Science

Climate models are the essential tools that allow scientists to understand past climatic shifts, attribute current warming to specific causes, and project future changes under different emission scenarios. These models are built on fundamental physical principles, including the conservation of energy, mass, and momentum, expressed through mathematical equations that describe the behaviour of the atmosphere, oceans, land surface, and ice. Running on powerful supercomputers, climate models divide the Earth into a three-dimensional grid of cells, sometimes with vertical layers that extend from the deep ocean to the upper stratosphere, and solve these equations forward in time. The resolution of these grids has improved dramatically over recent decades, moving from hundreds of kilometres to around twenty-five kilometres for global models and even finer for regional downscaling, allowing for more realistic representations of weather systems, topography, and coastlines.

The physical processes represented in climate models range from the large-scale circulation of the atmosphere and ocean currents to the complex interactions of clouds, aerosols, and radiation. Some of these processes, such as the general flow of westerly winds in mid-latitudes, are well understood and can be expressed with high confidence. Others, including the formation and dissipation of clouds, occur at scales far smaller than the model grid cells and must be parameterised—represented by simplified, empirically derived formulas. This parameterisation introduces uncertainty, as small changes in cloud cover can have a significant amplifying or dampening effect on warming. Aerosol particles from volcanic eruptions, industrial emissions, and dust also interact with radiation and serve as cloud condensation nuclei, adding further layers of complexity. The Intergovernmental Panel on Climate Change (IPCC) regularly assesses the performance of dozens of models from independent research centres worldwide, comparing their outputs against historical observations to gauge reliability.

One of the most powerful demonstrations of model reliability comes from their ability to simulate the observed warming of the past century and a half only when both natural and human-caused forcings are included. Models driven solely by volcanic and solar variability fail to reproduce the sustained temperature increase seen since the mid-twentieth century. When greenhouse gas emissions from fossil fuel combustion, land use change, and industrial processes are added, the simulated temperature curves match the instrumental record closely. This attribution fingerprint extends beyond surface temperatures to include the cooling of the stratosphere, the warming of the ocean’s subsurface layers, and the reduction of Arctic sea ice, each of which bears the distinct signature of an enhanced greenhouse effect. Such multi-variate agreement between models and observations provides a robust basis for the conclusion that human activity is the dominant driver of recent climate change.

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For most of human history, the question of whether planets existed around other stars was a matter of philosophical speculation. The night sky revealed only points of light, and the detection of an object as small and faint as a planet orbiting a distant sun seemed technically impossible. That changed in 1992, when astronomers discovered the first exoplanets around a pulsar, and then in 1995, when a Jupiter-mass planet was found orbiting the sun-like star 51 Pegasi. These detections marked the beginning of a scientific revolution that has since catalogued over five thousand confirmed exoplanets, with thousands more candidates awaiting verification. The sheer diversity of these worlds—from scorching hot gas giants orbiting perilously close to their stars to rocky planets in temperate zones where liquid water could exist—has fundamentally altered humanity’s understanding of its place in the cosmos.

The primary methods used to detect exoplanets rely on observing the subtle effects that planets have on their host stars. The transit method, employed by missions such as NASA’s Kepler and TESS, watches for the minute dip in starlight that occurs when a planet crosses the face of its star as seen from Earth. This technique reveals the planet’s radius and, when combined with radial velocity measurements that detect the star’s gentle wobble caused by gravitational tug, its mass and density can be inferred. From these data, astronomers can determine whether a planet is predominantly rocky, gaseous, or something in between. Direct imaging, though technically demanding because of the glare of the parent star, is becoming possible for young, giant planets at wide separations using advanced adaptive optics and coronagraphs. Gravitational microlensing, where a star-planet system bends and amplifies the light of a background star, can detect planets at great distances, even free-floating worlds unbound to any star.

A central goal of exoplanet science is to identify worlds in the habitable zone, the orbital region where a planet’s surface temperature could permit liquid water to exist given an appropriate atmosphere. This does not guarantee that a planet is habitable, as atmospheric composition, magnetic fields, and geological activity all play crucial roles. The Trappist-1 system, seven Earth-sized planets orbiting a cool red dwarf star, captured public imagination precisely because several of its worlds reside in this temperate region. However, red dwarfs, which are the most common type of star in the galaxy, frequently emit powerful flares that could strip away atmospheres and bathe planetary surfaces in radiation, complicating assessments of their habitability. Understanding these environmental factors requires studying not just the planet but the star-planet system as an integrated whole.

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Clustered Regularly Interspaced Short Palindromic Repeats, universally known as CRISPR, represents one of the most significant breakthroughs in molecular biology since the discovery of the DNA double helix. Originally identified as a bacterial adaptive immune system that recognises and cuts the genetic material of invading viruses, CRISPR was adapted by researchers into a programmable tool for editing the genomes of living organisms. The system uses a guide RNA sequence to direct the Cas9 protein, or variants thereof, to a specific location in the DNA, where it creates a double-strand break. The cell’s natural repair machinery then mends the break, and this process can be harnessed to disable a gene, correct a faulty sequence, or insert new genetic material. The technique is faster, cheaper, and more precise than earlier gene-editing methods, democratising access to genetic modification and opening up possibilities that span medicine, agriculture, and fundamental research.

In medicine, the therapeutic potential of CRISPR is being explored for a range of genetic disorders, particularly those caused by a single well-characterised mutation. Conditions such as sickle cell disease and beta-thalassaemia have been the focus of early clinical trials, where haematopoietic stem cells are extracted from a patient, edited to reactivate foetal haemoglobin production, and then reinfused after the bone marrow has been conditioned. Initial results have been encouraging, with some patients experiencing substantial reductions in disease symptoms over sustained periods. Research is also underway for conditions affecting the liver, eye, and muscle, where delivery of the editing components to the target tissue remains a key challenge. Adeno-associated viral vectors and lipid nanoparticles are among the delivery strategies being investigated, each carrying distinct advantages and limitations in terms of cargo capacity, immunogenicity, and tissue tropism.

