The algorithm was developed in support of NASA’s Polarized Submillimeter Ice-cloud Radiometer, or PolSIR, and the NASA–Japan Aerospace Exploration Agency Precipitation Measuring Mission. Submillimeter wavelengths occupy a particularly sensitive region for measuring ice clouds. Their frequencies interact strongly with ice particles, including scattering by particles whose dimensions are comparable to the observing wavelength, while penetrating more deeply than visible or infrared radiation.

The authors describe this combination as important for bridging gaps in cloud and precipitation remote sensing. Previous validation has involved instruments including CoSSIR and the International Submillimetre Airborne Radiometer, while spaceborne demonstrations include NASA’s IceCube, launched in 2017, and the European Space Agency’s Arctic Weather Satellite, launched in August 2024. PolSIR and the C2OMODO instrument planned for the Precipitation Measuring Mission represent further opportunities to observe ice clouds globally.

The central obstacle is that established database-driven retrieval methods depend on finding simulated atmospheric and cloud profiles whose brightness temperatures fall within measurement uncertainty of an observation. BMCI assigns Bayesian weights to matching database cases and integrates them to estimate cloud properties and uncertainty. It is computationally efficient and can accommodate a prior probability distribution that is not Gaussian, but it can fail when a multidimensional measurement space is sparsely represented.

Enlarging the database improves coverage but cannot eliminate this limitation. The hybrid method therefore uses BMCI for most cases and activates an optimal-estimation optimization when fewer than 25 sufficiently close cases are available. In the reported implementation, the assumed noise-equivalent differential temperature is first inflated in increments of two until the minimum number of matches is found; the resulting BMCI estimate then initializes the optimal-estimation search, which explores beyond the fixed database under broadly consistent prior constraints.

Applying the Optimal Estimation Method directly to ice-cloud variables would normally be difficult because the atmospheric and cloud parameters have strongly non-Gaussian distributions. The researchers address this with cumulative distribution functions and empirical orthogonal functions. Rank-based cumulative distribution functions transform the original variables into approximately Gaussian coordinates, while empirical orthogonal functions capture correlations between quantities and atmospheric levels and reduce the dimension of the optimization problem.

The optimal-estimation iteration begins with the BMCI solution, and a Levenberg–Marquardt procedure updates the state using numerically calculated sensitivities because the radiative transfer model has no analytical Jacobian. The resulting covariance is propagated back into physical variables, allowing uncertainty estimates for vertical profiles and column quantities. The approach therefore retains the nonparametric strengths of the database while adding a flexible optimization stage for poorly represented observations.

The mission-oriented retrieval database contains about 1.5 million atmospheric and cloud profiles assembled from CloudSat and CALIPSO products, with one orbit selected every three days from 2007 between 30 degrees south and 30 degrees north. Ice water content profiles come from the 2C-ICE product, which uses CloudSat radar and CALIPSO lidar observations; liquid water content profiles come from the radar-only 2B-CWC-RO product. The atmospheric and cloud profiles have a vertical resolution of 240 metres, while thermodynamic profiles and surface parameters are supplied separately by an auxiliary ECMWF dataset.

The forward model uses the ARTS radiative transfer solver and represents ice with five candidate particle habits: LargePlateAggregate, LargeBlockAggregate, LargeColumnAggregate, 6BulletRosette and EvansSnowAggregate. Liquid droplets are spherical, particle orientation is random, and the simulations currently include only the first Stokes component. Because both ice and liquid particle-size distributions use one-moment schemes, retrieved water contents can be mapped directly to characteristic particle sizes.

The same framework can be rebuilt for other regions, as the authors did for wintertime clouds around the East Coast of the United States. Ice water path was tracked closely down to roughly 30 grams per square metre, below which thin-cloud retrievals developed negative biases. Particle size was well constrained for mean mass diameters above approximately 400 micrometres but tended to be underestimated for smaller particles.

About 7% of test profiles triggered the optimal-estimation stage because BMCI could not find enough close database matches. Adding that stage reduced many chi-squared brightness-temperature mismatch values from above 100 to below 10 and produced moderate but consistent gains in ice water path and particle-size accuracy. These simulations used the same forward model and particle-habit assumptions to generate the observations and perform the retrievals, and all results assumed nadir viewing even though both target radiometers scan across track.

Diagnostics showed that the radiometer’s information is intrinsically limited. Averaging kernels indicated a median vertical resolution of roughly 2–3 kilometres for ice and liquid clouds and about 4 kilometres for water vapour. The effective number of independent pieces of information generally rose with ice water path and atmospheric moisture, reaching about 5–7 for appreciable ice clouds, but fell to 4–5 for the thickest clouds as information became saturated.

Shannon information analysis attributed approximately four additional bits to the 325 GHz channels when ice water path information from the 183 GHz channels was already present. The 89 GHz channel contributed relatively little to ice-water retrieval but supplied substantial information about liquid water and integrated water vapour, demonstrating the value of combining frequency bands rather than relying on a single spectral region. The information analysis also found that the 325 GHz channel closest to the water-vapour absorption line provided the largest incremental contribution among the 325 GHz channels.

The field evaluation used dual-polarized CoSSIR observations collected during the 2022–2023 phase of NASA’s IMPACTS campaign over winter storms along the East Coast. CoSSIR carried four subchannels near 183 GHz, three near 325 GHz and one at 684 GHz, while the W-, Ka- and Ku-band CRS and HIWRAP radars on the same aircraft provided collocated triple-frequency measurements used as a reference. In a representative scene on 15 January 2023, BMCI-only profiles overextended the observed cloud at its top and bottom and generated spurious ice in nearly clear air on either side.

