̽��ֱ�� of Cambridge - greenhouse gas

2023 was the hottest summer in two thousand years

sc604 — Tue, 14 May 2024 15:00:00 +0000

Although 2023 has been reported as the hottest year on record, the instrumental evidence only reaches back as far as 1850 at best, and most records are limited to certain regions.

Now, by using past climate information from annually resolved tree rings over two millennia, scientists from the ̽��ֱ�� of Cambridge and the Johannes Gutenberg ̽��ֱ�� Mainz have shown how exceptional the summer of 2023 was.

Even allowing for natural climate variations over hundreds of years, 2023 was still the hottest summer since the height of the Roman Empire, exceeding the extremes of natural climate variability by half a degree Celsius.

“When you look at the long sweep of history, you can see just how dramatic recent global warming is,” said co-author Professor Ulf Büntgen, from Cambridge’s Department of Geography. “2023 was an exceptionally hot year, and this trend will continue unless we reduce greenhouse gas emissions dramatically.”

̽��ֱ��results, reported in the journal Nature, also demonstrate that in the Northern Hemisphere, the 2015 Paris Agreement to limit warming to 1.5C above pre-industrial levels has already been breached.

Early instrumental temperature records, from 1850-1900, are sparse and inconsistent. ̽��ֱ��researchers compared early instrumental data with a large-scale tree ring dataset and found the 19th century temperature baseline used to contextualise global warming is several tenths of a degree Celsius colder than previously thought. By re-calibrating this baseline, the researchers calculated that summer 2023 conditions in the Northern Hemisphere were 2.07C warmer than mean summer temperatures between 1850 and 1900.

“Many of the conversations we have around global warming are tied to a baseline temperature from the mid-19th century, but why is this the baseline? What is normal, in the context of a constantly-changing climate, when we’ve only got 150 years of meteorological measurements?” said Büntgen. “Only when we look at climate reconstructions can we better account for natural variability and put recent anthropogenic climate change into context.”

Tree rings can provide that context, since they contain annually-resolved and absolutely-dated information about past summer temperatures. Using tree-ring chronologies allows researchers to look much further back in time without the uncertainty associated with some early instrumental measurements.

̽��ֱ��available tree-ring data reveals that most of the cooler periods over the past 2000 years, such as the Little Antique Ice Age in the 6th century and the Little Ice Age in the early 19th century, followed large-sulphur-rich volcanic eruptions. These eruptions spew huge amounts of aerosols into the stratosphere, triggering rapid surface cooling. ̽��ֱ��coldest summer of the past two thousand years, in 536 CE, followed one such eruption, and was 3.93C colder than the summer of 2023.

Most of the warmer periods covered by the tree ring data can be attributed to the El Niño climate pattern, or El Niño-Southern Oscillation (ENSO). El Niño affects weather worldwide due to weakened trade winds in the Pacific Ocean and often results in warmer summers in the Northern Hemisphere. While El Niño events were first noted by fisherman in the 17th century, they can be observed in the tree ring data much further back in time.

However, over the past 60 years, global warming caused by greenhouse gas emissions are causing El Niño events to become stronger, resulting in hotter summers. ̽��ֱ��current El Niño event is expected to continue into early summer 2024, making it likely that this summer will break temperature records once again.

“It’s true that the climate is always changing, but the warming in 2023, caused by greenhouse gases, is additionally amplified by El Niño conditions, so we end up with longer and more severe heat waves and extended periods of drought,” said Professor Jan Esper, the lead author of the study from the Johannes Gutenberg ̽��ֱ�� Mainz in Germany. “When you look at the big picture, it shows just how urgent it is that we reduce greenhouse gas emissions immediately.”

̽��ֱ��researchers note that while their results are robust for the Northern Hemisphere, it is difficult to obtain global averages for the same period since data is sparse for the Southern Hemisphere. ̽��ֱ��Southern Hemisphere also responds differently to climate change, since it is far more ocean-covered than the Northern Hemisphere.

̽��ֱ��research was supported in part by the European Research Council.

