New tested science shows your body’s heat tolerance is much lower than experts assume.  Dr. Daniel J. Vecellio warns of “Greatly enhanced risk to humans” as humid heat stress strikes billions of people sooner than expected.  We just lived through: the big heat jump of 2023.  Why? What happened? Spoiler alert: we are entering a time of multiple crises.

Listen to or download this Radio Ecoshock show in CD Quality (57 MB) or Lo-Fi (14 MB)


Go on and slaughter one another.  Take sides, bicker, and ban.  But from the pandemic to a breaking climate, only working together can help.  Divided we fall.  I’m Alex Smith.  Welcome to Radio Ecoshock.   We begin with information important for anyone with a body.



“In the future, moist heat extremes will lie outside the bounds of past human experience and beyond current heat mitigation strategies for billions of people.”

– Vecellio et al. PNAS 2023

As extreme heat ramps up around the world, more people die of heat than any other weather disasters, including hurricanes and floods.  But what is the danger zone?  Are authorities underestimating heat risks?  Scientists studying our heat resistance just issued a new warning.  The PNAS paper is called “Greatly enhanced risk to humans as a consequence of empirically determined lower moist heat stress tolerance.


We reached the lead author and specialist in the field of heat risks, Dr. Daniel J. Vecellio.  His recent work developed as Post Doctoral Scientist at PennState College of Health and Human Development.  Now he’s with the Virginia Climate Center at George Mason University.

Listen to or download my interview with Daniel Vecellio in CD Quality  or Lo-Fi


For decades, we have been told the danger point for the human body is known. It is 35 degrees C of wet bulb temperature –  a mixture of heat and humidity. But that was not tested.  Vecellio and his colleagues basically put volunteers in rooms and turned up the heat, the humidity, or both.  It, it was not necessary to heat the experimental volunteers to the level of medical emergency.  They just needed to establish the conditions beyond which the body begins to heat up and can’t stop, almost like a physiological tipping point.

That critical heat point was several degrees lower than 35 degrees C.  When applied to maps of expected global heating, and heat waves, for different emissions scenarios, the authors find many more people – billions more people – will experience that “too hot for a human body” combination of heat and temperature.

FROM THIS PAPER (Vecellio et al. 2023):

Heatwaves are associated with increased hospitalization and death for cardiovascular, respiratory, and renal ailments as well as diabetes. These specific outcomes are not solely due to the body becoming too hot, but rather are compounded by the physiological strain extreme heat puts on the body and the body having to compensate to cool itself. Direct heat-related death (i.e., heat stroke) occurs when the core (internal) temperature of the body becomes too high due to the fact that it no longer has the capability to cool itself and biological functions cease.

It increases the risk of both morbidity and mortality in vulnerable groups such as the elderly, children, outdoor workers, and those with comorbidities or those taking medication that causes diminished thermoregulatory capabilities.”

Governments attempt to reduce heat deaths partly by warnings, delivered by television weather personalities.  The United States used the Heat Index, or Humidex system.  We discuss its values and weakness, as well as the warning system used in Europe and the rest of the world: the Universal Thermal Climate Index (UTCI).

The National Weather Service “Heat Index” Is not based on physiological principles or empirical physiological data…. it does not include air movement, like a breeze, or the amount of radiant heat (which is partly determined by the surface, like pavement…) So it’s not that useful.  Yet a July 2022 paper led by Vecellio found the HI (Heat Index) works well enough to continue using it.  Heat Index works for limited physical activity, but is inferior to WBGT (wet bulb globe temperature) when any amount of activity is involved (like sports or working outside or even mowing the lawn).

Daniel was trained first as a geographer.  In this new study we find maps of heat for different levels of warming.  It shows deadly heat will not be evenly distributed, despite the comforting sound of “global mean average temperature”.  Some parts of the world be unlivable for weeks or months, and not others.  A very few places on Earth already breach the thermoregulation threshold even now around 1 degree C. of warming over pre-industrial.  During heat waves, we are also told to stay quiet, rest.  There are conditions where a person just sitting in the shade, with lots of bottled water, could still die on a very hot day.  Those super hot hours, or possibly days, will increase as the planet warms.

The  paper found widespread killer heat might not be a super problem if Earth stays below 2 degrees of warming.  But we we already had tens of thousands die in Europe’s heatwave of 2003.  Millions of people die of heat every year, including over 60,000 European heat deaths in 2022.

We may not be talking about the year 2100 for these danger zones .According to UK Met Office analyses, we could reach 4°C above pre-industrial levels as soon as the 2060’s.  Putting this together, unlivable heat could arrive in the United States, South America and Australia as early as 2060.  But we just had more 600 heat deaths over a few days in British Columbia during the heat dome of 2021.

