Global warming 'hiatus' definitions and representation in different datasets. a, Different definitions of the hiatus from literature: (i) the short-term global-mean surface temperature trend from observations (yellow line) relative to a zero trend (grey dashed line); (ii) difference between the short-term trend and ... Graphic: Medhaug, et al., 2017 / Nature

By Graham Readfearn
3 May 2017

(The Guardian) – People don’t talk about how global warming has stopped, paused, or slowed down all that much any more – three consecutive hottest years on record will tend to do that to a flaky meme.

But there was a time a few years ago when you couldn’t open your news feed without being told global warming had stopped by some conservative columnist, climate science denier, or one of those people who spend their waking hours writing comments on stories like this.

The issue at hand was one of the multiple measurements used by scientists to monitor the state of the planet – the globally averaged temperature.

Depending on which particular set of data you looked at, and how you calculated trends, there was an argument that temperature rises had slowed over a period of about 15 years.

When deniers and contrarians talked about this “slowdown” the implication was that somehow, the laws of physics had suddenly changed and loading the atmosphere with CO2 might not be a problem any more.

As I argued three years ago, this global warming pause was never really a thing.

Despite all the other indicators of global warming showing business as usual – sea-level rise, temperature extremes, glacier melt, species movements, ocean heating, permafrost melt – the unhealthy fixation on one aspect, the average temperature of the globe, stuck firm.

But scientists reacted to the public commentary in the only way they know how. They started to study this “pause” to find out what might be going on. They published scores and scores of papers in academic journals. […]

In one paper that appeared in the journal Bulletin of the American Meteorological Society, three researchers argued that the scientific community had unwittingly been distracted by the claims of global warming contrarians.

Now a new study in the leading journal Nature has tried to reconcile the differences between the various pause studies and make suggestions about what went wrong.

There was not a clear and agreed definition of what a pause was and if it was consequential. Scientists didn’t always communicate nuances clearly.

“In a time coinciding with high-level political negotiations on preventing climate change,” write the authors from Switzerland’s Institute for Atmospheric and Climate Science, “sceptical media and politicians were using the apparent lack of warming to downplay the importance of climate change. It is easy to paint a controversial picture, but as often the devil is in the detail.” [more]

Global warming scientists learn lessons from the pause that never was

ABSTRACT: Between about 1998 and 2012, a time that coincided with political negotiations for preventing climate change, the surface of Earth seemed hardly to warm. This phenomenon, often termed the ‘global warming hiatus’, caused doubt in the public mind about how well anthropogenic climate change and natural variability are understood. Here we show that apparently contradictory conclusions stem from different definitions of ‘hiatus’ and from different datasets. A combination of changes in forcing, uptake of heat by the oceans, natural variability and incomplete observational coverage reconciles models and data. Combined with stronger recent warming trends in newer datasets, we are now more confident than ever that human influence is dominant in long-term warming.

Reconciling controversies about the ‘global warming hiatus’



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