Reference:
Jan Esper, Max Torbenson, Ulf Büntgen. ‘2023 summer warmth unparalleled over the past 2,000 years.’ Nature (2024). DOI: 10.1038/s41586-024-07512-y

Researchers have found that 2023 was the hottest summer in the Northern Hemisphere in the past two thousand years, almost four degrees warmer than the coldest summer during the same period.

When you look at the long sweep of history, you can see just how dramatic recent global warming is

Ulf Büntgen

trekandshoot via Getty Images

Morning sun over Los Angeles, USA.

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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Cambridge heads to COP28

plc32 — Fri, 01 Dec 2023 17:43:08 +0000

̽��ֱ�� ̽��ֱ�� of Cambridge heads to COP28 in Dubai, UAE, with a film premiere and a host of higher education and research events.

Millions of carbon credits are generated by overestimating forest preservation

fpjl2 — Fri, 25 Aug 2023 07:28:16 +0000

Study analyses major carbon offset projects, and finds that – of a potential 89 million credits – only 5.4 million (6%) were linked to additional carbon reductions through tree conservation.

Shrinking Arctic glaciers are unearthing a new source of methane

cmm201 — Thu, 06 Jul 2023 14:23:15 +0000

As the Arctic warms, shrinking glaciers are exposing bubbling groundwater springs which could provide an underestimated source of the potent greenhouse gas methane, finds new research published today in Nature Geoscience.

Solar-powered system converts plastic and greenhouse gases into sustainable fuels

sc604 — Mon, 09 Jan 2023 16:00:00 +0000

̽��ֱ��researchers, from the ̽��ֱ�� of Cambridge, developed the system, which can convert two waste streams into two chemical products at the same time – the first time this has been achieved in a solar-powered reactor.

̽��ֱ��reactor converts carbon dioxide (CO2) and plastics into different products that are useful in a range of industries. In tests, CO2 was converted into syngas, a key building block for sustainable liquid fuels, and plastic bottles were converted into glycolic acid, which is widely used in the cosmetics industry. ̽��ֱ��system can easily be tuned to produce different products by changing the type of catalyst used in the reactor.

Converting plastics and greenhouse gases – two of the biggest threats facing the natural world – into useful and valuable products using solar energy is an important step in the transition to a more sustainable, circular economy. ̽��ֱ��results are reported in the journal Nature Synthesis.

“Converting waste into something useful using solar energy is a major goal of our research,” said Professor Erwin Reisner from the Yusuf Hamied Department of Chemistry, the paper’s senior author. “Plastic pollution is a huge problem worldwide, and often, many of the plastics we throw into recycling bins are incinerated or end up in landfill.”

Reisner also leads the Cambridge Circular Plastics Centre (CirPlas), which aims to eliminate plastic waste by combining blue-sky thinking with practical measures.

Other solar-powered ‘recycling’ technologies hold promise for addressing plastic pollution and for reducing the amount of greenhouse gases in the atmosphere, but to date, they have not been combined in a single process.

“A solar-driven technology that could help to address plastic pollution and greenhouse gases at the same time could be a game-changer in the development of a circular economy,” said Subhajit Bhattacharjee, the paper’s co-first author.

“We also need something that’s tuneable, so that you can easily make changes depending on the final product you want,” said co-first author Dr Motiar Rahaman.

̽��ֱ��researchers developed an integrated reactor with two separate compartments: one for plastic, and one for greenhouse gases. ̽��ֱ��reactor uses a light absorber based on perovskite – a promising alternative to silicon for next-generation solar cells.

̽��ֱ��team designed different catalysts, which were integrated into the light absorber. By changing the catalyst, the researchers could then change the end product. Tests of the reactor under normal temperature and pressure conditions showed that the reactor could efficiently convert PET plastic bottles and CO2 into different carbon-based fuels such as CO, syngas or formate, in addition to glycolic acid. ̽��ֱ��Cambridge-developed reactor produced these products at a rate that is also much higher than conventional photocatalytic CO2 reduction processes.

“Generally, CO2 conversion requires a lot of energy, but with our system, basically you just shine a light at it, and it starts converting harmful products into something useful and sustainable,” said Rahaman. “Prior to this system, we didn’t have anything that could make high-value products selectively and efficiently.”

