Environment

94 cards about Environment, with explanations, methods and source links.

Cards about Environment

• If trees cancel almost half the urban heat effect, why does the thermometer barely move?

  Two numbers about the same city trees sound like they are arguing. One says the trees cancel close to half of the urban heat effect. The other says they pull the thermometer down by a fraction of a degree. Both are correct, so how do they fit together?

  Source: Nature Communications

• Does the Amazon still absorb more carbon than it releases?

  A forest takes in carbon as its trees grow and gives it back when they burn or rot, so the balance can flip, and not in the same way everywhere. To find where the Amazon stands now, researchers measured the air above different parts of it and compared them. What came out of each region?

  Source: Gatti et al., Nature

• What comes out of the frozen ground of the north when it thaws?

  Permafrost is ground that stays frozen for years on end, and it covers vast areas of Siberia, Alaska and Canada. Locked inside it are the remains of plants and animals that never got the chance to rot. What happens when it thaws?

  Source: Schuur et al., Nature

• How many people in the world can no longer see the Milky Way?

  Street and building lights throw some of their light upward, and particles in the air scatter it into a dome of light over every city. A star is visible only if it is brighter than the background behind it. What does that do to the Milky Way?

  Source: Falchi et al., Science Advances

• Why does an ice shelf already floating in the sea still matter for sea level?

  An ice shelf is a tongue of floating ice reaching out from the land into the sea. Since it is already floating, melting it adds nothing at all to sea level, exactly like an ice cube melting in a full glass. So why does it matter whether it breaks up?

  Source: Fürst et al., Nature Climate Change

• Did the wolves in Yellowstone really change the course of the rivers?

  The familiar story says that returning wolves to Yellowstone thinned the elk herds, which let the trees grow, which stabilized the riverbanks and changed where the rivers ran. That is too good a story not to check, so researchers went back to the data. What held up?

  Source: Kauffman et al., Ecology

• How do beavers help a landscape survive drought and fire?

  Beavers build dams to make themselves a safe pond, with no intention of changing anything beyond that. But a dam slows the flow, raises the water table and spreads moisture out into the banks. What does that do to the land around?

  Source: Fairfax & Whittle, Ecological Applications

• Does cloud seeding actually work?

  Cloud seeding scatters particles, usually silver iodide, to supply condensation nuclei for droplets to form around, and physically the idea is entirely reasonable. The trouble is that proving it worked means knowing the counterfactual: how much rain that same cloud would have given without the seeding. How do you even test that?

  Source: Friedrich et al., PNAS

• Where is most of the carbon a mangrove forest stores?

  Mangrove roots slow the water and trap mud and organic matter, and the salty ground beneath them holds almost no oxygen, so decay is extremely slow. Which means the carbon is not sitting only in the trunks and the leaves. So where is it?

  Source: Donato et al., Nature Geoscience

• A moth circles a lamp and then dives. Is it really drawn to the light?

  In open air the brightest part of an insect’s visual field is usually the sky, and insects use it to keep their backs pointed upward. Next to a lamp that rule stops working. What happens to them?

  Source: Fabian et al., Nature Communications

• Why do leaves under a streetlight stay more intact?

  Artificial light at night counts as a nuisance for insects, and it falls on the trees as well. The researchers collected thousands of leaves from trees growing in pairs: one beside a streetlight and one in a darker spot. What was the difference?

  Source: Cao, Zhang & Ma, Frontiers in Plant Science

• Who punches an almost perfect circle through a layer of cloud?

  An almost perfect circular hole sometimes appears in a cloud layer, or a long straight channel. A cloud does not tear and does not get cut. So what is a hole doing there?

  Source: Heymsfield et al., Science

• What makes red snow speed up the melting around it?

  The red patches on snow are not spilled dye but a bloom of tiny algae, and the pigment protects them from strong radiation. Except that it also changes the surface. What does that do to the snow around them?

  Source: Lutz et al., Nature Communications

• How does a small crab expose human pressure on a whole beach?

  Counting visitors does not measure the damage to a beach: one person walks through leaving nothing, another leaves litter behind. Looking for a more sensitive gauge, several crab species were compared along a gradient of urbanization, visitors and rubbish. What turned up?

  Source: Suciu et al., Journal of Crustacean Biology

• How much greenery in a neighborhood is linked to less mental distress?

