Niña years.
Insects around the world are in a crisis, according to a small but growing number of long-term studies showing dramatic declines in invertebrate populations. One report suggests that the problem is more widespread than scientists realized. Huge numbers of bugs have been lost in a pristine national forest in Puerto Rico, a study published in October found. The forest's insect-eating animals went missing, too, the study authors said, though other scientists who recently reviewed the report disputed this.
In 2014, a team of biologists estimated that, in the past 35 years, the abundance of invertebrates such as beetles and bees had decreased by 45 percent. A 2017 study showed a 76 percent decrease in flying insects in the past few decades in German nature preserves.
The October report, published in the Proceedings of the National Academy of Sciences, suggests that this loss of insect abundance extends to the Americas. The study's authors implicate climate change in the loss of tropical invertebrates - moths, butterflies, grasshoppers and spiders. "Everything is dropping," said study author Bradford Lister, a biologist at Rensselaer Polytechnic Institute in New York.
Climate change is beginning to reorder the global wine industry, altering the patterns of how and where grapes are produced and testing whether the world's iconic regions can find ways to adapt. Many factors influence wine and its taste. Yet because of rising temperatures, some of Europe's biggest producers are buying up land in the Pyrenees foothills, in northern China and in southern England - where the climate now resembles the French Champagne region of the 1970s.
"So what happens to the existing regions that are famous?" said Elizabeth Wolkovich, a researcher at the University of British Columbia. "If they don't make changes or they don't make them fast enough, I think there will be a reshuffling of where the great wines are made."
If the planet's climate warms in coming decades as much as most scientists predict, there will be more pressing concerns than whether "you'll have a good Bordeaux from Bordeaux," Wolkovich said. But for growers - and for wine drinkers - the changes are nonetheless imperiling.
For instance, in northeast Italy, a region celebrated for the prosecco and pinot grigio it ships around the world, particularly sensitive white wine grapes have become a telltale of even gradual temperature increases - a climate slipping from ideal to nearly ideal. Vintners and farmers are noticing more disease, an accelerated ripening process and, most viscerally, a surge in the number of grapes that are singed by the intensifying summer heat.
Katey Walter Anthony has studied some 300 lakes across the tundras of the Arctic. But sitting on the mucky shore of her latest discovery, the Arctic expert said she'd never seen a lake like this one.
Set against the austere peaks of the Western Brooks Range, the lake, about 20 football fields in size, looked as if it were boiling. Its waters hissed, bubbled and popped as a powerful greenhouse gas escaped from the lake bed. Some bubbles grew as big as grapefruits, visibly lifting the water's surface several inches and carrying up bits of mud from below.
This was methane.
As the permafrost thaws across the fast-warming Arctic, it releases carbon dioxide, the top planet-warming greenhouse gas, from the soil into the air. Sometimes, that thaw spurs the growth of lakes in the soft, sunken ground, and these deep-thawing bodies of water tend to unleash the harder-hitting methane gas.
But not this much of it. This lake, which Walter Anthony dubbed Esieh Lake, looked different. And the volume of gas wafting from it could deliver the climate system another blow if lakes like this turn out to be widespread.
A new scientific survey has found that the glaciers of the Arctic are the world's biggest contributors to rising seas, shedding ice at an accelerating rate that now adds well over a millimeter to the level of the ocean every year.
That is considerably more ice melt than Antarctica is contributing, even though the Antarctic contains far more ice. Driven by glacier clusters in Alaska, Canada and Russia and the vast ice sheet of Greenland, the fast-warming Arctic is outstripping the entire ice continent to the south - for now.
However, the biggest problem is that both ice regions appear to be accelerating their losses simultaneously - suggesting that we could be in for an even faster rate of sea-level rise in future decades. Seas are rising by about three millimeters each year, according to NASA. That's mainly driven by the Arctic contribution, the Antarctic and a third major factor - that ocean water naturally expands as it warms.
Antarctic glaciers have been melting at an accelerating pace over the past four decades thanks to an influx of warm ocean water - a startling new finding that researchers say could mean sea levels are poised to rise more quickly than predicted in coming decades.
