Nitrogen fertilisers, manure and other agricultural sources drove almost three-quarters of human-caused nitrous oxide emissions in recent years.
That is according to the Global Carbon Project’s second “global nitrogen budget” – an assessment of the origins and climate impacts of the world’s nitrous oxide emissions.
The research, published in Earth System Science Data, finds that nitrous oxide emissions from human activities rose by 40% over the past four decades, partly driven by growing global demand for meat and dairy.
Nitrous oxide emissions over the past decade exceeded even the highest projected levels in emissions pathways, the research finds.
Continuing to emit the greenhouse gas at current rates would “really affect” the world’s ability to achieve the long-term goal of the Paris Agreement to limit global warming to “well below” 2C, the lead author of the study tells Carbon Brief.
One expert, who was not involved in the research, says the findings show “all too clearly” that nitrous oxide emissions “are still going rapidly in the wrong direction”.
Potent greenhouse gas
Nitrous oxide (N2O) is a long-lasting greenhouse gas that is around 270 times more potent than CO2. It is the third-largest contributor to climate change, after CO2 and methane.
Various natural sources generate nitrous oxide, including tiny organisms in the world’s oceans and soils. These natural emitters accounted for 65% of all nitrous oxide emissions over 2010-19.
Human activities caused the remaining 35% of emissions, particularly nitrogen fertiliser use and manure management in agriculture. The burning of fossil fuels and biomass also produce nitrous oxide, but to a lesser extent.
The new study assesses both natural and human-caused sources of nitrous oxide to see how they have changed over time and how they are contributing to climate change.
It divides the sources and sinks into 21 categories, such as direct emissions from nitrogen use in agriculture and the exchange of CO2 between the land and atmosphere .
The researchers use a range of satellite data, models, algorithms and inventories to assess emissions over time.
The study finds that human-caused nitrous oxide emissions “significantly increased” from 1980 to 2020, growing by 40% during this time period. This rise was spurred on, in part, by growing demand for meat and dairy.
This is a jump of 10% in these human-caused emissions from the last nitrous oxide assessment, which covered data over 1980-2016.
However, the new study includes more categories than the previous global assessment, including emissions from microbe activity in the shallow waters over continental shelves. The researchers in the study say this explains some of the higher estimates in the new report.
Concentrations of the greenhouse gas in the atmosphere have also risen faster in the past three years than any other time since 1980.
Prof Hanqin Tian is the lead author of the study and an environmental sciences professor at Boston College. He tells Carbon Brief that nitrous oxide emissions continuing at current rates would “really affect the Paris climate agreement” goals.
Natural nitrous oxide emissions, on the other hand, were “relatively stable” over the period covered by the research. Tian explains:
“In terms of the total number, natural emissions are very high. But over long time periods, they stay stable. So natural emissions do not really contribute to climate change from pre-industrial times to now.”
Human-caused emissions have increased significantly. The below infographic outlines the changes in different nitrous oxide emissions sources from 2010 to 2019.
Prof Dave Reay, the chair in carbon management and education at the University of Edinburgh, who was not involved in the study, says that the research is “really significant” for both scientists and policymakers. He tells Carbon Brief:
“Nitrous oxide’s importance can sometimes be obscured by the larger climate forcing effects of CO2 and methane, yet every missed opportunity to cut nitrous oxide emissions drags the world still further away from achieving the Paris climate goals.”
The researchers highlight that human-caused nitrous oxide emissions need to be cut by at least one-fifth by 2050 to help limit long-term warming to 2C, according to the Intergovernmental Panel on Climate Change (IPCC).
Reay says this study shows “all too clearly” that these emissions are “still going rapidly in the wrong direction”.
Agricultural emissions
Agriculture was the “major driver” of increased human-caused nitrous oxide emissions over the past four decades, the study says. In total, the researchers find that the sector was responsible for 74% of these emissions over 2010-19.
While agricultural emissions increased over time, other human-caused nitrous oxide emissions from fossil fuels and industry decreased slightly between 1980 and 2020.
Cutting nitrogen use in agriculture is a “quite complex issue related to food production, food security” and a range of other issues, Tian says.
Requirements to cut nitrous oxide emissions, particularly from livestock, have been a major political issue in the Netherlands and other countries. Nitrous oxide emissions are “expected to continue rising” over the next few decades due to the growing demand for food, the study says.