The hybrid method assigned those clouds to more plausible altitudes, reduced their geometric thickness, improved the representation of the cloud core and closely reproduced most observed brightness temperatures after the optimisation stage. Radar simulations generally agreed with measured reflectivities within about 4 decibels, although some biases remained in very thick and melting-layer regions. A broader evaluation covering four deep cloud scenes confirmed that the choice of ice-particle habit strongly affected performance.

LargePlateAggregate, LargeBlockAggregate and 6BulletRosette produced the most consistent brightness-temperature agreement, while LargeColumnAggregate and EvansSnowAggregate generally left larger mismatches. Averaging the median absolute logarithmic differences for those three better-performing habits, the hybrid CoSSIR retrievals differed from triple-frequency radar estimates by 3.75 decibels for layer-resolved ice water content, 0.82 decibels for layer-resolved particle size, 2.53 decibels for ice water path and 0.55 decibels for mean mass diameter. Relative to BMCI alone, the respective reductions were 0.21, 0.02, 0.85 and 0.13 decibels.

These are moderate improvements rather than a transformation of retrieval accuracy: radiometer-derived layer values still varied by nearly an order of magnitude around radar estimates, reflecting the limited information in brightness-temperature observations and the continuing influence of the prior distribution. Several constraints remain before the algorithm can be applied routinely to the planned missions. The radiative transfer simulations use a pencil-beam approximation and do not yet account for instrument beam width, footprint size or beam-filling effects at large scanning angles, even though both PolSIR and C2OMODO scan away from nadir.

The model also assumes randomly oriented particles and omits the additional Stokes components needed for polarized observations; preferential horizontal alignment could therefore introduce errors even in the unpolarized component. Numerical Jacobian calculations add computational expense, and the authors identify faster methods as a subject of continuing work. The study nevertheless demonstrates that the hybrid Bayesian framework can be extended to different sensors: radar reflectivities replaced brightness temperatures in the measurement vector, allowing the same retrieval machinery to process triple-frequency radar data.

The authors say that multi-sensor combinations and eventually hyperspectral measurements could provide additional information for constraining cloud microphysical properties, while future instrument-level simulations and faster Jacobian methods remain necessary for operational applications.

Subject of Research: Hybrid Bayesian retrieval of ice-cloud microphysics from submillimeter-wave radiometers

Article Title: A hybrid ice hydrometeor retrieval algorithm for submillimeter-wave radiometers in support of the PolSIR and PMM missions

Article References: Liu, Y., Gong, J., Adams, I. S., Kroodsma, R. A., Chen, R., Wu, D. L., Bennartz, R., & Braun, S. A. (2026). A hybrid ice hydrometeor retrieval algorithm for submillimeter-wave radiometers in support of the PolSIR and PMM missions. Atmospheric Measurement Techniques, 19(20), 6661-6679. https://doi.org/10.5194/amt-19-6661-2026

Image Credits: AI Generated

DOI: 10.5194/amt-19-6661-2026

Keywords: submillimeter radiometry, ice-cloud microphysics, Bayesian retrieval, brightness temperature, satellite missions, particle-size retrieval, PolSIR, Precipitation Measuring Mission, IMPACTS campaign, triple-frequency radar, hydrometeors, remote sensing

The investigation, reported in Aerosol Research, combined extensive configuration sampling, density functional theory and a machine-learning model to examine clusters containing sulfuric acid, methanesulfonic acid and one of three bases: ammonia, methylamine or dimethylamine. The mixed-acid calculations followed a systematic substitution pathway in which one sulfuric acid molecule was replaced by methanesulfonic acid in a cluster containing equal numbers of acids and bases; that pathway was used for the investigated mixed-acid clusters, while separate pure-methanesulfonic-acid and sulfuric-acid–base systems provided comparisons. The clusters contained up to 10 acid–base pairs, or 20 molecules in total. Initial structures were generated with ABCluster and further explored with CREST metadynamics, then optimized and treated with the B97-3c density functional method. For the larger clusters, a PaiNN neural network trained to reproduce B97-3c energies and forces accelerated part of the optimization workflow.

Under standard thermodynamic conditions of 298.15 kelvin and 1 atmosphere, clusters containing sulfuric acid were more stable than the corresponding clusters made only with methanesulfonic acid for all three bases. The gap was particularly large for dimethylamine: at 20 molecules, the pure sulfuric acid–dimethylamine cluster had a binding free energy of roughly minus 264 kilocalories per mole, compared with about minus 183 kilocalories per mole for the pure methanesulfonic acid–dimethylamine analogue. The resulting advantage for sulfuric acid was approximately 81 kilocalories per mole. For ammonia and methylamine, methanesulfonic-acid-only clusters at the largest size were about 55 to 62 kilocalories per mole less stable than their sulfuric-acid counterparts. This contrasts with previously reported mixed-base synergy, in which adding ammonia to sulfuric acid–dimethylamine clusters could stabilize larger structures. Replacing sulfuric acid with methanesulfonic acid did not produce an equivalent cooperative gain.

