Nuclear Expert Predicts How Launching a Single Nuke Could Wipe Out All of Humanity

She expands on the sheer magnitude of nuclear weapons by comparing the Oklahoma City bombing, a tragic but conventional terrorist attack with an equivalent of 2.5 tons of TNT, to the atomic bombings of Hiroshima and Nagasaki in 1945. These latter bombs yielded explosions equivalent to 15 and 21 kilotons of TNT—a difference of thousands of times in destructive power. This immense scale demonstrated that nuclear weapons are not simply more powerful explosives but fundamentally different instruments of devastation that operate on an unprecedented level of environmental, human, and geopolitical impact.

Historical Nuclear Tests

Hughes traces the development and testing history of nuclear weapons, highlighting some of the largest and most consequential detonations. Early atomic bombs, such as those used in Hiroshima and Nagasaki, gave way to hydrogen bombs or thermonuclear weapons with exponentially greater yields. She recounts the Castle Bravo test conducted by the United States in 1954 at the Marshall Islands—a detonation around 1,000 times the magnitude of Hiroshima's bomb. The resulting mushroom cloud was tens of miles high and tens of miles wide, raining radioactive fallout on nearby inhabited islands where residents suffered severe radiation sickness.

Further, Hughes points to the Soviet Union's Tsar Bomba, tested in the remote Novaya Zemlya archipelago, as the most powerful explosion ever detonated, with an estimated yield of 50–58 megatons. These tests extended the contamination of the atmosphere and environment globally. Even decades later—more than 70 years on—the Marshall Islands still bear unsafe levels of radioactive contamination, rendering some areas uninhabitable permanently. The extensive number of tests, over 2,000 worldwide, including atmospheric and underground detonations, have left an indelible mark on human health and geopolitical realities, far beyond their initial explosive moments.

The Impact of a Nuclear Explosion Over a City

Turning to a hypothetical but plausible scenario, Hughes vividly describes the effects of detonating a modern nuclear weapon, such as a one-megaton bomb, over a populous urban center like Times Square in New York City. The immediate fireball created reaches temperatures comparable to the surface of the sun and vaporizes everything within about a one-mile radius. This is followed by layers of devastating blast and shockwaves, which cause massive destruction of buildings and infrastructure, lethal radiation exposure, and thermal burns so intense as to literally melt human skin.

The difference between airbursts and surface bursts adds complexity: an airburst maximizes blast damage and shockwave impact over a larger area, while a surface burst produces significant local fallout and radiation contamination. Hughes estimates that such an explosion over New York would kill approximately 1.5 million people outright and severely injure two million more, creating a humanitarian catastrophe unprecedented in modern history. Beyond this immediate devastation, the city—and potentially the region—would be rendered uninhabitable for decades or longer, demonstrating the prolonged and irrevocable harm nuclear detonations inflict.

The Triggering of Global Nuclear War

Hughes stresses that the detonation of a single nuclear weapon anywhere does not remain an isolated event. Nuclear doctrines, particularly those held by the United States and Russia, are structured for immediate escalation. For example, the U.S. maintains a "launch on warning" policy: if it detects incoming missiles—even before any attack impacts U.S. soil—it is programmed to retaliate immediately. This rapid-response system, combined with tight decision windows often measured in minutes, creates a dangerously fragile situation where mistakes or misinterpretations could escalate into full-scale nuclear war.

She references a detailed war simulation described in Annie Jacobson's book, depicting a rapid sequence triggered by an initial limited attack (such as a missile targeting a U.S. nuclear power plant). Within just over an hour—the entire replay lasting approximately 72 minutes—a devastating nuclear exchange between superpowers unfolds, resulting in hundreds of millions of immediate casualties. Communication failures exacerbate this, as one side may misread aggressions and retaliate, setting off mutual destruction in a feedback loop with no contingency plans for de-escalation. This dire feedback cycle underscores how a "single nuke" could quickly spiral into a near-total annihilation.

The Radiation Aftermath

Radiological contamination following nuclear detonations is among the most persistent and insidious hazards. Hughes highlights several critical isotopes that impose long-term environmental and health risks: iodine-131, cesium-137, strontium-90, and various plutonium isotopes. Iodine-131, while short-lived with an eight-day half-life, immediately concentrates in the thyroid glands of exposed populations, significantly increasing rates of thyroid cancers in survivors—demonstrated notably in the aftermath of Hiroshima and Nagasaki.

Cesium-137 and strontium-90 possess half-lives of around 30 years, persisting in soils, plants, and animals for centuries. Notably, strontium-90 mimics calcium and embeds itself in bones, contributing to high leukemia incidences, referred to historically as "atomic bomb disease." Cesium-137 behaves like potassium, accumulating in soft tissues like the brain and causing various cancers. Plutonium isotopes, however, pose the longest threat, with half-lives spanning thousands of years, remaining a fixture in the environment and the geological record. Hughes details how these isotopes cycle through food chains, contaminating milk, crops, and ultimately human bodies, extending the death toll from nuclear blasts well beyond the initial explosion.

