Three degrees C warming by 2050? Catastrophe, and what we have to do to avoid it – famous American scientist V. Ramanathan from his life work & new science. Dr. Andy Ridgwell from UC Riverside on the last great warming of 5 degrees C. Radio Ecoshock 170927

Download or listen to this Radio Ecoshock show in CD Quality (56 MB) or Lo-Fi (14 MB)


Welcome to Radio Ecoshock, where we prepare for the horror and the hope. This week you’ll hear one of the most important interviews I’ve ever done, with one of the Gods of science. For a couple of decades, I’ve followed the work of V. Ramanathan from the Scripps Institution in California. “Ram” as he’s known, worked with one of his star post-docs, Yangyang Xu, to draw the big picture. They gathered up the four decades of Ram’s data collection, starting with his participation in the launch of an early climate satellite in the 1980’s, rolling through the many planes scooping up air over India and China, the ocean buoys, the works.

The result is as huge as any paper James Hansen has put out. They find that except for the dimming effect of pollution, the Earth energy has already surpassed 1.9 degrees C above pre-industrial levels, well above the danger zone. There is a 1 in 20 probability we will go past 3 degrees C by 2050. That is called catastrophe, and this paper looks even beyond catastrophe, into the existential threat of the unknown.

Knowing that, the pair calculated what we have to do to save ourselves, and they lay it out in 3 great steps. It’s difficult, but not impossible, Ramanathan says, to return to 1.5 degrees of warming by the end of this century.

In the second half hour, Professor Andy Ridgwell from the University of California Riverside joins us to explore the last time Earth warmed by five degrees in a relatively short time. His new paper says that volcanoes, not melting methane, caused the event known as PETM, 56 million years ago.


Veerabhadran Ramanathan is widely known as “Ram”.

The title of his new paper is “Well below 2°C: Mitigation strategies for avoiding dangerous to catastrophic climate changes” with lead author Yangyang Xua from Texas A&M.

You can listen to this Radio Ecoshock 24 minute interview with V. Ramanathan right now, or download it in either CD Quality or Lo-Fi


We start of discussing three categories or scenarios of warming. In addition to the possibilities accepted by the Intergovernmental Panel on Climate Change, this paper adds two new features: (1) they discuss warming beyond 5 degrees C (the IPCC stops at 4 degrees) and they add a Low Probability High Impact (LPHI) scenario. That only has a 1 in 20 chance (5%) of happening – but as Ram says, if you thought your airplane had a 1 in 20 chance of crashing, you would never get on it. Our climate has a 1 in 20 chance of crashing by 2050, warming up as much as 3 degrees C. in a little over 30 years time.

The current risk category of dangerous warming is extended to more categories, which are defined by us here as follows:

>1.5 °C as dangerous;

>3 °C as catastrophic; and

>5 °C as unknown, implying beyond catastrophic, including existential threats.

With unchecked emissions, the central warming can reach the dangerous level within three decades, with the LPHI warming becoming catastrophic by 2050.


Now we get to the brighter news in this paper. The authors propose three “levers” that humans can pull to veer away from climate disaster.

The first is to become carbon neutral.  The next lever involves “super-pollutants”.

The final necessary step is going to be the most difficult, I think. That is carbon extraction and sequestration, the technology known as CES. As far as I know, there is no working CES tech on a commercial scale on the planet today. Should we place our hope in a technology we don’t have yet?

Another paper has just been published in the journal Nature Geoscience tackling this same subject. It’s title is “Emission budgets and pathways consistent with limiting warming to 1.5°C“. The lead author is Richard Millar of Oxford.  And the excellent climate journalist Chris Mooney looks at both papers in this important article in the Washington Post.


I ask Dr. Ramanathan about something I call “the paralysis of climate doom”. Even reading this paper, by the time I got through the abstract and the helpful introductory boxes, I was so overwhelmed by the awful possibilities, that I had trouble concentrating on the solutions offered. It there a problem getting solutions going, when we are facing such a huge danger? I think so.

Are we seeing hints of “catastrophic” climate change in the record hurricanes just seen, destroying entire islands in the Caribbean, and drowning parts of Texas? Adding in the massive wildfires seen in more than 2 continents this summer – at what point do we say we are already entering the catastrophe?


We have already warmed by at least 1 degree C from pre-industrial levels, probably more. The authors say (following the Paris Agreement) that anything above 1.5 degrees is “dangerous” – and we are already almost there, even without considering the amount of warming “still in the pipeline” as James Hansen says – in part due to the masking effect of particulate pollution – in which V. Ramanathan was a pioneer. I must ask him about this.

