Over fourteen hundred maximum temperature records have been broken or tied across the United States so far this July as a heatwave lingers from the mid-western and southern states and expands to encompass the eastern states. High humidity accompanies the high temperatures making the heat further unbearable. Little relief is being found overnight with highest minimum temperatures recorded also breaking new records: with 1,951 new records and 1,421 tied records to 21st July.
Related: Human health limits of heat stress with climate change | The US 'normal climate' just got hotter | Higher Temperatures and Crop yields in the US
Climate scientists have been saying that approximately twice as many record-breaking high temperatures have been set compared to record lows across the U.S. in recent decades. The ratio of record high temperatures to record low temperatures is likely to increase from about 20-to-1 by mid-century and 50-to-1 by 2100.
"Climate change is making itself felt in terms of day-to-day weather in the United States," said Gerald Meehl, the lead author and a senior scientist at the National Center for Atmospheric Research (NCAR) in a 2009 media release. "The ways these records are being broken show how our climate is already shifting."
The present extreme heatwave fits the trend for setting new high temperature records. As the heat continues power companies will experience record electricity consumption.
Heatwaves tend to hit the weakest in our society the hardest: the very young, the very old, those suffering illness, and the poor.
Joe Romm on Climate Progress in the article 500 Days of Summer: We’re Having a Heat Wave, a Tropical — and Subtropical — Heat Wave - quotes a Washington Post report that "Many states hit hardest by this week’s searing heat wave have drastically cut or entirely eliminated programs that help poor people pay their electric bills, forcing thousands to go without air conditioning when they need it most. Oklahoma ran out of money in just three days."
Sarah Lovinger, Physician and Executive Director, Chicago chapter of Physicians for Social Responsibility, described the effect of the 1995 Chicago heatwave in this Huffington Post report posted on 20th July:
"The July 1995 Chicago heat wave led to more than 500 excess deaths in one week. Many high-level research studies published following the heat wave determined that most of the Chicagoans who succumbed to the heat were vulnerable elderly residents of this city who lived in high-crime neighborhoods, and were afraid to open their windows. Elderly people who often have underlying health problems are always more vulnerable to dehydration, heat stroke and death. During the Chicago heat wave of 1995, the addition of social isolation proved deadly for many people."
The 2003 European heatwave, which is estimated to have killed 30,000 people, was subsequently shown to be at least partially attributed to Climate change. (Human contribution to the European heatwave of 2003 (PDF)).
There are reports of people dying in the current heatwave, although good estimates won't be known for some time when statistics of heat related admissions to hospitals can be accurately compiled and compared against a similar period in previous years.
This account by CBS plays up the health impacts of extreme heatwave and is a good report as far as it goes....but no mention of the long term trend for more heatwaves, higher temperatures, climate change or global warming:
Media Matters for America have an interesting commentary on the bias inherent in Murdoch's Fox News. Well worth a read: It's Hot! But Fox Only Talks About Global Warming When It's Snowing, or watch their mini documentary on A climate deception: How Fox News Distorts the Climate Debate.
If we do not stabilise and start reducing greenhouse gas emissions there is every likelihood average global temperatures will increase by more than 4 °C (7.2 °F) this century, with temperatures continuing to increase in subsequent centuries. But this is average global temperatures, and inland areas of continents may have even higher average temperatures - perhaps by a 2 °C (3.6 °F) or more.
Researchers at Harvard School of Public Health (HSPH) and Johns Hopkins Bloomberg School of Public Health predict that global climate change will generate more heat waves in the decades ahead. They looked at Chicago and estimate the city could have 166 to 2,217 additional deaths annually due to heat waves in the years 2081–2100.
“Our results show that for a major U.S. city, the impact of future heat waves on human health will likely be profound,” said senior author Francesca Dominici, professor of biostatistics and associate dean for information technology at HSPH.
Human Health limits of heat stress
Scientific research has shown that there are human health limits of heat stress with climate change. When a fit human body exceeds a wet bulb temperature of about 35 °C (95 °F) for extended periods it results in the start of heat stress and hyperthermia - the inability of the body to dissipate excess heat. Heat stroke may occur which is an acute condition of hyperthermia that is caused by prolonged exposure to excessive heat and/or humidity. The heat-regulating mechanisms of the body eventually become overwhelmed and unable to effectively deal with the heat, causing the body temperature to climb uncontrollably. At wet bulb temperatures of 37-38 °C (98.6-100.4 °F) - lethal conditions are reached, even for acclimated and fit individuals.
"Most people are more familiar with the heat index, or the feels-like temperature they see on the weather report. The wet-bulb temperatures we are talking about would have a feels-like, or heat-index, temperature of between 170 to 196 degrees Fahrenheit," Professor Matthew Huber from Purdue University said as reported by the Union of Concerned Scientists (The Health Effects of Hotter Days and Nights).
These conditions that will challenge human physiological limits combining extreme heat with extreme humidity are very rare today, but with increasing global temperatures warming up the hydrological cycle they will increasingly threaten human populations.
Heat waves and Climate change are a public health issue which can only be effectively resolved through mitigation of greenhouse gas emissions.
Background on Climate Change, health and heatwaves:
- Tony McMichael et al, Lancet 2006; 367: 859–69, February 6, 2006 - Climate change and human health: present and future risks (PDF)
- Steven Sherwood and Matthew Huber, PNAS 2010, An adaptability limit to climate change due to heat stress (PDF)
- D´aith´ı Stone et al, University of OxfordHuman contribution to the European heatwave of 2003 (PDF)
Sources:
- NOAA, July 21, 2011 - Heat wave sweeps across the U.S.
- NCAR & UCAR News Center, Novmber 12, 2009 - Record high temperatures far outpace record lows across U.S.
- NOAA - U.S. Daily Highest Max Temperature Records set in July 2011
- Harvard School of Public Health, news May 2011 - Heat Waves Tied to Climate Change Could Increase Urban Fatalities
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