Heat of the moment: Can we hack our way through the sizzle?

Summer is over; floods are in the air. But still, let’s talk about heat. Why? Because while India's summer heatwaves may be over, the planet's heat continues to speak through many tongues.

- Mridula Ramesh

Let's start at the source. The Sun is made up largely of hydrogen, and a little helium. Deep in its core, where temperatures reach 15 million degrees Celsius and pressures are immense, hydrogen nuclei fuse into helium. This helium nucleus has slightly less mass than the four hydrogen nuclei that formed it. The difference in mass is released as energy.

In just one second, the sun releases enough energy to meet humanity's needs for 612,900 years. Only a fraction of that energy reaches the top of the atmosphere above Earth. Then, nearly a third of this energy is either absorbed by the ozone layer or reflected, by clouds, aerosols and shiny surfaces (think deserts and ice sheets).

A sliver (with enough energy to last us 4,400 years) reaches the planet's surface, which the planet, in turn, releases as heat. Some of this heat radiates back into space, but a lot of it is trapped by greenhouse gases and clouds. Importantly, the outgoing heat does not quite balance out the incoming solar energy, resulting in a planetary energy imbalance.

The gold standard in data for energy flows at the top of our atmosphere is CERES (Clouds and the Earth's Radiant Energy System; a project by NASA). Their instruments tell us that the energy imbalance has doubled, from 0.5 watt per square metre in the first decade of this millennium to 1.0 watt per square metre in 2013-22.

And it’s showing: 2024 was the hottest year on record, per NASA, beating 2023, which held the record before it.

The planet is currently absorbing as much extra energy as if eight Hiroshima bombs were detonating on its surface every second.

And we've been absorbing this energy for decades, slowly, invisibly, day and night, everywhere. We are literally sitting in an oven, and ratcheting up the thermostat.

Eight Hiroshima bombs a second. Every second. For the past decade. Let that thought sink in on this pleasant Sunday morning.