“What’s so special about this system is the versatility and tuneability – we’re making fairly simple carbon-based molecules right now, but in future, we could be able to tune the system to make far more complex products, just by changing the catalyst,” said Bhattacharjee.

Reisner recently received new funding from the European Research Council to help the development of their solar-powered reactor. Over the next five years, they hope to further develop the reactor to produce more complex molecules. ̽��ֱ��researchers say that similar techniques could someday be used to develop an entirely solar-powered recycling plant.

“Developing a circular economy, where we make useful things from waste instead of throwing it into landfill, is vital if we’re going to meaningfully address the climate crisis and protect the natural world,” said Reisner. “And powering these solutions using the Sun means that we’re doing it cleanly and sustainably.”

̽��ֱ��research was supported in part by the European Union, the European Research Council, the Cambridge Trust, Hermann and Marianne Straniak Stiftung, and the Engineering and Physical Sciences Research Council (EPSRC), part of UK Research and Innovation (UKRI). Erwin Reisner is a Fellow of St John’s College, Cambridge.

Reference:
Subhajit Bhattacharjee, Motiar Rahaman et al. ‘Photoelectrochemical CO2-to-fuel conversion with simultaneous plastic reforming.’ Nature Synthesis (2023). DOI: 10.1038/s44160-022-00196-0

For more information on energy-related research in Cambridge, please visit Energy IRC, which brings together Cambridge’s research knowledge and expertise, in collaboration with global partners, to create solutions for a sustainable and resilient energy landscape for generations to come.

Researchers have developed a system that can transform plastic waste and greenhouse gases into sustainable fuels and other valuable products – using just the energy from the Sun.

A solar-driven technology that could help to address plastic pollution and greenhouse gases at the same time could be a game-changer in the development of a circular economy

Subhajit Bhattacharjee

Reisner Lab

Solar-powered reactor for converting plastic and greenhouse gases into sustainable fuels

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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Greenhouse gas ‘feedback loop’ discovered in freshwater lakes

fpjl2 — Fri, 04 May 2018 09:00:06 +0000

A new study of chemical reactions that occur when organic matter decomposes in freshwater lakes has revealed that the debris from trees suppresses production of methane – while debris from reed beds actually promotes this harmful greenhouse gas.

As vegetation in and around bodies of water continues to change, with forest cover being lost while global warming causes wetland plants to thrive, the many lakes of the northern hemisphere – already a major source of methane – could almost double their emissions in the next fifty years.

̽��ֱ��researchers say that the findings suggest the discovery of yet another “feedback loop” in which environmental disruption and climate change trigger the release of ever more greenhouse gas that further warms the planet, similar to the concerns over the methane released by fast-melting arctic permafrost.

“Methane is a greenhouse gas at least twenty-five times more potent than carbon dioxide. Freshwater ecosystems already contribute as much as 16% of the Earth’s natural methane emissions, compared to just 1% from all the world’s oceans,” said study senior author Dr Andrew Tanentzap, from the ̽��ֱ�� of Cambridge’s Department of Plant Sciences.

“We believe we have discovered a new mechanism that has the potential to cause increasingly more greenhouse gases to be produced by freshwater lakes. ̽��ֱ��warming climates that promote the growth of aquatic plants have the potential to trigger a damaging feedback loop in natural ecosystems.”

̽��ֱ��researchers point out that the current methane emissions of freshwater ecosystems alone offsets around a quarter of all the carbon soaked up by land plants and soil: the natural ‘carbon sink’ that drains and stores CO2 from the atmosphere.

Up to 77% of the methane emissions from an individual lake are the result of the organic matter shed primarily by plants that grow in or near the water. This matter gets buried in the sediment found toward the edge of lakes, where it is consumed by communities of microbes. Methane gets generated as a byproduct, which then bubbles up to the surface.

Working with colleagues from Canada and Germany, Tanentzap’s group found that the levels of methane produced in lakes varies enormously depending on the type of plants contributing their organic matter to the lake sediment. ̽��ֱ��study, funded by the UK’s Natural Environment Research Council, is published today in the journal Nature Communications.

