The 3-minute story of 800,000 years of climate change, with a sting in the tail

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The Conversation

Ice cores are a window into the past hundreds of thousands of years. NASA Goddard Space Flight Center/Ludovic Brucker

Ice cores are a window into the past hundreds of thousands of years. NASA Goddard Space Flight Center/Ludovic Brucker

There are those who say the climate has always changed, and that carbon dioxide levels have always fluctuated. That’s true. But it’s also true that since the industrial revolution, CO₂ levels in the atmosphere have climbed to levels that are unprecedented over hundreds of millennia.

So here’s a short video we made, to put recent climate change and carbon dioxide emissions into the context of the past 800,000 years.

The temperature-CO₂ connection

Earth has a natural greenhouse effect, and it is really important. Without it, the average temperature on the surface of the planet would be about -18℃ and human life would not exist. Carbon dioxide (CO₂) is one of the gases in our atmosphere that traps heat and makes the planet habitable.

We have known about the greenhouse effect for well over a century. About 150 years ago, a physicist called John Tyndall used laboratory experiments to demonstrate the greenhouse properties of CO₂ gas. Then, in the late 1800s, the Swedish chemist Svante Arrhenius first calculated the greenhouse effect of CO₂ in our atmosphere and linked it to past ice ages on our planet.

Modern scientists and engineers have explored these links in intricate detail in recent decades, by drilling into the ice sheets that cover Antarctica and Greenland. Thousands of years of snow have compressed into thick slabs of ice. The resulting ice cores can be more than 3km long and extend back a staggering 800,000 years.

Scientists use the chemistry of the water molecules in the ice layers to see how the temperature has varied through the millennia. These ice layers also trap tiny bubbles from the ancient atmosphere, allowing us to measure prehistoric CO₂ levels directly.

Antarctic temperature changes across the ice ages were very similar to globally-averaged temperatures, except that ice age temperature changes over Antarctica were roughly twice that of the global average. Scientists refer to this as polar amplification (data from Parrenin et al. 2013; Snyder et al. 2016; Bereiter et al. 2015).
Ben Henley and Nerilie Abram

Temperature and CO₂

The ice cores reveal an incredibly tight connection between temperature and greenhouse gas levels through the ice age cycles, thus proving the concepts put forward by Arrhenius more than a century ago.

In previous warm periods, it was not a CO₂ spike that kickstarted the warming, but small and predictable wobbles in Earth’s rotation and orbit around the Sun. CO₂ played a big role as a natural amplifier of the small climate shifts initiated by these wobbles. As the planet began to cool, more CO₂ dissolved into the oceans, reducing the greenhouse effect and causing more cooling. Similarly, CO₂ was released from the oceans to the atmosphere when the planet warmed, driving further warming.

But things are very different this time around. Humans are responsible for adding huge quantities of extra CO₂ to the atmosphere – and fast.

The speed at which CO₂ is rising has no comparison in the recorded past. The fastest natural shifts out of ice ages saw CO₂ levels increase by around 35 parts per million (ppm) in 1,000 years. It might be hard to believe, but humans have emitted the equivalent amount in just the last 17 years.

How fast are CO₂ levels rising? Ben Henley and Nerilie Abram

Before the industrial revolution, the natural level of atmospheric CO₂ during warm interglacials was around 280 ppm. The frigid ice ages, which caused kilometre-thick ice sheets to build up over much of North America and Eurasia, had CO₂ levels of around 180 ppm.

Burning fossil fuels, such as coal, oil and gas, takes ancient carbon that was locked within the Earth and puts it into the atmosphere as CO₂. Since the industrial revolution humans have burned an enormous amount of fossil fuel, causing atmospheric CO₂ and other greenhouse gases to skyrocket.

In mid-2017, atmospheric CO₂ now stands at 409 ppm. This is completely unprecedented in the past 800,000 years.

Global Temperature and CO₂ since 1850. Ben Henley and Nerilie Abram

The massive blast of CO₂ is causing the climate to warm rapidly. The last IPCC report concluded that by the end of this century we will get to more than 4℃ above pre-industrial levels (1850-99) if we continue on a high-emissions pathway.

If we work towards the goals of the Paris Agreement, by rapidly curbing our CO₂ emissions and developing new technologies to remove excess CO₂ from the atmosphere, then we stand a chance of limiting warming to around 2℃.

Observed and projected global temperature on high (RCP8.5) and low (RCP2.6) CO₂ emission futures. Ben Henley and Nerilie Abram

The fundamental science is very well understood. The evidence that climate change is happening is abundant and clear. The difficult part is: what do we do next? More than ever, we need strong, cooperative and accountable leadership from politicians of all nations. Only then will we avoid the worst of climate change and adapt to the impacts we can’t halt.

The ConversationThe authors acknowledge the contributions of Wes Mountain (multimedia), Alicia Egan (editing) and Andrew King (model projection data).

Source: The Conversation. Reproduced with permission.  

  • john

    Perhaps an earlier one up until 2016.