The calculated structures nevertheless revealed a size-dependent change. As clusters grew, both sulfuric-acid and mixed-acid systems shifted from compact molecular complexes toward more extended, three-dimensional networks of hydrogen bonds. One methanesulfonic acid molecule did not fundamentally alter that transition, but its methyl group slightly disturbed the bonding arrangement and could reduce coordination efficiency. The energetic penalty associated with this substitution became smaller as size increased, especially for ammonia and methylamine. A plausible explanation is that a larger network can distribute the molecular perturbation more effectively than a compact initial complex can. In dimethylamine systems, however, the strong sulfuric acid–dimethylamine interaction dominated the energetics, leaving little room for methanesulfonic acid to make a substantial stabilizing contribution. The authors therefore distinguish the behavior of mixed acids from the previously observed synergy between sulfuric acid and mixed bases.

The researchers also recalculated binding free energies at prescribed gas concentrations and temperatures. The tested atmospheres included 278.15 and 298.15 kelvin, with sulfuric acid and methanesulfonic acid concentrations of either 10⁶ or 10⁸ molecules per cubic centimetre; base concentrations were fixed at 10 parts per billion for ammonia and 5 parts per trillion for methylamine and dimethylamine. These conditions were chosen to represent selected chamber and atmospheric regimes and to assess how relative acid abundance influences the stability and composition of the earliest clusters. A further sensitivity case at 258.15 kelvin used 10⁹ methanesulfonic acid molecules per cubic centimetre and 10⁶ sulfuric acid molecules per cubic centimetre, an intentionally extreme ratio designed to locate the regime in which methanesulfonic acid becomes thermodynamically important rather than to represent typical atmospheric abundance.

At 298.15 kelvin under low acid concentrations, sulfuric-acid-rich clusters had the lowest free energies. The distinction was most pronounced with dimethylamine, for which incorporating methanesulfonic acid offered essentially no energetic advantage. Ammonia and methylamine systems were somewhat more sensitive to acid composition, but pure or sulfuric-acid-rich clusters still tended to be most stable at the smallest sizes. Raising methanesulfonic acid to 100 times the sulfuric acid concentration made mixed-acid clusters more competitive in the ammonia and methylamine series, with one methanesulfonic acid molecule producing the most stable composition across much of the size range in the sulfuric acid–methanesulfonic acid–ammonia system. The dimethylamine result remained unchanged because the stronger sulfuric acid–dimethylamine pairing governed the cluster. Under these warm and dilute conditions, the authors judged the overall free-energy landscape uphill, making new particle formation unlikely.

Cooler and more concentrated conditions made particle-like growth more thermodynamically favorable overall, but did not reverse the acids’ relative roles. At 278.15 kelvin, free-energy surfaces for larger ammonia- and methylamine-containing clusters became more favorable, while the smallest clusters still presented an initial barrier. In the dimethylamine system, sulfuric acid again dominated, and the pure methanesulfonic acid clusters remained much less favorable. Under the sensitivity case at 258.15 kelvin, methanesulfonic acid became substantially more competitive at larger sizes, especially with dimethylamine, and its stabilizing contribution increased markedly. Even there, however, mixed clusters containing sulfuric acid remained among the most stable structures at the smallest sizes. The calculations therefore do not support methanesulfonic acid replacing sulfuric acid as the principal nucleating acid in the systems studied. They instead show that its contribution increases as the cluster grows and as the relative abundance of methanesulfonic acid rises.

The findings identify a systematic divide between initial nucleation and later growth. Sulfuric acid dominates the earliest cluster formation steps, most decisively in the presence of dimethylamine, where the interaction between the two compounds can yield nearly barrierless growth under favorable conditions. Ammonia and methylamine systems have larger initial barriers, but those barriers shrink at lower temperatures and higher methanesulfonic acid concentrations. The incorporation of one methanesulfonic acid molecule becomes increasingly favorable as clusters grow, especially in the sulfuric acid–methanesulfonic acid–ammonia and –methylamine systems. This pattern supports the interpretation of methanesulfonic acid as a secondary, growth-modifying species in the neutral, unhydrated clusters examined, rather than as a primary nucleating acid under all atmospheric conditions. The result applies specifically to the cluster compositions and conditions modeled; it does not establish a universal ordering for every atmospheric nucleation pathway.

Important limits prevent the calculations from being converted directly into atmospheric formation rates or particle-growth kinetics. The model is thermodynamic and does not simulate reaction pathways, cluster collisions, evaporation rates or atmospheric transport. It also omits water and ions, both of which can stabilize clusters. That omission is particularly important because recent experiments cited by the authors found rapid particle growth driven by methanesulfonic acid at high relative humidity but negligible contribution under low humidity. The comparatively weak role assigned to methanesulfonic acid by the dry calculations therefore may not apply to hydrated atmospheric clusters. Future work identified by the study should include water, ions, ammonia, clusters with multiple methanesulfonic acid molecules and explicit cluster-dynamics simulations. The calculations also use a controlled set of neutral acid–base systems, so their conclusions should not be extended to every mixture that may occur in the atmosphere.

For atmospheric science, the main implication is that two acids frequently associated with nucleation should not be treated as interchangeable. Within the selected neutral systems, sulfuric acid provides most of the thermodynamic foundation for the first molecular clusters, while methanesulfonic acid becomes more consequential as size, coldness and the methanesulfonic-acid-to-sulfuric-acid ratio increase. The results suggest that marine or other cold environments could favor a larger role for methanesulfonic acid in stabilizing growing clusters, but they do not establish when a methanesulfonic-acid pathway becomes kinetically competitive with sulfuric-acid-driven nucleation. The safest conclusion is a division of labor: sulfuric acid starts the cluster, and methanesulfonic acid can join or alter the structure as it grows, with the magnitude of that contribution controlled by cluster size, the choice of base and atmospheric conditions.