  It is easy to ask whether a city has a park, and harder to measure what a person actually meets day to day in their own street. Vegetation cover and the presence of birds in the afternoon were both measured, against the prevalence of depression, anxiety and stress. What was linked to what?

  Source: Cox et al., BioScience

• Half an hour in a park. Does it really do something to the body’s numbers?

  Everyone says half an hour in nature is calming, but is that a feeling or something you can measure in the body? 83 women walked in a city center, in a park and in an urban forest, with both mood and blood pressure recorded each time. What came out of each of the two measures?

  Source: Ojala et al., Health & Place

• Did the volcanoes in India erupt only after the dinosaurs died out?

  About 66 million years ago an asteroid struck the Earth, and around the same time enormous quantities of lava erupted in the Deccan region of India. The question of which came first is not technical: it decides who is to blame for an extinction. What does the dating say?

  Source: Schoene et al., Science

• Can you count park visitors from the pictures they post?

  Many parks have no gate where everyone entering is counted, so how many people really visited is hard to know. Visitors do post pictures from there. Official visit data from dozens of parks were set against posts on social networks. How well does it work?

  Source: Tenkanen et al., Scientific Reports

• What is a visit to a protected natural area worth to mental health?

  A protected natural area gives more than a place to walk, and a visit to nature may contribute to mental wellbeing. But a mental benefit appears in no budget, which makes it easy to ignore. How do you put a price on it at all?

  Source: Buckley et al., Nature Communications

• Can you hear a coral reef recovering?

  A reef is not a quiet place: fish and invertebrates produce clicks, grunts and other sounds in it. If the life returns, perhaps the sound returns with it. A healthy reef, a damaged reef and restored reefs were recorded in parallel. What could be heard?

  Source: Lamont et al., Journal of Applied Ecology

• Does climbers’ chalk affect the rock even where you cannot see it?

  Climbers rub magnesium powder on their hands to improve grip, and the powder transfers to the rock. The white marks can be seen and cleaned, and what happens in the places that look clean is less clear. What was found there?

  Source: Hepenstrick et al., Ecology and Evolution

• How fast did salmon return to a river after the dams were taken out?

  In 2024 four dams were removed from the Klamath river, reopening hundreds of kilometers of swimming routes blocked for decades. The question is how fast fish find a new way. So how fast?

  Source: Goodman et al., Scientific Reports

• What happens to a young seabird that swallows a few grams of plastic?

  Plastic in the belly of a seabird is not only a hard sight, and whether it really harms them is harder to know. Across fifteen years of monitoring, young shearwaters in Australia were tagged, the plastic they had swallowed before leaving the nesting island was weighed, and who came back was recorded. What was found?

  Source: Lavers et al., PNAS

• How much does one tree over a sidewalk change a summer afternoon?

  On a hot day the thermometer alone does not tell you how a person on the street feels. Shade changes the direct sunlight on the body, and it changes the heat coming off every surface around it. To put a number on that, a team measured sidewalk sections with trees and without them on three streets in Montevideo, and interviewed the people walking past. What did they say?

  Source: Heliyon

• Does a streetlight reach a moth that flies outside its circle of light?

  The familiar picture of a moth circling a lamp tells only part of the story, because it shows only the ones that arrived. To see the rest, researchers used harmonic radar to follow the flight paths of individual moths near a streetlight. What became of the ones that never came close?

  Source: PNAS

• What can a lichen tell you about the air coming off an oil refinery?

  A lichen is a partnership between a fungus and something that photosynthesizes, and it takes up what passes through the air around it. If distance from the source were the whole story, the readings should simply fall as you walk away from a refinery. Lichens were collected at 17 plots. What came out?

  Source: Toxics

• How much carbon sits in the kelp forests off northern Portugal?

  A kelp forest is not a forest of trees but a dense stand of large seaweeds under water, which makes any comparison with land awkward. Off northern Portugal a team measured how far the forests extend, how much seaweed they hold, and how fast that seaweed grows. How much carbon is sitting there?

  Source: Scientific Reports

• How far from a road does the de-icing salt reach?

  Salt spread on winter roads does not stay on the asphalt. Runoff carries it into low ground, including the seasonal pools where amphibians breed because the water dries up and fish cannot live there. Researchers measured conductivity at 541 wetlands in western Massachusetts. How far did the salt go?

  Source: Charney et al., PLOS ONE

• How does a round disk of ice start turning on still water?

