Skeptic journalist David Rose published a two-page spread in the Mail on Sunday yesterday entitled “Global warming stopped 16 years ago, reveals Met Office report quietly releasedâ?¦ and here is the chart to prove it.” This is the latest in a series of articles on the same theme. We take a look at why Rose’s claims are wrong this time.
The Mail on Sunday seems to print articles by Rose arguing that warming has stopped about once every six months – so maybe we were about due for one. The Met office has already responded to misleading information in an article in January by David Rose on the same topic, but he seems determined to peddle the same myths.
This time, the Mail on Sunday also gives Rose space for a half-page comment piece in which he argues that the slow-down in warming over the last decade “poses a fundamental challenge to the assumptions underlying every aspect of energy and climate change policy.”
Arguing that “global warming has stopped”
In his article, Rose presents the graph below, which shows global atmospheric temperature data for 1997 to 2012 compared to the average for this century, and uses it to claim that it is proof that global warming has stopped.
“The new data, compiled from more than 3,000 measuring points on land and sea, was issued quietly on the internet, without any media fanfare, and, until today, it has not been reported. This stands in sharp contrast to the release of the previous figures six months ago, which went only to the end of 2010 – a very warm year.”
But in a rebuttal blog, the Met Office says it has not released a new report this week – “quietly on the internet” or otherwise. It has simply updated the dataset to include data for 2011 and the first eight months of 2012. So in effect, Rose is trying to use a bit of new data to make an already widely discredited argument.
Data from Hadcrut4 shows that during the period that Rose uses in his argument, 1997 to 2012, atmospheric warming was about 0.03 degrees Celsius per decade, which is considerably slower than in previous decades. We’ll come on to the possible reasons for this haitus later, but the important point is that scientists don’t draw general conclusions about global temperature trends based on such small amounts of data.
Rose knows this – he admits that Professor Phil Jones, leading climate scientist at the CRU, that 15 or 16 years is too short a period from which to draw conclusions. Similarly, the Met office was careful to point this out in its interview with Rose – which you can read on its blog. It says:
“[C]hoosing a starting or end point on short-term scales can be very misleading…If you use a longer period from HadCRUT4 the trend looks very different”.
The bigger picture
The graph that Rose should have shown is this one, which shows roughly 0.8 degrees Celcius of warming since the beginning of the 20th Century.
This reveals Rose’s statements that “[b]efore , temperatures had been stable or declining for about 40 years” and that “global industrialisation over the past 130 years has made relatively little difference” are extremely short-sighted. As the Met Office explained to Rose:
“Looking at successive decades over this period, each decade was warmer than the previous – so the 1990s were warmer than the 1980s, and the 2000s were warmer than both. Eight of the top ten warmest years have occurred in the last decade”.
A prominent role for natural variability
The bottom line is that short-term excursions from the long term temperature trend do not mean that the warming trend apparent over the last century has stopped for good. We have written a previous post discussing this is more detail.
Alongside human impacts, the world’s temperature varies in response to natural cycles, in particular the El Nino/La Nina cycle and the 11-year solar cycle, as well as occasional one-off events like volcanic eruptions. As the Met Office explained to Rose, the most likely reason that we haven’t seen an upward trend over the last decade is that such natural variability has played a more prominent role in the climate, masking the impact of greenhouse gases on global temperature.
“Combined, several of these factors could account for some or all of the reduced warming trend seen over the last decade – but this is an area of ongoing research.”
Misquoting on climate models
Rose also quotes Professor Judith Curry, head of the climate research centre at Georgia Institute of Technology in the United States. Curry wrote about the article in her blog yesterday and echoed the same sentiments when Carbon Brief contacted her. She told us that at no point in her interview with Rose did she describe climate models as ‘deeply flawed’ or say that she disagreed with Jones that 16 years is not long enough to draw any conclusions.
What she actually said repeated Jones’s concerns that the climate is far more complex than the models can grasp at the moment, but that research continues to develop. She says:
“Climate models are very complex, but they are imperfect and incomplete…It is becoming increasingly apparent that our attribution of warming since 1980 and future projections of climate change needs to consider natural internal variability as a factor of fundamental importance”.
Ignoring other signs
Another problem with Rose’s analysis is that looking solely at atmospheric temperatures ignores a number of other indicators that global warming is happening. Most of the heat in the earth’s atmosphere actually enters the ocean, as this fantastically simple infographic from Skeptical science shows:
As the graph below shows, the global ocean has been warming considerably during the time that atmospheric temperatures appear to have stalled, which is causing sea level to rise substantially. The fact that ice sheets are melting in both the Arctic and the Antarctic is another stark indicator of global warming that Rose chooses to ignore.
All of this makes us wonder how many bits of established scientific data can Rose ignore or misrepresent in one article? However, he appears unlikely to stop producing his twice-yearly articles despite a wealth of evidence to the contrary. So for the next time a similar article comes up it’s worth remembering something that scientists said in a previous rebuttal of the ‘global warming has stopped’ claim: that considering only 10-15 years of atmospheric temperature data is like
“analysing the temperature observations from 10-17 April to check whether it really gets warmer during spring.”