Subject of Research: Computational study of sulfuric acid–methanesulfonic acid–base clusters in atmospheric new particle formation

Article Title: Stability and composition of large sulfuric acid–methanesulfonic acid–base molecular clusters

Article References: Hasan, G., Knattrup, Y., Wu, H., & Elm, J. (2026). Stability and composition of large sulfuric acid–methanesulfonic acid–base molecular clusters. Aerosol Research, 4(2), 501-515. https://doi.org/10.5194/ar-4-501-2026

Image Credits: AI Generated

DOI: 10.5194/ar-4-501-2026

Keywords: atmospheric new particle formation, sulfuric acid, methanesulfonic acid, molecular clusters, ammonia, methylamine, dimethylamine, quantum chemistry, machine learning, aerosol nucleation, Stability, composition

Conflict can affect every stage of food security, according to the commentary. It can leave farmland abandoned or make it difficult to cultivate, displace communities, restrict access to markets and reduce food affordability, potentially producing long-term health consequences. Robinson cites the Food and Agriculture Organization and World Food Programme’s 2026 Global Report on Food Crises, which identifies 13 hotspots where acute food insecurity is expected to increase.

Twelve of these hotspots are affected by armed conflict and violence, and the report identifies risks of famine in Sudan, South Sudan, the Gaza Strip and Somalia. The scale of the global burden is substantial. Robinson reports that around 60% to 70% of the world’s most undernourished people live in areas affected by conflict, while 85% of people facing hunger are reported to live in conflict-affected countries.

She also cites an estimate that 123.7 million additional people faced moderate or severe food insecurity in 2023 because heat-wave days and drought months were more frequent than during the 1981–2010 period. Rising temperatures and extreme weather can contribute to food insecurity through crop losses, disruption of supply chains and volatility in food prices. Food insecurity can also contribute to violence and instability, according to Robinson, creating a cycle in which conflict worsens food access and deteriorating food security can worsen conflict.

Major conflicts, including Russia’s invasion of Ukraine and the US–Iran war, have implications beyond their immediate locations, especially for countries dependent on food and agricultural imports from affected countries or on shipping routes that may be disrupted. Robinson identifies several potential responses: reducing global greenhouse-gas emissions, including emissions from the agri-food sector; shifting toward more plant-based diets; reducing food loss and waste; diversifying supply chains; increasing cooperation; and targeting support to farmers and vulnerable households. Short-term anticipatory action, such as protecting local agriculture or providing cash and food relief to affected households, can reduce food insecurity associated with conflict and climate change.

Longer-term resilience, however, requires systemic changes throughout the supply chain, from what is grown and how through to what is eaten. Because the article is a commentary rather than an original experiment or systematic review, it synthesizes reported evidence and policy options without comparing their effectiveness or demonstrating that any single measure will eliminate food shortages.

Subject of Research: Conflict, climate change and global food insecurity

Article Title: Sweeping changes to agri-food supply chain needed to tackle global food shortages

Article References: Sweeping changes to agri-food supply chain needed to tackle global food shortages. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: food insecurity, agri-food systems, armed conflict, climate change, crop losses, food prices, supply chains, famine risk, food waste, food security, Sweeping, changes

Crawford notes that the annual greenhouse-gas emissions of the US Department of Defence are larger than the annual emissions of many countries. The arms industry is another major source of emissions, while wars can cause large spikes in emissions, particularly when targets include oil and natural-gas infrastructure. She acknowledges that the military has an enormous emissions footprint that can be reduced, but argues that substantial reductions will occur only if armed forces reduce their overall size and footprint and transition to lower-emitting doctrines, including doctrines that do not require long-range aircraft missions.

Rather than financing defence by taking money from health, environmental protection and the energy transition, Crawford argues that governments should increase spending in those areas. She does not reject the need for defence. Instead, she calls for attention to how effective protection can be provided at lower emission levels and reduced cost. Her central argument is that expanded military expenditure does not by itself resolve the security risks associated with climate change when the armed forces and their supporting activities contribute to those risks.

A second commentary, by Mohammed Abba-Aji at Washington University and Nason Maani at the University of Edinburgh, warns that rising defence budgets may weaken security in another sense by diverting public resources from climate, education and other human needs. The article reports that world military expenditure reached $2,887 billion (£2,182 billion; €2,575 billion) in 2025, approaching 2.5% of world output. Official development assistance fell to $174 billion in 2025, described in the commentary as the largest annual reduction on record. These reported spending trends are not results from a causal analysis, but they frame the authors’ assessment of trade-offs between military and social expenditure.

Abba-Aji and Maani describe a potentially reinforcing cycle in which climate stress contributes to resource conflicts, which are then used to justify increased military spending. Such spending can divert funds from measures that could help interrupt the cycle. They further argue that wealthier governments need not participate directly in these conflicts to influence them: supplying arms that sustain them while reducing aid to affected states can contribute to the conditions associated with instability. Their proposed response is to weigh the health and climate implications of military-versus-social spending decisions and to direct a share of security funding toward climate adaptation, especially in vulnerable regions. They conclude that a government’s duty to protect citizens should include protection from climate-change effects, threats to health and environmental damage as well as protection against aggression.