  Ice circles turn slowly on rivers and lakes, and an earlier laboratory study concluded that a melting disk can induce its own rotation, with the cold meltwater sinking beneath it. A later team went back to the experiment, paying attention to how carefully the water was held still. Does a disk really turn itself?

  Source: Schellenberg, Newton and Hunt, Environmental Fluid Mechanics

• Can you measure how many species live in a forest from its sound alone?

  Record a forest or a reef, compute how complex and varied the recording is, and one microphone might track a whole ecosystem. It would be far cheaper and faster than counting species in the field. The idea rests on one assumption, that acoustic diversity tracks biological diversity, and a meta-analysis finally tested it. How well does it hold?

  Source: Alcocer et al., Biological Reviews

• A sand dune starts booming loud enough to hear from far away. Who is playing?

  Travelers have described singing dunes since Marco Polo, and they are rare enough that the cause stayed mysterious. Earlier work ruled out the wind around the dune and pointed at the avalanche, and ruled out the grains ringing and pointed at their relative motion. Millions of random collisions should sound like noise rather than a note. What organizes them?

  Source: Douady et al., Physical Review Letters

• Who draws hundreds of thousands of bare circles into the grass of the Namib?

  Fairy circles are nearly round barren patches in the Namib, ringed by taller grass and spaced at regular intervals across hundreds of kilometers of southwestern Angola, Namibia and northwestern South Africa. A pattern like that is not an accident. Fifty years and more than 30 papers after the first description, who draws it?

  Source: Meyer et al., South African Journal of Botany

• How long can a bird stay in the air without landing?

  The common swift catches food and nest material in flight, which led scientists to suspect it stays airborne through its whole non-breeding period, migration into sub-Saharan Africa included. Winter sightings are scarce and no roost has ever been found there. Suspicion is not measurement.

  Source: Hedenström et al., Current Biology

• What are we comparing today’s extinctions against?

  The familiar statement is that extinction rates now run 100 to 1,000 times pre-human levels. Measuring the current rate is straightforward. The other half of that comparison, the normal rate before people, is the hard part, and researchers had been using an approximate benchmark of one extinction per million species per year.

  Source: De Vos et al., Conservation Biology

• What do whales do for the water they swim in?

  Microbes, zooplankton and fish are well known as sources of recycled nitrogen in coastal waters. Marine mammals have largely been ignored or dismissed in that cycle, which is a reasonable default for animals that are large, scarce and hard to count. Counting them changes the answer.

  Source: Roman and McCarthy, PLOS ONE

• Are the world’s kelp forests disappearing?

  Kelp forests form key habitats in temperate and Arctic coastal seas, with ecosystem services valued in the billions of dollars a year. Local evidence suggests they are increasingly threatened by several stressors at once. No comprehensive global analysis of change in kelp abundance existed, so the direction of the global story was unknown.

  Source: Krumhansl et al., PNAS

• Why does a glacier in Antarctica run red?

  Blood Falls is the surface manifestation of brine released from below the Taylor Glacier in the McMurdo Dry Valleys. The color is iron, and the interesting question is where the brine comes from and whether anything lives in it. Geochemistry says the water is marine in origin.

  Source: Mikucki and Priscu, Applied and Environmental Microbiology

• What does life eat three kilometers underground?

  Subsurface microbial communities make up a significant fraction of the global prokaryotic biomass, and what sustains them has been relatively unexplored. Three kilometers down in Precambrian continental crust there is no light and no organic rain from above. Something has to supply the carbon.

  Source: Magnabosco et al., The ISME Journal

• Does biodegradable plastic break down in the sea?

  Plastic littering and the persistence of plastics in the environment have become a major focus in research and in the news, and biodegradable polymers like poly(lactic acid) are presented as the alternative. The word biodegradable sounds like a property of the material. It is a property of the material in a place.

  Source: Haider et al., Angewandte Chemie International Edition

• What lives on the rocks that deep-sea mining would collect?

  Polymetallic nodule fields provide hard substrate for sessile organisms on the abyssal seafloor, kilometers below the surface, and deep-seabed mining targets exactly those mineral-rich lumps. The debate has focused on the animals a mining machine would crush. What the nodules themselves support had stayed unclear.

  Source: Stratmann et al., Scientific Reports

• Why would a seabird mistake plastic for food?

  Plastic debris is ingested by hundreds of species, from zooplankton to baleen whales, and how such a diversity of consumers can mistake it for prey is largely unknown. Explanations usually reach for appearance. The sensory mechanisms behind plastic detection and consumption have rarely been examined.

