Portugal has registered its hottest May day in history, with temperatures in the central town of Mora reaching 40.1°C on Thursday. The record-breaking heat is part of a broader heatwave gripping western Europe, driven by a persistent high-pressure system and a plume of hot air from north Africa. The event underscores a worrying trend: according to the European Union's Copernicus Climate Change Service, the frequency of extreme heat events in Europe has increased by a factor of three in the past decade compared with the 1980s.
The immediate consequence for the United Kingdom is a surge in electricity demand. National Grid ESO, which manages the country's power system, has issued a 'capacity market notice' for Friday afternoon, signaling the need for additional generation reserves. While the UK is not experiencing the extreme heat itself, the high temperatures on the continent reduce the availability of interconnector imports from France, Belgium and the Netherlands. At the same time, British households and businesses are turning up air conditioning units and fans, pushing up domestic consumption. The grid operator expects peak demand to approach 32 GW, about 10% above the seasonal average.
This is not merely a logistical challenge. It is a physical test of infrastructure designed for a climate that no longer exists. The UK's energy system was built for mild summers and cold winters. Now, it must adapt to a regime where extreme heat events become annual occurrences. The current heatwave is a 'canary in the coal mine' a term I use advisedly, given the irony that coal plants are being fired up to meet the surge. National Grid has confirmed that two coal-fired units at West Burton A in Nottinghamshire will be put on standby to ensure grid stability.
The timing is acute. The UK is still heavily reliant on gas for power generation, and gas prices remain elevated due to the war in Ukraine. Moreover, nuclear capacity is reduced due to planned outages at several reactors. France, typically a net electricity exporter, is itself struggling with low nuclear availability and high domestic demand. This interlocking cascade of vulnerabilities exposes the fragility of a system built on assumptions of constant, affordable supply.
From a climate physics perspective, the thermodynamic driver is unambiguous. The Clausius-Clapeyron relation states that the water-holding capacity of the atmosphere increases by about 7% per degree Celsius of warming. This amplifies the intensity of heatwaves and also the potential for convective storms when the heat eventually breaks. For the Iberian Peninsula, heatwaves are projected to become more frequent, more intense and longer-lasting under all emissions scenarios. Even under the most optimistic pathway, the one aligning with the Paris Agreement goals, southern Europe will experience a significant increase in heat extremes.
The broader context is the ongoing biosphere collapse. While the heatwave dominates headlines, it is only one symptom of a systemic crisis. Ocean temperatures in the North Atlantic are currently at record highs for this time of year, which in turn influences weather patterns and marine ecosystems. The loss of Arctic sea ice is altering the jet stream, leading to more persistent blocking patterns like the one now causing the heatwave. These phenomena are not independent; they are linked through the Earth's energy imbalance, which has now reached about 1.1 watts per square metre, meaning the planet is accumulating heat at a rate equivalent to four Hiroshima bombs per second.
What can be done in the immediate term? The focus must be on protecting vulnerable populations. The UK Health Security Agency has issued a Level 3 heat-health alert for parts of England, urging people to stay hydrated, keep homes cool and check on elderly neighbours. For the energy system, investments in grid-scale storage, demand-side flexibility and more interconnector capacity are essential. But these are incremental measures. The root cause is the accumulation of greenhouse gases in the atmosphere, and no amount of engineering can fully insulate us from the consequences of failing to address that.
As I have said before, we are not in a crisis today. We are in a chronic condition that will worsen if left untreated. The record in Portugal is a data point. It is also a warning. Our civilisation's energy and food systems were calibrated for a climate that is vanishing. Each new extreme event should be a prompt for action, not just a headline to be forgotten when the temperature drops. The calm urgency I speak of is not alarmism. It is simply the recognition that the laws of physics do not negotiate.