Reay says that reducing nitrogen use in agriculture “can yield benefits not just for climate change mitigation, but for food production, air and water quality and biodiversity, too”. He adds:
“The array of strategies to address these losses – primarily through improving so-called nitrogen use efficiency across our food systems – are already showing positive results in some areas of Europe and south-east Asia.”
An excess of nitrogen used on the land can wash into lakes, rivers and oceans. This run-off causes damage to plants, animals and humans and spurs on toxic algae. Nitrous oxide also contributes to depletion of the ozone layer.
Top-emitting countries
The study also examines emissions in 18 different regions, finding that they grew in some countries and decreased in others over the past four decades.
China, India, the US, Brazil and Russia were the five biggest nitrous oxide emitters in 2020, the study findings show.
Human-caused emissions increased by 157% in India, 135% in China and 131% in Brazil over 1980-2020.
China alone made up 40% of the overall increase in global human-caused nitrous oxide emissions between 1980 and 2020.
Although the country remains the biggest emitter, China’s nitrous oxide emissions have decreased in recent years as a result of efforts to use nitrogen fertilisers more efficiently, Tian says.
Nitrous oxide emissions have reduced in several parts of the world since 1980: Europe, Russia, Australia, New Zealand, Japan and Korea.
Europe – the biggest nitrous oxide emitter in 1980 – has seen the most significant drop in the four decades since. Emissions fell by one-third (31%) during this time, largely due to fossil fuel and industry emissions cuts in the 1990s.
Agriculture-related nitrous oxide emissions also decreased in Europe during this time, but the drop has levelled off since the 2000s, the study notes.
Exceeding future projections
The scientists also explore how current nitrous oxide emissions compare with those from scenarios of future projections of climate change.
The charts below show how global nitrous oxide concentrations in the atmosphere (black line) compare with projections under the “Representative Concentration Pathways” (RCPs, left) and the “Shared Socioeconomic Pathways” (SSPs, right).
The charts highlight that atmospheric concentrations of the greenhouse gas over the past decade have exceeded even the projections under the very-high-emissions trajectory, RCP8.5 (red dashed line).
The researchers outline some “major uncertainties” with their findings and the scientific understanding of where nitrous oxide comes from.
These include the understanding of emissions from soils in tropical ecosystems in the Amazon Basin, the Congo Basin and south-east Asia, alongside areas using high levels of fertilisers, such as the US “corn belt”.
The study also mentions uncertainties around estimates for the impact of deforestation on nitrous oxide emissions.
The researchers propose setting up a global network to better monitor and model nitrous oxide emissions. Reay says that this is a “very timely suggestion”, adding:
“With all nations needing to submit their updated national plans for climate action in the run up to COP30 in Brazil next year, better measurement of nitrous oxide emissions holds the promise of better reporting and, crucially, better efforts to cut them.”
The post Agriculture ‘major driver’ of rise in nitrous oxide emissions over past 40 years appeared first on Carbon Brief.
Agriculture ‘major driver’ of rise in nitrous oxide emissions over past 40 years
Claver Gatete is Executive Secretary of the UN Economic Commission for Africa. Jason Veysey is Energy Modeling Program Director and Senior Scientist at the Stockholm Environment Institute. Lisa Sachs is Director of the Columbia Center on Sustainable Investment at Columbia University.
The case for global energy transition has rarely been clearer. The closure of the Strait of Hormuz earlier this year exposed the cost of unplanned, fossil-dependent systems, while the falling cost of renewables, the rising penetration of electric vehicles, and the growing value of demand flexibility have made the direction of travel obvious. The benefits of a clean, secure, integrated system are no longer in dispute. What remains unclear is how to build it.
Countries around the world have called for faster renewable energy deployment and alternative energy arrangements. A secure, affordable, resilient, decarbonised system requires specific investments in specific places in a specific sequence, optimised across sectors and borders. But very few governments have the analytical foundation to translate those imperatives into investment.
The two instruments that are supposed to determine investment priorities for decarbonisation – Nationally Determined Contributions (NDCs) and country platforms – cannot answer the most basic question facing any country undertaking an energy transition: what should the energy system look like?
