From the UK’s University of Exeter, Professor Tim Lenton explains the climate niche where most of humanity lives. But that zone is shifting, and billions of humans will migrate away from uninhabitable countries, mostly northward toward the Poles – not centuries but mere decades from now. Dr. Radley Horton from Columbia University warns killer heat and humidity are already popping up around the world, including the United States. Human productivity, crops, and lives are lost, with more to come in a rapidly warming world. Like the virus, the greenhouse world doesn’t care if you believe it, deny it, or postpone action. Now we are in a race to keep as much earth as we can within limits dictated by our health.

Almost anyone could see the new Coronavirus boiling up in China. In a global world it was bound to come, but still most other countries did not react and prepare. Now leading scientists have another warning: extreme and deadly heat is not just the future, it is already here. Will we listen this time?

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



New science finds home to billions of humans now living could become uninhabitable due to climate change. Some plants only live within narrow temperature bands. Now we learn, that is generally true of humans as well. But temperatures are changing – this planet is warming. In fact, people living during the next 50 years will see changes greater than any in human history.

Professor Timothy Lenton is Director of the Global Systems Institute at UK’s University of Exeter. He returns to Radio Ecoshock as co-author of a benchmark paper published this May in the journal Nature. It’s called: “Future of the human climate niche”. Beyond the startling headlines, we find a new understanding of humans and where we live.

Listen to or download this 30 minute interview with Tim Lenton in CD Quality or Lo-Fi


The fundamental concept of a human niche is characterized by a major mode around 11 °C [52 F] to 15 °C [59 F ] mean annual temperature (MAT). Rainfall is less of a factor, as are soils. Where we find that sweet spot of mean annual temperature, we find most of humanity (except for one hotter zone in India).

But some places where humans congregate are about to get much hotter. The zone where we humans thrive will move toward the Poles, meaning mostly North, as that is where the most land is. That expose more than a billion people to heat so uncomfortable, in fact so dangerous, that is can become impossible to be outside.

In the journal Nature, the authors summarize:

We demonstrate that depending on scenarios of population growth and warming, over the coming 50 y, 1 to 3 billion people are projected to be left outside the climate conditions that have served humanity well over the past 6,000 y[ears].

Absent climate mitigation or migration, a substantial part of humanity will be exposed to mean annual temperatures warmer than nearly anywhere today.”

As our next guest Radley Horton explains, even a very healthy person in sitting in the shade, taking it easy with plenty of fluids, could not survive the extreme heat coming withing a decade or three. The human body cannot sweat above what is called 35 degree Centigrade heat and humidity. If we cannot sweat, we cannot cool the blood, we overheat and suffer heatstroke or death. Even a healthy person could die.

But Lenton tells us the situation is not a simple equation of heat driving masses northward. There are other drivers, Lenton tells us, that may move people sooner, like the desire for a better life in a more developed economy. That is already an active force, more the carrot drawing people than the heat stick driving them. But we know that productivity in extreme heat drops, lowering the economy. In fact, Lenton tells us a study showed even factory workers inside an air conditioned building produce less when it is hot and sunny outside.

A few years ago, American author Stan Cox told our listeners the internal migration south to the American “Sun Belt” could not be maintained without air conditioning. So a trigger for mass migration within a country may not be heat directly, but possibly something like a massive failure of the electric power gid. So the actual trigger or threshold might be a social or technical development rather than a heat wave, or a series of heat waves. Listen to that 21 minute Stan Cox interview here.

Heading to Air Conditioned Hell



Yet some countries, in the Middle East, Asia and Africa will experience heat waves that are uninhabitable. Worse, the ultra hot zones, like sub-Saharan Africa – are exactly where population is expanding fastest. That adds more billions of people who will be exposed to extreme, lethal heat. It stands to reason that if they can, millions and millions of people will be on the move, searching for more livable places, for the “human niche”.

From this new paper:

Despite the formidable psychological, social, and political barriers to migration, a change in the geographical distribution of human populations and agricultural production is another likely part of the spontaneous or managed adaptive response of humanity to a changing climate.

I ask Tim whether he personally thinks a mass migration is likely this century due to climate change. He doesn’t find any other alternative. It looks to me like the Big Move is coming, whether distributed over decades as the new normal, or in unexpected waves much bigger than the migration to Europe or America in recent years. Perhaps by 2040, the approach of hazardous heat will be so obvious that governments, or global agreements, will facilitate the movement of millions or billions of people. That seems unlikely from what we see at present. I think it will happen anyhow, involving tragedy and perhaps conflict or mass death.


Officially, the worst predictions for global mean temperature by 2070 are maybe 2 degrees C. of warming. But this team of scientists suggest billions of people will experience 7.5 degree C temp rise, compared to the year 1700. That is because the land heats up much more than the ocean. The great seas lower the global mean temperature far below the actual heat we will live through.

