Extinction.

In the decades following the atomic bombings of Hiroshima and Nagasaki in 1945 that killed an estimated 120,000 people instantly, global nuclear arsenal swelled to a frighteningly dangerous level. Today, we are living in perpetual fear of ever-powerful nuclear weapons in the armoury of the US, Russia and China, hanging over our heads like the Sword of Damocles.

Our anxiety level about a nuclear war reached a new height after Russian President Vladimir Putin threatened to use nuclear weapons in Ukraine. However, most nuclear experts believe that the likelihood of Russia actually using a nuclear weapon in the Ukraine war is still relatively low. Regardless, given Putin's current predicament, his public statements and recent drills of Russian defence forces practising the delivery of a massive nuclear strike, the threat is seen as increasing.

As scientists study the likely ramifications of a nuclear war, a new term has been added to our vocabulary: nuclear winter. It is a phenomenon in which the Earth's atmosphere will be so full of smoke and noxious mixture of particulates and gases from the firestorms caused by nuclear bombs that sunlight will be drastically reduced or may not even reach the Earth's surface, resulting in a prolonged cooling of our planet.

Clearly, the concept of nuclear winter deals with environmental collateral damage of a nuclear war. Indeed, the idea of nuclear winter first gained attention in the 1970s, when a group of scientists, including the renowned astronomer Carl Sagan, considered the environmental consequences of a nuclear war.

Even though it is a chilling concept, there are credible precedents of nuclear winter. In 1980, the father-son duo of Luis and Walter Alvarez presented evidence that the impact of an asteroid hitting the Earth at the end of the Cretaceous Period some 65 million years ago scattered enough dust and debris into the air so as to darken the sky for an extended period of time. The subsequent climate change cooled the Earth by four to five degrees Celsius. Also, the abnormally cold summer of 1783, both in Europe and in the US, is attributed to the enormous eruptions of a chain of volcanoes in Iceland that lasted for eight months.

The effects of a full-scale war using strategic, long-range nuclear weapons may vary, depending on the severity of the war. In the worst case scenario, temperature at ground zero will reach several million degrees, the sky will blaze with the "radiance of a thousand suns," millions of lives will be burnt beyond recognition, cities and forests will be incinerated to embers, and streams of smoke will ascend into the atmosphere shrouding the planet in surging, black clouds of ash. Simply put, our planet will possibly become uninhabitable. Even on a small scale, regional nuclear war will disrupt life and the climate cycle beyond measure.