Extreme heat is wilting and burning forests, making it harder to curb climate change

High temperatures, droughts and wildfire last year caused some forests to wilt and burn enough to degrade the ability of the land to lock away carbon dioxide.

fire burning in Amazon rainforest understory vegetation

Earth’s land lost much of their ability to absorb the carbon dioxide humans pumped into the air last year, according to a new study that is causing concern among climate scientists that a crucial damper on climate change underwent an unprecedented deterioration.

Temperatures in 2023 were so high — and the droughts and wildfires that came with them were so severe — that forests in various parts of the world wilted and burned enough to have degraded the ability of the land to lock away carbon dioxide and act as a check on global warming, the study said.

1. Higher temperatures mean more energy to form hurricanes

To understand how hurricanes are being affected by climate change, it’s important to understand how hurricanes are formed. They are essentially clusters of thunderstorms, building strength as they sweep westward using the energy from warm tropical waters. Under the right conditions, the Earth’s rotation will cause the cluster to spin into a cyclone shape. Because heat is energy, increases in sea surface temperatures play a critical role in strengthening these storms.

The ocean is a major heat sink for the planet, absorbing over 90% of the excess heat trapped by greenhouse gasses in the Earth’s atmosphere over the past few decades. Global sea surface temperatures have increased approximately 2.8F since the beginning of the 20th century, and ocean heatwaves — large areas of above-normal temperatures that can last for months-– are much more common and widespread. A hotter ocean means there is more energy available to fuel tropical storms, ultimately making it a more destructive event when it hits land.

2. The hotter the air, the more water it can hold

The second thing a hurricane needs to form is moisture. Water is evaporated and pulled up into the developing storm as it spins across warm waters of the tropical Atlantic. Hotter air temperatures mean more moisture can be held as vapor in the atmosphere, which allows storms to ingest greater amounts of water that will eventually condense into clouds and be released as rainfall. Condensation also releases heat into the storm, fueling its intensification. Models estimate that human-caused global warming has increased hurricane extreme hourly rainfall rates by 11%.

3. ENSO fluctuations are becoming more extreme

Climate change is also contributing to larger swings between the two phases of the El Niño Southern Oscillation (ENSO)—meaning stronger versions of both El Niño or La Niña patterns. Currently, the Atlantic is headed towards a La Niña, which favors hurricane formation because it lessens vertical wind shear. Differences in wind speeds at different heights in the atmosphere can tear a storm apart, while less shear (more consistency in wind speeds between altitudes) allows storms to stay together and build strength.

4. Tropical storms are undergoing rapid intensification more frequently

All these factors add up to more intense tropical storms in a world altered by climate change— meaning more category 3-5 storms and more big storms back-to-back. Since 1975 the number of category 4-5 cyclones has roughly doubled.

This doesn’t necessarily mean that there will be more hurricanes; however, the ones that do form can be bigger and cause more damage (on top of the already estimated $2.6 trillion in damages since 1980.) If anything, data shows a slight decrease in the number of storms, moving more slowly along their path, releasing their extreme wind and rain over a single location for longer periods.

5. Rising sea levels are making hurricanes more deadly

Sea level rise due to climate change has also made hurricanes a more dangerous threat for more people. As sea levels rise, coastlines are put at increased risk of flooding.

Sea levels have risen roughly 8 in since the late 19th century, and the rate of rise is accelerating as climate change worsens. When a hurricane makes landfall, water is pushed inland by high-speed winds in an event known as storm surge. Every additional inch of sea level rise allows the surge to travel farther inland, threatening a wider area and causing more damage, death, and injury— especially in areas where human development along the coast has exposed people and homes to greater risk.

As temperatures continue to rise, communities along the East and Gulf coasts can expect to be hit harder by destructive storms. Despite this, more and more people are choosing to live and build along the coasts, increasing the cost of damages when hurricanes do strike. Slowing warming temperatures and building adaptation measures to protect coastal communities will become more urgent as Atlantic hurricanes intensify.

The Center for Climate and Security (CCS) is joined by Dr. Christopher Schwalm, Senior Scientist and Risk Program Director at the Woodwell Climate Research Center, to discuss key topics in climate change and security. In this episode, Dr. Schwalm covers climate science and its relation to climate security policymaking.

Amazingly, forests are still sucking up as much carbon as they were 30 years ago. But there’s a catch.