Despite its precision, CRISPR is not infallible. Off-target effects, where the editing machinery cuts DNA at unintended sites, remain a safety concern, as such unintended modifications could disrupt important genes or regulatory elements, potentially increasing the risk of cancer or other conditions. Bioinformatic tools and engineered protein variants with enhanced specificity are continuously being developed to minimise these risks, and whole-genome sequencing is employed to screen edited cells before therapeutic use. A separate concern arises from the mosaicism that can occur if editing takes place after a cell has already divided, meaning that not all cells in a tissue will carry the intended change. For somatic gene editing, which affects only non-reproductive cells in the treated individual, these risks are contained within the patient and are subject to the same risk-benefit evaluation as any experimental therapy. However, when editing is applied to early embryos, gametes, or germline cells, the changes become heritable, raising a fundamentally different order of ethical and societal questions.

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The transition to a low-carbon energy system depends not only on generating electricity from renewable sources but also on the capacity to store that energy efficiently and release it when demand peaks. Solar and wind power are inherently variable, producing energy when the sun shines or the wind blows, which does not always align with consumption patterns. Energy storage bridges this gap, capturing surplus generation and delivering it during periods of high demand or low renewable output, thereby enhancing grid stability and reducing reliance on fossil fuel peaker plants. Over the past decade, investment and innovation in storage technologies have accelerated dramatically, driven by falling costs, policy support, and the urgent need to decarbonise electricity networks worldwide. From grid-scale installations to household battery systems, storage is reshaping how energy is managed, traded, and consumed.

Lithium-ion batteries remain the dominant technology for both electric vehicles and stationary storage applications. Their widespread adoption has been propelled by manufacturing scale, particularly from the consumer electronics and automotive sectors, which has slashed costs by over eighty per cent since 2010. Modern lithium-ion chemistries, including lithium iron phosphate and nickel manganese cobalt variants, offer differing balances of energy density, lifespan, and safety, allowing system designers to tailor solutions to specific use cases. Utility-scale battery storage facilities, often co-located with solar farms, can respond to grid signals in milliseconds, providing frequency regulation services that help prevent blackouts. In Great Britain, the deployment of large battery storage projects has grown substantially, with operators participating in the balancing mechanism and capacity market auctions, demonstrating that these systems are now a commercially viable component of the national energy infrastructure.

Beyond lithium-ion, a portfolio of alternative storage technologies is emerging to address the limitations of current batteries, particularly regarding duration, material supply chains, and environmental impact. Flow batteries, which store energy in liquid electrolytes held in external tanks, offer the advantage of decoupled power and energy capacity; scaling up storage duration simply involves larger tanks. Vanadium redox flow batteries have reached commercial maturity for applications requiring four to twelve hours of discharge, making them suitable for shifting solar energy into evening peak periods. Other chemistries, including iron-chromium and organic flow batteries, aim to use more abundant, less costly materials. Meanwhile, sodium-ion batteries are attracting significant attention as a potential complement to lithium-based systems, as sodium is widely available and less subject to geopolitical supply risks, though their energy density currently remains lower, making them better suited for stationary storage rather than vehicles.

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The human digestive tract is home to trillions of microorganisms, including bacteria, viruses, fungi, and archaea, collectively known as the gut microbiota. This complex ecosystem begins to establish itself at birth and evolves throughout a person’s life, influenced by diet, environment, medication use, and genetics. Far from being passive passengers, these microbes engage in a dynamic, symbiotic relationship with the host, performing functions that human cells cannot accomplish alone. They assist in breaking down complex carbohydrates, synthesising essential vitamins such as vitamin K and certain B vitamins, and metabolising bile acids. The composition of an individual’s gut microbiota is as unique as a fingerprint, and scientists have increasingly recognised its profound impact on overall health, extending well beyond the digestive system to influence immune function, metabolic processes, and even brain activity.

One of the most well-studied roles of the gut microbiota is its contribution to immune system development and regulation. The gut-associated lymphoid tissue, which represents a significant portion of the body’s immune cells, is in constant dialogue with resident microbes. This interaction educates the immune system to distinguish between harmless substances and pathogenic invaders, helping to establish appropriate tolerance to food proteins and commensal bacteria while maintaining the capacity to mount a defence against infection. When this delicate balance is disrupted, a state known as dysbiosis, the immune system may become misdirected. Research has linked such imbalances to a higher incidence of allergic conditions, autoimmune disorders, and inflammatory bowel disease. The mechanisms involve microbial metabolites like short-chain fatty acids, which bind to receptors on immune cells and modulate inflammation, highlighting a molecular language that shapes host defences from infancy onwards.

Metabolic health is another area where the gut microbiota exerts considerable influence. Different bacterial species possess varying abilities to extract energy from food, meaning that two individuals consuming identical meals may not derive the same caloric value. Studies in both animals and humans have shown that the microbial profile of individuals with obesity often differs from that of lean individuals, typically showing a reduced diversity of species and a shift in the ratio of major bacterial phyla. Furthermore, gut microbes produce signalling molecules that affect insulin sensitivity, fat storage, and appetite regulation. They convert dietary fibre into short-chain fatty acids that act as energy sources for colon cells and as signalling molecules that can influence the production of hormones involved in hunger and satiety, such as peptide YY and glucagon-like peptide-1. This has prompted extensive investigation into the potential of dietary interventions to positively influence metabolic health by reshaping the microbial community.

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