Overnight minimums skyrocket as WMO pleads for more early warnings

Effective early warning systems need to be implemented quickly in light of prolonged heat conditions in the northern hemisphere and the prospect of lengthier, hotter heatwaves, says the World Meteorological Organization.

Europe and North America have baked through July with record-breaking heatwaves most keenly felt in Italy, France and Spain and the US, with many local maximum temperature records being smashed. Forecasters are warning there are more heatwaves to come throughout August.

The heatwave covering much of the west and southern USA over the last week impacted 100 million people, with excessive heat warnings issued across the states of California, Nevada, Arizona and parts of Utah, Texas and Oklahoma.

But pushing the mercury to new levels isn’t the only issue confronting nations. Overnight minimums are also peaking at record highs, offering people little respite from heat.

“We need the world to broaden its attention beyond the maximum temperature alone,” says WMO extreme heat senior advisor Dr John Nairn.

“In many locations where the maximum is reaching into the high 40°Cs and higher, the temperature may still be near 40°C at midnight. In these circumstances, the minimum temperature is more important for health … during extreme heatwaves.”

Complicating matters for many parts of the world are the amplifying impacts of other natural climate phenomena – like El Nino – and human activity beyond increasing greenhouse gas emissions adding to the planet’s heat blanket. Increasing urbanisation, for instance, replaces natural areas with materials like concrete that are better absorbers and retainers of heat. During heatwaves, this means some city areas can experience temperatures well above long term averages.

The emergence of the urban heat island effect further reinforces climate change as a health issue.

“Worldwide, more intense and extreme heat is unavoidable – it is imperative to prepare and adapt as cities, homes, workplaces are not built to withstand prolonged high temperatures – and vulnerable people are not sufficiently aware of the seriousness of the risk heat poses to their health and wellbeing,” Nairn says.

To address the threat of more intense and frequent heatwaves, climate scientists and national governments have emphasised the importance of early warning systems to help people prepare for deadly conditions. These extend beyond heatwaves to fire, flood and cyclonic warnings.

Early warning systems are particularly important in developing countries, where investing US$800 million in such systems could avoid losses of US$3-16 billion annually. For all nations, these systems can cut by up to a third, the cost of damage from climate events, according to research from the Global Commission on Adaptation. When effective, early warning systems can avert hazards from becoming disasters that cause damage and take lives.

While the situation in the northern hemisphere, particularly the US where El Nino has been declared, does not necessarily translate to a forecast for the southern hemisphere’s summer, several years of record-breaking heat will be a cause for concern in nations below the equator, particularly those affected by recent cool summers like Australia.

Australia’s weather bureau is yet to declare El Nino, however predicts hotter and drier conditions for the continent into Spring.