To test how organic matter affects methane emissions, the scientists took lake sediment and added three common types of plant debris: deciduous trees that shed leaves annually, evergreen pine-shedding coniferous trees, and cattails (often known in the UK as ‘bulrushes’) – a common aquatic plant that grows in the shallows of freshwater lakes.

These sediments were incubated in the lab for 150 days, during which time the scientists siphoned off and measured the methane produced. They found that the bulrush sediment produced over 400 times the amount of methane as the coniferous sediment, and almost 2,800 times the methane than that of the deciduous.

Unlike the cattail debris, the chemical makeup of the organic matter from trees appears to trap large quantities of carbon within the lake sediment – carbon that would otherwise combine with hydrogen and get released as methane into the atmosphere.

To confirm their findings, the researchers also “spiked” the three samples with the microbes that produce methane to gauge the chemical reaction. While the forest-derived sediment remained unchanged, the sample containing the bulrush organic matter doubled its methane production.

“ ̽��ֱ��organic matter that runs into lakes from the forest trees acts as a latch that suppresses the production of methane within lake sediment. These forests have long surrounded the millions of lakes in the northern hemisphere, but are now under threat,” said Dr Erik Emilson, first author of the study, who has since left Cambridge to work at Natural Resources Canada.

“At the same time, changing climates are providing favourable conditions for the growth and spread of aquatic plants such as cattails, and the organic matter from these plants promotes the release of even more methane from the freshwater ecosystems of the global north.”

Using species distribution models for the Boreal Shield, an area that covers central and eastern Canada and “houses more forests and lakes than just about anywhere on Earth”, the researchers calculated that the number of lakes colonised by just the common cattail (Typha latifolia) could double in the next fifty years – causing current levels of lake-produced methane to increase by at least 73% in this part of the world alone.

Added Tanentzap: “Accurately predicting methane emissions is vital to the scientific calculations used to try and understand the pace of climate change and the effects of a warmer world. We still have limited understanding of the fluctuations in methane production from plants and freshwater lakes.”

Latest research finds plant debris in lake sediment affects methane emissions. ̽��ֱ��flourishing reed beds created by changing climates could threaten to double the already significant methane production of the world’s northern lakes.

̽��ֱ��warming climates that promote the growth of aquatic plants have the potential to trigger a damaging feedback loop in natural ecosystems

Andrew Tanentzap

Andrew Tanentzap.

Lake near Sudbury, Ontario, in the Canadian Boreal Shield, with aquatic plants in the foreground providing fuel for methane production.

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Opinion: Worthless mining waste could suck CO₂ out of the atmosphere and reverse emissions

Anonymous — Thu, 20 Apr 2017 16:06:39 +0000

̽��ֱ��Paris Agreement commits nations to limiting global warming to less than 2˚C by the end of the century. However, it is becoming increasingly apparent that, to meet such a massive challenge, societies will need to do more than simply reduce and limit carbon emissions. It seems likely that large scale removal of greenhouse gases from the atmosphere may be called for: so-called “negative emissions”.

One possibility is to use waste material from mining to trap CO₂ into new minerals, locking it out of the atmosphere. ̽��ֱ��idea is to exploit and accelerate the same geological processes that have regulated Earth’s climate and surface environment over the 4.5 billion years of its existence.

Across the world, deep and open-pit mining operations have left behind huge piles of worthless rubble – the “overburden” of rock or soil that once lay above the useful coal or metal ore. Often, this rubble is stored in dumps alongside tiny fragments of mining waste – the “tailings” or “fines” left over after processing the ore. ̽��ֱ��fine-grained waste is particularly reactive, chemically, since more surface is exposed.

A lot of energy is spent on extracting and crushing all this waste. However, breaking rocks into smaller pieces exposes more fresh surfaces, which can react with CO₂. In this sense, energy used in mining could itself be harvested and used to reduce atmospheric carbon.

This is one of the four themes of a new £8.6m research programme launched by the UK’s Natural Environment Research Council, which will investigate new ways to reverse emissions and remove greenhouse gases from the atmosphere.

