When we see records being broken and unprecedented events such as this, the onus is on those who deny any connection to climate change to prove their case. Global warming has fundamentally altered the background conditions that give rise to all weather. In the strictest sense, all weather is now connected to climate change. Kevin Trenberth
HIT THE PAGE DOWN KEY TO SEE THE POSTS
Now at 8,800+ articles. HIT THE PAGE DOWN KEY TO SEE THE POSTS
Meltwater and surface lakes on the Greenland ice sheet. Credit: contains modified Copernicus Sentinel data (2021), processed by ESA
For the first time ever recorded, in the late summer of 2021, rain fell on the high central region of the Greenland ice sheet. This extraordinary event was followed by the surface snow and ice melting rapidly. Researchers now understand exactly what went on in those fateful summer days and what we can learn from it.
The never-before-seen rainfall, on 14 August 2021, made headlines around the world. The upper-most parts of Greenland's enormous ice cap used to be too cold for anything other than snow to fall, but not anymore.
What caused this extreme rainfall and how did it affect the ice?
Researchers from the Department of Glaciology and Climate at the Geological Survey of Denmark and Greenland (GEUS) in collaboration with colleagues from France and Switzerland have scrutinized these questions and come up with the answers.
It didn't only rain at Summit Camp—rain was measured by new automatic weather stations placed across the ice sheet by GEUS' ice-sheet monitoring projects PROMICE and GC-Net.
Studying detailed data from these stations alongside measurements of surface reflectivity, or albedo, from the Copernicus Sentinel-3 satellite mission and information on atmospheric circulation patterns, the researchers discovered that the rain had been preceded by a heatwave at a time of year when seasonal melting is usually slowing down.
Greenland air temperature for August 2019, 2020, 2021, compared to the 1991–2020 August average. Credit: Copernicus Climate Change Service/ECMWF/ESA (data ERA5)
It wasn't the rain
"It turns out that the rain itself wasn't the most important factor," says Prof. Jason Box from GEUS and lead author of the paper reporting their results, which has been accepted for publication in Geophysical Research Letters.
"There is an irony. It's not really the rain that did the damage to the snow and ice, it's the darkening effect of the meltwater and how the heat from the event erased snow that had overlaid darker ice across the lower third of the ice sheet.
"Unusually warm atmospheric rivers swept along Greenland in the late summer months, bringing potent melt conditions when the melt season was drawing to a close."
In fact, this sudden increase of surface ice melt on Greenland could have happened without any rain ever touching the ground.
The never-before-seen rainfall, on 14 August 2021, made headlines around the world. The upper-most parts of Greenland's enormous ice cap used to be too cold for anything other than snow to fall, but not anymore.
What caused this extreme rainfall and how did it affect the ice?
Researchers from the Department of Glaciology and Climate at the Geological Survey of Denmark and Greenland (GEUS) in collaboration with colleagues from France and Switzerland have scrutinized these questions and come up with the answers.
It didn't only rain at Summit Camp—rain was measured by new automatic weather stations placed across the ice sheet by GEUS' ice-sheet monitoring projects PROMICE and GC-Net.
Studying detailed data from these stations alongside measurements of surface reflectivity, or albedo, from the Copernicus Sentinel-3 satellite mission and information on atmospheric circulation patterns, the researchers discovered that the rain had been preceded by a heatwave at a time of year when seasonal melting is usually slowing down.
Greenland air temperature for August 2019, 2020, 2021, compared to the 1991–2020 August average. Credit: Copernicus Climate Change Service/ECMWF/ESA (data ERA5)
It wasn't the rain
"It turns out that the rain itself wasn't the most important factor," says Prof. Jason Box from GEUS and lead author of the paper reporting their results, which has been accepted for publication in Geophysical Research Letters.
"There is an irony. It's not really the rain that did the damage to the snow and ice, it's the darkening effect of the meltwater and how the heat from the event erased snow that had overlaid darker ice across the lower third of the ice sheet.
"Unusually warm atmospheric rivers swept along Greenland in the late summer months, bringing potent melt conditions when the melt season was drawing to a close."
In fact, this sudden increase of surface ice melt on Greenland could have happened without any rain ever touching the ground.
