No 15-year pause in global warming

[Guardsman Bass]

A new study by British and Canadian researchers shows that the global temperature rise of the past 15 years has been greatly underestimated. The reason is the data gaps in the weather station network, especially in the Arctic. If you fill these data gaps using satellite measurements, the warming trend is more than doubled in the widely used HadCRUT4 data, and the much-discussed “warming pause” has virtually disappeared.

Obtaining the globally averaged temperature from weather station data has a well-known problem: there are some gaps in the data, especially in the polar regions and in parts of Africa. As long as the regions not covered warm up like the rest of the world, that does not change the global temperature curve.

But errors in global temperature trends arise if these areas evolve differently from the global mean. That’s been the case over the last 15 years in the Arctic, which has warmed exceptionally fast, as shown by satellite and reanalysis data and by the massive sea ice loss there. This problem was analysed for the first time by Rasmus in 2008 at RealClimate, and it was later confirmed by other authors in the scientific literature.

The “Arctic hole” is the main reason for the difference between the NASA GISS data and the other two data sets of near-surface temperature, HadCRUT and NOAA. I have always preferred the GISS data because NASA fills the data gaps by interpolation from the edges, which is certainly better than not filling them at all.

A new gap filler

Now Kevin Cowtan (University of York) and Robert Way (University of Ottawa) have developed a new method to fill the data gaps using satellite data.

It sounds obvious and simple, but it’s not. Firstly, the satellites cannot measure the near-surface temperatures but only those overhead at a certain altitude range in the troposphere. And secondly, there are a few question marks about the long-term stability of these measurements (temporal drift).

Cowtan and Way circumvent both problems by using an established geostatistical interpolation method called kriging – but they do not apply it to the temperature data itself (which would be similar to what GISS does), but to the difference between satellite and ground data. So they produce a hybrid temperature field. This consists of the surface data where they exist. But in the data gaps, it consists of satellite data that have been converted to near-surface temperatures, where the difference between the two is determined by a kriging interpolation from the edges. As this is redone for each new month, a possible drift of the satellite data is no longer an issue.

Prerequisite for success is, of course, that this difference is sufficiently smooth, i.e. has no strong small-scale structure. This can be tested on artificially generated data gaps, in places where one knows the actual surface temperature values but holds them back ​​in the calculation. Cowtan and Way perform extensive validation tests, which demonstrate that their hybrid method provides significantly better results than a normal interpolation on the surface data as done by GISS.

The surprising result

Cowtan and Way apply their method to the HadCRUT4 data, which are state-of-the-art except for their treatment of data gaps. For 1997-2012 these data show a relatively small warming trend of only 0.05 °C per decade – which has often been misleadingly called a “warming pause”. The new IPCC report writes:

Due to natural variability, trends based on short records are very sensitive to the beginning and end dates and do not in general reflect long-term climate trends. As one example, the rate of warming over the past 15 years (1998–2012; 0.05 [–0.05 to +0.15] °C per decade), which begins with a strong El Niño, is smaller than the rate calculated since 1951 (1951–2012; 0.12 [0.08 to 0.14] °C per decade).


But after filling the data gaps this trend is 0.12 °C per decade and thus exactly equal to the long-term trend mentioned by the IPCC.

The corrected data (bold lines) are shown in the graph compared to the uncorrected ones (thin lines). The temperatures of the last three years have become a little warmer, the year 1998 a little cooler.

The trend of 0.12 °C is at first surprising, because one would have perhaps expected that the trend after gap filling has a value close to the GISS data, i.e. 0.08 °C per decade. Cowtan and Way also investigated that difference. It is due to the fact that NASA has not yet implemented an improvement of sea surface temperature data which was introduced last year in the HadCRUT data (that was the transition from the HadSST2 the HadSST3 data – the details can be found e.g. here and here). The authors explain this in more detail in their extensive background material. Applying the correction of ocean temperatures to the NASA data, their trend becomes 0.10 °C per decade, very close to the new optimal reconstruction.

This is all too true. A media analysis has shown that at least in the U.S., about half of all reports about the new IPCC report mention the issue of a “warming pause”, even though it plays a very minor role in the conclusions of the IPCC. Often the tenor was that the alleged “pause” raises some doubts about global warming and the warnings of the IPCC. We knew about the study of Cowtan & Way for a long time, and in the face of such media reporting it is sometimes not easy for researchers to keep such information to themselves. But I respect the attitude of the authors to only go public with their results once they’ve been published in the scientific literature. This is a good principle that I have followed with my own work as well.

The public debate about the alleged “warming pause” was misguided from the outset, because far too much was read into a cherry-picked short-term trend. Now this debate has become completely baseless, because the trend of the last 15 or 16 years is nothing unusual – even despite the record El Niño year at the beginning of the period. It is still a quarter less than the warming trend since 1980, which is 0.16 °C per decade. But that’s not surprising when one starts with an extreme El Niño and ends with persistent La Niña conditions, and is also running through a particularly deep and prolonged solar minimum in the second half. As we often said, all this is within the usual variability around the long-term global warming trend and no cause for excited over-interpretation.