The Antarctic lost 40 billion tons of melting ice to the ocean each year from 1979 to 1989. That figure rose to 252 billion tons per year beginning in 2009, according to a study in the Proceedings of the National Academy of Sciences. That means the region is losing six times as much ice as it was four decades ago, an unprecedented pace in the era of modern measurements. (It takes about 360 billion tons of ice to produce one millimeter of global sea-level rise.)
"I don't want to be alarmist," said Eric Rignot, an Earth-systems scientist for the University of California at Irvine and NASA who led the work. But he said the weaknesses that researchers have detected in East Antarctica - home to the largest ice sheet on the planet - deserve deeper study.
"The places undergoing changes in Antarctica are not limited to just a couple places," Rignot said. "They seem to be more extensive than what we thought. That, to me, seems to be reason for concern."
In little more than a day, 2018's Hurricane Florence exploded in strength, jumping from a Category 1 to a Category 4 behemoth with 140 mph winds. This process - hurricanes intensifying fast - is both extremely dangerous and poorly understood. But a new study shows that as the climate continues to warm, storms will do it faster and more often, and in some extreme cases, grow so powerful that they might arguably be labeled "Category 6."
The study draws on enhanced computer power to achieve something that until now has been very difficult - capturing a reasonable representation of hurricanes in a global climate change model that simulates both the atmosphere and the oceans.
Dividing the globe up into squares roughly 16 miles by 16 miles in size, researchers were able to simulate Category 4 and 5 storms, and where they currently occur around the globe - not perfectly, but in a way that was broadly representative. But when the researchers moved from simulating the hurricanes of the late 20th century to those of the future under a middle-of-the-road climate change scenario, they found big changes. For the period between 2016 and 2035, there were more hurricanes in general and 11 percent more hurricanes of the Category 3, 4 and 5 classes; by the end of the century, there were 20 percent more of the worst storms.
The research also found that storms of super-extreme intensity, with maximum sustained winds above 190 mph, became more common. While it only found nine of these storms in a simulation of the late 20th century climate, it found 32 for the period from 2016 to 2035 and 72 for the period from 2081 to 2100.
There is no "Category 6" on the Saffir-Simpson hurricane scale, but the Category 5 grouping, which is open-ended, begins at 157 mph, far lower than the intensities of such storms. And the lower categories require a smaller increase in wind speeds before reaching the next category. For example, the weakest Category 5 storm would be 24 mph stronger than the weakest Category 4.
More explosive and rapidly spreading fires leave communities with little notice or chance to evacuate. Such fire behavior stood out in the deadly 2018 Carr and Camp fires in California.
In the West, human-caused climate change is a significant factor in worsening wildfires, scientists at the University of Idaho and Columbia University in New York have found. The hotter and drier conditions parch soil and wither plants and brush, increasing fuel for more forest fires.
The Carr Fire, which killed eight, generated an enormous tornado-like vortex that stunned fire researchers. The "firenado" was "one of two scientifically documented cases of that happening," said Neil Lareau, a wildfire expert at the University of Nevada at Reno. "Not only is it extreme, we're talking about events that have only been recorded a handful of times."
The Camp Fire - the worst fire in California history - destroyed an entire town, Paradise, and killed at least 85 people. It cost an estimated $16.5 billion in damage, according to insurance company Munich Re, making it even more destructive than the year's worst hurricanes.
About 40 historic Mediterranean sites, representing cultures extending from the Phoenicians through the Venetians, are already at risk due to rising seas, research finds. Among them are:
--The old city of Dubrovnik, a main setting for HBO's "Game of Thrones"
--The original site of Carthage
--Historic regions of Istanbul
--Early Christian monuments of Ravenna, Italy
--The archaeological area and patriarchal basilica of Aquileia in Italy
The study used the database of UNESCO World Heritage sites and projections of future sea level to arrive at its conclusions. It found that out of 49 total such sites along the coasts of the Mediterranean, 37 are already vulnerable to a 100-year storm surge event.
"What surprised me the most is that actually even under current conditions, there are so many World Heritage sites that are at risk," said Lena Reimann, a researcher at Kiel University in Germany and a lead author of the study.