For the first time ever recorded, in the late summer of 2021, rain fell on the high central area of the Greenland ice sheet. This extraordinary event was preceded by a heatwave and followed by the surface snow and ice rapidly melting. The animation is a series of five images captured by the Copernicus Sentinel-2 mission and shows how the surface of the ice sheet changed between on 1, 3, 5, 20, and 23 August 2021. The melt, which also created lakes on the surface of the ice, is clear to see. Researchers, supported by ESA’s Science for Society program, discovered that it wasn’t actually the rain that caused the melt, it was unusually warm ‘atmospheric rivers’ that swept along Greenland, bringing potent melt conditions when the melt season would normally be drawing to a close. Credit: contains modified Copernicus Sentinel data (2021), processed by ESA.
Even though the rainfall was a shock and a milestone in climate history, researchers knew it was bound to happen sooner or later, given the rising temperatures of the Arctic.
Therefore, Prof. Box and the co-authors encourage research to look further into the workings behind atmospheric rivers and not just rainfall.
They conclude that understanding the frequency of heatwaves, appears to be a more significant research target than the liquid precipitation that heatwaves may or may not produce.
By Alan Buis, NASA's Jet Propulsion Laboratory, August 3, 2021
Earth is surrounded by a system of magnetic fields, called the magnetosphere. The magnetosphere shields our home planet from harmful solar and cosmic particle radiation, but it can change shape in response to incoming space weather from the Sun. Credit: NASA's Scientific Visualization Studio
A constant outflow of solar material streams out from the Sun, depicted here in an artist's rendering. This solar wind is always passing by Earth. Credit: NASA Goddard's Conceptual Image Lab/Greg Shirah
Earth is surrounded by an immense magnetic field, called the magnetosphere. Generated by powerful, dynamic forces at the center of our world, our magnetosphere shields us from erosion of our atmosphere by the solar wind, particle radiation from coronal mass ejections (eruptions of large clouds of energetic, magnetized plasma from the Sun’s corona into space), and from cosmic rays from deep space. Our magnetosphere plays the role of gatekeeper, repelling these forms of energy that are harmful to life, trapping most of it safely away from Earth’s surface. You can learn more about Earth’s magnetosphere here.
Since the forces that generate our magnetic field are constantly changing, the field itself is also in continual flux, its strength waxing and waning over time. This causes the location of Earth’s magnetic north and south poles to gradually shift, and to even completely flip locations every 300,000 years or so. That might be somewhat important if you use a compass, or for certain animals like birds, fish and sea turtles, whose internal compasses use the magnetic field to navigate.
The Sun unleashed a series of four coronal mass ejections (CMEs) on May 22-24, 2010 as the STEREO Ahead spacecraft watched the action. In the coronagraph images, the Sun, blocked out by an occulting disk (seen as red), is represented by a white disk to show its relative size. CMEs are large solar storms that expel a billion tons of matter at a million miles per hour or more. Credit: NASA/European Space Agency
Some people have claimed that variations in Earth’s magnetic field are contributing to current global warming and can cause catastrophic climate change. However, the science doesn’t support that argument. In this blog, we’ll examine a number of proposed hypotheses regarding the effects of changes in Earth’s magnetic field on climate. We’ll also discuss physics-based reasons why changes in the magnetic field can’t impact climate.
Launched in November 2013 by the European Space Agency (ESA), the three-satellite Swarm constellation is providing new insights into the workings of Earth’s global magnetic field. Generated by the motion of molten iron in Earth’s core, the magnetic field protects our planet from cosmic radiation and from the charged particles emitted by our Sun. It also provides the basis for navigation with a compass.
Based on data from Swarm, the top image shows the average strength of Earth’s magnetic field at the surface (measured in nanotesla) between January 1 and June 30, 2014. The second image shows changes in that field over the same period. Though the colors in the second image are just as bright as the first, note that the greatest changes were plus or minus 100 nanotesla in a field that reaches 60,000 nanotesla. Credit: European Space Agency/Technical University of Denmark (ESA/DTU Space)
NOAA NCEI and CIRES scientists created this animation depicting the wandering of Earth’s North Magnetic Pole over the past 50 years. Credit: NOAA/NCEI
The position of Earth’s magnetic north pole was first precisely located in 1831. Since then, it’s gradually drifted north-northwest by more than 600 miles (1,100 kilometers), and its forward speed has increased from about 10 miles (16 kilometers) per year to about 34 miles (55 kilometers) per year. This gradual shift impacts navigation and must be regularly accounted for. However, there is little scientific evidence of any significant links between Earth’s drifting magnetic poles and climate.