  Source: Savoca et al., Science Advances

• Can planting trees warm a place rather than cool it?

  Restoring tree cover removes carbon, which is the whole case for it. It also changes albedo, the fraction of sunlight reflected from the surface, because a forest is darker than the grass or snow it replaces. Previous efforts to quantify the global benefit have not accounted robustly for that, for want of spatially explicit data.

  Source: Hasler et al., Nature Communications

• Can a rice field be left to dry out without losing the harvest?

  Rice systems provide a major source of calories for more than half of the world’s population, and they use more water than other major crops. Letting the soil go unsaturated during the season would cut that. Fear of losing yield is a large part of why farmers have not adopted it.

  Source: Carrijo et al., Field Crops Research

• What arranges stones into stripes and circles on cold ground?

  Cold landscapes carry patterned ground, where stones gather into stripes and polygons with soil between them, and no hand placed them. Self-organization is increasingly recognized as fundamental to pattern formation in geomorphology. Relative to other fields, the underlying mechanisms have received little attention from theoreticians.

  Source: Li et al., PNAS

• What are the stacks of white bubbles frozen into a northern lake?

  Microbes in the oxygen-free mud of a lake bed produce methane, which rises in bubbles. Over a northern winter the ice grows downward into water that is still bubbling, and the result is visible from above: columns of trapped bubbles stacked through the ice. Greene and colleagues asked what that storage does to the gas budget.

  Source: Greene et al., Biogeosciences

• What makes those hanging pouches on the underside of a storm cloud?

  Mammatus are the sagging pouches that appear under a thunderstorm anvil, and they also turn up beneath cirrus, altocumulus, stratocumulus, jet contrails and volcanic ash clouds. For something this photographed they have almost no quantitative research behind them. A review gathered what exists and listed the proposed mechanisms. The answer is more interesting than a mechanism. How many candidates are there?

  Source: Schultz et al., Journal of the Atmospheric Sciences

• Where does the water come from in a frost flower on sea ice?

  Frost flowers are clusters of ice crystals that grow on freshly formed sea ice and sometimes on frozen lakes. Two explanations had been assumed: condensation out of a supersaturated atmosphere, or brine wicked up through porous sea ice. Both require a supply of water from somewhere. So the authors worked out the physics and then tried growing them on solid pure ice in dry air. Where did the water come from?

  Source: Style and Worster, Geophysical Research Letters

• What decides how thick a field of pancake ice ends up?

  Pancake ice is the field of circular floes that forms when the sea freezes while waves are running. Cores drilled through such ice show distinct layering, which hints that the floes are being stacked by the waves rather than simply thickened by cold. Nobody had related the resulting thickness to the waves themselves. So the authors built a theory, then tested it in a tank and in simulation.

  Source: Dai et al., Journal of Geophysical Research: Oceans

• How long does it take for a rock face to turn into honeycomb?

  Tafoni are the pits that form by non-uniform weathering in rock that looks perfectly uniform, leaving a honeycombed face. Two equations had been proposed for how fast they grow, both calibrated on outcrops from the coast of Japan around two thousand years old. That is a short baseline for a slow process. So measurements were taken at Meteor Crater and across the Colorado Plateau.

  Source: Norwick and Dexter, Earth Surface Processes and Landforms

• Where in the world do waterspouts actually happen?

  A waterspout is a funnel running from a cloud base down to the sea surface, and it looks like a tornado that wandered offshore. Most of what circulates about them is anecdote and photographs. A review gathered the open-access records of waterspouts forming anywhere on Earth between 2000 and 2022 and analyzed where they cluster. Does the geography follow anything?

  Source: Kalmykova, Izvestiya Atmospheric and Oceanic Physics

• Does a crack race through sea ice as fast as through lake ice?

  A crack in ice looks like a brittle fracture, and brittle fractures run at a large fraction of the speed of sound. Sea ice is not pure ice, though: it keeps pockets of unfrozen brine and drainage channels threaded through it. Whether that changes how fast a crack travels was an open question across ice types. So one lab recorded crack velocities in lake, sea and laboratory-grown ice.

  Source: Petrenko and Gluschenkov, Journal of Geophysical Research: Solid Earth

• How does shallow-water sea life cross thousands of kilometers of open ocean?