Nuclear Winter

Among the most frightening long-term effects Hughes discusses is the concept of nuclear winter. In this scenario, widespread fires ignited by nuclear blasts would loft vast quantities of soot into the upper atmosphere, blocking sunlight and dramatically cooling the planet. Simulations indicate that temperatures could plummet by 10–15°C (18–27°F) within weeks, creating conditions akin to an ice age. Such a radical shift would devastate global agriculture, particularly in the Northern Hemisphere breadbasket regions, leading to the collapse of food systems and mass starvation.

According to research led by scientists at Rutgers University and others, the death toll from resultant famine could surpass 5 billion people worldwide within two years of a large-scale war between nuclear powers. This figure exceeds immediate casualties and speaks to how nuclear war would not just kill through blast and radiation but starve humanity en masse. Hughes underscores nuclear winter as a planetary-scale disaster, eradicating ecosystems and jeopardizing human civilization at a level more profound than any prior natural catastrophe.

Ozone Layer Destruction

The interview also covers ozone layer depletion caused by nuclear warfare. The intense nitric oxide production from nuclear detonations would deplete stratospheric ozone, the Earth's shield against harmful ultraviolet radiation. Hughes draws on early research from the 1970s, updated by modern models, estimating up to 70% destruction of the ozone layer following a large-scale nuclear exchange.

This destruction means that not only would humans be exposed to deadly higher doses of UV radiation—raising skin cancer and cataract risks—but agricultural systems would suffer further damage as many crops and plant species are sensitive to UV levels. The resulting environmental stress compounds the challenges posed by nuclear winter and radiation, leading to a cascade of ecological and food security collapses that would deepen human suffering and mortality worldwide.

The Global Nuclear Arsenal

Hughes outlines the current status of global nuclear weapons, noting that about 12,500 warheads exist within nine recognized nuclear-armed states. The United States and Russia account for over 90% of these arsenals, possessing vast numbers of warheads often vastly more powerful than those used in 1945. The other nuclear states include the United Kingdom, France, China, India, Pakistan, Israel, and North Korea, with several countries outside the Non-Proliferation Treaty (NPT).

The NPT remains the cornerstone of anti-proliferation efforts, recognizing five nuclear weapon states and attempting to limit the spread to others. Hughes discusses how Israel maintains a policy of nuclear ambiguity and estimates that it holds nearly 90 warheads, while North Korea has developed sufficient arsenal and delivery capabilities to strike the U.S. homeland. The broad availability and modernization of nuclear weapons, along with geopolitical tensions, make disarmament and control increasingly complex.

The Danger of Accidents

Beyond deliberate use, the threat posed by accidents and erroneous launches places humanity at constant risk. Hughes recounts historical incidents during the Cold War, such as the near-catastrophic Cuban Missile Crisis and various false alarms triggered by satellite glitches and misinterpretations. She highlights heroic individuals like Stanislav Petrov and Captain Arkhipov, whose sound judgment prevented accidental nuclear launches during critical moments.

Moreover, lost nuclear weapons—known as "Broken Arrows"—remain on the ocean floor or in unknown locations following submarine and aircraft accidents. There are about 50 such warheads unrecovered today. These devices pose risks of unintended detonation or environmental contamination. Combined, these mishaps reveal the extreme danger of maintaining active nuclear arsenals without fail-safe human or technological systems capable of preventing accidental escalation or loss.

The United States' Nuclear Policies

Hughes discusses the U.S. nuclear policy, emphasizing that the current doctrine motivates rapid retaliation almost automatically if an attack is suspected, which leaves little room for diplomacy or de-escalation. She critiques ongoing efforts to modernize the U.S. nuclear arsenal, an endeavor initiated during the Obama administration and continuing despite calls for disarmament.

The $2 trillion projected cost for upgrading weapons systems, delivery mechanisms, and infrastructure stands in stark contrast to the risks involved. While advocates argue modernization keeps the arsenal reliable, Hughes and other experts view it as perpetuating a cycle of dependence on nuclear weapons, fueled partly by vested interests such as defense contractors. This vast spending on instruments of mass destruction diverts resources from addressing global challenges and underscores the paradox of planning to perfect tools intended to end civilization.

Prospects for Nuclear Disarmament

Despite the formidable challenges, Hughes points to progress within international frameworks aimed at ending the nuclear threat. The Treaty on the Prohibition of Nuclear Weapons, which entered into force in 2021, seeks to outlaw all nuclear weapons-related activities among its signatories. Though no nuclear-armed states have joined, the treaty represents a growing humanitarian-based movement condemning nuclear weapons as unacceptable threats to all humanity.

The treaty builds on decades of evidence about nuclear weapons' human and environmental toll and attempts to create stigmatization that could pressure nuclear states to disarm. Hughes acknowledges skepticism about enforcement and political will but stresses that public awareness and advocacy—echoing the activism that fostered the Atmospheric Test Ban Treaty in the 1960s—remain essential paths toward eventual abolition.