2. Magnetic Pole Reversals
Supercomputer models of Earth's magnetic field. On the left is a normal dipolar magnetic field, typical of the long years between polarity reversals. On the right is the sort of complicated magnetic field Earth has during the upheaval of a reversal. Credit: University of California, Santa Cruz/Gary Glatzmaier
During a pole reversal, Earth’s magnetic north and south poles swap locations. While that may sound like a big deal, pole reversals are common in Earth’s geologic history. Paleomagnetic records tell us Earth’s magnetic poles have reversed 183 times in the last 83 million years, and at least several hundred times in the past 160 million years. The time intervals between reversals have fluctuated widely, but average about 300,000 years, with the last one taking place about 780,000 years ago.
Geomagnetic polarity over the past 169 million years, trailing off into the Jurassic Quiet Zone. Dark areas denote periods of normal polarity, light areas denote reverse polarity. Credit: Public domain
During a pole reversal, the magnetic field weakens, but it doesn’t completely disappear. The magnetosphere, together with Earth’s atmosphere, continue protecting Earth from cosmic rays and charged solar particles, though there may be a small amount of particulate radiation that makes it down to Earth’s surface. The magnetic field becomes jumbled, and multiple magnetic poles can emerge in unexpected places.
No one knows exactly when the next pole reversal may occur, but scientists know they don’t happen overnight: they take place over hundreds to thousands of years.
In the past 200 years, Earth’s magnetic field has weakened about nine percent on a global average. Some people cite this as “evidence” a pole reversal is imminent, but scientists have no reason to believe so. In fact, paleomagnetic studies show the field is about as strong as it’s been in the past 100,000 years, and is twice as intense as its million-year average. While some scientists estimate the field’s strength might completely decay in about 1,300 years, the current weakening could stop at any time.
The Sun expels a constant outflow of particles and magnetic fields known as the solar wind and vast clouds of hot plasma and radiation called coronal mass ejections. This solar material streams across space and strikes Earth’s magnetosphere, the space occupied by Earth’s magnetic field, which acts like a protective shield around the planet. Credit: NASA Goddard/Bailee DesRocher
Plant and animal fossils from the period of the last major pole reversal don’t show any big changes. Deep ocean sediment samples indicate glacial activity was stable. In fact, geologic and fossil records from previous reversals show nothing remarkable, such as doomsday events or major extinctions.
3. Geomagnetic Excursions
Recently, there have been questions and discussion about “geomagnetic excursions:” shorter-lived but significant changes in the magnetic field’s intensity that last from a few centuries to a few tens of thousands of years. During the last major excursion, called the Laschamps event, radiocarbon evidence shows that about 41,500 years ago, the magnetic field weakened significantly and the poles reversed, only to flip back again about 500 years later.
Earth’s magnetic field. Credit: NASA
While there is some evidence of regional climate changes during the Laschamps event timeframe, ice cores from Antarctica and Greenland don’t show any major changes. Moreover, when viewed within the context of climate variability during the last ice age, any changes in climate observed at Earth’s surface were subtle.
Bottom line: There’s no evidence that Earth’s climate has been significantly impacted by the last three magnetic field excursions, nor by any excursion event within at least the last 2.8 million years.
Physical Principles
1. Insufficient Energy in Earth’s Upper Atmosphere
Electromagnetic currents exist within Earth’s upper atmosphere. But the energy driving the climate system in the upper atmosphere is, on global average, a minute fraction of the energy that drives the climate system at Earth’s surface. Its magnitude is typically less than one to a few milliwatts per square meter. To put that into context, the energy budget at Earth’s surface is about 250 to 300 watts per square meter. In the long run, the energy that governs Earth’s upper atmosphere is about 100,000 times less than the amount of energy driving the climate system at Earth’s surface. There is simply not enough energy aloft to have an influence on climate down where we live.
2. Air Isn’t Ferrous
Finally, changes and shifts in Earth’s magnetic field polarity don’t impact weather and climate for a fundamental reason: air isn’t ferrous.
Ferrous? Say what?? Bueller? Bueller?
