Hexbyte Glen Cove Limiting fossil fuel extraction to keep global warming below 1.5° C target thumbnail

Hexbyte Glen Cove Limiting fossil fuel extraction to keep global warming below 1.5° C target

Hexbyte Glen Cove

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Nearly 60% of both oil and fossil methane gas and almost 90% of coal must remain in the ground by 2050 in order to keep global warming below 1.5° C, finds a study by UCL researchers.

Global oil and gas production must decline by 3% annually until 2050 in order to reach this target. Many fossil fuel extraction projects, both planned and operational, are not conducive to meeting internationally agreed target limits on global warming, as set out by the Paris Climate Agreement in 2015. A significant number of regions have therefore already reached peak fossil fuel production, and any increase in production from one region must be offset by a greater production decline elsewhere.

The findings, published in Nature, are based on a 50% probability of limiting warming to 1.5° C this century, meaning that increasing the likelihood of reaching this target would require an even more rapid decline in production and more fossil fuels left in the ground.

The researchers used a global energy system model to assess the amount of fossil fuels that would need to be left unextracted regionally and globally.

The required unextracted reserves are estimated as the percentage of the 2018 reserve base. This needs to be 58% for oil, 59% for fossil methane gas and 89% for coal by 2050.

Lead author Dan Welsby (UCL Institute for Sustainable Resources) says that “in 2015, 196 parties signed the Paris Climate Agreement, aiming to keep average global temperature rise to well-below 2° C, with 1.5° C the desired target. Since then, the IPCC Special Report on 1.5° C, successive Production Gap Reports and the IEA Net Zero Report have indicated beyond doubt that dramatic cuts in fossil fuel production are required immediately in order to move towards net zero emissions, and that current and indicated fossil fuel production trajectories are moving us in the wrong direction.

“Our new paper adds further weight to recent research, indicating that global oil and fossil methane gas production has already peaked. From a regional perspective, our results suggest significant transition risk for large fossil fuel producers. Oil production in the Middle East for example roughly halves between 2020 and 2050, suggesting the diversification of economies away from a dependence on hydrocarbon revenues is absolutely critical.”

The work builds on previous research in 2015, which found that in order to limit warming to 2° C, a third of oil reserves, nearly half of fossil methane gas (49%) reserves and over 80% of coal reserves should remain in the ground.

The researchers used the TIMES Integrated Assessment Model at UCL (TIAM-UCL). The model captures primary energy sources—oil, fossil methane gas, coal, nuclear, biomass and renewables—from production through to conversion (e.g. electricity, hydrogen and biofuel production or oil refining), and distribution to meet a set of demands in each end-use sector.

Countries of the world are represented as 16 regions, which allows for a detailed characterization of regional energy sectors. The model assessed different scenarios including lower demands in key carbon intensive sectors (aviation and chemicals) and uncertainty around the availability and deployment of key carbon capture, utilization and storage (CCUS) and negative emissions technologies (NETs).

In terms of the regional distribution of unextractable fossil fuel reserves, the researchers found that the Middle East must leave around 60% of oil and gas reserves in the ground, which given the large size of its reserve base also results in huge absolute volumes. Additionally, regions with high concentrations of relatively high cost and high carbon intensive deposits of oil within the reserve base show high proportions of unextractable reserves including the oil sands in Canada (83%) and ultra-heavy oil in Central and South America (73%). The regional differences in the proportion of fossil fuels which must remain unextracted is down to a combination of factors including extraction costs, the carbon intensity of production and the costs of alternative technologies to fossil fuels.

Mr. Welsby continued, “We stress that our estimates of unextractable reserves and production decline rates are likely underestimates, given we use a budget consistent with only a 50% chance of meeting 1.5° C and the huge uncertainty around the deployment of negative emission technologies. However, assuming the political will is present to fulfill the commitments made in Paris, the reductions in suggested in our work are entirely feasible.”



More information:
Dan Welsby et al, Unextractable fossil fuels in a 1.5° C world, Nature (2021). DOI: 10.1038/s41586-021-03821-8

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Hexbyte Glen Cove Dead zones formed repeatedly in North Pacific during warm climates, study finds thumbnail

Hexbyte Glen Cove Dead zones formed repeatedly in North Pacific during warm climates, study finds

Hexbyte Glen Cove

Sediment cores from the Bering Sea hold a record of past low-oxygen events in the form of layered or “laminated” sediments. Credit: IODP

An analysis of sediment cores from the Bering Sea has revealed a recurring relationship between warmer climates and abrupt episodes of low-oxygen “dead zones” in the subarctic North Pacific Ocean over the past 1.2 million years.

