Permafrost and Wetland Emissions Could Cut 1.5°C Carbon Budget ‘by Five Years’
By Robert McSweeney
These natural processes are "positive feedbacks"—so called because they release more greenhouse gases as global temperatures rise, thus reinforcing the warming. They have previously not been represented in carbon budget estimates as they are not included in most climate models, the researchers say.
The findings suggest that human-caused emissions will be need to be cut by an additional 20 percent in order to meet the Paris agreement's 1.5°C or 2°C limits, the researchers estimate.
'Engines for Turning CO2 Into Methane'
Over the last year or so, there has been a flurry of new carbon budget studies—using slightly different approaches to estimate how much CO2 we can emit and still hold global temperature rise to no more than 1.5°C or 2°C above pre-industrial levels. Carbon Brief summarized all the 1.5°C budgets in a recent analysis piece.
Many of these studies use global climate models to make their estimates. However, there are some processes which affect the climate that are not yet incorporated into these models.
The new study, published in Nature Geoscience, aims to fill that gap. It focuses on two processes on the land surface: thawing permafrost and natural wetlands.
These are both positive feedbacks for the climate because, as they respond to rising temperatures, they cause the release of more greenhouse gases into the atmosphere.
Permafrost thawing causes disturbances to the soils. This photo was taken on Forsheim Peninsula, Ellesmere Island, Nunavut, Canada.A. Cassidy, UBC Geography / CC BY 2.0
These soils hold a huge amount of carbon, accumulated from dead plants and animals over thousands of years. Rising temperatures put this carbon at risk of being released, explained Dr. Chris Jones, head of the earth system and mitigation science team at the Met Office Hadley Centre. Jones is not an author on the new study, but his team was involved closely in the work. He told Carbon Brief:
"While [permafrost] is frozen, it is inert. As it thaws, this carbon is vulnerable to decomposition—like any other soil carbon. Depending on whether it is waterlogged or not this can be emitted to the atmosphere as CO2 or methane."
How much is released as CO2 and how much as methane is still uncertain, and is an active area of research. Methane is a potent greenhouse gas—approximately 26 times more powerful than CO2 at trapping heat in the atmosphere, although it only lasts for around a decade in the atmosphere.
In natural wetlands, plants absorb CO2 from the atmosphere as they grow. But, because they are waterlogged, when the plants decompose they release methane, rather than CO2. This makes wetlands "effectively engines for turning CO2 into methane," said Jones.
In the Amazon, for example, flooded forests actually release methane through the trees themselves.
Wetlands respond to a warming climate in three ways, Jones explained:
"As [the climate] warms, the local decomposition rate increases. Also, as rainfall changes, we may see increased or decreased areas of wetlands. This varies regionally and, again, is a large uncertainty across climate models. Finally, a direct effect of increased CO2 in the atmosphere is to increase the growth rate of the vegetation and, hence, increase the amount of CO2 being turned into methane."
The study is the first to bring all these factors together, he noted.
The researchers used a "multi-layered soil carbon model" called JULES (Joint UK Land Environment Simulator), explained lead author Dr. Edward Comyn-Platt, a land surface modeller at the Centre for Ecology & Hydrology. JULES has an improved representation of soil chemistry and the way that wetlands create methane.
With permafrost, for example, "this not only improves our estimates of the carbon stored in soils at high latitudes, but also allows us to estimate how much of this soil will be lost as the permafrost regions thaw," Comyn-Platt told Carbon Brief.
To estimate carbon budgets, the researchers use an "inverted" form of the model. This means that rather than plugging in pathways of future greenhouse gas emissions and seeing how global temperatures respond, the researchers input pathways of global temperature rise and use the model to estimate the corresponding levels of greenhouse gases in the atmosphere.
The study looks at three scenarios of future global warming: holding temperature rise at 1.5°C and 2°C, and one where warming "overshoots" 1.5°C, reaches 1.75°C, then returns to 1.5°C.
In their "control" model runs with no permafrost or wetland feedbacks, the researchers estimate the 1.5°C budget at 720bn-929bn tonnes of CO2 from the beginning of 2018—equivalent to 20-25 years of emissions at current rates.
