The GISP2 ice core record was used in a number of papers in the late 1990s and 2000s that examined changes over the last ice age and the start of the current warm era – the Holocene – around 11,000 years ago. Neither of these papers provided a comparison of GISP2 record with current conditions, as the uncertainties in the ice core proxy reconstruction were too large and the proxy record only extended back to 1855. Prof Richard Alley of Penn State University also used the record in a 2000 paper. Odyssey of errorsĪ temperature reconstruction using the Greenland Ice Sheet Project 2 (“ GISP2”) ice core was first published by Prof Kurt Cuffey and Dr Gary Clow in a 1997 paper published in the Journal of Geophysical Research: Oceans. Since scientists cannot directly measure temperatures from ice cores, they have to rely on measuring the oxygen isotope – 18O – which is correlated with temperature, but imperfectly so. Ice cores are one of the best available climate proxies, providing a fairly high-resolution estimate of climate changes into the past. Credit: Jim West / Alamy Stock Photo.Ĭlimate proxies can be obtained from sources, such as tree rings, ice cores, fossil pollen, ocean sediments and corals. Scientists investigating how temperatures have changed prior to the invention of thermometers need to rely on a variety of climate “ proxies”, which are correlated with temperature and can be used to infer, with some uncertainties, how it has changed in the past.Īn ice core from Greenland is prepared for cutting at the National Ice Core Laboratory. Widespread thermometer measurements of temperatures only extend back to the mid-1700s. However, warming is expected to continue in the future as human actions continue to emit greenhouse gases, primarily from the combustion of fossil fuels.Ĭlimate models project that if emissions continue, by 2050, Greenland temperatures will exceed anything seen since the last interglacial period, around 125,000 years ago. That said, they are likely still cooler than during the early part of the current geological epoch – the Holocene – which started around 11,000 years ago. This modern temperature reconstruction, combined with observational records over the past century, shows that current temperatures in Greenland are warmer than any period in the past 2,000 years. More recently, researchers have drilled numerous additional ice cores throughout Greenland and produced an updated estimate past Greenland temperatures. A misleading graph purporting to show that past changes in Greenland’s temperatures dwarf modern climate change has been circling the internet since at least 2010.īased on an early Greenland ice core record produced back in 1997, versions of the graph have, variously, mislabeled the x-axis, excluded the modern observational temperature record and conflated a single location in Greenland with the whole world.
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