Subject of Research: Military expenditure, armed-forces emissions, climate change and public security

Article Title: Investing more in the military is not a solution to climate change, and may cost us our security

Article References: Investing more in the military is not a solution to climate change, and may cost us our security. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: military emissions, defence spending, climate change, armed forces, greenhouse gases, public security, climate adaptation, official development assistance, arms industry, BMJ commentaries, Investing, military

The required emissions trajectory is far steeper than the reductions expected from national climate pledges. Full implementation of nationally determined contributions, or NDCs, would lower emissions by only 5–8% from 2025 levels by 2030 and by 11–15% by 2035, according to the report. The IIASA-led Scenario Compass Initiative supplied the scenario data used in the analysis. These figures are policy-pathway estimates rather than observed reductions: they describe what would be required under the lowest-possible-overshoot pathway and how far current commitments fall short. The report also warns that the earlier starting point has deteriorated because of changes in participation in the Paris Agreement and revised estimates of historical emissions.

Current policies point toward particularly high warming, while stronger delivery of existing NDCs produces only a limited improvement. If current policies continue, warming could reach 2.8°C this century and continue increasing after 2100, compared with 2.6°C if all NDCs are delivered and comparable efforts continue. Even the achievement of additional net-zero targets would limit projected warming to 2.1°C. These results are worse than the projections in the previous year’s report, and the report’s authors state that new NDCs have made a negligible difference to that deterioration. They also calculate that every five years of carbon dioxide emissions at current levels adds approximately 0.1°C to peak warming.

The report’s lowest-possible-overshoot pathway is not simply a continuation of present trends. It requires rapid cuts across the economy, sustained implementation of climate policies and major changes in electricity production. By 2035, electricity generated by solar and wind would need to be at least three times its current level, while carbon dioxide emissions from energy systems would need to decline by at least 35%. Globally, coal-fired electricity generation would have to be effectively phased out by 2040, and solar and wind generation would need to grow at least five-and-a-half-fold. The scenario also calls for a transition away from fossil fuels in energy systems, reductions in non-carbon-dioxide greenhouse gas emissions, and measures to halt and reverse deforestation and forest degradation.

Some elements of the first Global Stocktake under the Paris Agreement are already showing progress. Countries agreed to triple renewable energy capacity, double the annual rate of energy-efficiency improvement by 2030, transition away from fossil fuels in energy systems, reduce non-CO2 emissions, and halt and reverse deforestation and forest degradation. Since the Paris Agreement was adopted, global renewable electricity capacity has expanded three times faster than anticipated. Yet the report finds insufficient progress in other areas. Sophie Boehm of the World Resources Institute said that renewables are already a game-changing element of climate action and the only area found to be on track for 2030, but their growth alone cannot close the emissions gap.

Fossil-fuel use remains a central obstacle. According to Louise Jeffery of the New Climate Institute, coal and oil consumption grew much more slowly over the past decade than expected in 2015, while gas use broadly followed the trajectory previously projected. Jeffery said this progress still requires a U-turn across all fossil fuels, with the most rapid change needed in electricity supply. The contrast illustrates why additions of renewable capacity are not by themselves sufficient: generation must also displace fossil-fuel sources at a pace capable of producing the deep emissions reductions required by the report’s pathway. Setu Pelz of IIASA said meeting the minimum effort levels for minimizing 1.5°C overshoot will require cooperation that reflects differences in responsibility and capability.

The report also finds growing evidence that climate policies can reduce emissions in developed and developing countries and can produce structural changes rather than merely short-term adjustments. Its review draws on more than 220 evaluations covering different sectors and national contexts. Evaluated electricity-sector policies were associated with average emissions reductions of 9%, while economic instruments such as carbon taxes and cap-and-trade schemes produced reductions of 5–13% over the periods examined. These outcomes are averages from a varied policy literature, not uniform effects, and the report cautions that successful interventions remain concentrated in particular countries, sectors and time periods. Their wider value depends on replication, extension and sustained implementation.

Even the lowest-possible-overshoot pathway would require removing and permanently storing roughly 320 gigatonnes of carbon dioxide over the century, an amount equivalent to about eight years of global CO2 emissions in 2024. The report describes the feasibility of this requirement as uncertain because of socioeconomic and technological challenges. Carbon dioxide removal therefore cannot substitute for near-term emissions cuts; the scenario depends on both sharply reducing emissions and deploying large-scale removal and permanent storage later in the century. Keywan Riahi of IIASA said the policy challenge is to scale up proven emissions reductions through fast, deep and sustained action while limiting reliance on large-scale carbon dioxide removal.

IIASA researchers involved in the report characterized the remaining window as narrow but not closed. Shonali Pachauri, who coauthored Chapter 1, said every additional fraction of a degree and every additional year above 1.5°C increases climate risks and narrows the options for a safe future. Joeri Rogelj, who served as a lead author for Chapter 4, emphasized the gap between the emissions reductions needed and those implied by current policies and national commitments. The report’s central conclusion is that the Paris Agreement goals remain reachable, but only with fast, deep and sustained emissions reductions and greater delivery of the first Global Stocktake commitments. The modeled return to 1.5°C remains uncertain, and the report’s low-overshoot pathway is designed to minimize the peak and duration of warming rather than guarantee a specific temperature in 2100.

Subject of Research: UN scenario analysis of emissions cuts, technology transitions and policy measures needed to limit and reverse global warming above 1.5°C.

