Extreme Temperature Diary-July 20, 2019/ Major U.S. Heat Wave Day Five + A Warning From The Union Of Concerned Scientists

Saturday July 20th … Dear Diary. The main purpose of this ongoing blog will be to track United States extreme or record temperatures related to climate change. Any reports I see of ETs will be listed below the main topic of the day. I’ll refer to extreme or record temperatures as ETs (not extraterrestrials).😉

Major U.S. Heat Wave Day Five + A Warning From The Union Of Concerned Scientists

Are you hot enough yet? Today will be the peak of the current U.S. heatwave north of Washington D.C. I’m expecting to see and report many “ETs” by Monday from the Midwest into the Northeast due to the intensity of this episode of heat. On Sunday we will see very little relief along the East Coast, but a front will put a big dent in extreme heat across the Midwest:

Meteorologically, from my experience looking at upper air patterns for about 35 years, this years’ most intense U.S. heat wave could have been so much worse and lasted much longer had a) there been a stronger 500 millibar heat dome well above 594 decameters and b) had there been a more stable pattern with the ridge not having a tendency to retrograde towards the Rockies. Certainly, compared with heats domes building over Europe this year, the U.S. will be lucky.

This week the Union of Concerned Scientists put out a report warning that should carbon pollution not get checked, indeed heat waves on the par of this weeks’ will be very common, and perhaps last for most of the summer, not just for a few days:

Please read all the links contained in the above report, which have eye popping charts. Here are some highlights:

About this:

The analysis and data used to create these interactive maps comes from two sources:

The results presented here represent the average over distinct 30-year periods—a historical baseline (1971–2000), midcentury (2036–2065), and late century (2070–2099)—and the average of 18 high-resolution climate models.

The heat index and “off-the-charts” conditions:

The heat index is a combination of temperature and relative humidity that was originally formulated to capture all but the most extreme conditions occurring on Earth. The US National Weather Service (NWS) uses heat index-based thresholds as the basis for issuing heat advisories and excessive heat warnings.

For heat that exceeds the ranges of the temperature and relative humidity values that were considered in the original heat index formulation, skin moisture levels are so high that sweating is significantly inhibited and the equations used by the NWS to calculate the heat index become unreliable. In these cases, the heat index exceeds the upper limit of the NWS scale, which falls at or above 127°F, depending on the combination of temperature and humidity. In other words, the heat index is literally “off the charts.”

While health risks exist at all heat index values above 80°F, the severity of those risks varies depending on who is exposed, whether they are engaged in physical activity, and how long the exposure lasts.

For off-the-charts conditions, the health risks are not well documented; historically fewer than 2,000 people in the US are exposed to off-the-charts conditions in an average year. NWS guidance does indicate, however, that for heat index values above 130°F, heat stroke, the most severe heat-related illness, is “highly likely with continued expo

The analysis found large reductions in the intensity and frequency of extreme heat days in a scenario that limits global warming to 2°C (3.6°F), compared with a scenario in which heat-trapping emissions continue to rise along their current path.

To limit future extreme heat, the United States must contribute to global efforts to constrain climate change and invest in solutions that get us to net-zero carbon emissions by midcentury. Solutions such as an economy-wide price on carbon, a national low-carbon electricity standard that helps drive more zero-carbon electricity generation, and policies to reduce transportation emissions would help to achieve meaningful emissions reductions at the national level.

In the years to come, we will also need to significantly ramp up efforts to prepare for the effects of extreme heat in all communities, and to especially bring resources to those most at risk. Among other things, these efforts need to include a national extreme heat early warning system, expanded funding to provide cooling assistance to low- and fixed-income households, and a national heat health protective standard for outdoor workers.

For additional information on the heat index, the methods used in this study, and solutions that will limit future extreme heat and its harms, please refer to the full report.

More results:

A Snapshot of Results Our results show that, with no action to reduce heat-trapping emissions by midcentury (2036–2065), the following changes would be likely in the United States, compared with average conditions in 1971–2000:

• The average number of days per year with a heat index above 100°F will more than double, while the number of days per year above 105°F will quadruple.

• More than one-third of the area of the United States will experience heat conditions once per year, on average, that are so extreme they exceed the current NWS heat index range—that is, they are literally off the charts. • Nearly one-third of the nation’s 481 urban areas with a population of 50,000 people or more will experience an average of 30 or more days per year with a heat index above 105°F, a rise from just three cities historically (El Centro and Indio, California, and Yuma, Arizona).

• Assuming no changes in population, the number of people experiencing 30 or more days with a heat index above 105°F in an average year will increase from just under 900,000 to more than 90 million—nearly one-third of the US population.

• Countrywide, more than 1,900 people per year have historically been exposed to the equivalent of a week or more of off-the-charts heat conditions; this number is projected to rise to more than 6 million people by midcentury—again, assuming no population changes. Late in the century (2070–2099), with no action to reduce heat-trapping emissions, the following changes can be expected:

• The United States will experience, on average, four times as many days per year with a heat index above 100°F, and nearly eight times as many days per year above 105°F, as it has historically.

• At least once per year, on average, more than 60 percent of the United States by area will experience off-thecharts conditions that exceed the NWS heat index range and present mortal danger to people.

• More than 60 percent of urban areas in the United States—nearly 300 of 481—will experience an average of 30 or more days with a heat index above 105°F.

• The number of people who experience those same conditions—still assuming no population change—will increase to about 180 million people, roughly 60 percent of the population of the contiguous United States.

• The number of people exposed to the equivalent of a week or more of off-the-charts heat conditions will rise to roughly 120 million people, more than one-third of the population. Our results show that failing to reduce heat-trapping emissions would lead to a staggering expansion of dangerous heat. In contrast, aggressive emissions reductions that limit future global warming to 3.6°F (2°C) or less would contain that expansion and spare millions of people in the United States from the threat of relentless summer heat. With these aggressive emissions reductions, the above impacts would, in most cases, be held at or below their midcentury levels and would not grow progressively worse during the second half of the 21st century.


Tomorrow we will take a look at an upcoming forecast historic episode of heat slated for Europe next week. Here is a preview:

Here are some more social media messages with article links on this ongoing heatwave. As usual, any newer messages that cross my radar during Saturday will be listed at the top of this article. Check back from time to time to see if I have listed more:

(Dear Diary. As expected, it was a very hot day in the Plains, Midwest, and East. At the tail end of this post I have reports of “ET’s” for your perusal.)

Here is more climate and weather news from Saturday:

(As usual, this will be a fluid post in which more information gets added during the day as it crosses my radar, crediting all who have put it on-line. Items will be archived on this site for posterity. In most instances click on the pictures of each tweet to see each article.)

(This is not weather or climate related but a big scientific deal marking a 50th anniversary):

Here are some of today’s “ETs”:

Here are some worthy mentions that won’t quite make my record count statistical cut:

(If you like these posts and my work please contribute via the PayPal widget, which has recently been added to this site. Thanks in advance for any support.) 

Guy Walton- “The Climate Guy”

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