The paper says:

Compared with the preindustrial situation 300 y BP, the mean human-experienced temperature rise by 2070 will amount to an estimated 7.5 °C, about 2.3 times the mean global temperature rise, a discrepancy that is largely due to the fact that the land will warm much faster than the oceans, but also amplified somewhat by the fact that population growth is projected to be predominantly in hotter places

Nothing in our stories, legends, or religions, deal with the kind of temperature and ecological changes this paper suggests. Barring a climate miracle, we have no historical model for the changes we are about to experience.

According to credits published in Nature, China is the primary funder of this research. The lead author is Chinese scholar Chi Xu. Looking at the figures in this paper, it becomes apparent there will be geographic winners and losers as the world warms extraordinarily rapidly. But during this century, the human niche doesn’t shift dramatically to northern Canada or Siberia. Instead, it looks like Northern Europe and the northern U.S. States will become more habitable, while the Equatorial zones, from Brazil through Africa and a lot of India will suffer.

This new science shows that humans have their preferred habitat, just like other animals and plants. Despite our technology, and thinking we are somehow above nature, the actual demographics show that humans have the ecological niche, with limits we are breaking as we alter the atmosphere and the climate. This is fine science, explained by a veteran scientist, and produced by some of the best in the field. I urge you to listen, learn, and pass this program on to others.

I previously interviewed Tim Lenton for the January 2020 show.

Disaster in the Making: Cascading Tipping Points & Permafrost

If you have access, here are two key articles about this paper, from the Washington Post and the New York Times. Canadian scientist Paul Beckwith made a video about this paper as well.




A new paper warns high heat and humidity will become deadly over the next decades as the climate shifts. Well, as American novelist William Gibson said: “The future is already here – it’s just not evenly distributed.” Another paper just released in Science Advances, says lethal pockets of heat are already appearing in some countries, including the United States. The title is: “The emergence of heat and humidity too severe for human tolerance”.

From Columbia University’s Earth Institute, we have reached co-author Dr. Radley Horton. He is an Associate Research Professor at the Lamont-Doherty Earth Observatory, a Convening Lead Author for the U.S. National Climate Assessment, and serves on numerous climate task forces, with a long list of important scientific papers.

Listen to or download this 27 minute interview with Radley Horton in CD Quality or Lo-Fi


In 2017, Horton co-authored an article on projections for “a rapid rise in global heat stress exposure “ exceeding “limits of human tolerance by mid- to late-century.” Then their team wondered: what if that future is already here?

Global climate models use such large grids that they miss super heat and humidity in localities, even in large cities. So these scientists checked masses of actual weather records, and found the new extreme heat has popped up all over the world – even in Biloxi Mississippi. My estimate is that what was formerly a few hours on uninhabitable conditions becomes a few days, and then a month or two, as we continue to heat the planet. The coming heat is not “evenly distributed” – yet.

Frankly, the whole concept of a sliding scale of temperature and humidity is hard for the public to grasp. Canadian meteorologists call it “the Humidex Index” and that’s what we see on TV weather reports. American weather casters talk about the “Heat Index”, but that is based on something different. I don’t know what it is in Europe, or India, or what scientists call it. If this is a matter of life and death, why is it all so confusing? The broad public does not understand this combination intellectually, but we all get it when it happens. It’s just too hot and muggy to go outside. We can’t stand it. And those who ignore that feeling can suffer serious health problems including possible death.

From my interviews with previous guests, including Camilo Mora [“Twenty-Seven Ways a Heat Wave Can Kill You: Deadly Heat in the Era of Climate Change”] and Alex de Sherbinin, we know that heat deaths are poorly recorded. The actual cause on the death certificate may be heart attack or something else.

Fatal Heat Warning

The Dark Edges Of Climate Change

The difficulty getting this across to the public was covered in a 2017 paper led by Radley’s co-author Tom Matthews in the Proceedings of the National Academy of Sciences. Their team found “by 2050, at least 350 million more megacity inhabitants [will be] afflicted by midcentury.“ Whether we know it or not, the coming heat is a threat to megacities in many parts of the world.

When I interviewed Kristina Dahl, the climatologist from the Union of Concerned Scientists, she suggested some cities are sometimes already beyond the limits of heat tolerance, due to the heat island effect.

Big Questions About Your Future


One of the strange symptoms of heat stroke is confusion. People may not realize they are in danger, and may not seek shelter or help. In a way, we are already in that position with all of global warming,


No doubt about it, everything is harder during the biggest pandemic and economic crash of our lives. Connecting with guests is harder and we are all distracted in the headlights of this oncoming time. I’m Alex Smith. Thank you for listening to Radio Ecoshock, and caring about what really matters in this world.

Jackson Browne – The Pretender (Solo Piano) (BBC TV 1994)