The landscapes and climate in many parts of the world could be nearly unrecognizable by the end of the century if greenhouse gas emissions continue at their current pace, research suggests.
In the mountains and high latitudes, snow and ice are vanishing. In drier areas, large swaths of forests are dying. Along the coast, the rising ocean and stronger storms are taking bigger bites of land while the warming waters change the ecosystems under the waves.
Earth's physical features and its ecosystems are woven into a complex and dynamic system, and scientists are studying its many strands to paint a picture of how the world may look by 2100, and how that will affect people, landscapes and resources.
These five science teams are racing global warming as the landscapes they study change before their eyes.
Changing Glaciers, Future Lakes
As glaciers melt in mountain regions around the world, scientists are tracking the formation of hundreds of new lakes that will change the habitat for plants and animals, increase flood risks, and reduce the water supply relied on for irrigation and energy production downstream.
A 2017 outburst flood from a glacial lake in Austria's Stubai Valley showed one of the dangers ahead, said Kay Helfricht, a researcher with the Austria-based Institute for Interdisciplinary Mountain Research. The flood, triggered by a heavy rainstorm, scoured out a new outflow channel from the lake and damaged homes in the valley below.
In the Himalaya, mile-long lakes have formed in just the last 30 years as water from melting glaciers pools, sometimes behind unstable walls of glacier-tilled rocks and mud. There, as in the Andes, scientists are concerned about big floods wiping out towns if those natural dams fail.
The most detailed mapping of emerging lakes has been done in the Alps, where Helfricht and other researchers spent three years scrambling across jumbled rock fields to measure flows in icy streams and ponds and assess flows in the deep channels under the ice and in the surrounding rocks.
The rapid meltdown of the glaciers is threatening to reduce the downstream flow relied on by farms and communities, and it is approaching a tipping point when it comes to hydropower, Helfricht said.
In a soon-to-be-published study, he documents how Austrian glaciers lost 22 percent of their total volume in a 10-year span, between 2006 and 2016. As those glaciers get smaller, less water will feed into mountain streams, and that will start to affect hydropower electricity production.
Within the next one to two decades, the water available for hydropower will decline, and "some model simulations show decreasing runoff from glacier melt starting now," Helfricht said.
The Alpine region is home to some 14 million people, and millions more in big cities hundreds of miles away rely partly on water supplies from the mountains. Understanding how global warming will affect the water cycle helps communities plan more effective flood protection and boost the resilience of water supplies, ecosystems, agriculture and energy supplies.
The research in the Alps can also be used in climate models to help better assess the risk from new mountain lakes in less developed regions that have fewer resources for the intensive monitoring needed to track the threats.
One of the reasons glaciers are melting faster is because the warming climate fosters growth of dark-colored algae and microbial colonies on the surface of the ice. This biological darkening has been identified as an important driver of melting on the Greenland Ice Sheet, but it hasn't been studied as much on mountain glaciers, where melting also contributes to sea level rise.
Last year, University of Innsbruck ecologist Birgit Sattler started the Black Ice project, trudging up steep Alpine valleys and through crevasse fields to measure the spreading carpet of living organisms on Austria's Jamtal Glacier and scraping sticky samples off the ice to bring back to the lab.
Just getting to the sites is an adventure. During the team's first visit to their field research site in June 2018, the access road was blocked by an avalanche, so researcher Klemens Weisleitner said he carried his mountain bike over the slide, rode several more kilometers and then strapped on snowshoes for the final section.
Global warming is making the glacier more hospitable to more microbial life, including potentially harmful organisms hitching their way to the mountains aboard particles of dust from the Sahara.
"It's like a revelation," Sattler said. "The biology of glacial surfaces has never been taken into account with regard to glacier melting."
"The dust particles are like little sponges flying through the air, picking up microbes, which eat their transport vehicle as they're being transported," she said.
The Black Ice project aims to quantify that process, which will help figure out how fast the glaciers are melting. That will determine when and how communities dependent on the water will have to adapt and rethink reservoirs and irrigation systems.
Sattler and her fellow researchers are also growing some of the microbes they find on the glacier in controlled conditions in a lab to see how they respond to different levels of warming, and the team is working with local school science classes, who help the researchers collect samples from the ice and then study them under microscopes in the classroom.
Earth's forests are one of the key links in the global carbon cycle, absorbing about 40 percent of fossil fuel carbon dioxide emissions each year. But research shows global warming is harming forests around the world.
In North America, drought and heat make trees more susceptible to damaging insects and fires and hinder forest regeneration. Drying and warming in the Amazon, the world's most important forest carbon sink, is reducing the region's ability to take up carbon.
It's tough to measure the global scale of impacts in such dynamic living systems, but Cornelius Senf is developing ways to show just how widespread they are.
Senf, a scientist at Humboldt University in Berlin, recently used thousands of satellite images and field trips to assess the damage in Central Europe's forests that turned crackling dry during last summer's record-setting drought.