Ferrous means “containing or consisting of iron.” While iron in volcanic ash is transported in the atmosphere, and small quantities of iron and iron compounds generated by human activities are a source of air pollution in some urban areas, iron isn’t a significant component of Earth’s atmosphere. There’s no known physical mechanism capable of connecting weather conditions at Earth’s surface with electromagnetic currents in space.
Thermal and compositional structure of the atmosphere. The upper atmosphere, comprising the mesosphere, thermosphere, and embedded ionosphere, absorbs all incident solar radiation at wavelengths less than 200 nanometers (nm). Most of that absorbed radiation is ultimately returned to space via infrared emissionsfrom carbon dioxide (CO2) and nitric oxide (NO) molecules. The stratospheric ozone layer absorbs radiation between 200 and 300 nm.
The plot on the left shows the typical global-average thermal structure of the atmosphere when the flux of solar radiation is at the minimum and maximum values of its 11-year cycle. The plot on the right shows the density of nitrogen (N2), oxygen (O2), and atomic oxygen (O), the three major neutral species in the upper atmosphere, along with the free electron (e−) density, which is equal to the combined density of the various ion species. The F, E, and D regions of the ionosphere are also indicated, as is the troposphere, the atmosphere’s lowest region. Credit: Naval Research Laboratory/J. Emmert
Solar storms and their electromagnetic interactions only impact Earth’s ionosphere, which extends from the lowest edge of the mesosphere (about 31 miles or 50 kilometers above Earth’s surface) to space, around 600 miles (965 kilometers) above the surface. They have no impact on Earth’s troposphere or lower stratosphere, where Earth’s surface weather, and subsequently its climate, originate.
In short, when it comes to climate, variations in Earth’s magnetic field are nothing to get charged up about.
For a long time, the story went that the tobacco industry cooked up disinformation and then spread it to the fossil fuel guys, the chemical industry, pharma, you name it. But one thing that became incredibly clear when we began digging into PR firms and specific publicists was that this version of history is not quite right; if disinformation strategies were cooked up by any particular industry it was the public relations industry, which put these strategies to work on behalf of fossil fuels, tobacco, chemical manufacturers and more, often all at the same time. The very first publicist, Ivy Ledbetter Lee, worked on behalf of both Standard Oil and, shortly after, American Tobacco, for example. Daniel Edelman developed astroturf campaigns for both RJ Reynolds tobacco company and the American Petroleum Institute, as did John Hill, who went so far as to have tobacco folks join the API. He also worked with Monsanto, juggling all three clients at the same time. E. Bruce Harrison worked for the chemical guys first, then managed front groups for tobacco and fossil fuels at the same time. You get the drift.
These industries all surely learned from each other at various points in time, but that was mostly because they were working with the same publicists. The history is less that tobacco or oil embraced disinformation first and then passed it on and more that a handful of PR firms and consultants created the disinformation industry, and then put it to work on behalf of whatever industry needed it at any given time.
Today, those same strategies are at work on behalf of those who worry that the response to COVID-19 will undermine capitalism, which is why climate folks keep noting how familiar the whole anti-science component of the rightwing response to the pandemic feels. It’s familiar because the exact same strategies are being deployed, in some cases by the same people. Here are a few key examples:
Disinformation Strategy #1: He who controls the language controls the narrative. Ivy Lee’s big thing, way back 100+ years ago when he was working with the Rockefellers... oh, and advising Hitler and Goebbels too… was to take control of language. If the government wanted to impose safety regulations on your industry, you described them as “extra” or “additional” or “surplus.” In climate, we’ve seen language shift from “the greenhouse effect” to global warming to climate change. When media finally seized the power to make its own language choices, opting for “climate crisis” or “climate emergency," it was deemed radical, even by other journalists. In the COVID-19 context, we’ve seen this too. It’s gone from a “flu” to “a really bad flu” to “a pandemic” in a relatively condensed amount of time. But you’ll see those trading in disinformation continue to refer to it as “just a bad flu” or point out how many people the flu kills every year.
