Global Warming Since 1997 Underestimated By Half 534
Layzej writes "A new paper shows that global temperature rise of the past 15 years has been greatly underestimated. The reason is that the weather station network covers only about 85% of the planet. Satellite data shows that the parts of the Earth that are not covered by the surface station network, especially the Arctic, have warmed exceptionally fast over the last 15 years. Most temperature reconstructions simply omit any region not covered. A temperature reconstruction developed by NASA somewhat addresses the gaps by filling in missing data using temperatures from the nearest available observations. 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. The researchers describe their methods and findings in this YouTube video. 'The most important part of our work was testing the skill of each of these approaches in reconstructing unobserved temperatures. To do this we took the observed data and further reduced the coverage by setting aside some of the observations. We then reconstructed the global temperatures using each method in turn. Finally, we compared the reconstructed temperatures to the observed temperatures where they are available... While infilling works well over the oceans, the hybrid model works particularly well at restoring temperatures in the vicinity of the unobserved regions.' The authors note that 'While short term trends are generally treated with a suitable level of caution by specialists in the field, they feature significantly in the public discourse on climate change.'"
Re:youtube? (Score:5, Informative)
Re:youtube? (Score:4, Informative)
*FACEPALM*
I understand not reading the story. This is Slashdot after all. But not reading the summary? Come on man. There's a link to paper right at the start of the summary. The youtube vid was to explain it to the average Joe, not for passing a scientific review.
Re:High School Physics (Score:5, Informative)
Fail.
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.
Re:Headline - by half? (Score:5, Informative)
The only thing in TFS is that they cover 85% of the globe, where does the "half" come from?
From the paper, which actually found 2.5 times as much warming by leveraging satellite data as the CRUtemp does by ignoring the unobserved region. The paper shows that the Arctic is warming at about eight times the pace of the rest of the planet. This is not an unexpected finding: see polar amplification [wikipedia.org]
Re:Orders of magnitude errors dont inspire confide (Score:2, Informative)
A factor of a half is not "orders of magnitude" larger. It's of order 0 in fact.
Comment removed (Score:3, Informative)
OK, enough (Score:4, Informative)
Look, I am fed up with this. Just turned 40 last Sunday. Have pictures from all the 40 birthdays. All the way through the 70-ties and half 80-ies I am on ski - 50 cm or more snow, winter is in full swing. Late 80-ties and early 90-ties - cold but not freezing. After that it became ridiculously hot until last Sunday when the absolute record was set - it was 23 (I repeat 23 degrees!!!). And BTW, this 20-23 degrees lasted for 4 weeks in total (mid-October -mid November). Utterly ridiculous and unheard off.
Since 10 years the fruit trees in our garden do not bear fruit because it is too hot in January and February, so they start blossoming too early. Then a few frosts in March and they are gone. 17 degrees Celsius in mid-February (for a week or longer)? In my country where this is the coldest month? WTF?!?
Say what you will about anecdotes, I don't give a damn. My experience is unambiguous. The Earth is warming.
Re:Especially (Score:4, Informative)
The method used works well over the oceans - is that where they omitted data and the used the prediction method? But it works "particularly well" where we have no actual data to validate it...
no - while the infilling that NASA uses works well over the oceans. The hybrid method (leveraging satellite data) works particularly well over the unobserved regions.
And yes - they do have data to validate it. Read the preceding paragraph: The most important part of our work was testing the skill of each of these approaches in reconstructing unobserved temperatures. To do this we took the observed data and further reduced the coverage by setting aside some of the observations. So to test the skill of the various methods they just compare the results against the data that they set aside during the tests.
Re:Double down (Score:2, Informative)
A bit of a lull in temperature increase (AFAIK, it's still going up, but more slowly) is nothing significant when you've got long-term trends that are flagrantly obvious, such as decreasing seasonal ice in the Arctic (last year was the sixth smallest ice cover since monitoring started in the 1970s), more glacial ice sliding off Antarctica (probably due to more melting at the base, which speeds glacier flow), more melting on the surface of the Greenland ice sheet than ever before observed, and the great majority of glaciers being in retreat for at least the last century. Long-term and short-term trends are not the same thing. With your logic you would be saying global warming was over every time we go from summer into fall and winter in the northern hemisphere. No, that is a short-term seasonal trend. Likewise, fluctuations on decadal scale are expected regardless of what's going on. That's always been the pattern. They don't negate averaged trends observed over many decades. Nobody expects the same or even necessarily an increase in temperature *every*single*year* due to global warming. It's going to vary.