He found that forest mortality in the region had doubled since the 1980s. This summer, he will extend the research to all of Europe's forests across nearly 100 million acres, including the vast boreal forests of Scandinavia, which are crucial to capturing huge quantities of CO2 and storing it in the living wood.
The exact reasons for the sharp increase in tree deaths are still not fully understood—human land use changes, such as expanding farms, and global warming that leads to spread of pests and rising temperatures, both play a role.
Senf said scientists expect tree deaths to increase even more with the extreme heat and dryness during recent summers.
"Those short-term extremes certainly contribute to increasing forest mortality, as warmer summers facilitate the development of native bark beetle species. Further, very hot and dry summers reduce the trees' defensive capacity, as they produce less resin and it is less fluid. Some trees might even die as a direct consequence of heat and drought, but this is rather rare for Central Europe," he said.
Marine Heat Waves
Hillary Scannell was studying marine science at the University of Maine in 2012 when unusual ocean warming near her small coastal community put a world of hurt on the lobster fishery.
The warming, now called a marine heat wave by an emerging group of ocean scientists, ended up being a major climate-driven economic and ecological shift in the region, and it spurred Scannell to focus her graduate studies at the University of Washington on that subject.
"We're putting a lot of work into understanding how climate change will influence when and where marine heat waves will appear in the future. We want to be prepared going into the future by eliminating any surprises," she said.
Oceans have taken up about 93 percent of the heat trapped by greenhouse gases. That is making the oceans warm up fast and to greater depths, and that will inevitably manifest in more ocean heat waves.
On land, where heat waves scorch crops and dry up forests, heat waves are measured by extended periods of time when temperatures are significantly above average for the area and season. Marine heat wave researchers are establishing a similar measurement system for the oceans, where excessively warm water kills coral reefs and carbon-storing sea grass, and can drive fish out of reach of coastal communities that depend on seafood.
Globally, the oceans have seen a 34 percent increase in the frequency of marine heat waves and a 17 percent increase in their duration, recent research in the journal Nature shows. Under global warming, "marine heat waves, will become very frequent and extreme, probably pushing marine organisms and ecosystems to the limits of their resilience and even beyond," that study concluded.
That means marine organisms and ecosystems are far more likely to face damaging extreme ocean temperatures now than during the mid-20th Century, said Dan Smale, an ocean researcher with the Marine Biological Association in Plymouth, United Kingdom.
"Extreme temperatures experienced during marine heat waves can cause widespread devastation to marine ecosystems. Mass fish kills, coral bleaching, loss of kelp forests and seagrass meadows, reduced fisheries catches, starving sea birds and mammals, and increased disease have all been attributed to extreme temperatures," he said.
Understanding patterns of intensifying marine heat waves can help design marine protected areas to support biodiversity, and adaptive management of fisheries to help ensure sustainable food supplies.
Archaeologists like Craig Lee are literally racing against global warming to study and catalog new finds emerging from melting snow and ice patches in nearly all the world's mountains. Some recent finds have been frozen in time and space for as long as 10,000 years, but anything made of fabric, wood or leather will degrade quickly once it's exposed to warm air and sun.
"There is obviously a crisis," said Lee, an environmental archaeologist with the Institute of Arctic and Alpine Research at the University of Colorado, Boulder. Wooden arrow shafts or food remnants are a treasure trove of information about how people lived in the early days of North American settlement. But organic items can crumble and blow away in the wind within a few weeks.
In the Yellowstone region, melting ice and snow recently uncovered what Lee said may be the world's oldest organic archaeological find from an ice patch: a dart shaft made from a birch branch about 10,000 years ago. A detailed mark on the shaft may be a clue to ancient social structures, and about how people first settled North America.
Across the Atlantic in Norway, Lars Holger Pilø and his team worked overtime last summer as a record heat wave melted snow and ice patches faster than ever. "We are losing the history of this landscape and we're trying save the history of this melting world," he said after a long trek to a site in July. "That work has to go on until the ice is gone."
Pilø said recovering artifacts from the melting snow and ice is like watching history in reverse at a dizzying clip, with ever-older finds.
"It's going back from the bronze age to the stone age, and it's going so fast, it's not a good feeling. It's the great acceleration, with the landscape speeding into the past, but it's not reversing the way it would in a natural cycle. This is an anthropogenic landscape," he said.
Finding organic samples preserved by ice also helps climate scientists make a more accurate record of temperatures in the past 10,000 years, which is important for understanding global warming impacts, he said.
Some of the finds emerging from the ice right now date back to the Holocene Thermal Maximum, about 9,000 to 5,000 years before present, when temperatures in parts of the Northern Hemisphere may have spiked for a short time to near today's level.
The latest clues from melting ice may help determine whether any ice will survive the era of human-caused global warming.
Top photo: Scientists use ground penetrating radar pulled behind a snowmobile to measure ice thickness. Courtesy of Kay Helfricht/Institute for Interdisciplinary Mountain Research