Disinformation Strategy #2: Leverage science illiteracy to create doubt: This has been a hugely effective tactic for multiple industries because the vast majority of public don’t spend a lot of time reading scientific studies, nor do they understand that scientific research has its own language. That makes it very easy to point to something like the uncertainty inherent in any scientific research and say “see, they don’t really know.” The best recent example of this is the re-emergence of Michael Fumento, as Drilled News contributor Paul Thacker pointed out recently. Fumento questioned health models for the tobacco guys, climate models for the oil guys, and has now returned to question public health models used to predict the spread and likely death toll of COVID-19. Fumento was also famously fired when Businessweek outed him for accepting $60,000 from Monsanto one year to write GMO-friendly pieces in his column, which was syndicated to dozens of papers across the country. Of course models, like science in general, have a bit of uncertainty baked in; they represent both the most extreme outcomes and the most likely scenarios, they encapsulate multiple variables. And if you know enough about them, it’s quite easy to cherry pick data and flaws and argue, as Fumento does, that modeling in general is bunk that ought to be thrown out.
Disinformation strategy #3: Astroturfing This weekend, social media was awash in the news that those anti-lockdown rallies in Minnesota, Michigan, Wisconsin and Colorado were all fomented by rightwing donors. Someone on Reddit figured out all the “re-open the economy” websites were made by one guy in Florida. This is astroturfing 101, and it’s a strategy that’s been a key tool in the disinformation toolbox for at least 100 years. When coalminers and steelworkers were striking regularly back in the late 1800s and early 1900s, publicists like Ivy Lee, Edward Bernays and John Hill helped create fake protest groups that supposedly represented all the coal miners who just wanted these strikes to be over so they could get back to work. In more recent years, fossil fuel companies have backed fake advocacy groups like the California Drivers Alliance or the Washington Consumers for Sound Fuel Policy to fight against everything from emissions regulations to a carbon tax. Astroturfing is fake activism meant to give the illusion of grassroots opposition to policy. My favorite example is the Save the Plastic Bag Coalition, a petrochemical and plastic manufacturers-backed group that protests bag bans and bag taxes. It’s somewhat rare, however, to get a sitting U.S. President supporting and promoting your astroturf campaign, as Trump has done with the fake “re-open the economy” movement.
Season 3 of Drilled gets into these strategies and more in great detail, and you’re bound to see in this history the roots of today’s pandemic disinformation machine.
This week is Earth Week and a lot of media outlets are focused on solutions to climate change, a conversation that COVID-19 has certainly changed. Which got me thinking: often people act like climate accountability is not a solution, like all we do is point out problems or play the blame game. Sorry for harshing your mellow about carbon capture occasionally, but for the team at Drilled News, accountability is an absolutely necessary part of addressing climate change. How can you move forward functionally if you don’t know where things went wrong in the past? How can any technological solution possibly work if it’s plugged into the same old system (carbon capture is an excellent example of this, come to think of it)?
Our hope, of course, is that when people learn to recognize these strategies and know what’s behind them, they might become less effective. Disempowering the disinformation industry is a necessary part of any climate solution.
A Youtube video emerged on Earth Day eve making charges about me and about 350.org — namely that I was a supporter of biomass energy, and that 350 and I were beholden to corporate funding, and have misled our supporters on the costs and trade-offs related to decarbonizing our economy. These things aren’t true. Apparently there are lots of other falsehoods and misrepresentations in the film as well, but I’ll let others speak to those.
Like the film-maker, I previously personally supported burning bio-mass as an alternative to fossil fuels—in my case, when the rural college where I teach replaced its oil furnaces with a wood-chip burner more than a decade ago, I saluted it. But as more scientists studied the consequences of large-scale biomass burning, the math began to show that it would put large amounts of carbon into the atmosphere at precisely the wrong moment: if we break the back of the climate system now, it won’t matter if forests suck it up fifty years hence. And as soon as that became clear I began writing and campaigning on those issues. Here’s a piece of mine from 2016 that couldn’t be much clearer, and another from 2019 in the New Yorker about the fights in the Southeast, and another from 2020 as campaigners fought to affect policy in the Northeast. The other side has definitely noticed—here’s an article from the biomass industry attacking me, 350.org, and others. I’m reasonably sure that most of the valiant people here and in the UK that have been fighting this fight will vouch that I’ve been a help, not a hindrance.
As for taking corporate money, I’ve actually never taken a penny in pay from 350.org, or from any other environmental group. Instead, I’ve donated hundreds of thousands of dollars over the years in honoraria and prizes. And 350.org hasn’t taken corporate money, (though it did accept the donation of hundreds of irregular parkas from The North Face in 2009 to warm the hundreds of young people it brought from around the world to the Copenhagen climate conference) 350.org has no financial interest in the campaigns it runs to clean our financial system of dirty fossil fuels, and does not act as financial adviser; it’s untrue to suggest it ever promoted one fund over another or profited from doing so.