Another 2023 study in Bangladesh found evidence of high anxiety and depression during heat waves.  More studies show extreme heat reactions like increasing violence, memory loss, and poor decision making as brains and bodies overheat.  Maybe humans will make poor decisions about global warming because of global warming.

When heat strikes, authorities tell us to take shelter, just stay home.  But in the tin shacks of Ghana and slums over the world, indoor heat can be just as deadly.  In fact most of the deaths in the great Chicago heat disaster of 1995 died in their homes.  We need to add indoor heat to the risks found in this study and to public heat education, but Dr. Vecellio says that is difficult to do.  Construction materials and process are so different.  Do people feel safe enough to leave windows open (they did not in Chicago in 1995)?  There may be too many variables to establish a rule for indoor heat danger.

A key paper on survivability was published in 2020 by Colin Raymond and colleagues.  The title is “The emergence of heat and humidity too severe for human tolerance.”  But they also used the “wet-bulb temperature (TW) of 35°C [as] our upper physiological limit…”  According to the new research, that paper, disturbing as it is, underestimated the true danger – but not by much, Vecellio tells us.

The Raymond paper stressed something really important.  Killer heat doesn’t just cover the world like the Global Mean Temperature.  It arrives in small patches.  That may make it harder to believe extreme heat is a killer, if it hasn’t happened where you live (yet).

This whole discussion is about heat/humidity conditions that HUMANS can survive.  What about other mammals, all other animals, insects, bacteria and especially plants?  We learn that plants stop photosynthesis at high temperatures and close their water vents.  At what hotter temperatures will our ecosphere begin to die off around us seems a more important question, or at least as important.




– Analysis by Alex Smith

Earth is steaming, north and south from a mass heating event over the last few months.  Yes, winter will come, into a destabilized atmosphere with record warm ocean below.  Europe has already received a cold blast.  But in the Northern Hemisphere what kind of winter will it be?  A see-saw of almost summer alternating with Arctic incursions?  We do not know, and we cannot know because all the rules of weather have abruptly changed, for a while, or forever, again we do not know.

Based on over 700 hundred interviews with scientists, a new deep dive into breaking research, and my poor brain’s best effort, here is a story about these climate times.

Record-breaking global temperature and crises with strong El Niño

Chinese scientists have a prediction.  From the Academy of Sciences, published September 15, we have this paper: “Record-breaking global temperature and crises with strong El Niño in 2023-2024.”  Crises, plural. I sent several requests for an interview, based on recommendations from another senior scientist. Are my emails even received? The Chinese Academy of Sciences should provide English speaking spokespeople, scientists who can explain their important work as it comes out.

We do have a good article posted at by LI Yuan, from the Academy. Reading from that article:

During the development of a strong El Niño in 2023, warm anomalies are expected to predominantly affect the tropical central-eastern Pacific, the Eurasian continent, and Alaska. However, in the following year, 2024, warm anomalies are likely to encompass the entire continents, significantly increasing the chance of land-based heat waves, droughts, and wildfires.

According to Prof. Zheng Fei, corresponding author of the study, ‘In addition to the surge in surface temperatures, the strong El Niño in 2023-2024 is predicted to trigger a cascade of climate crises.’ These include marine heat wave intensification, ocean deoxygenation, oceanic diversity reduction, damages of marine ecosystems, sea level rise, and crop yields reduction.

Furthermore, China may face multiple climate anomalies during this period. For instance, the suppressed winter monsoon in 2023 may lead to elevated winter temperatures in most regions of China and could also increase the probability of air pollution. In 2024, northern China may experience drought in spring, while southern regions are most likely need to face the risk of extreme rainfall and flooding during the summer.

Remember, a series of posts from former NASA head scientist James Hansen warned “Global Warming is Accelerating.”  That was posted September 14 at the Columbia University site.  Paul Beckwith covers that Hansen post on his YouTube channel with the title “Acceleration of Global Temperature Rise and Climate Mayhem Expected over the Next Year.”




From it all we must learn several harsh lessons.  First, global warming does not go up steadily as shown in too many graphs.  It rises in steps, going further upward fairly quickly with a strong El Nino.  Then it may appear to stabilize, or even decline in temperature for a few years, but never goes anywhere close to heat levels before the step.

Image credit: PBS

A big step happened after the very strong El Nino year in 1997 and ’98.  The warming continued near the high levels set that year, but not by as much.  It was a mistake to call that period, going at least until 2009, a “hiatus”.  The rate of increase slowed, but did not stop.