The new study, led by researchers at UC Santa Cruz, was published June 2 in Science Advances. The findings provide crucial information for understanding the causes of low oxygen or “hypoxia” in the North Pacific and for predicting the occurrence of hypoxic conditions in the future.

“It is essential to understand whether is pushing the oceans toward a ‘tipping point’ for abrupt and severe hypoxia that would destroy ecosystems, food sources, and economies,” said first author Karla Knudson, who led the study as a graduate student in Earth sciences at UCSC.

The researchers based their findings on an analysis of deep sediment cores from a site in the Bering Sea. Over long periods of time, sediments are deposited and build up on the seafloor. The activity of organisms living in the seafloor sediments usually disrupts and mixes them as they accumulate, but if hypoxia has killed those organisms, an orderly pattern of layers is preserved. Thus, scientists can find a record of past hypoxic events in the form of these layered or “laminated” sediments in cores drilled from the seafloor.

Scientists have long known about a major episode of widespread hypoxia in the North Pacific at the end of the last ice age, when the melting of the ice sheets sent a massive influx of fresh water into the . The new study provides the first records of earlier low-oxygen events, and shows that the most recent occurrence was not representative of most of these events in terms of mechanisms or timing.

“It doesn’t take a huge perturbation like melting ice sheets for this to happen,” said corresponding author Ana Christina Ravelo, professor of ocean sciences at UC Santa Cruz. “These abrupt hypoxic events are actually common in the geologic record, and they are not typically associated with deglaciation. They almost always happen during the warm interglacial periods, like the one we’re in now.”

The hypoxia occurs after intense growth of phytoplankton (marine algae) in the surface waters. When the phytoplankton die, they sink deeper into the ocean and decompose, which depletes the oxygen and releases carbon dioxide into the water below the surface. What triggers these events, however, remains unclear. Ocean warming, high sea levels, and the availability of iron (a limiting factor for growth of phytoplankton) all seem to play a role.

Crew members abroad the research vessel JOIDES Resolution drilled sediment cores from the seafloor in the Bering Sea during a 2009 IODP expedition on which UCSC ocean scientist Christina Ravelo was co-chief scientist. Credit: Carlos Alvarez Zarikian, IODP/TAMU

“Our study shows that high sea levels, which occur during warm interglacial climates, contributed to these hypoxic events,” Knudson said. “During high sea levels, dissolved iron from the flooded can be transferred to the open ocean and promote intense phytoplankton growth in the surface waters.”

Although high sea level is an important background condition, it is not enough to trigger a hypoxic event by itself. Changes in ocean circulation, including intensified upwelling to bring more nutrients into the surface waters and stronger currents that could transfer iron from the continental shelf to the open ocean, may play a critical role, Knudson said.

Currently, regional dead zones occur in coastal areas around the world due to the temperature effects of climate warming, as well as nutrient enrichment of coastal waters from agricultural fertilizers. But even the massive dead zone at the mouth of the Mississippi River pales in comparison to the widespread hypoxia that occurred all across the North Pacific Ocean at the end of the last ice age.

Because the new study is based on sediment cores from a single site, the researchers do not know the extent of the it records—whether they were confined to the Bering Sea or extended across the North Pacific rim as the most recent event did.

“We don’t know how extensive they were, but we do know they were very intense and lasted longer than the deglaciation event that has been so well studied,” said Ravelo, who was co-chief scientist of Integrated Ocean Drilling Program Expedition 323, which recovered the Bering Sea cores in 2009.

Knudson said the cores record multiple events during each interglacial period throughout the Pleistocene, with abrupt transitions where laminated sediments appear and disappear in the core.

The new findings raise concerns about whether climate change and ocean warming will lead to a tipping point that would trigger widespread hypoxia in the North Pacific Ocean.

“The system is primed for this type of event happening,” Ravelo said. “We need to know how extensive they were, and we need to rethink how these events are triggered, because we now know that it doesn’t take a huge perturbation. This study sets the stage for a lot of follow-up work.”



More information:
“Causes and timing of recurring subarctic Pacific hypoxia” Science Advances (2021). DOI: 10.1126/sciadv.abg2906

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Dead zones formed repeatedly in North Pacific during warm climates, study finds (2021, June 2)
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