Besieged by logging, fires, and pests, this global balancing act might not last long.

forest video screenshot

Each year, burning fossil fuels puffs tens of billions of metric tons of planet-warming carbon dioxide into the atmosphere. And for decades, the Earth’s forests, along with its oceans and soil, have sucked roughly a third back in, creating a vacuum known as the land carbon sink. But as deforestation and wildfires ravage the world’s forests, scientists have begun to worry that this crucial balancing act may be in jeopardy.

A study published in the journal Nature on Wednesday found that, despite plenty of turmoil, the world’s forests have continued to absorb a steady amount of carbon for the last three decades.

Will the Seine be clean enough by the Olympics? Not even the experts know yet

the Seine river with a white bridge, cutting through a city of light-colored buildings

With the Paris Olympics less than two weeks away, a question hangs over the Games: Will the Seine River be clean enough for athletes to swim in?

Triathlon and marathon swimming are scheduled to take place in the Seine, where it has been illegal to swim for more than a century. Despite the city’s efforts to clean up the long-polluted river, the water has tested unsafe for humans in recent weeks, and cleaner on other days. The Games run from July 26-Aug. 11.

To clean up the river, Paris invested 1.4 billion euros ($1.5 billion) in building infrastructure to catch more stormwater when it rains — the same water that contains bacteria-laden wastewater that enters the river during periods of heavy rain and makes it unsafe to swim in.

Continue reading on Associated Press.

Despite facing regional threats like deforestation and wildfires, the world’s forests continue to be a powerful weapon in the fight against climate change. A new study reveals these vital ecosystems have consistently absorbed carbon dioxide for the past three decades, even as disruptions chip away at their capacity. The study, based on long-term ground measurements combined with remote sensing data, found that forests take up an average of 3.5 ± 0.4 billion metric tons of carbon per year, which is nearly half of the carbon dioxide emissions from burning fossil fuels between 1990 and 2019.

The study titled “The enduring world forest carbon sink,” published in the June issue of the journal Nature, highlights the critical role of forests in mitigating climate change. The study further shows that deforestation and disturbances like wildfires are threatening this vital carbon sink.

The research is co-led by U.S. Department of Agriculture (USDA) Forest Service Northern Research Station Senior Research Scientist Yude Pan and Woodwell Climate Senior Scientist Richard Birdsey, and includes 15 additional co-authors from 11 countries.

Some of the key findings include:

Boreal forests in the Northern Hemisphere, spanning regions like Alaska, Canada, and Russia, have experienced a significant decline in their carbon sink capacity, dropping by 36%. This decrease is attributed to factors including increased disturbances from wildfires, insect outbreaks, and soil warming.
Tropical forests have also seen a decline, with deforestation causing a 31% decrease in their ability to absorb carbon. However, regrowth in previously abandoned agricultural lands and logged areas has partially offset these losses, keeping the net carbon flux in the tropics close to neutral.
Temperate forests, on the other hand, have shown a 30% increase in their carbon sink capacity. This rise is largely due to extensive reforestation efforts, particularly in China.

“Our research team analyzed data from millions of forest plots around the globe,” Pan explained. “What sets this study apart is its foundation in extensive ground measurements – essentially, a tree-by-tree assessment of size, species, and biomass. While the study also incorporates remote sensing data, a common tool in national forest inventories and landsurveys, our unique strength lies in the detailed on-the-ground data collection.”

“The persistence of the global forest carbon sink was a surprise given global increases in wildfire, drought, logging, and other stressors,” according to Birdsey. “But it turns out that increasing emissions in some regions were balanced by increasing accumulation in other regions, mainly re-growing tropical forests and reforestation of temperate forests. These findings support the potential for improving protection and management of forests as effective natural climate solutions.”

The study describes how certain land management policies and practices can help preserve this global carbon sink. According to co-author Professor Oliver Phillips from the University of Leeds, who coordinates the pan-tropical ForestPlots.net coalition of scientists supporting key networks such as AfriTRON and RAINFOR, “the extraordinary persistence of the carbon sink shows that forests have mostly coped with climate change, so far. Deforestation, fire, and logging are damaging forests everywhere, but drought less so. Helping Earth’s forests resist climate change will mean keeping them as intact, healthy and vibrant ecosystems.”