Article Title: New UN report lays out emissions cuts needed for return to 1.5°C

Article References: New UN report lays out emissions cuts needed for return to 1.5°C. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: 1.5°C warming, greenhouse gas emissions, UNEP Emissions Gap Report, climate policy, nationally determined contributions, renewable electricity, fossil fuels, carbon dioxide removal, Scenario Compass Initiative, global warming, report, lays

Neimark cites estimates that the first 14 days of the Iran war produced more than five million tonnes of carbon dioxide, exceeding Iceland’s total climate pollution in 2024. He also cites an estimate of almost 311 million tonnes released during five years of war in Ukraine, described as equivalent to France’s annual emissions. For Gaza, the commentary reports that carbon emissions during the first 15 months of the conflict exceeded 30 million tonnes. Neimark compares that quantity with the amount of carbon absorbed by 33 million acres of forests in one year. These figures are estimates presented in the commentary to illustrate the potential scale of emissions associated with recent conflicts.

The emissions considered by Neimark have both direct and indirect sources. Direct emissions include fossil fuels burned by fighter jets, cargo planes, tanks and naval ships. Indirect emissions can arise from activities such as powering military bases, making weapons, deploying troops and reconstruction after conflicts. Since the 2015 Paris agreement, military reporting of conflict-related emissions has been voluntary. As a result, researchers must conduct their own assessments of how much carbon was emitted during a conflict. Neimark argues that governments should establish mandates requiring militaries to report emissions during both peacetime and active conflict, creating a more consistent basis for evaluating the military sector’s climate footprint.

The proposal is presented against a developing legal framework. In 2025, the International Court of Justice issued an advisory opinion affirming that governments have legal responsibilities to protect the climate system, prevent harm to the best of their abilities and cooperate internationally. The commentary notes that the opinion did not directly address military emissions, but a supplementary declaration said state obligations include responsibility to address impacts resulting from armed conflict and other military activities. Several climate cases have subsequently been brought against major polluters in domestic and international courts, but Neimark says that no legal action had been taken against militaries specifically for climate-related emissions.

Emissions data could provide evidence of conflict-related environmental costs in legal proceedings, help set targets for reductions and strengthen mechanisms for accountability, according to the commentary. Such data could also distinguish the economic consequences of war from its costs to people and the climate system on which they depend. Because the source is a commentary and not an empirical evaluation of a reporting policy, it does not demonstrate that mandatory reporting alone would reduce emissions or establish the result of any future court case. Its central claim is more limited: dependable emissions measurements are a necessary foundation for documenting the climate effects of military activity, identifying responsibility and setting reduction targets.

Subject of Research: Measurement and legal accountability for greenhouse gas emissions from military activity and armed conflict

Article Title: Data vital in holding militaries accountable for the environmental toll of war

Article References: Data vital in holding militaries accountable for the environmental toll of war. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: military emissions, armed conflict, greenhouse gases, carbon dioxide, climate accountability, emissions reporting, The BMJ, Paris Agreement, International Court of Justice, Data, vital, holding

The reconstructed record shows that a large cooling event associated with the Younger Dryas lowered estimated mean July temperatures at Lake Prokoško by approximately 2.3°C, a change intermediate between estimates from Alpine lakes and those farther east. The lake, which covers 4.8 hectares at an elevation of 1,670 metres in the Vranica Mountains of the Dinaric Alps, also records a later Middle Holocene interval in which estimated summer temperatures may have exceeded present-day levels. These findings emerge from a paleoclimate reconstruction based on biological, chemical and physical evidence preserved in lake sediments, rather than from direct instrumental measurements.

Lake Prokoško occupies a climatically significant position between Western, Central and Eastern Europe. Over thousands of years, remains from the surrounding landscape and the lake’s own ecosystem accumulated in bottom sediments, providing material for reconstructing regional environmental and climatic history. One study, published in Palaeogeography, Palaeoclimatology, Palaeoecology, focused on rapid changes between approximately 16,000 and 10,000 years ago during the Late Glacial and beginning of the Holocene. A separate study in Quaternary Science Reviews traced conditions through the Holocene to the present, extending the interpretation of the sediment sequence across the full period represented by the two investigations.

Chironomids, a group of aquatic insects also known as non-biting midges, supplied the principal temperature indicator. Their larvae occupy lake sediments and differ in their preferences for water temperature, oxygen levels and nutrient conditions. After moulting, larvae leave chitinous head capsules that sink to the lake bed, where they can be preserved for tens of thousands of years. The researchers identified the species represented in different sediment layers and compared the fossil assemblages with faunal and climate data from hundreds of modern European lakes. This comparison supported estimates of mean July temperature, while the accompanying pollen, sediment, organic-matter and chemical records provided evidence about forests, soil erosion, lake productivity and other environmental changes.

The oldest layers examined reflect cold conditions near the end of the last glacial period. At around 14,600 years ago, reconstructed mean July temperatures around Lake Prokoško were below 8°C. They subsequently rose by approximately 2.6°C within a comparatively short interval, reaching around 10.2°C. The reconstruction associates this warming with increased biological activity in the lake, spreading vegetation and more stable conditions in the catchment. The youngest sediments in the study cover the most recent millennium, where the chironomid community reflected not only temperature changes but also centuries of alpine grazing, greater nutrient input and the later expansion of nutrient-rich conditions.

The early warming ended abruptly when the Younger Dryas began around 12,900 years ago, the last major cooling episode at the close of the last glacial period. Estimated mean July temperatures at Lake Prokoško fell by approximately 2.3°C to about 7.9°C. Cold-water chironomid species became more abundant, while increased erosion transported more clastic material into the lake. Comparisons with reconstructions elsewhere in Europe revealed a marked spatial contrast: summer cooling of 3–4°C has been reconstructed at many Alpine lakes, whereas decreases in the Eastern and Southern Carpathians were generally less than 1°C. The Lake Prokoško estimate falls between those geographic extremes.