Spoil tips from current and historic mining operations, such as this gold mine in Kazakhstan, could provide new ways to draw CO₂ from the atmosphere. Photo Credit: Ainur Seitkan, Earth Sciences, ̽��ֱ�� of Cambridge

̽��ֱ��process we want to speed up is the “carbonate-silicate cycle”, also known as the slow carbon cycle. Natural silicate rocks like granite and basalt, common at Earth’s surface, play a key part in regulating carbon in the atmosphere and oceans by removing CO₂ from the atmosphere and turning it into carbonate rocks like chalk and limestone.

Atmospheric CO₂ and water can react with the silicate rocks to dissolve elements they contain like calcium and magnesium into the water, which also soaks up the CO₂ as bicarbonate. This weak solution is the natural river water that flows to the oceans, which hold more than 60 times more carbon than the atmosphere. It is here, in the oceans, that the calcium and bicarbonate can recombine, over millions of years, and crystallise as calcite or chalk, often instigated by marine organisms as they build their shells.

Today, rivers deliver hundreds of millions of tonnes of carbon each year into the oceans, but this is still around 30 times less than the rate of carbon emission into the atmosphere due to fossil fuel burning. Given immense geological time scales, these processes would return atmospheric CO₂ to its normal steady state. But we don’t have time: the blip in CO₂ emissions from industrialisation easily unbalances nature’s best efforts.

̽��ֱ��natural process takes millions of years – but can we do it in decades? Scientists looking at accelerated mine waste dissolution will attempt to answer a number of pressing questions. ̽��ֱ��group at Cambridge which I lead will be investigating whether we can speed up the process of silicate minerals from pre-existing mine waste being dissolved into water. We may even be able to harness friendly microbes to enhance the reaction rates.

Another part of the same project, conducted by colleagues in Oxford, Southampton and Cardiff, will study how the calcium and magnesium released from the silicate mine waste can react back into minerals like calcite, to lock CO₂ back into solid minerals into the geological future.

Whether this can be done effectively without requiring further fossil fuel energy, and at a scale that is viable and effective, remains to be seen. But accelerating the reaction rates in mining wastes should help us move at least some way towards reaching our climate targets.

This article was originally published on ̽��ֱ��Conversation. Read the original article.

Could waste material from mining be used to trap CO₂emissions? A new £8.6 million research programme will investigate the possibilities. Simon Redfern (Department of Earth Sciences) explains, in this article from ̽��ֱ��Conversation.

Mundus Gregorius

Tagebau / Open cast mine

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

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High ozone levels in tropical Pacific caused by fires burning in Africa and Asia

sc604 — Wed, 13 Jan 2016 10:00:31 +0000

While efforts to limit emissions of greenhouse gases, including ozone, tend to focus on industrial activities and the burning of fossil fuels, a new study suggests that future regulations may need to address the burning of forests and vegetation. ̽��ֱ��study, published in the journal Nature Communications, indicates that ‘biomass burning’ may play a larger role in climate change than previously realised.

Based on observations from two aircraft missions, satellite data and a variety of models, an international research team showed that fires burning in tropical Africa and Southeast Asia caused pockets of high ozone and low water in the lower atmosphere above Guam – a remote island in the Pacific Ocean 1,700 miles east of Taiwan.

“We were very surprised to find high concentrations of ozone and chemicals that we know are only emitted by fires in the air around Guam,” said the study’s lead author Daniel Anderson, a graduate student at the ̽��ֱ�� of Maryland. “We didn’t make specific flights to target high-ozone areas – they were so omnipresent that no matter where we flew, we found them.”

For the study, two research planes on complementary missions flew over Guam measuring the levels of dozens of chemicals in the atmosphere in January and February 2014. One aircraft flew up to 24,000 feet above the ocean surface during the UK Natural Environment Research Council’s Coordinated Airborne Studies in the Tropics (CAST) mission. ̽��ֱ��other flew up to 48,000 feet above the ocean surface during the CONvective Transport of Active Species in the Tropics (CONTRAST) mission.

“International collaboration is essential for studying global environmental issues these days,” said CAST Principal Investigator Neil Harris, of Cambridge’s Department of Chemistry. “This US/UK-led campaign over the western Pacific was the first of its kind in this region and collected a unique data set. ̽��ֱ��measurements are now starting to produce insight into how the composition of the remote tropical atmosphere is affected by human activities occurring nearly halfway around the world.”

