Global warming dwarfs climate variations of past 2,000 years

Pablo Tucker
July 27, 2019

In order to obtain a robust sampling of data around the world, the researchers used 700 records obtained from trees, ice, coral, sediment and more. The data are sourced from all of Earth's continental regions and major ocean basins.

In statistical terms, all instrumental 51-year temperature trends starting after the 1950s exceed the 99th percentile of reconstructed pre-industrial 51-year trends.

Scientists have only just begun to mine the PAGES data for insights into trends of the past, but already they have made some intriguing discoveries.

As France, India, the US, and other nations face unprecedented and deadly heat waves, new research published Wednesday showed the planet has warmed more quickly in recent decades than at any point in the past 2,000 years.

What's more, the data also suggest that this warming has been uniform across all regions of the globe, a phenomenon that scientists say has not been seen in the past 2,000 years.

By comparing the new reconstructions with existing climate simulations generated using the Coupled Model Intercomparison Project 5 (CMIP5) climate models, the PAGES research team was able to determine the relative contributions of several influences on global temperatures over time.

Michael Evans, author of the study and University of Maryland associate professor of geology, said in a press release that "the results were consistent regardless of how we created the reconstructions or which randomly chosen subset of input data we used".

The study crunched data covering two millennia from nearly 700 sources ranging from tree rings and coral to sediments and ice cores.

Some of the new findings contradict, or at least complicate, previously held truths.

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Such records show the first few centuries of the Common Era were warm until about 400 A.D., when the Late Antique Little Ice Age set in.

The identical sample noticed for the upper temperatures seen through the Medieval Warm Period.

"The traditional understanding was that climate over these periods were globally coherent" said Nathan Steiger, a paleoclimatologist at Columbia University in NY who worked on the paper. Following these temporary cooling periods our reconstructions show there is an increased probability of a temporary warming period due to the recovery from volcanic cooling.

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"This paper should finally stop climate change deniers claiming that the recent observed coherent global warming is part of a natural climate cycle".

"For example the Little Ice Age, or the Medieval Climate Anomaly - natural factors have caused those", said Dr Henley, who is a researcher Melbourne University's School of Earth Sciences.

For instance, climate variability over the past 2,000 years has been subject to great debate.

But the rapid warming over the past 150 years is very different, with the warmest period of the past two millennia occurring during the 20th century for more than 98 per cent of the globe.

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Their peek completely went as a ways because the 365 days 2000, but nine of the ten warmest years on anecdote have came about since then, with the previous 5 years being the warmest.

"The familiar maxim that climate is always changing is certainly true", wrote Scott St George, a geographer at the University of Minnesota at Minneapolis who was not involved in the work.

It is yet further evidence of human-induced warming of the planet and illustrates that Earth is getting warmer, faster. This proxy data can be brought together to tell us a lot about the global climate system in the past.

This worldwide collaboration, part of the PAGES 2k Consortium, used a new, highly curated set of paleoclimate data and compared seven different statistical methods for reconstructing past global average temperature. They found no even, global shifts-either warm or cold-before the industrial era.

They also give us a clearer picture of decade-to-decade temperature variations and what drove those fluctuations before the industrial revolution.

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