  Coastal and shallow marine ecosystems are separated by stretches of deep water that their inhabitants cannot cross. Something must occasionally ferry them. Pumice is a candidate, because an explosive submarine eruption produces rock that floats for months. The 2006 eruption of Home Reef Volcano in Tonga provided a natural experiment, and the resulting raft was tracked across the southwest Pacific. What was riding on it?

  Source: Bryan et al., PLOS ONE

• Why are some Antarctic icebergs green instead of blue?

  Ice is blue because it absorbs red light. Some Antarctic icebergs are green, which requires something else in the ice absorbing blue. Dissolved organic carbon had been the proposed culprit for decades. Then measurements of green icebergs came back low in it, while marine ice from the Amery Ice Shelf turned out to be loaded with something else. What is actually coloring them?

  Source: Warren et al., Journal of Geophysical Research: Oceans

• What makes the red stain pouring down an Antarctic glacier?

  Blood Falls is a rust-red fan spreading from the terminus of Taylor Glacier in Antarctica, fed by brine that discharges irregularly from beneath the ice. Red usually means iron oxide, and iron oxide usually means identifiable crystalline minerals. The site also doubles as a Martian analogue, so the mineralogy matters beyond curiosity. A battery of techniques was pointed at the surface material.

  Source: Sklute et al., Frontiers in Astronomy and Space Sciences

• Why was the whole decade around the year without a summer so cold?

  The decade from 1810 to 1819 is probably the coldest in five hundred years or more, and it contains the year without a summer in 1816. The explanation has been the Tambora eruption of 1815. That leaves a problem of timing, because the early years of the decade were already cold before Tambora erupted. So polar snow was examined for the chemical signature of stratospheric volcanic sulfur.

  Source: Cole‐Dai et al., Geophysical Research Letters

• If you want moss to measure your air for you, which moss?

  Mosses have no roots and take what they need from the air, which makes them accidental air samplers and a cheap alternative to instruments. Treating them as interchangeable is the problem, since species differ in shape and surface. So five common pleurocarpous mosses were hung in moss bags beside roads and assayed for traffic metals, with magnetic susceptibility as a rapid screen. Which species collected most?

  Source: Plášek et al., Scientific Reports

• What happened to the dogs left behind at Chernobyl?

  Free-roaming dogs still live inside the Chernobyl exclusion zone, including on the grounds of the power plant itself. If they are a single wandering population they are of limited scientific use. If they are separate groups that have stayed put for generations, they become something rarer. So 302 dogs were sampled from the plant, from Chernobyl City, and from sites 15 to 45 kilometers out.

  Source: Spatola et al., Science Advances

• Which hits a meadow harder, future climate or this year’s weather?

  Climate change and land-use change are both named as key drivers of global change, and they are usually studied one at a time. Crossing them needs a field experiment that manipulates both at once. The Global Change Experimental Facility in Central Germany does exactly that, superimposing regional climate projections onto real weather across large plots. Eight years of grassland data came out of it. Which driver dominated?

  Source: Korell et al., Global Change Biology

• Can a soil animal evolve fast enough to track a warming climate?

  Whether species can respond evolutionarily to current climate change decides whether many of them persist. Almost all the evidence comes from models or from laboratory selection, because very few studies have looked for genetic responses in manipulated experiments under natural field conditions. So a replicated field experiment manipulated climate in a natural setting, and the transcribed genome of a common annelid worm was sequenced across the plots.

  Source: Bataillon et al., Global Change Biology

• If you dig a buried city stream back out, does anything move into it?

  Cities buried their streams in culverts, and some are now reopening them, a practice called daylighting. The aim is to restore ecosystem functions and services, and the outcomes of such projects usually go unreported, which makes the method hard to improve. So a recently daylighted stream in Oslo was monitored: a buried channel turned into interconnected riffles and ponds, seeded with plants. What colonized it, and how fast?

  Source: Baho et al., Restoration Ecology

• What breaks first when flowers and their bees get a warmer spring?

  Warming is expected to disrupt plant and pollinator partnerships, either by pushing their calendars out of step or by changing the traits that decide whether an interaction is worth having. Studies so far have manipulated one partner, or looked at timing or traits but not both. So whole communities were assembled, three annual plants and a solitary bee, before flowering and emergence, and then warmed through spring.

  Source: de Manincor et al., Ecology Letters

• Does the shade in a city follow the money or the demographics?