This is slightly higher than some recent budgets because the JULES model tends to simulate a large amount of carbon uptake from the land surface, explained Comyn-Platt, freeing up space for more CO2 emissions in the budget.
The researchers then used the model to simulate the response of permafrost and natural wetlands to climate change. When the additional CO2 and methane emissions are incorporated, the available carbon budget shrinks substantially—falling to 533bn-753bn tonnes of CO2 for 1.5°C, or 14-20 years of emissions.
That means accounting for the impacts of permafrost and wetlands takes around five years off the 1.5°C budget. And, as the table below shows, the budgets for the 1.5°C overshoot and 2°C scenarios are similarly reduced.
This "nice work" shows that even if we were to get net emissions to zero in the next few decades, emissions would need to fall further in order to stabilize temperatures at 1.5°C or 2°C, said Piers Forster, professor of physical climate change at the University of Leeds and director of the Priestley International Centre for Climate. He told Carbon Brief:
"The extra carbon released from thawing permafrost and warming wetlands would continue beyond the date of net-zero emissions and this would need to be countered for in order to consider carbon budgets applicable for 2100 and beyond."
The study also highlights the constant evolution in the complexity of climate models, said Jones, with new model components being developed and run separately before being incorporated into global models.
The graphic below shows how new components have been added to global climate models over time.
In this case, the wetland model "scheme" will be shortly be brought into UKESM1—the UK Earth System Model run by the Met Office Hadley Centre and partners, said Jones. And the permafrost scheme "will follow in due course."
Methane Meltdown: Thawing Permafrost Could Release More Potent Greenhouse Gas Than Expected https://t.co/vP6G7WFkbw… https://t.co/3GS36bTgDu— EcoWatch (@EcoWatch)1521717907.0
Reposted with permission from our media associate Carbon Brief.
- Redwoods are the world's tallest trees.
- Now scientists have discovered they are even bigger than we thought.
- Using laser technology they map the 80-meter giants.
- Trees are a key plank in the fight against climate change.
They are among the largest trees in the world, descendants of forests where dinosaurs roamed.
Pixabay / Simi Luft<p><span>Until recently, measuring these trees meant scaling their 80 meter high trunks with a tape measure. Now, a team of scientists from University College London and the University of Maryland uses advanced laser scanning, to create 3D maps and calculate the total mass.</span></p><p>The results are striking: suggesting the trees <a href="https://www.nature.com/articles/s41598-020-73733-6" target="_blank" rel="noopener noreferrer">may be as much as 30% larger than earlier measurements suggested.</a> Part of that could be due to the additional trunks the Redwoods can grow as they age, <a href="https://www.nature.com/articles/s41598-020-73733-6" target="_blank" rel="noopener noreferrer">a process known as reiteration</a>.</p>
New 3D measurements of large redwood trees for biomass and structure. Nature / UCL<p>Measuring the trees more accurately is important because carbon capture will probably play a key role in the battle against climate change. Forest <a href="https://www.wri.org/blog/2020/09/carbon-sequestration-natural-forest-regrowth" target="_blank">growth could absorb billions of tons</a> of carbon dioxide from the atmosphere each year.</p><p>"The importance of big trees is widely-recognised in terms of carbon storage, demographics and impact on their surrounding ecosystems," the authors wrote<a href="https://www.nature.com/articles/s41598-020-73733-6" target="_blank"> in the journal Nature</a>. "Unfortunately the importance of big trees is in direct proportion to the difficulty of measuring them."</p><p>Redwoods are so long lived because of their ability to <a href="https://www.nature.com/articles/s41598-020-73733-6" target="_blank" rel="noopener noreferrer">cope with climate change, resist disease and even survive fire damage</a>, the scientists say. Almost a fifth of their volume may be bark, which helps protect them.</p>