I am used to ceaseless harassment and attack from the fossil fuel industry, and I’ve done my best to ignore a lifetime of death threats from right-wing extremists. It does hurt more to be attacked by others who think of themselves as environmentalists. I have spent much of the last ten years doing my best to enlarge the environmental movement in every way I can think of, and to support others in their work; I think that a broad big movement is our best hope. And I have found great joy and satisfaction in that work. I don’t understand the reasoning behind these particular attacks; when I first heard rumors of them last summer I wrote the producer and director to set the record straight, and never heard back from them. That seems like bad journalism, and bad faith.
Obviously there are worse things going on in the world right now, from the pandemic we are all dealing with, to the efforts of the oil industry to use its cover to build new pipelines; they overshadow these attacks, which in any event aren’t on me alone but on lots of others who work, day by day, for change—we’re well aware our victories won’t come all at once, but also that we need to keep pushing. So while you shouldn’t waste any sympathy on me, I am very grateful for the solidarity people have been showing. That feels good.
The rainforest in Yangambi, Congo. A new study shows that trees in the region are losing their ability to absorb carbon dioxide. The same has been seen in the Amazon, raising concerns that the world’s two largest rainforests may eventually add to global warming. (De Agostini/Getty Images)
by Daniel Grossman, The Washington Post, March 4, 2020
Scientists have determined that trees in the Congo Basin of central Africa are losing their capacity to absorb carbon dioxide, raising alarms about the health of the world’s second-largest contiguous rainforest and its ability to store greenhouse gases linked to climate change.
A study published Wednesday in the journal Nature found that some sites in the Congo Basin showed signs of weakened carbon uptake as early as 2010, suggesting that the decline in Africa may have been underway for a decade.
Increasing heat and drought is believed to be stifling the growth of the trees in the African rainforest, a phenomenon previously noted in the Amazon. The new data provides the first large-scale evidence that tropical rainforests around the world that have been untouched by logging or other human activity are losing their potency to fight climate change.
The study predicts that by 2030, the African jungle will absorb 14% less carbon dioxide than it did 10 to 15 years ago. By 2035, Amazonian trees won’t absorb any carbon dioxide at all, the researchers said.
By the middle of the century, the remaining uncut tropical forests in Africa, the Amazon and Asia will release more carbon dioxide than they take up — the carbon “sink” will have turned into a carbon source.
Tropical forests will “add to the problem of climate change, rather than mitigating against,” said Simon Lewis, an ecologist at the University of Leeds in England and one of the paper’s co-authors.
The results imply that unless nations accelerate efforts to counter climate change, temperatures will rise even faster than anticipated. The Earth “is more sensitive to carbon dioxide emissions than we thought,” said Lewis, who published a less comprehensive study of the African carbon sink in 2009.
The findings contradict models used by the Intergovernmental Panel on Climate Change and governments around the world, which predicted that the Congo Basin rainforest would continue to absorb carbon for many decades to come.
Richard Betts, head of climate impacts research at Britain’s Hadley Centre, who was not involved in the new study, called the results “a really important finding.”
Scientists have warned for decades that increased temperatures and reduced rainfall could hamper the tropical carbon sink, or the absorption of carbon dioxide by tropical forests.
The researchers estimate that in the 1990s, 17 percent of the carbon dioxide pumped out of smokestacks and tailpipes was taken up by uncut tropical jungles rather than accumulating in the atmosphere, slowing climate change. That figure has dropped to only 6 percent, they say.
The Congo Basin research took more than a decade of work, requiring travel in dugout canoes, on motorcycles and by foot to some of the world’s most inaccessible jungles, and the measurement of tens of thousands of trees by hand. “This has been a huge endeavor,” said Wannes Hubau, a forest ecologist at the Africa Museum in Brussels and a co-author of the paper.
Tough research environment
The new study’s origins date to 2005 when, with a research fellowship from Britain’s venerable Royal Society, Lewis began assembling a network of forest plots in Africa that had not been degraded by logging to track the amount of carbon the trees there absorb each year.
A group of several hundred Amazon plots had been set up by a colleague five years earlier. But no one had done a similar survey of trees in the Congo Basin. And Africa is different.
