Temperatures are now 1.1 degrees Celsius above the preindustrial average and only rising - all at an unprecedented rate. The burning of fossil fuels has put an end to that. Nearly all of human civilisation, from the invention of agriculture to the turn of the 21st Century, has occurred in a narrow band of global temperatures about one degree wide called the Holocene. But once we take a look through the time machines all around us at what those changes truly meant, that thought should not be a mollifying one - it should terrify us. The deniers are right - the planet itself has undergone these changes and worse many times before. Now, in just a century, through what amounts to a planetary-level experiment in terraforming, we have thrust our civilisation into new and uncharted waters. In the length of that blink, the climate has been remarkably stable, rarely varying more than half a degree from the norm, but this is an outlier when the broader history of the planet is taken into view. The truth is that the entirety of human civilisation has taken place in the blink of a geologic eye. Taken together, they also show an undeniable trend - when carbon dioxide levels rise in the atmosphere, so do temperatures.Ĭlimate change deniers like to say the "climate is always changing", as if that is a reassuring thought. These time machines offer us a glimpse at ancient Earths, at once familiar and alien to our own. Measure the ratios of faintly different types of oxygen trapped in the fossilised shells of microscopic marine organisms and you'll be able to tell the temperature at the ocean's surface 15 million years ago. Take the pores on the surface of ancient leaves or the rings of petrified trees or even the striations in the formerly-marine sediments that line Whanganui's beaches and you can glean the level of carbon dioxide in prehistoric atmospheres. If you look around hard enough, you can find time machines like this one just about everywhere. More than 3.6 kilometres of the stuff, drilled from the centre of the East Antarctic Ice Sheet and sliced into even pillars, two metres long and 13 centimetres in diameter.
Or rather, it is more accurate to say that the ice itself was the time machine. In 1996, scientists found a time machine buried deep in the Antarctic ice.
Special Report: What can three-kilometre long ice cores, fossilised leaves and Whanganui's oceanside cliffs tell us about the climate of ancient Earth - and what warnings do they hold for humanity's current, high-carbon trajectory? Marc Daalder reports Climate Emergency Long read: How past climates hold secrets for our future
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