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Global warming continues and won’t be stopped by wishful thinking

Ocean Warming

Global warming has mainly been absorbed by the oceans in recent years, but has continued rapidly. Photograph: Alamy


Powered by article titled “Global warming continues and won’t be stopped by wishful thinking” was written by Dana Nuccitelli, for on Thursday 30th January 2014 14.00 UTC

Global warming has continued rapidly in recent years, mostly accumulating in the oceans. Yet there remains a pervasive myth that it has somehow magically stopped.

Most recently displaying this confusion was Georgia Tech climate scientist Judith Curry, who testified about climate change before a US Senate committee. Curry’s testimony was riddled with mistakes and misleading arguments, the worst of which involved disputing that climate scientists are more confident in human-caused global warming than they were six years ago.

Curry based this argument in large part on the supposed global warming ‘pause’, which is itself a fictional creation. While the warming of average global surface temperatures has slowed (though not nearly as much as previously believed), the overall amount of heat accumulated by the global climate has not, with over 90 percent being absorbed by the oceans, and 30 percent of that in the deep oceans (below 700 meters) over the past 15 years.

A few days after her Senate testimony, Curry took to her blog to dispute these data, essentially arguing that the amount of heat absorbed by the oceans has also ‘paused’, which would then support her arguments. However, in evaluating the ocean heat content data and scientific literature, Curry made a number of mistakes.

First, she claimed that the only evidence of buildup of heat in the deep oceans comes from reanalysis products. A ‘reanalysis’ is a climate, ocean, or weather model simulation of the past that incorporates data from historical observations. However, in reality, the increase in deep ocean heat accumulation is a robust result also observed in data sets that do not include reanalysis.

In fact in a paper my colleagues and I published in 2012, we showed that according to the observational ocean temperature data compiled by the National Oceanographic Data Center, about 30 percent of global warming has gone into the deep oceans since the year 2000 – the same result as in subsequent studies using reanalysis data. On top of that, the new paper that Curry referenced in her blog post by scientists from the National Oceanic and Atmospheric Administration (NOAA) found that even more heat has built up in the deep oceans – over 40 percent of overall global warming since 2004.

So what caused Curry to claim that global and ocean warming had ‘paused’ since 2003? In her blog post, she tried to do science by eyeball. Scientists use statistics because our senses can introduce bias and deceive us. Instead, Curry looked at the following figure from the NOAA paper and decided it looked like ocean warming had stopped in 2003.

Ocean Heat Content

Time series of annual average global integrals of upper ocean heat content anomaly (10^21 J, or ZJ) for (a) 0–100 m, (b) 0–300 m, (c) 0–700 m, and (d) 0–1800 m. Thin vertical lines denote when data coverage reaches 50% for (a) 0–100 m, (b) 100–300 m, (c) 300–700 m, and (d) 900–1800 m. From Lyman & Johnson (2013)


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