In a box in this paper, the authors say

By 2015, the warming due to CO2 is about 0.8 °C and that due to SLCPs [Short-Lived Climate Pollutants] is about 1.1 °C. The sum of the CO2 and SLCP warming is already close to the Paris Agreement limit of 2 °C by 2015. On the other hand, the aerosols have a cooling (“masking”) effect of about -0.9 °C. When we add the sum of the CO2, SLCPs, and aerosol effects to the warming due to non-CO2 LLGHGs, the estimated warming by 2015 is ~1.1 °C, which can be compared with the observed warming of about 1 °C

So, we are already close to 2 degrees C of real energy imbalance, the real warming if cooling aerosols did not mask it, and beyond the point the authors call “catastrophic”. We are only protected by the cooling effect of soot, dust, sulfates and nitrates. But James Lovelock suggested it’s possible that whole dust mask, if you will could tumble down in a matter of weeks. Without further production of aerosol pollution, rainfall could bring it down in a few weeks.

I suggest that any event that brings industrial production, commerce and shipping to even a temporary halt could bring down that shield. A nuclear war would not do so, because it kicks up it’s own even greater dust cloud with soot from burning cities. An asteroid strike would also create great clouds of dust (coming up in my interview with Dr. Charles Burdeen soon). But an electro-magnetic pulse from a solar storm could knock out electric-dependent society and commerce, or a simple giant economic crash might do it. The 911 terrorist attack created clear skies for a few days, after aircraft stopped moving. But I believe Ramanathan has already said that soot and dust from developing countries, including Indian cooking, would continue as long as those people were alive.

After this study, does Ramanathan think cooling aerosols are projected to increase along with greenhouse gases? What would be the net result by 2050, if all current trends are continued? Is there a point, or a date, at which GHG’s overwhelm the cooling aerosol effect?  That has already happened, Ramanathan tells us.

Isn’t it ironic that Ramanathan’s campaign to reduce particulate pollution, particularly over Asia, if successful – would increase warming to the actual energy imbalance that has been hidden by pollution? Should we be thankful for the pollution, as a short-term protection until we can act on climate change, even though it endangers the health of millions, and may even be reducing agricultural and natural performance (e.g. if China is receiving up to 9 percent less sunlight due to pollution)?

This paper says we will reach the dangerous level within 30 years (i.e. by about 2047) if emissions are not reduced. But by 2050, essentially in the same time period, the low probability (5%) high impact scenario would be “catastrophic” (implying greater than 3 degrees C warming over pre-industrial) by 2050! That’s a tremendous risk, no matter how small the odds. Do we have a 5% chance of nuclear war by 2050? Perhaps, but even that is less certain than the physics behind the climate modeling.

We have had scientists on this program suggesting that at least 3 degrees of warming is possible on our current trajectory of emissions. That is “catastrophic” these authors say. But that is our destination on our current emissions path.


It is interesting that scientists with a Chinese and an Indian background bring up this seldom-discussed problem of the grave imbalance of climate change impacts as we go along.

This is from the new paper:

Climate risks can vary markedly depending on the socioeconomic status and culture of the population, and so we must take up the question of “dangerous to whom?”. Our discussion in this study is focused more on people and not on the ecosystem, and even with this limited scope, there are multitudes of categories of people. We will focus on the poorest 3 billion people living mostly in tropical rural areas, who are still relying on 18th-century technologies for meeting basic needs such as cooking and heating. Their contribution to CO2 pollution is roughly 5% compared with the 50% contribution by the wealthiest 1 billion.

This bottom 3 billion population comprises mostly subsistent farmers, whose livelihood will be severely impacted, if not destroyed, with a one- to five-year mega drought, heat waves, or heavy floods; for those among the bottom 3 billion of the world’s population who are living in coastal areas, a 1- to 2-m rise in sea level (likely with a warming in excess of 3 °C) poses existential threat if they do not relocate or migrate. It has been estimated that several hundred million people would be subject to famine with warming in excess of 4 °C . However, there has essentially been no discussion on warming beyond 5 °C.


Veerabhadran Ramanathan: Climate change morphing into an existential problem

Published on Apr 12, 2017




When it comes to rapid global warming, the best example we have happened around 56 million years ago. The planet warmed up about 5 degrees C. in less than 5 thousand years, which is very fast in geologic time. To know what can happen now, we badly need to find out about a rapid warming event called the Palaeocene-Eocene Thermal Maximum or (PETM).

With no humans burning fossil fuels, what happened? The best guess was that frozen methane on the sea floor reached a tipping point, and came burping up into the atmosphere as major warming gases. That was the story I accepted, until a revolutionary new paper was published in the journal Nature on August 30, 2017.

We’ve reached a co-author of that paper, Dr. Andy Ridgwell. He’s a former roads and trees activist in rural Devon. Andy got his Doctorate in the UK, at the University of East Anglia. After research in Canada, Ridgwell became a Professor at the University of California, Riverside. He specializes in bio-geochemical modeling and climate change. Find his web site here.