  • JimTheGeordie

    The problem with a lot of high-profile carbon control projects is that they carry out mitigation. What is needed are projects to physically remove carbon dioxide from the air and oceans until a desirable point of balance is reached. This has actually been done at a couple of US universities. This leaves us with another problem. What do we do with the CO2. There is some work going on in this area in various countries (talk to christophe jospe whose website is, but I think to be really effective, we need a single world-wide program with the various members sharing all information. No patents, please!). I have made an approach to the rural affairs people in the Australian Broadcasting Company (ABC) because they have a wide range of contacts in mining, agriculture and so forth. I have received no reply as yet.

    • Dhyani Doshi


    • Mark Roest

      We divide up the remaining jobs, and each of us learns to garden in the Permaculture and/or BioIntensive Gardening manner, and each also learns to make biochar, or at least provides fuel for it, and buries biochar in the soil, to both provide nutrients & moisture when they’re in short supply, and sequesters carbon taken from trees and grasses for a thousand years or more. It gets to geological scale if each of us pitches in with a will.

      • Alastair Leith

        BZE Land Use Report started as the Land Use Plan figuring bio-char and other sequestration methods would be the silver bullet to zero land use sector emissions, it didn’t check out, given how high livestock emissions are. As for mitigating the rest of developed economy emissions, that remains the domain of speculation at best.

        There’s limits on soil carbon acquisition rates, saturation limits and limits on how much plant growth biochar will foster, and compared with emissions it’s not going to cut it the current science says (though I hold hopes for organic farming methods that build soil carbon rather than destroy it with synthetic fertilizers and sprays).

  • DJR96

    I’ve had this conversation before with sceptics, including my parents……

    Yes, the climate and atmosphere continually change. It has been warmer and cooler in the past. Sea levels have been higher and lower in the past. But the issue is how fast it changes. Are we prepared for the consequences of these effects? What if the sea level does rise by 2 metre? Yes, we and nature does and will adapt to changes. But how quickly can it change, or at what expense are we prepared to pay to adapt? The answer is not much at all, particularly in comparison to what it may well cost us. Which leaves us needing to do whatever we can to prevent such changes from happening too quickly.

    • Alastair Leith

      Storm surge flooding events can be many multiples of the SL rise too, eg NYC, 30cm of SL rise since pre-industrial times and 2m+ of flooding during superstorm Sandy causing disruption to Manhattan Island for at least two days and billions of dollars in property damage.

      And we’re looking a 0.6-3m SL rise just from the Western Peninsular of Antarctica alone which is now in terminal decline, it would take so much cooling for the glacial system at the land/sea interface to refreeze it’s unfeasible with given technology of today. 61m of SL rise locked up in all the polar cap land ice. That’s not all going to melt this century, but it’s melting alarming fast and most climate scientists at the time of early IPCC Assessment Reports didn’t fathom sea ice free summers in the Arctic this century. Now it’s just years/decades off, not centuries.

  • Lesando

    Our oceans are the biggest producer of CO2 there is so what are we going to do with that pump out the oceans (to where outer space?) and of course the climate and CO2 keep changing it’s nature but people like Al Gore have worked out a way to make Climate Change a multi trillion business so we get stuck with all the continuouse lies.

    • Shane Egan

      Did you not actually read the article which explains clearly why your view is in error?

    • john

      Where exactly is this ” multi trillion business ” ?

    • john

      The original story was volcanoes produce most of the CO2 oops the isotopic make up proved that a furphy, now you are trying to say the ocean is emitting the CO2, well once again check the make up.
      Yes the climate does change and we should be moving to a cooler climate is that what you see?
      I would encourage you not to get your misguidance from WUWT because it is a hideous insidious mire of rubbish dished up as platitude to the misinformed.
      Try for instance.

    • Alastair Leith

      Ah Al Gore, it’s Al Gore you want to talk about. Try reading some science and get back to us.

    • Shane White

      Lesando you’re so confused and so far behind the eight ball that I think you’d be best off concerning yourself with matters that do not involve any analysis of science. Have you tried spending most of your spare time following the lifestyles of your favourite movie celebrities, or watching cat videos? If not then I think you might find that rewarding. Good luck and all the best.

  • Robin_Harrison

    I find the exclusive preoccupation with carbon emissions troubling. They are only the most recent manifestation of our species damage to the environment. Taking an almost vanishing back seat is the major contributor to the changing of our climate; deforestation, which has been truly epic over the last few thousand years and is continuing at the the rate of over 20 acres/minute globally. When we remove forest we remove biodiversity and we are currently in the middle of the 6th, and largest, major species extinction event in the history of life on earth.
    The Finkel report incessantly faffs on about emissions when the economics of RE are much more telling.

    • Alastair Leith

      Agree about Finkel (though it was chiefly it seems a political gesture rather than science), agree about anthropocene, disagree about Climate Change, it’s a different order of destruction again, and a threat multiplier for all the other bad things we are doing to the environment. CSIRO has found that nearly all endemic species will be lost in Australia by 2070 on BAU from climate change destroying habitat. See image (green is less change, purple is more change and species loss)