Sudden temperature swings are a rising health hazard

Scientists have identified a new kind of climate hazard, sudden day-to-day temperature swings that are intensifying worldwide.

By 2100, these violent swings could grow strong enough to regularly affect regions where about 80 percent of people live.

Sudden temperature changes

The work was led by Qi Liu, a climate scientist at Nanjing University, who studies rapid weather variability and its health impacts. 

Liu’s team used decades of global data and computer simulations to show that these jumps behave as a separate kind of extreme event.

The researchers defined “extreme day-to-day temperature change,” as unusually large jumps in the daily high between consecutive days, using the 90th percentile of local history.

Across many locations, that means day-to-day jumps of roughly 7 to 11 degrees Fahrenheit, big enough to strain the body.

Temperature swings are intensifying

Using global records, the new study finds that extreme swings are more frequent across low- and mid-latitude land regions.

Some of the strongest increases appear over the western United States, eastern China, parts of South America, and around the Mediterranean basin.

Record events in eastern China and the western United States that previously occurred once a millennium now appear roughly every 50 years.

Across low- and mid-latitude belts, these extremes account for much of the day-to-day temperature variability emerging under human caused warming.

Climate change causes

A key conclusion is that greenhouse gas forcing, the heat-trapping effect of human emissions, has the strongest influence on temperature extremes.

“Global warming exacerbates soil drought and intensifies variability in sea-level pressure and soil moisture,” said Xu Zhongfeng, an atmospheric scientist in Beijing.

Variability in sea-level pressure, the weight of the air at Earth’s surface, strengthens winds and clouds that quickly move warmer or cooler air.

In high northern latitudes, stronger Arctic warming reduces temperature contrasts, so the day-to-day swings there have generally weakened instead of growing.

A growing health risk 

A multi-country analysis of 372 locations found that larger temperature variability increased deaths, even after accounting for average temperature.

A global study estimated that temperature variability contributes to roughly 1.7 million deaths each year worldwide, a sizable share of total mortality.

Using mortality data from Jiangsu Province and the United States, the authors found that day-to-day temperature swings increased cardiovascular and respiratory risks.

One public-facing summary notes that across 308 cities, large daily swings may explain around 2.5 percent of deaths over several decades.

Where temperature metrics fail

Standard climate indices used by the World Meteorological Organization mainly track individual hot or cold days, not quick temperature jumps between days.

When the team compared extreme day-to-day swings with fifteen temperature metrics, 90 to 99 percent of land locations showed little correlation.

Many people know diurnal temperature range, the difference between each day’s high and low; that measure misses sudden jumps between days.

From a health perspective, sudden jumps between cooler and hotter days can be more taxing than a string of similarly hot days.

Unequal human impact

Abrupt temperature swings pose the greatest risk to older adults, infants, and people with chronic heart or lung disease. They also disproportionately affect anyone without reliable access to heating or cooling.

Across the United States, analyses of daily temperature swings suggest that many low-income and minority neighborhoods face larger swings than wealthier areas.

Rural communities that depend on outdoor work in agriculture or construction can be hit hard because pay and schedules still depend on weather.

The people who are most exposed to fast swings are often the same groups living in crowded housing with fewer trees and limited medical access.

Frequent temperature swings ahead

In a high-emissions scenario, climate models show these events increasing by about 17 percent in low- and mid-latitude regions.

Over the same regions, the combined intensity of those swings – capturing both their size and frequency – increases by about 20 percent.

Under more moderate emissions, models show increases in extreme swings across subtropical and mid-latitude regions, while the far north sees declines.

Projections suggest that these extreme swings could dominate future day-to-day temperature variability in regions where most people live.

Reducing the health risks

Many early warning systems focus on single day heat or cold thresholds, so they often miss dangerous jumps between days.

Health agencies can adjust heat and cold plans to flag days when predicted temperatures jump well beyond conditions from the previous day.

People can reduce some risk by watching forecasts for large swings, adjusting clothing and indoor temperatures, and checking on vulnerable neighbors.

City planners, utilities, and building designers can treat fast swings as a design condition and upgrade insulation and shade so homes stay safer.

A distinct climate hazard

Because they behave differently and hit hardest where many people live, the team argues that temperature swings deserve a separate category in climate discussions.

“This study establishes extreme day-to-day temperature change as a distinct and independent category of extreme climate event,” said study co-author Fu Congbin.

The researchers urge international scientific organizations to recognize extreme day-to-day temperature change as a distinct category of weather hazard.

As communities plan for a hotter future, they must recognize that rapid temperature swings can rival traditional heatwaves in their impact on health.

The study is published in the journal Nature Climate Change.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–