Dr. Andy Ridgwell

You can listen to this Radio Ecoshock 26 minute interview with Andy Ridgwell right now, or download it in either CD Quality or Lo-Fi


We should note this new science of the PETM was let by Dr. Marcus Gutjahr of the Helmholtz Centre for Ocean Research in Kiel, Germany. This new paper in the journal Nature is titled “Very large release of mostly volcanic carbon during the Paleoeocene-Eocene Thermal Maximum“.

For me, there are several important angles to the story Ridgwell can now tell us.


For example, should we worry a little less about frozen methane (“clathrates”) melting at the ocean floor, giving us a kick of super warming methane? That’s been raised by the Arctic Methane Emergency Group (including our guest Paul Beckwith) – and by research by Natalia Shahkova from the University of Alaska, and Russian scientist Igor Semiletov.

Now the research by Ridgwell et al shows the last great warming was caused when Greenland separated from Europe, leading to major eruptions of volcanoes – not methane hydrates under the sea. But when I asked Andy Ridgwell about this, he can say methane was not the cause then, but nobody can be sure it won’t happen under our current warming, which we assume is much faster (a couple of hundred years, versus a few thousand years).

In addition, the delicate research on the shells of ocean creatures can NOT show whether there were shorter bursts of methane during that great warming period. They can’t zero in on a decade or two.

By the way, don’t miss this important related article:

Methane from tundra, ocean floor didn’t spike during previous natural warming period – “A greater percentage of the methane in the atmosphere today is due to human activities, including oil drilling, and the extraction and transport of natural gas”.


We’ve seen that even one major volcano erupting can cool the Earth for a couple of years. The eruption of Mount Pinatubo in the Philippines in 1991 cooled the Earth by about 1 degree Fahrenheit. In 1815, the Indonesian volcano Tambora erupted, dropping temperatures several degrees. So why would volcanic eruptions lead to global warming in the PETM?

The story is pretty simple. Volcanoes send a lot of particulate matter, clouds of dust, rock and stuff, into the atmosphere, and even into the upper atmosphere. There is an immediate cooling, because the sun is shaded, but the lower particulates wash out after just a few weeks of rain. It may take a little longer for the higher stuff, but that does come down, likely within a decade.

But many global warming gases also come out of the Earth. These include lots of carbon dioxide, but other gases also. The carbon dioxide lasts for centuries, and continues to warm the earth. In the case of chains of volcanoes going off, Andy tells us some of their magma (molten rock) goes sideway in the Earth as well. It may have encountered fossil fuels, like underground coal fields, and caused them to burn. Nature may have burned fossil fuels too!


All that led to a warming of about 5 degrees C. – but it warmed that much from an Earth that was already hotter than today. There were no ice caps at the poles, and we presume, no glaciers.

For whatever reason, perhaps because the warming began from a hot time, and then took up to 5,000 years to reach a new peak heating – this event 56 million years ago is NOT included as one of the great mass extinction events. No doubt many animals and plants died, but some of most species found a way to keep going. The one exception are the creatures that lived in the deep sea bed. Many of them died off, in part because of extreme acidification of the sea, as the planet quickly warmed.

There’s lots more to this interview, it’s intriguing science. While conditions and results are not the same as now, this paper answers a lot of questions we have about how the planet has warmed in the past. Scientists will draw on this to modify their projections of the future.


A review article by Turner et al says his newest paper this year found peak carbon emission rates during the PETM were less than a tenth of current fossil fuel emissions. And yet there was a warming of 5 degrees C.


Here are some other articles and papers you may need to follow up:

Along with Sandra Kirtland Turner of UC Riverside, Ridgwell co-authored what I would call a companion piece in Nature Communications, August 25th. The title is “A probabilistic assessment of the rapidity of PETM onset.”

In March 2016, Andy co-authored the paper published in Nature Geoscience titled “Anthropogenic carbon release rate unprecedented during the past 66 million years.”  That got a lot of press.

In my own research for this interview I’m also drawing from a commentary on the Ridgwell paper, published in Nature August 31st. The lead author is Katrin J. Meissner from the University of New South Wales in Sydney Australia. The title is “Volcanism caused ancient global warming“. There’s a cool graphic that helps compare the two scenarios of methane versus volcanism.


New study: We’re outpacing the most radical climate event we know of“. Ars technica. August 30, 2017.

Volcanic eruptions triggered global warming 56m years ago, study reveals“. The Guardian. August 30, 2017.


Let’s not forget, most of the already dire predictions still don’t include the soil carbon feedback. Our guest in December 2016, Thomas Crowther explained it, and I ran a short reminder clip this week.

Dr. Thomas Crowther is from the Netherlands Institute of Ecology, as broadcast on Radio Ecoshock on December 14, 2016.


We are out of time, for this show, and for climate action a few years from now. It’s well past now or never.

I want to thank those who sent in donations this week, and of course, the hardy group of supporters who donate $10 every month to keep Radio Ecoshock going. Your support makes this happen!

Thank you for listening, and thank you for caring about our world.

The music at the end of this program is taken from one of my own tunes: “Change This Thing”.