July 24, 2019

expert reaction to three studies on temperature trends over the past two millennia

Studies, published in Nature Geoscience and Nature, report on global temperature trends over the last 2000 years.

Prof Simon Lewis, Professor of Global Change Science, University College London, said:

“Another week and scientists are publishing another set of reports reinforcing the abundant evidence that human actions are driving rapid changes to the climate of our home planet. Earth’s surface temperature is rising fast. With new robust analyses and new and painstakingly collated data, the last few decades are again shown to stand out: it is warming everywhere.

“As I sit in a sweltering heatwave in London, the big question remains: are people going to force governments and businesses to take swift action to drive down greenhouse gas emissions to zero to stabilise the climate?”

Prof Peter Stott, Head of Climate Monitoring and Attribution, Met Office Hadley Centre, said:

“This new research provides an important piece of corroboration for the fingerprinting studies that begin in the 1990s to identify the distinctive nature of human influence on atmospheric temperature changes, in particular the pioneering studies of Ben Santer and Gabi Hegerl published in 1996. We knew then that human activities were playing a significant role in climate change and we knew then enough to act by starting to reduce our greenhouse gas emissions. What we didn’t have then was direct confirmation from the distant pre-industrial past that such similar rates and patterns of warming had not happened before.

“This new research looks back in more detail over the last 2000 years than previous studies and finds that the rate and geographical pattern of warming seen over recent decades has not been seen before. It provides yet another confirmation that those early fingerprinting studies were correct. It is yet another piece of evidence that current warming is now proceeding at an unprecedented rate, one that has not been seen over millennia.”

Prof Mark Maslin, Professor of Climatology, University College London (UCL), said:

“Neukom and colleagues using 700 climate records from around the world covering the last 2,000 years demonstrate that the Little Ice Age and the Mediaeval Warm period were localised climatic events. Over the last 2000 years the only time the global climate has change synchronically has been in the last 150 years when over 98% of the surface of the Planet has warmed.

“This paper should finally stop climate change deniers claiming that the recent observed coherent global warming is part of a natural climate cycle. This paper shows the truly stark difference between regional and localised changes in climate of the past and the truly global effect of anthropogenic greenhouse emissions.”

Prof Daniela Schmidt, Professor in Palaeobiology, University of Bristol, said:

“We know that climate has changed throughout earth history. The journey of the Norse to Canada has been attributed to favourable climates and Flemish painters recorded frozen rivers in Europe. This paper show that this cold spell did not happen everywhere at the same time. The author team have generated an exceptionally detailed record, result of a large community effort, which allows us to compare these past records with the climate change in the 20th century in different regions of the world. The findings highlight how exceptional these decades have been. Not only is the climate change in the 20th century the fasted warming in the record, it is the first time when climate is changing everywhere on the globe in the same fashion.

“Splicing geological and biological archives has inherent issues as every system records this data in a slightly different way. The team addressed this challenge with exceptional care. Still, the records for the Southern Hemisphere are to sparse to show reliable spatial patterns.”

* ‘No evidence for globally coherent warm and cold periods over the preindustrial Common Era’ by Neukom et al. was published in Nature at 18:00 UK time on Wednesday 24 July. 

DOI: 10.1038/s41586-019-1401-2

** ‘Consistent multidecadal variability in global temperature reconstructions and simulations over the Common Era’ by Neukom et al. and ‘Last phase of the Little Ice Age forced by volcanic eruptions’ by Brönnimann et al were both published in Nature Geoscience at 18:00 UK time on Wednesday 24 July. 

DOI (Neukom): 10.1038/s41561-019-0400-0

DOI (Brönnimann): 10.1038/s41561-019-0402-y

Declared interests

Prof Mark Maslin: “No declarations”

Prof Daniela Schmidt: “I am an IPCC CLA for WGII Impacts, adaptation and Vulnerability”