The whole "15-year pause" thing was bullshit even before this, since others have pointed out that something like seven of the eight hottest years on record occurred in the past 12-13 years. But it's still an interesting read.

[Kitsune]

With this, I sometimes feel like throwing up my hands because I really don't know what can be done
Once I was a global warming skeptic but there is just too much accumulated material

[madd0ct0r]

nice, and a clever solution.

[Crake]

A while back I watched a visually stunning, and simultaneously depressing as hell documentary called Chasing Ice. I wholeheartedly recommend giving it a watch. If you don't know it's about a Nat Geo photographer who did a time lapse photographical study of a bunch of glaciers up North in Greenland, Alaska, and elsewhere, over the course of a few years (don't remember all of the details). Anyway, probably, won't convince anyone who's in chronic global warming denial, but it's definitely worth a watch.

[Kitsune]

A while back I watched a visually stunning, and simultaneously depressing as hell documentary called Chasing Ice. I wholeheartedly recommend giving it a watch. If you don't know it's about a Nat Geo photographer who did a time lapse photographical study of a bunch of glaciers up North in Greenland, Alaska, and elsewhere, over the course of a few years (don't remember all of the details). Anyway, probably, won't convince anyone who's in chronic global warming denial, but it's definitely worth a watch.

Kind of in an argument with deniers right here
http://warships1discussionboards.yuku.c ... -we-though

Trouble is the more I research from scientific sources, the more certain I am that Man Made Global arming is real

[Simon_Jester]

Me, I don't see the trouble with that.

Looking at these guys on the chat you linked to, they don't sound amenable to reason. They've already decided global warming is a conspiracy, to the extent that new data has no impact on them- they just dismiss it as more bullshit coming from the same bullshit conspiracy sources that produced the previous data. It's like, if you have already decided that your obnoxious neighbor is in the habit of forging legal documents, are you going to be impressed when he pulls out another legal document attesting to the validity of the first document? No, you will not; you'll simply assume he forged that one too.

So essentially, data is a conspiracy to falsify the evidence except when it (occasionally) validates their predictions. And you'll note how much time and energy they devote to talking about various conspiracy-like things such as "Goddard Spaceflight Center is actually a division of Columbia University, which is run by this guy, who we KNOW is maximum total evil!"

Basically, when the facts aren't on your side, you pound the table and condemn your opponent. In this case, that means endlessly repeating that climate scientists are librul liars in it for the money. So any theoretically unbiased group of scientists who support global warming are part of the conspiracy. Any urban legend about who's pulling the strings of those scientists is automatically believed: "What, it's all coming from Jewish financiers? Quislings who want to weaken us so they can sell us out to the Muslim hordes? Nefarious hippies who've been secretly plotting to pull down God-fearing American military-industrial civilization for fifty years? Oh, ALL THREE? Even better! Let me visit your poorly formatted website about the importance of this, while I'm on a break from poring over Time Cube!"

Oh, and trying to attribute all our concerns about global warming to Al Gore because he actually (gasp) ran for president as a Democrat thirteen years ago so we KNOW he's an overlord of the librul conspiracy! Never mind that various fictional sources were trumpeting alarm bells about global warming for at least twenty years, maybe thirty, before the release of An Inconvenient Truth, and that this release was something Gore did most of a decade after retiring from politics.


We've actually had people do this on this site, it's very predictable and works a lot like any other conspiracy theory. You start out be being privately convinced that the consensus reality can't be the real one. Then you become very open to the idea that the experts who speak for the consensus are lying. Then you find out there's a vast conspiracy among experts and elites to lie to you... at which point, you are no longer amenable to persuasion by normal means.

Any attempt to deprogram a person who thinks this way must begin by weakening their faith in the conspiracy. You can't do it by presenting yet more evidence produced by people they already think are lying for nefarious reasons. Especially since the conspiracy theory has a prepared fallback position- "all right, even if the Earth IS getting warmer, it must be [insert natural phenomenon that like one study's been done on here]!" Like "oh, subsea volcanoes are heating up the Arctic!" as though that actually works.


Meanwhile, the percentage of the scientists who actually make a study of climate that think global warming is manmade is... I don't actually know, but based on everything I've seen and heard I'm pretty sure it's upwards of ninety percent. With the vast majority of the remainder being stubborn old coots who say "well, we've proven a warming trend, but we aren't totally 100% sure yet that it's manmade- and this is still a narrow minority position.

[Kitsune]

I know it is long but this video is really good

[Kitsune]

Can about help me this article
http://www.faz.net/aktuell/politik/ener ... 78882.html
Tried a Google translate but barely makes any sense
Looking for a German speaker who might be able to tell me about the "spin"