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Global Warming Pause Due To Natural Variability, New Study Claims

Reporting Climate Science

A slow-down in global warming is not a sign that climate change is ending, university researchers have found. The phenomenon is a natural blip in an otherwise long-term upwards trend, their research shows.

In a detailed study of more than 200 years’ worth of temperature data, results backed previous findings that short-term pauses in climate change are simply the result of natural variation.

 From the paper’s supplementary material. Timeseries for internal variability samples a) ALL forced Multi-Model ensemble mean maroon. Proxy reconstruction blue. b) CMIP5/PMIP3 all forced Multi-Model ensemble mean red, GISSTEMP instrumental observations green. c) Residuals: between models and proxy reconstruction blue, between models and instrumental observations green. d) 8 year trends: between models and proxy reconstruction blue, between models and instrumental bservations green. Dashed horizontal lines indicate the threshold for classification as a hiatus event (below line) and accelerated warming event (above line), where selected events are highlighted by a filled circle. Courtesy: authors

The findings support the likelihood that a current hiatus in the world’s year-on-year temperature increases – which have stalled since 1998 – is temporary.

Scientists from the University of Edinburgh analysed real-world historic climate records from 1782 to 2000, comparing them with computerised climate models for the same timescale.

They were able to separate the influence on climate trends of man-made warming – such as from greenhouse gas emissions – and of natural influences in temperature – such as periods of intense sunlight or volcanic activity.

This showed that random variations can cause short term interruptions to climate patterns in the form of a pause or surge in warming, in both the real data and in the models, typically lasting up to a decade.

Extreme natural forces, such as strong volcanic eruptions, were shown to disrupt climate trends for decades. 

The research highlights the impact of volcanic eruptions on climate, when particles produced can reflect sunlight from Earth, causing long-lasting cooling.

The eruption of Mount Tambora in Indonesia in 1815 was among the biggest in recent times, causing a so-called year without summer.

Scientists estimate that, if it occurred today, it would cause a 20-year climate hiatus.

Their study, published in Geophysical Research Letters, was supported by the European Commission.

“Human activity is causing the word to warm, and natural variability can cause this trend to slow down or speed up. Our study backs scientific understanding that climate change can experience periods of hiatus, but the overall trend is towards a warmer,” planet,” said lead author Andrew Schurer from the School of GeoSciences at the University of Edinburgh.

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