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To close this gap, every country needs a bankable, economy-wide optimisation model for its energy system. A model is not a plan, but it can help answer the critical question of what the future energy system should look like. It shows how optimal scenarios vary as assumptions and policies are adjusted, calculates investment requirements and sequencing, and quantifies how system costs are affected by assumptions, policies, and exogenous variables like trade policy and financing terms.
Tool for efficient investment
Optimisation is a simplified way of simulating an energy system, but it can be an extremely powerful tool for moving energy planning from reactive (how do we manage the disparate actions in the energy system?) to intentional (what energy system underpins our national objectives?). A model can show how optimal scenarios vary as assumptions and policies are adjusted, and how investment requirements are quantified and sequenced.
Optimisation models can treat the energy system and the sectors it serves as an integrated whole, optimising across sectors and projects in ways that can be mutually reinforcing. If considered independently, growth in industrial demand, transport electrification, and digital infrastructure can add stress to the energy system. But an optimised plan can arrange these and other changes in an efficient, synergistic way.
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New load can be added where low-cost power is available; industrial customers can ensure the viability of investments in energy supply; electric vehicle charging policy can smooth load curves and reduce costs for all consumers.
Additionally, optimisation modeling can also change the financeability of investments. Taken alone, each project faces uncertainty about the rest of the system, which raises the cost of capital and causes projects to stall or unwind after contracts are signed. A coherent, optimised plan makes visible the coordination that private capital would otherwise have to bet on: identified offtake, sequenced and committed transmission, contracted power supply, and so on.
What COP31 and COP32 should do
The upcoming COPs in Turkey and Ethiopia can shift the center of gravity of international climate cooperation from fragmented commitments to planning. Three moves are urgently needed.
First, optimised, economy-wide, long-term energy system planning must be the foundation on which any meaningful NDC, country platform, or finance commitment rests. NDCs are typically drafted by environment or single-line ministries, with limited cross-sectoral input from ministries of energy, finance, and planning. They contain targets, derived from sectoral strategies or national commitments, not from an analytically grounded picture of what the energy system should look like and what investments would make it work. Country platforms are generally a portfolio of investments assembled from existing project pipelines, rather than derived from a system-level analysis of what an optimised, decarbonised energy system would require.
Second, recognise regions as a key planning unit. Modern integrated energy systems are inherently regional. Renewable endowments are unevenly distributed; balancing variable supply across borders lowers aggregate cost, reduces redundant backup capacity, and unlocks economies of scale no individual nation can achieve. Many energy investments in Southeast Asia, East Africa, Southern Africa and Central Asia may only be financeable in a regional context. Assessing domestic infrastructure without regional optimisation perpetuates the perception that decarbonisation is more expensive than it is.
COP31 leaders unveil global targets, with spotlight on electrification
Third, finance the planning capacity. A coordinated commitment by multilateral development banks, bilateral donors, and philanthropic partners to help every region and its constituent countries develop and maintain their own modelling capability, with open-source tools and regional analytical hubs, would close the most consequential gap in the current architecture. The cost is small relative to current spending on country platforms, failed project preparation, and misallocated infrastructure investment.
This includes supporting regional institutions such as the ASEAN Centre for Energy, the African Energy Commission, regional power pools, and the Latin American and Caribbean Energy Organization to determine what optimised regional systems require. Country-by-country pledging, repeated at every COP, will not deliver what meaningfully integrated systems can.
The 2026 energy crisis made the cost of unplanned, fossil-dependent systems newly visible. That window of clarity will close. The international community should seize the moment to build the planning foundation that has been missing for thirty years, rather than commissioning another round of NDCs or pledges, striving for outcomes neither was designed to deliver.
The post Every country needs a model to help optimise its energy transition appeared first on Climate Home News.
Every country needs a model to help optimise its energy transition
The world is currently experiencing what is expected to become the strongest El Niño on record – dubbed a “super El Niño” by many.
El Niño is the warm phase of a recurring climate pattern in the tropical Pacific that releases heat from the ocean into the atmosphere.
This temporarily raises global temperatures and reshapes rainfall and extreme weather around the world – impacting the lives of billions of people.
The current El Niño event began in June and is expected to last into 2027.
El Niño is part of a wider climate pattern called the El Niño-Southern Oscillation (ENSO) cycle.
