Climate skeptics have a new favourite argument – ‘global warming has stopped’. It’s been popping up online for a while, and formed the central point of a fairly misleading article in the Mail on Sunday a week ago.
Over the weekend the Sunday Times ran an effort to get to the bottom of the meme, written by their Science and Environment Editor Jonathan Leake. As well as concluding that global warming hasn’t ‘stopped’, the piece is also interesting in providing an insight into where these kind of Mail stories about global warming having ‘stopped’ are coming from.
Leake’s article is titled ‘ So, do we freeze or fry?“. He writes:
“Research based on Met Office figures pointed to temperatures having been flat since 1997.
It was the kind of admission that those who doubt climate science pounce on. “Forget global warming,” trumpeted The Mail on Sunday, because “the planet has not warmed in 15 years”. It then cited other research, into the declining energy output of the sun, to suggest the real danger was from a big freeze”
“Some scientists appear to be warning we will fry, while other sources fear we will freeze. For the public the outcome is, increasingly, confusion. Where might the truth lie?”
Temperature records show we’re still warming
Climate scientists agree that the global warming trend continues, as a group of experts explained last week in a letter to the Wall Street Journal:
“Climate experts know that the long-term warming trend has not abated in the past decade. In fact, it was the warmest decade on record. Observations show unequivocally that our planet is getting hotter. And computer models have recently shown that during periods when there is a smaller increase of surface temperatures, warming is occurring elsewhere in the climate system, typically in the deep ocean. Such periods are a relatively common climate phenomenon, are consistent with our physical understanding of how the climate system works, and certainly do not invalidate our understanding of human-induced warming or the models used to simulate that warming.”
For his article Leake consults three records of global temperature – the Met Office’s HadCRUT3 dataset, NOAA’s NCDC dataset, and satellite data compiled by John Christie at the University of Huntsville, Alabama.
It is Christie’s satellite record that has shown the largest increase this century, Leake notes:
“Oddly, given [Christie’s] reputation as a climate sceptic, he found the biggest rise of all.
‘From 1997-2011 our data show a global temperature rise of 0.15C,’ he said
‘What’s more, our satellites have been taking this data since 1979, and over that period [the] global temperature has risen 0.46C, so the world has been getting warmer.'”
All three of these records show a small rise in temperature over the last decade or so, leading Leake to the inevitable conclusion that the world is warming. He concludes:
“Overall, then, the world has got slightly warmer since 1997.”
But, he asks,
“why has it warmed so much less than was predicted by the climate models?”
This is a slightly odd question, as the current behaviour of global temperatures is within expectations of many climate modellers. Scientists explain that this is down to natural climate variability masking the long-term warming trend, a point made in the article by Peter Stott of the Met Office:
“For most climate scientists the answer is simple. ‘Fifteen years is just too short a period over which to measure climate change,’ said Peter Stott, head of climate monitoring at the Met Office. ‘The world undergoes natural temperature changes on all kinds of time scales from daily variations to seasonal ones. It also varies naturally from year to year and decade to decade.'”
The research behind ‘warming has stopped’ claims
Leake reveals that it was David Whitehouse, science editor at the Global Warming Policy Foundation, who provided the analysis of Met Office data which underpinned Rose’s suggestion that ‘the planet has not warmed for the past 15 years’.
“Research based on Met Office figures pointed to temperatures having been flat since 1997… [Dr Whitehouse], it turns out, was a source of the research that sparked the whole row.
‘We set out to see how long it had been since the temperature had risen, and 15 years was what emerged from the data set,’ [Dr Whitehouse] said. ‘It raises serious questions about how the Met Office models future climate.'”
This source of the analysis wasn’t noted in the Mail article – of which the Met Office said:
“This article includes numerous errors in the reporting of published peer reviewed science undertaken by the Met Office Hadley Centre and for Mr. Rose to suggest that the latest global temperatures available show no warming in the last 15 years is entirely misleading.”
As we have noted, looking at temperatures since only 1997 is the kind of cherrypicking that considers only a relatively short time period, over which temperatures are known to be dominated by natural variation. This can mask the overall global warming trend.
The Sunday Times article does appear to show that Dr Whitehouse accepts that global warming has not ‘stopped’ –
“‘The records do show that global temperatures have risen by about 0.4C over the past three decades, most of it in the 1990s,’ [Whitehouse] said.
‘I accept that CO2 is a greenhouse gas that might warm the world but the key issue is how strong the effect is and how the data compare with the models used to predict the future.'”
“This is an interesting admission, turning what had appeared to be an attack on the keystones of climate science – that greenhouse gases cause global warming – into a ‘shades of grey’ debate over whether global warming will happen slowly and steadily or in jerks, accelerating in some decades but then slowing or even reversing a little in others.”
It’s also worth pointing out that this admission rather undermines the introductory headline to the Mail on Sunday piece, which read: ‘As the Met Office releases new figures which show no warming in 15 years…’, and also the line in the third paragraph which states that the Met Office data ‘confirms that the rising trend in world temperatures ended in 1997.’
False balance on how sun will affect climate
Leake’s article also addresses how the sun might affect the climate in the future in the context of man-made climate change.
It’s worth noting here that whilst there is ongoing research into the sun’s effect on climate, there is general agreement that its impact will only be a small fraction compared to projected man-made climate change.
Interestingly, the Sunday Times has done a poor job on accurately representing the impact of solar activity on climate change before. A 2010 review of the peer-reviewed research summarised the current scientific understanding on the topic, concluding:
“…The predicted solar cycleâ?related surface temperature change is small relative to [man-made] changes.”
“…one of the key unresolved issues lies in the behaviour of the sun, whose output appears to be undergoing a steady but small decline. Most scientists accept that this will reduce global warming. The debate is over just how strong this effect will be, with people such as [Judith] Curry suggesting it could be powerful while others see it as small.”
…the considered scientific opinion appears considerably less doubtful.