“It’s a difficult research environment,” Lewis said. The road network in central Africa is spare and poorly maintained, and perennial political upheaval often halts work. Moreover, there’s little funding to support such research, and few African researchers with whom to collaborate.
Wannes Hubau, a forest ecologist from the Africa Museum in Brussels, measures one of the massive trees in a plot at the Yangambi Research Station in Congo. He is using a forester’s tape measure that converts the trunk’s circumference into its diameter, a figure used to determine the amount of carbon the tree contains. (Daniel Grossman)
Computing the carbon content of a forest requires boots on the ground, measuring the girth of every tree in a patch about twice the size of a football field as frequently as every few years, Lewis said.
Scientists have come up with standard equations for converting the diameter of a tree trunk into the amount of carbon contained in the wood. The quantity of carbon absorbed, or lost, by a plot is simply the mathematical difference between how much the trees contain in successive censuses.
Lewis set up several dozen sites himself in Cameroon and Congo. But he wanted a record of carbon uptake in the years even before he began. So he sought out plots that had been set up earlier, often for different purposes by other researchers, and often later abandoned.
One study site was started in 1979 in Liberia by a group of German foresters. The researchers fled the country in the late 1980s during Liberia’s civil war, and the records there were destroyed. But Lewis ferreted out a database of measurements that had been saved on a computer in the Netherlands. After hostilities ended, he drove to Liberia’s only remaining rainforest in 2007 with a sketch of the research locations and found a local resident who had helped conduct the original census. “He led us straight to tree number one of the census,” Lewis said. “Now they’re a core part of our network.”
Expanding the network
In 2013, Lewis hired Hubau to expand the network and look into questionable data on existing sites. It wasn’t easy. They wanted patches scattered all across central Africa, as far as possible from human influence.
Hubau reached one site in Congo by motorcycle to find trunks as expansive and true as Greek columns, rising 10 stories above him. He had brought along a sheaf of papers that contained the vitals of each tree with a trunk thicker than his wrist. It amounted to 376 trees, when last counted in 2014.
Hubau noted which trees had died since then and which trees had grown big enough to be added to the roster. He wrapped a tape measure around the trunk of each tree. For trees too broad for Hubau’s lanky arms to hug, a helper would pass the dangling end of the tape measure around.
But the site had serious complications. The 2014 crew had nailed numbered tags identifying each tree too tightly to the trunks. Subsequent growth had swallowed up some of them. Termites had attacked red blazes that a 2012 team had painted to mark the height from the ground at which they had applied their tapes. Tree girth must be checked at the same place each time. Even a slight change in the measurement point introduces errors that throw off the carbon tally.
After two days of sweaty labor and detective work, Hubau had identified and measured every tree in that plot.
Predicting the sink's future
The new Nature paper combines the work of researchers and field assistants who studied 135,625 trees at 244 African plots in 11 countries with data that, in some cases, goes back to the 1960s. It concludes that, on average, African trees absorbed the same amount of carbon dioxide for two decades through 2014. But a subset of trees began to lose their capacity to absorb carbon as early as 2010.
A typical acre of African jungle accumulates an extra 1,200 pounds of wood every year, equivalent to about half a cord of firewood. Like their Amazonian counterparts, the African forests appear to benefit from carbon dioxide fertilization — they grow more quickly as the amount of carbon dioxide in the atmosphere steadily increases.
But higher temperatures and increased drought, both detrimental to tree growth, are eroding the benefits of carbon fertilization, according to the new study.
Lewis, Hubau and a long list of colleagues used the African records, combined with a comparable set already available from the Amazon, to tease out the factors that influence the health of the tropical carbon sink and to predict its future.
Researchers have already documented a reduction in carbon uptake in the Amazon rainforest. In a 2015 paper also published in Nature, scientists found that intact Amazon jungle absorbed 30 percent less carbon in the 2000s than in the 1990s. The new study finds that Africa is lagging only 10 or 20 years behind the Amazon. Hubau says central African forests are cooler than those in the Amazon, a factor that has delayed the impact of rising temperatures.
“This carbon sink is turning off far earlier than even the most pessimistic of these climate models,” Lewis said.
Now, “we’ll have to cut emissions faster than expected,” said Betts, of the Hadley Centre.
Grossman’s reporting in Congo was supported by the Pulitzer Center on Crisis Reporting.
Posts