The ENSO cycle also has a cool phase, known as La Niña, as well as a “neutral” phase. El Niño and La Niña events typically last between nine and 12 months, but can go on longer.
Below, Carbon Brief explains how the ENSO cycle works, its impacts on extreme weather and global temperatures and why this El Niño event is projected to be the most intense since records began.
The post Explainer: How the ‘super El Niño’ will reshape the world’s weather appeared first on Carbon Brief.
https://interactive.carbonbrief.org/el-nino-explainer/index.html
The second-largest reservoir in the US reached a record-low water height on Saturday – just days after the country’s largest reservoir broke its own record.
Both Lake Mead and Lake Powell are located on the Colorado River.
They provide water for populations across seven US states in the south-western US, with around 40 million people getting some or all of their municipal water from the Colorado River.
The river also provides water for around 5.5m acres (22,258 square kilometres) of farmland across Colorado, Arizona, California and the other states in the river basin.
Experts tell Carbon Brief that climate change, population growth and over-consumption are all contributing to the current record-low levels of the reservoirs.
Record lows
At full capacity, Lakes Mead and Powell can hold a combined 68 cubic kilometres of water – enough to supply all household consumption in the contiguous US for nearly 1.5 years. However, the water level in both reservoirs has been declining for decades.
The chart below shows the water level of Lake Mead, in metres above mean sea level. The reservoir, which began to fill in 1935 following the construction of the Hoover Dam, has a “full pool” maximum capacity of 347.60 metres. The water level in Lake Mead reached a record low of 317.11 metres on 7 August.
The following chart shows the water level of Lake Powell, in metres above mean sea level. Lake Powell’s full-pool level is 1,127.76 metres.
While the reservoir reached its maximum capacity several times in the 1980s, it has not done so since. On 15 August, the water level in Lake Powell was recorded at a new record-low of 1,072.87 metres.
Both reservoirs have continued to decline in the days since breaking their respective records. The downward trend will largely continue in both lakes until next spring, when the snowpack in the mountains of the Upper Colorado River Basin begins to melt, says Dr Jack Schmidt, a senior research scientist at Utah State University’s Center for Colorado River Studies. He tells Carbon Brief:
“The big dilemma of the moment is that we’re only in the middle of August, and we have no assurance of what the coming winter will be. The only thing we can be sure of is that we will be depleting overall total basin reservoir storage from now until, roughly, early April.”
Compounding factors
The record lows across the two reservoirs are the result of several compounding factors, experts tell Carbon Brief.
Since the turn of the 20th century, the amount of water flowing along the Upper Colorado River has declined by about 20%. Research suggests that half of this decline can be attributed to human-induced climate change.
Most of the river’s streamflow comes from the snowpack of the Upper Colorado River Basin, which stretches across five western US states but is primarily located in Colorado and Utah.
This region has been gripped by a historic “megadrought” for more than a quarter of a century. Nearly half of the megadrought’s intensity over 2000-18 is attributable to climate change, according to a 2020 study.
At the same time, the increasing population in the US south-west has put added pressure on the Colorado River’s water supply. The number of people obtaining some or all of their water from the Colorado system has grown by 15 million (around 60%) since 1992.
Schmidt tells Carbon Brief:
“There’s an ultimate cause of the present water crisis, and there’s a proximate cause. The ultimate cause is a warming climate, a warming planet and a pretty clear correlation between warming conditions and decreased runoff in the Colorado River Basin.
“The proximate cause is that in this messy democratic republic of ours, big policy decisions that match the variability of the climate occur painfully slowly – with intense political negotiations – and only incrementally.”
On 31 July, the US Bureau of Reclamation, which manages water resources in the western US, released an environmental impact statement on its proposed post-2026 strategy for managing Lakes Powell and Mead. The strategy itself has not been released yet.
Schmidt notes that the statement does appear to give the Bureau flexibility to “respond to crisis” by reducing the delivery of water to several states. However, he adds:
“They acknowledge it won’t work if we just stay critically dry, and of course every climate model for the 21st century, especially with a continually warming planet, says that that’s exactly what’s going to happen.”
The post Analysis: The two largest reservoirs in the US have hit record-low levels appeared first on Carbon Brief.
Analysis: The two largest reservoirs in the US have hit record-low levels
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