The capital of India has recorded a temperature of 43.5 degrees Celsius, a figure that is not merely a statistic but a visceral reminder of the energy accumulating in our climate system. As a climate scientist, I must state plainly: this is not an aberration, but a direct consequence of greenhouse gas emissions trapping heat in the atmosphere. The heatwave gripping Delhi is a physical reality, and the UK's scientific community is clear on the urgent need for global action.
Let us examine the numbers. 43.5°C is 10 degrees above the average maximum for this time of year. This excess heat is not random; it is consistent with a warming trend observed over decades. The physics is straightforward: carbon dioxide and other greenhouse gases absorb infrared radiation, re-emitting it back to the surface. Each degree of warming amplifies the severity of heatwaves, as a warmer baseline means extreme events become more frequent and intense.
The situation in Delhi is a microcosm of a global phenomenon. The urban heat island effect exacerbates the problem: concrete and asphalt absorb solar radiation, releasing it at night, preventing any respite. For the 20 million residents, this is a public health emergency. Heat stress can overwhelm the body's thermoregulation, leading to heatstroke, cardiovascular failure, and death. Already, hospitals report surges in admissions. But the crisis extends beyond human health: agriculture suffers, energy grids strain under air-conditioning demand, and inequality deepens as those without cooling face disproportionate risk.
From a UK perspective, this is a call for leadership. Our Met Office and Hadley Centre have been at the forefront of climate modelling. The data shows that if global temperatures rise by 2°C, heatwaves like Delhi's will become the new normal for many regions. The UK itself experienced its first 40°C day in 2022, a stark warning that no country is immune. The science demands a rapid transition to net-zero emissions, not just by mid-century but within this decade. The solutions exist: solar, wind, nuclear, and energy storage are technologically mature. The barrier is political will.
I must stress a point often lost in the discourse: the inertia of the climate system. Even if emissions ceased today, the heat already trapped would continue to warm the planet for decades. This is the calm urgency I speak of. Every fraction of a degree matters. The difference between 1.5°C and 2°C of warming means billions more people exposed to extreme heat. Delhi is a bellwether. The world is watching, and the physics is not negotiable.
To policymakers, I say: treat this as the systemic threat it is. Invest in adaptation—cool roofs, green spaces, early warning systems—but do not mistake adaptation for a solution. The only durable path is decarbonisation. The UK must accelerate its own transition and use its diplomatic weight to drive global action. The alternative is a world where 43.5°C becomes a routine summer temperature, not just in Delhi but in London, Paris, and beyond.
The planet is warming. The science is settled. The response is not.