Findings support a focus on curtailing deforestation across all forest biomes, for example, promoting forest restoration on lands that may be unsuitable for agriculture, and improving timber harvesting practices to minimize emissions from logging and related activities. The research also highlights the limitations in data collection, particularly in tropical regions. The study calls for increased research and establishment of more ground sampling plots in these areas to reduce uncertainties in carbon estimates and improve understanding of the global carbon budget.

On May 18th, Morris Alexie, Permafrost Pathways Tribal Liaison for the Alaska Native Village of Nunapicuaq (Nunapitchuk), traveled for three days to South America to join EarthRights International and other Indigenous leaders from around the world at the Public Hearing on the Advisory Opinion on Climate Emergency and Human Rights.

What are ice wedges, and why are they important to climate change?

“I think ice wedges are what make permafrost interesting,” says Dr. Anna Liljedahl.

Liljedahl works on Woodwell Climate’s Arctic team as an Associate Scientist. She aims to understand how climate change is affecting water storage and movement. Much of her recent work focuses on ice wedges and how they are reacting to warming Arctic summers. But just what are ice wedges anyway?

Ice wedges are one of the three main features of the Arctic’s land surface. Permafrost, ground that remains below 0˚C for at least two consecutive summers, lies under a thinner layer of thawing and refreezing soil, called the active layer. When permafrost cracks during cold winter days, snowmelt and runoff water seep into the empty space. These eventually freeze and create a wedge-shaped spear of ice that extends vertically down into the permafrost.

Ice wedges actively re-shape the tundra. When they freeze, they grow and expand outward, pushing against the bordering permafrost and active layer. With nowhere else to go, permafrost and soil push upwards, and ridges form on the surface of the tundra. The ridges interlock and form distinct shapes, referred to as ice-wedge polygons.

The ridged borders of ice-wedge polygons form directly above expanding ice wedges below the surface, and are therefore more elevated. The lower internal portion of the polygon allows pools of water from runoff and snowmelt to form atop the active layer. These polygons are visible all the way from space.

Thanks to satellite imagery, scientists like Liljedahl are able to monitor ice-wedge polygons remotely. Satellite images date back to the mid-20th century and can be used to observe changes in the landscape overtime.

During unusually warm summers, the tops of ice wedges can melt, which removes underlying support of the ground surface, causing slumps along the borders of ice-wedge polygons. These leveling borders form channels that siphon the water from pools in the centers of neighboring polygons. The resulting runoff streams can drain small pools and even larger lakes that took thousands of years to form.

With the progression of climate change, these drainage systems have become more common. Liljedahl refers to them in the title of her manuscript, just published in the July issue of Nature Water, “The Capillaries of the Arctic Tundra.”

The increase in creation of new “capillaries” in the Arctic is impacting not only the topographical landscape of the region, but also the livelihoods of all beings that find their home there.

At first, the melt of these ice wedges can spark an uptick in the variation of vegetation due to moisture along the sides of the channel. This, however, is temporary. When the ice wedges stabilize again in the winter, this variation decreases once more.

Aquatic mosses— one of the most productive vegetal forms in the Arctic, equivalent in productivity to Arctic shrubs— inhabit pools formed alongside the edges of ice-wedge polygons. They lose their homes when bodies of water drain away. Major vegetation changes can alter carbon storage, availability, and emissions across the tundra.

Humans are also impacted. Homes become too dangerous to live in as the ground supporting vital infrastructure collapses. Roads connecting communities to important resources are destroyed by subsiding ground.

Despite their widespread impact, ice wedges are often overlooked in Arctic climate models. Historically, their inclusion “costs too much computer time,” Liljedahl says, to factor in. Many climate models take a holistic approach to the Arctic landscape, as opposed to focusing on smaller details.

To remedy this, Liljedahl suggests utilization of developing technology such as Artificial Intelligence (AI). Classifying the Arctic landscape by type, for example, into high-center polygons, low-center polygons, and capillary networks, would factor ice wedge change into climate models. As AI advances and becomes a more common research tool, it could help decrease the human computing time that Liljedahl identifies as a barrier.

Arctic research is likely to change drastically in the coming years. With new technologies, and as we learn more about the Arctic landscape, research models will likely become more inclusive of the varied features within it, and much more accurate.

“There are exciting years ahead,” Liljedahl says, “I think we’re going to see some cool stuff coming out [of tundra research] in the next five to ten years.”