Earlier this week I was in Potsdam to interview Professor John Schellnhuber, the founding Director of the Potsdam Institute for Climate Impact Research (PIK). The interview coincided with the release of a new iconic paper in the scientific journal, Nature, titled, ‘Critical insolation - CO2 relation for diagnosing past and future glacial inception’ that finalises the assertion that we are in a new geological epoch called the “Athropocene”.


Man made climate

Schellnhuber says with restrained poignancy: “Humankind is a stronger force on Earth now than, you know, the orbital forces and all things like that. It is fascinating but also very scary!”

By looking at ice core data covering the last 800,000 years, the research shows how scientists can determine the function that causes periods of “glacial inceptions”, or more commonly known as ice ages.

Although there has been much speculation around the longer lasting role of increased levels of greenhouse gases, this paper confirms that “the timing of glacial inceptions can be explained  by the CO2 concentration and the -CO2 relation.” This is essentially warming or cooling of the planet based on the concentration of CO2 in the atmosphere.

The importance of the evidence that humans are now driving, climate led Schellnhuber to state: “I think it is a fascinating paper; one of the best I was involved with.”

Did we call off an ice-age 200 years ago?

The paper says: “Ice core data shows that at every previous glaciation period, CO2 in the atmosphere was lower, usually around 240 parts per million (ppm).” 

Before the industrial revolution atmospheric carbon was at around 280ppm, thus 40ppm above the level needed to trigger an ice age. There is a lot of speculation and uncertainty as to whether changes in land use by humans prior to the industrial revolution caused the increase from 240ppm to 280ppm. If this were to be the case then it would show that human action literally called off an ice age.

Predicting future ice ages

Schellnhuber makes it very clear: “Actually the next two natural ice ages would happen in eighty and ninety thousand years, but they are called off… by human interference. The emissions so far already suffice to suppress the next ice ages.”

It is precisely this human interference from burning fossil fuels that caused the initial speculation that we might be altering the Earth’s climate, leading Nobel Prize winning scientist, Paul Crutzen, to label it the “anthropocene”


Worsening impacts of climate change are taking effect around the world. Having evidence that the next ice ages will be delayed adds a layer of concern regarding the geophysical changes that occurring on Earth due to human activity.

We maybe the drivers of global climate but we appear to be asleep at the wheel, as the evidence for anthropogenic global warming has been around for decade. Only now are politicians, the public and big business starting to take the risks posed more seriously.

On the positive side we can sigh with relief that we have called off the next two ice ages that would represent a very difficult challenge for human civilisation. However, temper that relief with the growing likelihood that if we don’t wake up to climate change, it is unlikely that humanity will exist on Earth in anything like fifty thousand years!


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