Carbon Capture Champions<p><span>Earlier research by scientists at Humboldt University and the University of Washington found that </span><a href="https://www.sciencedirect.com/science/article/pii/S0378112716302584" target="_blank" rel="noopener noreferrer">Redwood forests store almost 2,600 tonnes of carbon per hectare</a><span>, their bark alone containing more carbon than any other neighboring species.</span></p><p>While the importance of trees in fighting climate change is widely accepted, not all species enjoy the same protection as California's coastal Redwoods. In 2019 the world lost the equivalent of <a href="https://www.worldwildlife.org/threats/deforestation-and-forest-degradation" target="_blank" rel="noopener noreferrer">30 soccer fields of forest cover every minute</a>, due to agricultural expansion, logging and fires, according to The Worldwide Fund for Nature (WWF).</p>
Pixabay<p>Although <a href="https://c402277.ssl.cf1.rackcdn.com/publications/1420/files/original/Deforestation_fronts_-_drivers_and_responses_in_a_changing_world_-_full_report_%281%29.pdf?1610810475" target="_blank" rel="noopener noreferrer">the rate of loss is reported to have slowed in recent years</a>, reforesting the world to help stem climate change is a massive task.</p><p><span>That's why the World Economic Forum launched the Trillion Trees Challenge (</span><a href="https://www.1t.org/" target="_blank" rel="noopener noreferrer">1t.org</a><span>) and is engaging organizations and individuals across the globe through its </span><a href="https://uplink.weforum.org/uplink/s/uplink-issue/a002o00000vOf09AAC/trillion-trees" target="_blank" rel="noopener noreferrer">Uplink innovation crowdsourcing platform</a><span> to support the project.</span></p><p>That's backed up by research led by ETH Zurich/Crowther Lab showing there's potential to restore tree coverage across 2.2 billion acres of degraded land.</p><p>"Forests are critical to the health of the planet," according to <a href="https://www.1t.org/" target="_blank" rel="noopener noreferrer">1t.org</a>. "They sequester carbon, regulate global temperatures and freshwater flows, recharge groundwater, anchor fertile soil and act as flood barriers."</p><p><em data-redactor-tag="em" data-verified="redactor">Reposted with permission from the </em><span><em data-redactor-tag="em" data-verified="redactor"><a href="https://www.weforum.org/agenda/2021/03/redwoods-store-more-co2-and-are-more-enormous-than-we-thought/" target="_blank">World Economic Forum</a>.</em></span></p>
EcoWatch Daily Newsletter
- Offshore Wind Power Is Ready to Boom. Here's What That Means for ... ›
- American Skyscrapers Kill an Estimated 600 Million Migratory Birds ... ›
Kentucky is coping with historic flooding after a weekend of record-breaking rainfall, enduring water rescues, evacuations and emergency declarations.
<div id="0f31c" class="rm-shortcode" data-rm-shortcode-id="4290ab3e7ec4e142f8bce774bab39f03"><blockquote class="twitter-tweet twitter-custom-tweet" data-twitter-tweet-id="1366307788155219969" data-partner="rebelmouse"><div style="margin:1em 0">Just got back from my office... downtown Beattyville Kentucky is not a pretty sight. @KySportsRadio… https://t.co/6nXwyMKtRb</div> — Tom Jones (@Tom Jones)<a href="https://twitter.com/8atticus/statuses/1366307788155219969">1614588136.0</a></blockquote></div>
<div class="rm-shortcode" data-rm-shortcode-id="b41a2da6bf23cc19a5f38c2dc6c5f9fc"><div class="fb-post" data-href="https://www.facebook.com/dekalbtnfire/photos/a.924258171004562/3713119618785056/"></div></div>
Spring is coming. And soon, tree swallows will start building nests. But as the climate changes, the birds are nesting earlier in the spring.
- Spring Is Arriving Earlier Across the U.S. - EcoWatch ›
- Climate Change Leading to Fatal Bird Conflicts - EcoWatch ›
- The Unsettling Reason Why We're Seeing More Snowy Owls ... ›
Citigroup will strive to reach net-zero greenhouse gas pollution across its lending portfolio by 2050 and in its own operations by 2030, the investment group announced Monday.
- 20 Attorneys General Launch Climate Fraud Investigation of Exxon ... ›
- Exxon Plans to Increase Its Climate Pollution - EcoWatch ›
- Exxon to Slash 14,000 Jobs Worldwide as Oil Demand Drops ... ›