The researchers connect this west-to-east gradient, which becomes weaker toward the east, to oceanic and atmospheric changes in the North Atlantic region. For the Carpathian Basin, the contrast illustrates that the same large-scale climatic event can produce different responses in Western, Central and Eastern Europe. Lake Prokoško consequently provides a regional reference point for examining how the magnitude of a shared climate signal varied geographically. The researchers also emphasize that alpine lakes respond sensitively to relatively small temperature changes: variations in ice-cover duration, water stratification, oxygen content and biological activity can accompany those changes, making small mountain lakes useful environmental archives.

Warming resumed at the end of the Younger Dryas. Between approximately 11,800 and 11,400 years ago, reconstructed mean July temperatures increased by around 2.9°C. By about 10,500 years ago, they may have reached approximately 12.6°C. The lake became more productive, its ice-free season lengthened, and closed-canopy forests developed in the catchment, reducing erosion. Temperatures did not remain constant throughout the Holocene. Around 6,800 years ago, reconstructed mean July temperatures may have reached approximately 14°C, meaning that some summers around Lake Prokoško were warmer than those experienced today. The researchers distinguish this Middle Holocene warmth from present-day warming: the earlier conditions were mainly seasonal and driven by gradual changes in Earth’s orbital parameters that increased Northern Hemisphere summer insolation, whereas current warming is global, year-round, more rapid and primarily associated with human-caused greenhouse gas emissions.

A cooling trend began around 6,000 to 5,500 years ago during the Neoglacial transition toward a cooler Late Holocene. Reconstructed mean July temperatures fell from approximately 14°C to around 12.8°C, then to 11.8°C by about 5,670 years ago. Pollen evidence indicates that people were altering the landscape around the lake by the end of the Neolithic, approximately 6,000 years ago. Plants associated with grazing and open habitats became more common, followed later by more intensive forest use and the expansion of open areas. The same sediment archive therefore records both reconstructed climatic variability and the growing influence of human land use, although it does not by itself establish that human activity caused the temperature changes documented in the sequence.

Later Holocene temperatures continued to vary. Around 3,000 years ago, another significant cooling began, with mean summer temperatures falling from approximately 14.7°C to 12°C. Around 2,000 years ago, reconstructed temperatures rose during the Roman Warm Period, reaching approximately 13.3°C. Over the past millennium, centuries of alpine grazing opened the surrounding landscape and increased the nutrient load entering Lake Prokoško. The chironomid community changed significantly around 700 years ago, and species preferring more nutrient-rich waters became increasingly common over the following 500 years. Together, the two studies show that the lake’s fossil and sediment record captures environmental responses shaped by both regional climate change and local human transformation, while also demonstrating that estimates for individual periods remain reconstructions derived from sediment proxies and modern comparative data.

Subject of Research: Paleoclimate reconstruction of summer temperature variability in the Western Balkans

Article Title: Where three climate zones meet

Article References: Where three climate zones meet. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: Lake Prokoško, Western Balkans, summer temperatures, paleoclimate, chironomid fossils, Younger Dryas, Holocene, climate reconstruction, land use, alpine lake, three, climate

Published in Environment International, the study was conducted as part of the European EXPANSE project, which examines how the urban exposome influences cardiometabolic and respiratory diseases. Researchers from the Swiss Tropical and Public Health Institute and the University of Basel led the work, with participation by the GCAT team at the Germans Trias i Pujol Research Institute in Spain. By evaluating air pollution, temperature, temperature variability and green spaces together, the investigators aimed to assess how different environmental conditions may relate to metabolic changes before diabetes develops. As an observational analysis, the study establishes statistical associations rather than showing that any of these exposures directly caused changes in blood glucose.

The analysis found that higher exposure to PM10 particles, higher temperatures and greater temperature variability were each associated with elevated HbA1c among participants who had not developed diabetes. The exposure effects were not independent: the model identified interactions among the environmental conditions. No consistent association was found between the presence of green spaces and HbA1c, although the investigators did not directly assess beta-cell function or insulin secretion. The authors suggested that inflammation and insulin resistance may be involved, describing them as possible mechanisms consistent with previous scientific evidence rather than mechanisms established by the study.

The researchers also evaluated different environmental scenarios using statistical models. In those estimates, improvements in air quality were associated with reductions in HbA1c, while certain temperature changes linked to climate change were associated with the opposite pattern. The combined context mattered: the same reduction in air pollution had a greater beneficial association with blood glucose under warmer temperature scenarios. These are model-based scenario estimates, not results from an intervention trial or measurements of what would necessarily occur in an individual person following an air-quality improvement.

GCAT co-author Natàlia Blay said the findings highlight the association between air pollution, temperature variability and HbA1c in people who have not developed diabetes. She said including temperature is particularly relevant in the climate-change context, where environmental exposures cannot be understood in isolation. GCAT principal investigator Sílvia Bonàs-Guarch said studies of the exposome can help investigate how environmental factors may contribute to metabolic changes before diabetes develops and may contribute to understanding the heterogeneous course of type 2 diabetes. The team is also working on approaches for assessing how genetic predisposition and environmental exposures may influence physiological processes such as pancreatic beta-cell insulin secretory capacity, but the reported study did not directly test that relationship.