Take this example.  Suppose world population increased at 2% a year for a decade, and then drops to a 1% increase for a few years.  Media pundits and social media hacks tell us humans face a major population decline because look – the increase is slowing down, dropping to half what it was!  So if the world population is 8 billion in 2022, and adds 2%, that adds 160 million more humans.  Suppose in 2023 that drops to 1% increase, a supposed slow-down – that still means roughly 80 million more humans for the already overstretched ecosystem to support.  A declining rate of increase is still an increase.  It sounds simple, but millions of people get this wrong, over and over, including educated ones.

After the year 2000, as many countries industrialized and added fossil-driven infrastructure, including both car culture and air travel in China, India, and more, humans released huge amounts of greenhouse gases into the atmosphere.  Emissions were much higher than even the 1990’s.  Why didn’t Earth respond with more heating right away?


We now know, from many scientific studies, during recent decades, the extra energy reflected back to Earth was absorbed into the ocean, rather than overheating land.

The ability of the ocean to absorb excess energy and carbon is well known and yet not well known.  In a recent work, a group of scientists including optimist Michael Mann and less-optimistic Kevin Trenberth deduced that if fossil fuel emissions stopped today, the world would not keep warming due to feedback effects like permafrost thaw.  See: “The ocean response to climate change guides both adaptation and mitigation efforts” led by John Abraham.

These top scientists say the oceans have the power to re-balance Earth’s temperature regime at whatever level of warming exists at the time when fossil fuel burning ends.  The seas could even capture new carbon from feedbacks like thawing permafrost.  It is like a pardon for our industrial sins.  although really the result is a long delay in warming, postponing the heat to later centuries.  All the heat captured by the seas and mixed down would eventually return to warm a future Earth, centuries to a millennia later.

Discussing that paper by Mann et al. in our Radio Ecoshock interview, Kevin Trenberth discounted the value of this mechanism as a savior, saying we are not ending fossil fuels but in fact increasing them.  So it is just an intellectual argument for now.  In private correspondence Trenberth wrote: “The concept of net zero is academic.  It will not happen.  There is no progress toward the commitments most nations have made and some aspects are fraught with difficulty, but the main difficulty is political and ethical.”

But the paper shows two things: first, ocean absorption of heat can be the most powerful climate moderating force on the planet and second, it is possible that whatever crazy temperature humans create, it we stop planetary predation, contrary to earlier fears, Earth may not go on to runaway heating ever after.  Climate may reach a new resting point of relative stabilization with a gradual warming after that.  Perhaps humans and other species could adapt, IF we survive the wrenching rate of change.


While all the media and attention goes to the great judgment of La Nina or El Nino in the Pacific,  Chinese scientists say the Pacific is not the place to look for climate determination.  The decider is the Atlantic, and the other end of the Great Conveyor Belt of currents, the Southern Ocean.  The tipping point that can cascade into multiple tipping triggers is the Atlantic Meridional Overturning Circulation.  Known as AMOC, that will determine the big change they say.

Many times even during the last million years, overturning in the North Atlantic has shifted between two states   AMOC has a positive or strong phase, and a negative or weak phase.  During the strong phase, huge volumes of water flow from the tropics toward Greenland.  There, with a change in their salt content and cooler, they sink toward the bottom, to begin a long journey back toward Antarctica.  That is part of the Great Conveyor Belt.  This civilization developed during a strong phase, but now it is weakening.

Several scientists on Radio Ecoshock, including Susanne Ditlevsen, Johannes Lohmann, and Levke Caesar, document weakening in the North Atlantic ocean circulation system.

But the impact of AMOC shifting to a weak phase appears to have changed.  In all earlier ages, a weakening AMOC announces and leads to a cold period, like the Younger Dryas.  Now, (due to changes in energy imbalance I suppose?), a weakening AMOC adds more global heating.  I have to find out why.

Keeping that conundrum in mind, there are several kinds of El Nino events, with different impacts.  In his series of Radio Ecoshock interviews in Fall 2022, Kevin Trenberth also told us the El Nino cycle has been overwhelmed by increasing greenhouse gases as the major driver of climate change on this planet.  El Nino or La Nina has become the handy hook for news stories that obscure real causes and our role in them.  But we have to look elsewhere to explains the sudden rash of heat waves all over the world in 2023.

Earth’s oceans were in a decade-long period of mixing.  Heat from the surface was mixed into a layer further down.  Earth’s energy imbalance, as measured at the top of the atmosphere, was hidden in the sea.  But that oscillation period ended. The ocean began to release more of that heat.  Look up the Pacific Decadal Oscillation.  That twenty to thirty year cycle is affecting the way new heat appears.  The release of stored sea heat during the Pacific Decadal Oscillation is accelerated by an El Nino condition.