  Tree canopy in a city is not decoration. It cools streets, filters air and tracks who gets those benefits, which makes its distribution an equity question rather than a landscaping one. The usual assumption is that canopy follows race. So seven American cities were analyzed with high-resolution land cover data against census data, using correlations and two kinds of regression. What held up?

  Source: Schwarz et al., PLOS ONE

• How can a cloud hang motionless over a mountain in a gale?

  A lens-shaped cloud parked above a summit looks like a flying saucer or a stack of pancakes, and it looks stationary while the wind up there is anything but. Either the cloud is somehow anchored, or it is not the same cloud from one moment to the next. The National Weather Service explains which, and the answer also carries a warning for anyone flying nearby.

  Source: NOAA National Weather Service, Altocumulus Standing Lenticular Clouds

• Why does the ocean get colder the deeper you go?

  The deep ocean is cold, and the obvious explanation runs the wrong way. The Earth gets hotter with depth, because heat from radioactive decay leaks outward from the core, and that heat does reach the seafloor. So the water at the bottom sits on a warm surface and is nonetheless the coldest water in the column. Something must be supplying it faster than the planet can warm it.

  Source: NOAA Ocean Service

• How much hotter is a city than the countryside around it?

  Buildings, roads and other infrastructure absorb and re-emit the sun’s heat more than forests and water do. Concentrate them, cut the greenery, and a city becomes an island of higher temperature than the land outside it. That much is intuitive. The useful question is how large the gap actually is, and whether it is a daytime or a nighttime problem.

  Source: US EPA

• Could you stand on the Great Pacific Garbage Patch?

  The name does a lot of work. A garbage patch sounds like a floating landfill. Reports comparing it to Texas, or twice Texas, or twice the continental United States, reinforce the picture of a surface you could walk out onto. NOAA, as a science agency, set out to separate what is known from what the name implies. Is there a patch there?

  Source: NOAA Marine Debris Program

• What does carbon dioxide do once the ocean absorbs it?

  The ocean is a great sponge for carbon dioxide, which is usually reported as good news about where our emissions go. Absorbing a gas is a chemical event, though, not a storage event. NOAA’s ocean acidification program sets out what the chemistry actually does, and the first thing it clears up is a wording problem that trips up almost every conversation about it.

  Source: NOAA Ocean Acidification Program

• Which ecosystem holds the most carbon per hectare, and gets talked about least?

  Forests are what anybody pictures when carbon storage comes up, and they are the subject of most of the pledges. Peatlands are waterlogged ground where dead plant matter cannot fully decay, so it accumulates instead. They occur in almost every country and almost nobody campaigns for them. The UN Environment Programme puts the comparison in a headline, and the ratio is not close.

  Source: UN Environment Programme

• How much of the ocean do coral reefs actually cover?

  Reefs dominate how people picture ocean life, which makes their actual footprint surprising when you look it up. NOAA gives both numbers, the share of the ocean reefs occupy and the share of marine life they shelter, and the gap between the two is the whole point. The agency then works through what else follows from that concentration, from fisheries to the sand on the beach.

  Source: NOAA

• How do you rebuild a species from the animals left in zoos?

  The European bison is Europe’s largest living wild land mammal, and it came within a few dozen animals of disappearing. When the last wild one was shot in the Caucasus in 1927, every survivor was in captivity. Rebuilding a free-living population from that starting point is a long experiment in conservation, and Rewilding Europe gives both the recovery figures and what the recovery has not fixed.

  Source: Rewilding Europe

• Why does a thin spike of ice sometimes grow out of an ice cube?

  Because the water freezing last has nowhere to go but up. Libbrecht and Lui grew ice spikes in the lab, between ten and fifty millimeters long, and worked out which conditions produce them. Under the best conditions about half the cubes in an ordinary ice cube tray grow one. Pure water helps. Dissolved salts almost stop it happening.

  Source: Libbrecht and Lui, An Investigation of Laboratory-Grown Ice Spikes

• Why does rain sometimes stop halfway to the ground?

  It does not stop, it evaporates. When the air under a cloud is very dry, falling rain or ice turns to vapor before reaching the surface, leaving feathery streaks hanging from the cloud base. Radar sees an ordinary shower. Nothing arrives at your feet. The streaks are called virga, and they trace the path the rain took on its way to disappearing.

  Source: NOAA National Weather Service, Owlie’s Weird Weather

• Is the dark stain on desert rock actually a sedimentary rock?

