Launching the National Integrated Heat Health Information System (NIHHIS) and the heat.gov site on July 26, 2022, the Biden administration cited heat waves and the warming climate as serious health threats. As the new initiative promises a “science informed response” to hotter conditions, five stories from The Conversation’s archive explain what researchers know about heat and health.

1. It’s the humidity

Heat waves can be deadly in a variety of ways, wrote William Calvin, who teaches physiology and neuroscience at the University of Washington.

“Heat waves can kill via the dehydration caused by heavy sweating; the altered sodium and potassium concentrations in the blood confuse both heart and nerve cells, and so breathing or heartbeat may suddenly stop,” he wrote.

Calvin explained that human bodies have not evolved to handle extreme heat with humidity. “Normally, sweat evaporates off your skin and you cool down. But with high humidity, the air is already saturated with water vapor, and so evaporative cooling stops. However, you keep sweating anyway, threatening dehydration.”

2. Lower tolerance for higher temps

“That combination of temperature and humidity whereby the person’s core temperature starts to rise is called the ‘critical environmental limit,’” wrote a group of Penn State University scholars researching the health effects of heat: W. Larry Kenney, Daniel Vecellio, Rachel Cottle and S. Tony Wolf.

In a rare lab test of the human body’s heat tolerance, the researchers found that the limit is lower than previously thought. When the air temperature is around 100 degrees Fahrenheit (38 Celsius), people can begin to feel ill effects at just 60% humidity – a higher temperature and lower humidity than researchers determined in 2010.

“Above those limits, core temperature rises continuously and risk of heat-related illnesses with prolonged exposures is increased,” they wrote. “The results of these tests show an even greater cause for concern.”

3. Age matters

Extremely hot whether is particularly dangerous for those over 70, according to family physician Dr. Gabriel Neal, who teaches at the Texas A&M Health Science Center College of Medicine.

In his article on avoiding heat stroke, Neal described factors making older adults vulnerable to heat-related illnesses.

“As people age, our bodies’ ability to cool declines, and the elderly often take medication that further impairs this ability,” Neal wrote. “In addition, the elderly may not be aware of the dangerous heat wave and may not have working air conditioning in their home, nor have anyone to check on them.”

4. Wet or dry, hot is hot

It’s the heat and the humidity, wrote Mississippi State University exercise physiologist JohnEric Smith.

“Hot desert climates are stressful due to extreme temperatures, while humid subtropical climates are stressful because the body has trouble removing heat when sweat doesn’t evaporate readily,” he wrote.

Smith added that how heat and humidity affect people depends on factors like the weather that’s typical where they are, and the cooling systems in local homes and buildings.

5. Warming up food

Tufts University epidemiologist Elena Naumova warns that keeping food safe to eat is becoming more challenging in a warming climate. “That’s because warm, wet weather conditions stimulate bacterial growth,” she wrote.

Naumova named several climate-related factors in spreading foodborne illnesses. “One growing problem is that heat waves, wildfires and severe storms are increasingly triggering power outages, which in turn affect food storage and food handling practices in stores, production and distribution sites and homes,” she wrote.

Editor’s note: This story is a roundup of articles from The Conversation’s archives.

Leah Samuel, Health + Equity Editor, The Conversation

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Vacancy BOS Letter 1 by LakeCoNews on Scribd

Powerful storm systems triggered flash flooding across the U.S. in late July, inundating St. Louis neighborhoods with record rainfall and setting off mudslides in eastern Kentucky, where at least 16 people died in flooding. Another deluge in Nevada flooded the Las Vegas strip.

The impact of climate change on extreme water-related events like this is becoming increasingly evident. The storms in the U.S. followed extreme flooding this summer in India and Australia and last year in Western Europe.

Studies by scientists around the world show that the water cycle has been intensifying and will continue to intensify as the planet warms. An international climate assessment I coauthored in 2021 for the Intergovernmental Panel on Climate Change lays out the details.

It documented an increase in both wet extremes, including more intense rainfall over most regions, and dry extremes, including drying in the Mediterranean, southwestern Australia, southwestern South America, South Africa and western North America. It also shows that both wet and dry extremes will continue to increase with future warming.

Why is the water cycle intensifying?

Water cycles through the environment, moving between the atmosphere, ocean, land and reservoirs of frozen water. It might fall as rain or snow, seep into the ground, run into a waterway, join the ocean, freeze or evaporate back into the atmosphere. Plants also take up water from the ground and release it through transpiration from their leaves. In recent decades, there has been an overall increase in the rates of precipitation and evaporation.

A number of factors are intensifying the water cycle, but one of the most important is that warming temperatures raise the upper limit on the amount of moisture in the air. That increases the potential for more rain.

This aspect of climate change is confirmed across all of our lines of evidence discussed in the IPCC report. It is expected from basic physics, projected by computer models, and it already shows up in the observational data as a general increase of rainfall intensity with warming temperatures.

Understanding this and other changes in the water cycle is important for more than preparing for disasters. Water is an essential resource for all ecosystems and human societies, and particularly agriculture.

What does this mean for the future?

An intensifying water cycle means that both wet and dry extremes and the general variability of the water cycle will increase, although not uniformly around the globe.

Rainfall intensity is expected to increase for most land areas, but the largest increases in dryness are expected in the Mediterranean, southwestern South America and western North America.

Globally, daily extreme precipitation events will likely intensify by about 7% for every 1 degree Celsius (1.8 degrees Fahrenheit) that global temperatures rise.

Many other important aspects of the water cycle will also change in addition to extremes as global temperatures increase, the report shows, including reductions in mountain glaciers, decreasing duration of seasonal snow cover, earlier snowmelt and contrasting changes in monsoon rains across different regions, which will impact the water resources of billions of people.

What can be done?

One common theme across these aspects of the water cycle is that higher greenhouse gas emissions lead to bigger impacts.

The IPCC does not make policy recommendations. Instead, it provides the scientific information needed to carefully evaluate policy choices. The results show what the implications of different choices are likely to be.

One thing the scientific evidence in the report clearly tells world leaders is that limiting global warming to the Paris Agreement target of 1.5 C (2.7 F) will require immediate, rapid and large-scale reductions in greenhouse gas emissions.

Regardless of any specific target, it is clear that the severity of climate change impacts are closely linked to greenhouse gas emissions: Reducing emissions will reduce impacts. Every fraction of a degree matters.

This is an updated version of an article originally published on Aug 9, 2021.

Mathew Barlow, Professor of Climate Science, UMass Lowell

This article is republished from The Conversation under a Creative Commons license. Read the original article.