When temperature increase doesn't merely slow, but reverses for, say, the next 40 years, undoing the increasing trends of the previous 40, then people would admit there was a problem with the interpretation of global warming. Otherwise the only thing a lull in temperature guarantees is that a lot of global warming deniers are going to pop out of the woodwork and use it to push their case while ignoring all the other evidence that still contradicts their claims.
As far as I'm concerned, if there's a bit of a lull in the temperature increase, that's good news. But I dread what it might mean if things tilt the other way, and we get a decade of faster-than-predicted temperature increases.
Re:Models all the way down (Score:4, Informative)
Re:Double down (Score:4, Informative)
Re:Double down (Score:5, Informative)
Why do you think the IPCC no longer uses the Hockey-stick graph?
They don't use Mann's original hockey stick graph from 1998 any more because it's 15 years old and numerous other newer reconstructions have been done since then. But if you take a look at Chapter 5 - "Information from Paleoclimate Archives" [climatechange2013.org] of the IPCC AR5 - WG I report you'll find that figures 5.7 & 5.8 still look remarkably like the original hockey stick graph. So they've got newer versions of it.
Re:youtube? (Score:4, Informative)
Another idiot who doesn't understand the difference between weather and climate and the effects of natural variability.
Amazing (Score:4, Informative)
I thought Slashdot was the place for rational individuals. Instead many of the posters are simply in denial what's happening. Of course AGW is being exploited, but the change is still real, and the humans have changed the Earth's atmosphere and the capacity to react to such sudden changes. What's happening now on the global scale is a natural feedback for the historically sudden input by one species and its technology.
If you still don't find that logical - taking into account simple physical phenomena known for over 100 years (and direct observations) - imagine this:
Alien race starts to pour greenhouse gases into the Earth's atmosphere. Who do you think is guilty of the resulting warming? What if the alien race starts to chop trees and rain forests, and - gasp - what if they actually maintain billion head cattle population (responsible of major chunk of the greenhouse gas emissions)?
The cattle population for example would be at its natural level if we stopped feeding it, letting the cattle to find its own food.
It's amazing how denial can work, isn't it? It's natural however - the first phase of confronting something uneasy - but it's still there on the path to understanding, so don't worry you are well on your way.
Re:Double down (Score:2, Informative)
Just as they get to the point where they can admit there's been no warming for 17 years and started coming up with excuses, here comes another "estimate".
Haha, I don't think any scientists made that claim. Just a bunch of cranks [amazon.com] who think measuring data from 1998 isn't cherry picking [youtube.com].
Double down on stupid.
Psychologists have a term for that [wikipedia.org].
Re:Double down (Score:4, Informative)
What this video to learn about how people like you think about whether it is warming or not [youtube.com].
If. You. Dare.
It's not that you disagree with people, but that you are incapable of processing information. like the above video. I'm sure it will make no sense to you, but typical people will laugh and shake their head.
An ideologue as the ability to look at a black wall and call it white. That is you.
Re:Double down (Score:4, Informative)
This video explains the source of the confusion [youtube.com].
Re:Double down (Score:5, Informative)
| And, really, it's right to be quite skeptical of any scientist who argues that "my theory wasn't wrong, 15 years of data was all wrong". That's an extraordinary claim.
Indeed, but that's not the claim.
And it's quite right be be skeptical of any internet poster who is "skeptical" of results which are disliked who doesn't really understand where they came from but is smug about their skepticism.
Closer to actual facts:
a) there are no calibrated ground-based stations in the Arctic because there is no ground in the Arctic.
b) the physics of increased greenhouse effect predicts larger effects in polar regions. (This also distinguishes global warming from enhanced greenhouse from global warming from increased solar output).
c) global warming is, of course global
d) combine (b) and (c) and you recognize that accurate quantification of global warming requires good evaluation of polar temperatures.
e) previous temperature reconstructions used simple extrapolation or ignored Arctic regions with no data.
f) authors propose new technique to assimilate data from multiple sources like satellites to improve coverage
g) authors calibrate/validate technique where good data were known
h) authors run the method and apply to Arctic regions with authentic missing data
i) results show substantial warming larger than estimates previously used in (e).
j) results with substantial warming in Arctic are more consistent with estimates using first-principles physics of greenhouse effects and what mainstream climate scientists have been predicting since 1992 or so.
next up:
k) scientists doing improved data processing showing closer correspondence to physics get accused of being shrill anti-capitalist nazis or the like.
Remember the previously skeptical Berkeley statistics professor---a favorite of the usual "skeptical" right-wing deception machine---who was convinced that the climatologists were doing their data analysis wrong and showing excessive global warming. And he & students got the underlying data sets and worked for years. And they found that the climatologists had the right answer all along (in fact their own estimates of warming were a touch higher than the climatologists).