Once upon a time, crocodiles roamed the arctic1, along with turtles, fish and other warmth-loving creatures. How do we know this? Because bones from these animals have been found there. The bones of a Champsosaur – an extinct crocodile-like animal – were found in the high Canadian Arctic by researchers from the University of Rochester more than a decade ago. Footprints belonging to a pantodont, also warmth-loving and not unlike a hippopotamus, have also been found2 along with a variety of subtropical plants. This suggests the Arctic once had a climate not unlike that of Florida today, where the temperature did not drop below freezing, where there was no snow, no ice and the sea surface temperatures were over 23oC.3
Antarctica has been similarly warm in the past. Evidence of coniferous forests were first discovered by Ernest Shackleton and his team in 19084. These can be dated from between 100 to 40 million years ago, when the continent was in much the same place as it is today, thereby excluding theories of continental drift.
There is evidence that the mid-latitudes were also much warmer – 10oC warmer – and wetter than now, according to Matt Huber5 and that sea surface temperatures in the tropics were extremely high: 32-36oC6.
A few years ago the fossilised remains of a giant snake were found in Colombia. The size of this snake dwarfs everything Hollywood has dreamt up with conservative estimates putting it at 13 metres long and weighing around a tonne7. What is significant though, is that its size is indicative of a much warmer climate: 3-4 degrees warmer than the same location is today.
What made the Earth so warm during this time? The best explanation is atmospheric CO2, which was much higher 50 million years ago: >1000ppm8. CO2 warms the Earth by effectively installing a layer of pink batts around our planet. Heat from sunlight comes in but cannot radiate back into space as readily.
Earth’s neighbour, Venus, has an atmosphere choked with CO2 and a stifling surface temperature of 460oC. But it wasn’t always this way. Venus is thought to have once had liquid water and a livable climate but fatally fell victim to the ‘runaway greenhouse effect’. Atmospheric CO2 increased, causing water to evaporate, the increase in water vapour – also a greenhouse gas – in turn caused an increase in temperature until all the water boiled away leaving the surface hot enough to melt lead9.
Could this ‘runaway greenhouse effect’ occur here on Earth? A recent paper, “The runaway greenhouse”10, explores just this scenario. They think this catastrophe is unlikely here but there is a caveat. Our current understanding of the physics is weak and so the authors cannot completely rule out this possibility. They also note that if we are wrong about our planet avoiding this “ultimate climate emergency”, then our only option will be geoengineering: giving Earth a hat and some sunscreen to deflect sunlight or in the more distant future, altering Earth’s orbit.
Geoengineering is essentially giving humans a dial to control global temperature. One proposal is to inject the stratosphere with sulphates which will cool the planet by reflecting incoming sunlight. A sort of planetary sunscreen. David Keith, Professor of Applied Physics at Harvard University thinks we need to research this area big time, right now11.
What if we did have a temperature dial for Earth? Who gets to control it? Many people own cars which allow the occupants to independently set the temperature of each other. The person in the driver’s seat can set a different temperature to the person in the passenger’s seat and so on. Such is the amount we disagree on what constitutes a comfortable temperature that people sitting together inside a car can’t even agree. I think probably David Keith is right, this area needs to be explored, but I am slightly worried by the prospect of a heat-loving citizen of Greenland (if he/she exists) wanting to set the temperature higher than a cold-loving Celt like myself. Or what if something goes wrong and the reverse happens, plunging us into another ice-age?
What about sea level? The sea is expected to rise by 1m over the next century from melting ice. Some people, like James Hansen – former NASA scientist – thinks it could be as high as 5m12. Animals can also give us evidence here but this time, the animals are living. Two separate but identical populations of octopi were recently found living in Antarctica on either side of the West Antarctic Ice Sheet (WAIS)13. This particular species does not venture far from home and would not have been able to swim the 10,000km of ocean to get to the other side. This indicates that the WAIS has collapsed in the past, allowing the octopi to swim the much shorter distance through the middle. The West Antarctic Ice Sheet is melting fast and is expected to contribute 3.3m of sea level rise14.
To say we have no alternative but to continue our dependence on fossil fuels is to have very low expectations of ourselves. This is a defeatist argument. Human innovation, creativity and scientific curiosity gave us the power to light our homes in the first place. It is surely a much more smaller hurdle to stop digging up fossil fuels and foster alternative energy sources than it is to engineer a comfortable climate for 9 billion people, find new homes for the vast swarms of people unable to live in their habitat and to keep the sea from flooding our coasts and rivers. The defeatist argument also ignores some of the innovative solutions already in existence, for instance:
1. A power station in east London plans to power 39,000 homes from the cooking fat deposited in London’s sewer system15.
2. Methane from a rubbish dump in the Phillipines is giving local residents free power16.
3. A British company, Blue Energy, recently announced plans to build Africa’s largest solar power plant in Ghana17.
3. 84% of primary energy use in Iceland comes from renewable sources18.
Our ancestors gave us power to light our homes and the technology to transport us quickly to far away places. Let’s give our descendants a power and transport sector of which they can be proud and more importantly, a habitable planet.
3.Subtropical Arctic Ocean temperatures during the Palaeocene/Eocene thermal maximum. Sluijs et al. Nature, 2006.
8.Persistent near-tropical warmth on the Atlantic continent during the early Eocene epoch. Pross et al. Nature. 2012
13.Persistent genetic signatures of historic climatic events in an Antarctic octopus. Strugnell et al. 2012