Researchers examined 17 CAST and 11 CONTRAST flights and compiled over 3,000 samples from high-ozone, low-water air parcels for the study. In the samples, the team detected high concentrations of chemicals associated with biomass burning—hydrogen cyanide, acetonitrile, benzene and ethyne.

“Hydrogen cyanide and acetonitrile were the smoking guns because they are emitted almost exclusively by biomass burning. High levels of the other chemicals simply added further weight to the findings,” said study co-author Julie Nicely, a graduate student from the ̽��ֱ�� of Maryland.

Next, the researchers traced the polluted air parcels backward 10 days, using the National Oceanic and Atmospheric Administration (NOAA) Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model and precipitation data, to determine where they came from. Overlaying fire data from NASA’s moderate resolution imaging spectroradiometer (MODIS) on board the Terra satellite, the researchers connected nearly all of the high-ozone, low-water structures to tropical regions with active biomass burning in tropical Africa and Southeast Asia.

“ ̽��ֱ��investigation utilised a variety of models, including the NCAR CAM-Chem model to forecast and later analyse chemical and dynamical conditions near Guam, as well as satellite data from numerous instruments that augmented the interpretation of the aircraft observations,” said study co-author Douglas Kinnison, a project scientist at the ̽��ֱ�� Corporation for Atmospheric Research.

In the paper, the researchers also offer a new explanation for the dry nature of the polluted air parcels.

“Our results challenge the explanation atmospheric scientists commonly offer for pockets of high ozone and low water: that these zones result from the air having descended from the stratosphere where air is colder and dryer than elsewhere,” said ̽��ֱ�� of Maryland Professor Ross Salawitch, the study’s senior author and principal investigator of CONTRAST.

“We know that the polluted air did not mix with air in the stratosphere to dry out because we found combined elevated levels of carbon monoxide, nitric oxide and ozone in our air samples, but air in the higher stratosphere does not contain much naturally occurring carbon monoxide,” said Anderson.

̽��ֱ��researchers found that the polluted air that reached Guam never entered the stratosphere and instead simply dried out during its descent within the lower atmosphere. While textbooks show air moving upward in the tropics, according to Salawitch, this represents the net motion of air. Because this upward motion happens mostly within small storm systems, it must be balanced by air slowly descending, such as with these polluted parcels released from fires.

Based on the results of this study, global climate models may need to be reassessed to include and correctly represent the impacts of biomass burning, deforestation and reforestation, according to Salawitch. Also, future studies such as NASA’s upcoming Atmospheric Tomography Mission will add to the data collected by CAST and CONTRAST to help obtain a clearer picture of our changing environment.

In addition to those mentioned above, the study’s authors included UMD Department of Atmospheric and Oceanic Science Professor Russell Dickerson and Assistant Research Professor Timothy Canty; CAST co-principal investigator James Lee of the ̽��ֱ�� of York; CONTRAST co-principal investigator Elliott Atlas of the ̽��ֱ�� of Miami; and additional researchers from NASA; NOAA; the ̽��ֱ�� of California, Irvine; the California Institute of Technology; the ̽��ֱ�� of Manchester; the Institute of Physical Chemistry Rocasolano; and the National Research Council in Argentina.

This research was supported by the Natural Environment Research Council, National Science Foundation, NASA, and National Oceanic and Atmospheric Administration.

Reference:
Daniel C. Anderson et al. ‘A pervasive role for biomass burning in tropical high ozone/low water structures’ Nature Communications (2016). DOI: 10.1038/ncomms10267.

Inset image: Air Tracking. Credit: Daniel Anderson

Adapted from a ̽��ֱ�� of Maryland press release.

Study indicates ‘biomass burning’ may play a larger role in climate change than previously realised.

̽��ֱ��measurements are now starting to produce insight into how the composition of the remote tropical atmosphere is affected by human activities occurring nearly halfway around the world.

Neil Harris

Loretta Kuo/Shawn Honomichl

CONTRAST and CAST Mission Planes

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

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