Climate Is Warming Faster Than It Has in the Last 2,000 Years

Bern says that the authors of the study in Nature see the explanation for that as being that regional climates in pre-industrial times were primarily influenced by random fluctuations within the climate systems themselves. External factors such as volcanic eruptions or solar activity were not intense enough to cause markedly warm or cold temperatures across the whole world for decades, or even centuries.

The researchers relied on a database from the international research consortium PAGES (Past Global Changes, www.pastglobalchanges.org), which provides a comprehensive overview of climate data from the last 2,000 years, for their investigation of five pre-industrial climate epochs. In addition to tree rings, it also includes data from ice cores, lake sediments and corals. To really put the results to the test, the team led by Raphael Neukom analyzed these data sets using six different statistical models – more than ever before. This allowed for the calculation of the probability of extremely warm or cold decades and centuries, and not just the calculation of absolute temperatures. The result was that no globally coherent picture emerged during the periods being investigated. “The minimum and maximum temperatures were different in different areas,” says Raphael Neukom. So thermal extremes across the world cannot be inferred from regional temperature phenomena like the oft-mentioned “Medieval Warm Period” in Europe and North America.

The Current Warm Period is Happening Across the World for the First Time
The results look very different for recent history. Both studies show that the warmest period of the last 2,000 years was most likely in the 20th century. They also show that this was the case for more than 98 percent of the surface of the earth. This shows – once again – that modern climate change cannot be explained by random fluctuations, but by anthropogenic emissions of CO2 and other greenhouse gases. What we didn’t know until now is that not only average global temperatures in the 20th century are higher than ever before in at least 2,000 years, but also that a warming period is now affecting the whole planet at the same time for the first time. And the speed of global warming has never been as high as it is today.

— Read more in R. Neukom et al., “No evidence for globally coherent warm and cold periods over the pre-industrial Common Era,” Nature (24 July 2019) (DOI: 10.1038/s41586-019-1401-2); PAGES 2k, “Consortium. (2019). Consistent multidecadal variability in global temperature reconstructions and simulations over the Common Era,” Nature Geoscience (24 July 2014) (DOI: 10.1038/s41561-019-0400-0)