  Dickerson argues it is, on a very small scale. Desert varnish is the dark coating coating bedrock and surface sediments across arid regions, and under a microscope it is layered. Each lamination records the climate conditions in which it was laid down. So a stain barely thicker than a hair carries a readable sequence of local climate history.

  Source: Dickerson, Geology Today

• Has the Earth been getting greener, and if so why?

  Zhu and colleagues put three long satellite leaf area records next to ten global ecosystem models. Between 1982 and 2009, growing-season leaf area rose persistently over a quarter to a half of the vegetated land surface, while less than four percent of the globe showed a decline. The models point to one dominant cause, and it is not a comfortable one.

  Source: Zhu et al., Nature Climate Change

• Can a lake suffocate the valley below it?

  Lakes Nyos and Monoun in Cameroon did exactly that in the nineteen eighties, in events geologists call limnic eruptions. Carbon dioxide had accumulated in the deep water until the lake released it. Kusakabe and colleagues monitored both lakes for twenty-one years, and their record shows the gas quietly building back up afterwards at a steady rate.

  Source: Kusakabe et al., Geochemical Journal

• Is there real evidence behind forest bathing?

  Hansen and colleagues went looking. Starting from a hundred and twenty-seven papers on Shinrin-Yoku, forest bathing and nature therapy, sixty-four met their inclusion criteria, sorted into physiological effects, psychological effects, sensory metrics and frameworks. Almost all of the research comes from Japan and China. The review supports the health benefits, and then says plainly what the evidence base still lacks.

  Source: Hansen et al., International Journal of Environmental Research and Public Health

• What rolls a field of snow into doughnuts overnight?

  Wind, within a narrow range. Snow rollers are doughnut-like formations of rolled snow that appear when moisture, snow, wind and temperature arrive in exactly the right combination. The snow must be a light dusting, sticky enough to adhere to itself but lying on a surface it will not cling to. The wind has to be strong enough to curl it and no stronger.

  Source: NOAA National Weather Service, Owlie’s Weird Weather

• What is a coral losing when it turns white?

  Its tenants, and its food supply with them. Bleaching is the process by which corals lose the symbiotic algae that give them their distinctive colors and their main energy sources. The white is the coral’s own skeleton showing through tissue that has been emptied. If the bleaching is severe, disease and death become likely.

  Source: NOAA Coral Reef Watch

• Have microplastics been found inside a human placenta?

  Yes, in four of six examined. Ragusa and colleagues collected placentas from consenting women with normal pregnancies and analyzed them by Raman microspectroscopy. They found twelve microplastic fragments between five and ten micrometers across: five on the fetal side, four on the maternal side and three in the chorioamniotic membranes.

  Source: Ragusa et al., Environment International

• Is the ozone hole actually closing?

  The long-term trend says yes. The World Meteorological Organization reported in September 2025 that the ozone layer is healing, and that the 2024 ozone hole was smaller than in recent years. The Montreal Protocol has phased out more than ninety-nine percent of the production and consumption of controlled ozone-depleting substances.

  Source: World Meteorological Organization

• Where has almost all the trapped heat actually gone?

  Into the water. NOAA estimates the ocean is storing about ninety-one percent of the excess heat energy that greenhouse gases have trapped in the Earth’s climate system. Averaged over the full depth of the global ocean, the heat-gain rate for 1993 to 2024 works out at roughly 0.66 to 0.74 watts per square meter of the Earth’s surface.

  Source: NOAA Climate.gov

• Is sea level rising by the same amount everywhere?

  No, and the reasons are mostly local. The surface of the ocean is not flat, and it is not changing at the same rate globally. NOAA lists what shifts the figure locally: subsidence, upstream flood control, erosion, regional currents, variations in land height, and whether the land is still rebounding from the weight of Ice Age glaciers.

  Source: NOAA National Ocean Service

• Does the Amazon depend on dust blown from Africa?

  For some of its phosphorus, yes. Amazon productivity is limited by nutrients, phosphorus in particular, and African dust crossing the Atlantic is a recognized but poorly quantified source of it. Yu and colleagues produced a first multiyear satellite estimate: about 28 million tonnes of dust deposited into the Amazon Basin each year.

  Source: Yu et al., Geophysical Research Letters

• How much of the atmosphere is the part we live in?

