Has Global Warming Stopped?
By Paul Homewood
We are now, no doubt, all familiar with the debate about whether global warming has stopped. However, it is only relatively recently that most of the public will have had any inkling of this at all.
One of the principal reasons for this has been the dismal failure of journalists, in particular, and the media, in general, to bother checking the facts out for themselves. Instead, they have, by and large, been content to simply cut and paste whatever propaganda they have been handed.
(One of the exceptions here in the UK has been David Rose, who put his head above the parapet a year ago).
Even now, I would guess that most of the public are still none the wiser, and, despite recent reports on what the IPCC might say about the hiatus, many people are at best confused and at worst think such claims are concocted by “deniers”.
Two instances, that have cropped up this week, reinforce my suspicions.
1) The Sunday Telegraph, reporting on the upcoming IPCC report, stated:
In a leaked draft, dating from June, the IPCC said that the rate of warming between 1998 and 2012 was about half the average rate since 1951.
It is not clear whether the leaked draft quoted this figure, or whether the journalist got mixed up.
What is clear, though, is that a quick two minute check would have revealed that the claim was palpable nonsense, and that there has effectively been no warming since 1998, no matter how you calculate it.
Such failures to check the facts are, unfortunately, only too common amongst journalists these days.
(The “pause” is still often referred to, grudgingly, as a “slowdown in warming” in many media reports)
2) We then had the thoroughly bizarre spectacle of David Suzuki admitting on Australian TV that he did not even know what the main global temperature datasets were, never mind how to access them or what figures they were actually showing.
Instead, all he could offer was the “hottest decade” meme, and a sly reference to “sceptics in Huntsville coming to their own conclusion”.
So what are the facts?
Are Comparisons With 1998 Fair?
Most claims of “flatlining” use 1997 or 1998 as their start point. Critics complain that this is cherry picking, because 1998 was an unusually hot year. Both sides of the argument can be seen on the Wood For Trees graph below, which uses a combination of all four temperature sets.
The critics’ argument at first sight seems plausible, except for two reasons:-
1) Although 1998 was unusually warm, it was followed by two unusually cold years, which came as a result of La Nina conditions. If you average the three years of 1998-2000 together, they tend to cancel each other out, as the HADCRUT4 figures below show.
|HADCRUT4 Annual Temperature Anomalies|
By contrast with this 3-Year average, the figure for 1997 was higher, at 0.39C, while the current 10-Year average is 0.47C. In other words, the choice of 1998 is not creating an artificially high start point. (Remember that the trend line is not a straight line from 1998 to 2013, but a “least squares” one that weighs up all the intervening years as well).
2) 2010 was just as warm as 1998 – both GISS and HADCRUT4 show it as slightly warmer. Therefore, it cannot be argued that 1998 was an “unusual year”, or that it has unduly affected the underlying trend, as it is counterbalanced by 2010.
Of course, El Ninos and La Ninas are all part and parcel of the climate system, and therefore cannot just be “excluded” from calculations as one offs. Nevertheless, it is unsatisfactory that different trends can be arrived at simply by changing the start year.
So, let’s try at a different way of looking at trends, using 10-year running averages. By using 10-year averages, instead of annual figures, we can take away the inter annual variability caused by ENSO changes, particularly between 1998 and 2000. It also means that the choice of start and finish years is no longer so significant.
Figure 1 below is a plot of RSS satellite monthly temperature anomalies, with the red line showing the 10-Year running average.
Since December 2010 this 10-Year average has been falling. This, of course, does not mean that temperatures started falling two years ago. It is telling us that the latest 10 year period, 2004 to 2013, is colder than the period of 2001-10.
Indeed, the current 10-year average is lower than it was back in June 2006 and for two years afterwards. (The dip in 2008 & 2009 reflects the removal of 1998 from the average, before the removal of 1999 & 2000 counteract it).
So what we can say is that the period of 2004 to 2013 is about the same as, or slightly lower than, 1997 to 2006.
Ah, you might say, but have temperatures been increasing within the last 10 years?
Well, no. As Figure 2 shows, the 12-month averages during the last 10 years have also been flat.
So, to put it another way, temperatures have flatlined for the last 16 years, and, if anything, are going down.
We can do the same exercise using HADCRUT4 numbers, (still only available up to July 2013).
Again, you get a very similar picture, although this time the current average is very slightly above what it was in 2007, rather than below as RSS is.
The 12-month running averages for both RSS and HADCRUT4 show that temperatures have been flat for the last decade. Furthermore, the longer, 10-year averages indicate that this flatlining :-
1) Is not due to year to year fluctuations.
2) Started around 1997.
Would it be too much for our pampered journalists to do what I thought they were paid to do? That is, go, investigate, and check the facts for themselves? It’s really not that difficult, is it?