Subject of Research: Environmental exposures and HbA1c in people without diabetes across nine European cohorts

Article Title: Air pollution and temperature variability are associated with higher blood glucose levels

Article References: Air pollution and temperature variability are associated with higher blood glucose levels. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: air pollution, PM10, blood glucose, HbA1c, temperature variability, climate change, urban exposome, type 2 diabetes, European cohorts, observational study, pollution, temperature

SpongeBoost is a Horizon Europe project focused on restoring the natural sponge function of landscapes, an approach intended to help ecosystems retain and manage water more effectively. Its award highlights practical restoration as well as collaboration, environmental education, public engagement and the capacity to inspire comparable work elsewhere in Europe. The announcement describes these qualities as evidence of approaches worth sharing, rather than treating the award as a measure of scientific performance alone. The 2027 award will recognise one project after the consortium first selects three nominees for further information and a final assessment.

Eligible initiatives must contribute to restoring or improving natural water retention, have been implemented or substantially developed within the previous five years, and be located in an eligible European country. The geographic scope includes European Union Member States as well as Switzerland, the United Kingdom, Norway and the Balkan countries. Projects should primarily involve restoration, rewetting or other nature-based measures carried out in outdoor landscapes. SpongeBoost says it is particularly interested in projects that combine on-the-ground restoration with strong local cooperation, innovative methods, environmental education or activities designed to help others learn from and reproduce their results.

After reviewing all nominations, the SpongeBoost consortium will contact three selected projects and invite them to provide further details about their work. The winner will then be chosen from that group. Members of the consortium will visit the winning project for a field visit, where they will present the award and exchange experiences with the people behind the initiative. The visit is also intended to showcase the project’s approaches and lessons for other restoration initiatives across Europe. The announcement does not provide a judging rubric, a prize amount or a claim that the nominated projects have been independently evaluated for a defined outcome such as a measured reduction in flooding or drought impacts.

The final award builds on previous editions that highlighted examples of sponge-landscape restoration and drew attention to projects addressing land and water challenges. Because the call is open to anyone, nominees are not limited to formal research partnerships, although the project must meet the stated eligibility criteria. The announcement positions public participation and recognition as central parts of the 2027 process: a project may be nominated by its participants or by others who regard it as inspiring or deserving of wider recognition. SpongeBoost is funded by the European Union’s Horizon Europe research and innovation programme under grant agreement No. 101112906, and the announcement states that the views expressed are those of the author or authors and do not necessarily represent those of the European Union or the European Climate, Infrastructure and Environment Executive Agency.

Subject of Research: SpongeBoost award nominations for European landscape restoration

Article Title: SpongeBoost invites nominations for inspiring restoration projects across Europe

Article References: SpongeBoost invites nominations for inspiring restoration projects across Europe. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: SpongeBoost, landscape restoration, natural water retention, flood resilience, drought resilience, nature-based solutions, rewetting, European Union, environmental awards, invites, nominations, inspiring

Only a few hundred of the estimated three to five million fungal species on Earth are capable of infecting humans, partly because most cannot grow at the human body temperature of 37 degrees Celsius. The researchers argue that rising temperatures associated with climate change could allow additional fungi to adapt to warmer conditions and potentially colonize the human body. That pathway remains unproven for C. auris.

Its original habitat is still unknown, and possible locations include coastal areas, wetlands and other saline environments. Agricultural fungicide use and other human-driven environmental changes are also under discussion, leaving several possible explanations for the organism’s sudden appearance and rapid spread. C. auris was first identified in Japan in 2009 in a patient’s ear, a discovery that inspired its common name, “yeast of the ear.” Within a few years, genetically distinct lineages had been detected on several continents.

The Würzburg researchers describe this pattern as an indication of a globally active selective factor, but they also caution that it does not by itself prove the role of climate change. The yeast grows readily at 37 degrees Celsius and can withstand temperatures as high as 47 degrees Celsius, unlike its closest relatives. It can also survive on hospital surfaces for extended periods and is often resistant to several antifungal medicines at once.

These characteristics make C. auris especially dangerous for immunocompromised people, including some hospital patients and care-home residents. The mortality rate reported in studies of bloodstream infections ranges from 20% to 67%, while the figure is around 52% in many countries. During one European outbreak involving 140 confirmed cases, 41% of affected patients died within a month.

The review places these outcomes in the context of an organism that is difficult to control in healthcare environments, can tolerate elevated temperatures and frequently resists multiple available treatments. The analysis synthesizes published evidence rather than testing an intervention or directly measuring the effect of climate change on infection risk. The review also examines global evidence on how environmental changes affect the spread of fungal diseases, including Cryptococcus gattii, Aspergillus fumigatus and other fungi that are colonizing new regions or frequently developing resistance.

Researchers broadly agree that fungal infections are becoming more significant worldwide, but debate continues over their precise causes and the contribution of individual factors. Schuh and Gokhale propose closer integration of environmental monitoring, climate research, evolutionary biology and medicine, including systematic surveillance of fungi in soil, water, air and hospitals, to detect emerging pathogens before major outbreaks occur. They acknowledge that such early-warning systems would require substantial investment in diagnostics, laboratory capacity and drug development.

The authors expect other closely related species could follow a similar trajectory, making predictive frameworks important for anticipating future fungal threats.

Subject of Research: Environmental and climate drivers of emerging human fungal pathogens, with emphasis on Candida auris

Article Title: Candida auris: A harbinger of further dangerous fungal species?

Article References: Candida auris: A harbinger of further dangerous fungal species?. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: Candida auris, fungal pathogens, climate change, antifungal resistance, environmental surveillance, emerging infections, hospital transmission, pathogen evolution, Candida, auris, harbinger, further