  A sliver at the bottom. The troposphere starts at the ground and extends up to about ten kilometers, and nearly all weather happens inside it, along with most clouds, because ninety-nine percent of the atmosphere’s water vapor is there. The boundary conventionally taken as the edge of space sits at about a hundred kilometers.

  Source: UCAR Center for Science Education

• What is the red flash that appears above a thunderstorm?

  A sprite, which is lightning going the other way. Sprites appear directly above an active thunderstorm as a large but weak discharge, usually at the same moment as a powerful positive cloud-to-ground stroke below. They can extend up to sixty miles from the cloud top, last no more than a few seconds, and are mostly red.

  Source: NOAA National Severe Storms Laboratory

• Which clouds are still lit when the sky has gone dark?

  The highest ones. Noctilucent clouds are thin, silvery-blue and cirrus-like, seen in summer twilight at latitudes above fifty degrees in both hemispheres. They occur in the upper mesosphere at heights of about eighty-five kilometers, which makes them the highest visible clouds in the atmosphere, and high enough to catch sunlight long after the ground is in shadow.

  Source: American Meteorological Society, Glossary of Meteorology

• Does the night sky glow even where there are no auroras?

  Continuously. Airglow is the quasi-steady radiant emission from the upper atmosphere over middle and low latitudes. The point of the definition is the contrast. Auroras are sporadic and happen over high latitudes, while airglow is always there. The glossary even lists permanent aurora among its older names.

  Source: American Meteorological Society, Glossary of Meteorology

• What is the difference between a shelf cloud and a roll cloud?

  Whether it is attached. A roll cloud is a low-level, horizontal, tube-shaped arcus cloud associated with the gust front of a convective storm, or occasionally a cold front. What differentiates it from the more familiar shelf cloud is that it is completely detached from the storm’s cloud base. Roll clouds are relatively rare.

  Source: American Meteorological Society, Glossary of Meteorology

• Does frost come from dew that froze?

  No. Frost is the fuzzy layer of ice crystals on a cold object that forms by direct deposition of water vapor to solid ice. There is no liquid stage. Hoarfrost, the proper name for the interlocking hoar crystals you find on branches and wires, forms much as dew does, except that the object’s temperature must be below freezing.

  Source: American Meteorological Society, Glossary of Meteorology

• How does the world’s fourth-largest lake disappear?

  By having its rivers taken away. The shallow Aral Sea, straddling the border between Kazakhstan and Uzbekistan, was once the fourth largest body of inland water on Earth. Its shrinkage began in the second half of the twentieth century, while the region was part of the Soviet Union, and continued into the twenty-first.

  Source: Encyclopaedia Britannica

• How much carbon is standing in a country’s kelp forests?

  For Norway, about 2.6 million tonnes. The authors applied statistical models to six hundred and thirty scuba samples of Laminaria hyperborea along the Norwegian coast. They estimated 56 million tonnes of living biomass in fresh weight, and a carbon standing stock of 2.6 million tonnes. That is equivalent to 9.5 million tonnes of carbon dioxide, over roughly five thousand square kilometers of kelp forest.

  Source: Frontiers in Marine Science

• How does anyone know how thick Arctic sea ice is?

  From orbit, and then checked from underneath. Many approaches have been applied to retrieving sea ice thickness, and according to this analysis only satellite altimetry, radar or laser, has been proven to provide hemispheric estimates across a sufficient thickness range. Independent observations from moored upward-looking sonar and from submarines are what the satellite algorithms get tested against.

  Source: Sensitivity, uncertainty analyses and algorithm selection for Sea Ice Thickness retrieval from Radar Altimeter

• Is the night sky getting brighter faster than satellites say?

  The two records disagree sharply. The radiance of nighttime artificial lights measured from orbit by the VIIRS-DNB instrument on Suomi-NPP increases at an average of about 2.2 percent a year worldwide. The artificial radiance of the night sky, inferred from Globe at Night counts of stars visible to the unaided eye, rises at about 9.6 percent a year.

  Source: Bará and Castro-Torres, Journal of Quantitative Spectroscopy and Radiative Transfer

• What made sailors’ stories of freak waves believable?

  A measurement. Freak or rogue waves are so called because of their unexpectedly large size relative to the population of smaller waves around them. The 25.6 meter Draupner wave, observed in a sea with a significant wave height of 12 meters, was one of the first confirmed field measurements of one. The mechanisms behind such waves are still contentious.

  Source: Draycott et al., Journal of Fluid Mechanics

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