El Nino is marked by hotter surface temperatures in the Pacific, releasing so much heat that weather around the world is affected.  As Hansen and others, like Radio Ecoshock guest Kevin Trenberth explain, measurements of past El Nino events show the largest effect is delayed until the second year.  That would be 2024, as the Chinese Academy paper also predicts.

But something else is happening at the same time, because even at the very start of this El Nino, Earth shattered every major heat record in both hemispheres, regardless of the season, summer or winter.  That is a novel climate change developing not in the second year, but immediately.  Most scientists that I follow are struggling to find out why.

A small group of scientists and researchers claim the early heat rise is due to changes in aerosols.  People like James Hansen and Ecoshock guest Leon Simons point to a large reduction in sulfur particles in the atmosphere, following new ship pollution regulations in 2020.  That did happen, and no doubt has some heating power.

Others are looking at the missing mirror at the bottom of the Earth.  Sea ice around Antarctica practically disappear, leaving a dark heat-absorbing ocean surface instead of reflective white ice.  But that alone doesn’t seem enough energy change to power record heat we experienced in 2023.

There is a scramble to assess all the pieces.  Was a tipping point crossed?  That could have happened even a few years ago, coming into sight and experience now.  Is a complex of positive feedbacks somehow interacting?  Answers seem important, as all life as we know it may hang in the balance.


A second lesson from these chaotic climate times: figures used for global mean temperature rise, over industrial levels, are misleading when assessing risk and reality where you live.  The globe doesn’t warm as one planet.  Warming is patchy.  The United States is warming faster than average.  The Arctic is warming four times faster than average.  Some places are warming only slowly, less than average.  And all the new heat is moved around by large weather systems, the Jet Stream, planetary waves, and ocean currents.

In the radio program, I play you a few minutes from an excellent piece from PBS Terra, posted on YouTube in April 2023.


That is from PBS Terra.  The program “Weathered” is hosted by weather expert Maiya May and produced by Balance Media.

Another aspect of using global mean temperature, like 1.5 degrees C or 2 degrees over pre-industrial is misleading.  Land will warm much more than the sea.  It takes unimaginable amounts of energy to warm the vast sea even a little.  Land heats up relatively quickly, sometimes in a few days.  Oceans cover more than 70% of the planet.  If the ocean heats up 1 degree, land temperatures might go up 2 degrees C or more in some places, yielding a global average of 1.5 degrees C. heating.  In reality, the heat you and I experience will be much more than this small-sounding 1.5 degrees C. or 2.7 degrees Fahrenheit rise.

Authorities from governments to traditionalist scientists talk about 1.5 degrees C of warming, and then nice even numbers going up.  The Celsius measuring system makes the change sound small.  But as we learn from multiple climate-driven crisis in 2023, even a small change, say .1 degree C, can destabilize major systems, from wildfires to monsoons to rainfall.  Each tenth of a degree needs to be elevated to become a big number, not a small sounding fraction.  Who can blame the public and their alleged leaders for underestimating the power of climate change?  Even the number system conspires to downplay dangers already destabilizing our crops, our lives, and all species from microscopic life to the largest species.  Perhaps our brains are too small to understand, though we try.


An overview from a large mind might help.  Last June, videographer Nick Breeze interviewed Dr. David King, former Chief Scientist for the United Kingdom.  This 13 minute condensed version released by Nick Genn on YouTube brings an overview of where we are and what we could.  There is a longer version for Genn’s supporters.


Find Nick Breeze’s ongoing climate film project “ClimateGenn” at

One final tip.  Even if you have stopped reading books, get and read Naomi KIein’s new book “Doppleganger”.  Many troubling faces of our times will be explained.

I’m Alex Smith.  We are out of time.  Please join me again next week for more Radio Ecoshock.  Thank you for listening, and caring about our world.


Nick Breeze ClimateGenn
Premiered Jun 18, 2023 (full 26 minute version for Patreon and YouTube members).

Full 26 min members version Contents:

1. Antarctica Sea Ice Decline
2. Antarctic versus Arctic differences
3. Greenland can change the global map
4. Arctic methane release and potential warming
5. Have we crossed a global threshold
6. Can we repair climate
7. Interventions – climate repair
8. Climate is only one of our challenges
9. We need new economic models
10. UN COPs and broken promises
11. Climate is a today problem from Bangladesh to Vietnam
12. Loss & Damage is the insurance of the future
13. Can we save Antarctic Ice Sheets
14. COP28 nightmare