In a world of rising sea levels, those risks will grow only more severe, threatening the destruction of irreplaceable cultural landmarks. "We cannot put a value on what we will lose" if action isn't taken to protect such sites, Reimann said. "It's our heritage - things that are signs of our civilization. It cannot really be put in numbers. It's more an ethical question, a moral question. We will not be able to replace them once they are lost."
For Joseph Manning - a professor of ancient Greek history at Yale who praised the new research - rising seas could be the next destroyer of human culture to come along after massive losses in the past decade alone tied to violence and civil war in Syria, Iraq and Egypt, among other countries. "In terms of cultural heritage in the last decade, it's shocking. It's alarming and depressing," he said.
More than a thousand low-lying tropical islands risk becoming "uninhabitable" by the middle of the century - or possibly sooner - because of rising sea levels, upending the populations of some island nations and endangering key U.S. military assets, according to new research.
The threats to the islands are twofold. In the long term, the rising seas could inundate the islands entirely. More immediately, as seas rise, the islands will more frequently deal with large waves that crash farther onto the shore, contaminating their drinkable water supplies with ocean saltwater. The islands face climate-change-driven threats to their water supplies "in the very near future," according to the study, published in the journal Science Advances.
The study focused on a part of the Marshall Islands in the equatorial Pacific Ocean. Hilda Heine, president of the Marshall Islands, said in an interview that the journal article "brings home the seriousness" of the predicament facing her island nation. "It's a scary scenario for us," she said.
Preliminary research has shown that Hurricane Florence, which struck North Carolina in September 2018, was probably somewhat larger and dumped more rain than it would have if the same storm had arrived in a world without humans' greenhouse gas emissions in the atmosphere. While each hurricane springs from a complex string of atmospheric events, scientists say all are occurring in an environment that's warmer and wetter. Florence traveled across offshore waters that were several degrees warmer than usual (warm seas are the central energy source for hurricanes).
In addition, rising seas, caused by the melting of the planet's ice and the swelling of the ocean as it warms, make any coastal flooding event worse, even on sunny days. One sea level expert, Benjamin Strauss with Climate Central, said seas off the East Coast have risen by nine inches since 1900. "We can say, with a high probability, that at least five or six of those inches are human-caused climate change," he said.
Over time, as seas continue to rise (and rise at a faster rate), more and more water driven inland by storms will be attributable to climate change.
Earth's largest hot desert, the Sahara, is getting bigger, according to a study. It is advancing south into more-tropical terrain, turning green vegetation dry and soil once used for farming into barren ground in areas that can least afford to lose it.
Also frightening is that this is happening during the African summer, when there is usually more rain. But the precipitation has dried up, allowing the desert's boundaries to expand. The authors say their study suggests that climate changes could be causing other hot deserts to expand as well - with potentially harsh economic and human consequences.
"The desert advance over a long period might capture many countries unawares," said Sumant Nigam, a professor of atmospheric and oceanic science at the University of Maryland and senior author of the study. "It's sort of creeping up on you."
In a new report, global energy experts have found that not only are planet-warming carbon-dioxide emissions still increasing, but the world's growing thirst for energy has led to higher emissions from coal-fired power plants than ever before.
Energy demand around the world grew by 2.3 percent over the past year, marking the most rapid increase in a decade, according to the report from the International Energy Agency. To meet that demand, largely fueled by a booming economy, countries turned to an array of sources, including renewables.
But nothing filled the void quite like fossil fuels, which satisfied nearly 70 percent of the skyrocketing electricity demand, according to the agency, which analyzes energy trends on behalf of 30 member countries, including the United States.
In particular, a fleet of relatively young coal plants located in Asia, with decades to go on their lifetimes, led the way toward a record for emissions from coal-fired power plants - exceeding 10 billion tons of carbon dioxide "for the first time," the agency said. In Asia, "average plants are only 12 years old, decades younger than their average economic lifetime of around 40 years," the agency found.
Greenhouse-gas emissions from the use of energy - by far their largest source - reached a record high of 33.1 billion tons in 2018. Emissions showed 1.7 percent growth, well above the average since 2010.
The report underscores an unnerving truth about the world's collective efforts to combat climate change: Even as renewable energy rapidly expands, many countries - including the United States and China - are nevertheless still using fossil fuels to satisfy ever-growing energy demand.