Which is a bit of a mouthful, so they call it SREX. In the traditional and slightly unlovely IPCC way, you can read the SPM now but will have to wait awhile for the report. But it provides enough for me to mount my hobby horses, so giddy-up!
The first point is that extremes are useless for detecting or attributing climate change: if you want to know if the globe is warming, you should look at the global temperature series. Attempting to say "floods in Pakistan - global warming must be real" is silly (depending on what you mean by "real". I mean, "is actually happening". If you mean "will have actual noticeable effects on you in real life more interesting and alarming than just a gradual rise in average temperature" then you might just justify the "real", but its a confusing use of the word. And of course, floods in Pakistan don't have any effect on me. Or you). Extreme events don't have stable statistics, because they are extreme, so concluding anything from them is much harder than concluding things from averages. So they start with
There is evidence from observations gathered since 1950 of change in some extremes. Confidence in observed changes in extremes depends on the quality and quantity of data and the availability of studies analyzing these data, which vary across regions and for different extremes. Assigning "low confidence" in observed changes of a specific extreme on regional or global scales neither implies nor excludes the possibility of changes in this extreme.
which is really only preparing you for the lack of excitement later on:
It is very likely that there has been an overall decrease in the number of cold days and nights, and an overall increase in the number of warm days and nights, on the global scale... there is medium confidence that the length or number of warm spells, or heat waves, has increased... There have been statistically significant trends in the number of heavy precipitation events in some regions. It is likely that more of these regions have experienced increases than decreases, although there are strong regional and subregional variations in these trends.
So far so dull: it has got warmer. We knew that anyway. Then they go on to wind up the cyclone-trend folks:
There is low confidence in any observed long-term (i.e., 40 years or more) increases in tropical cyclone activity (i.e., intensity, frequency, duration), after accounting for past changes in observing capabilities. It is likely that there has been a poleward shift in the main Northern and Southern Hemisphere extra-tropical storm tracks. There is low confidence in observed trends in small spatial-scale phenomena such as tornadoes and hail because of data inhomogeneities and inadequacies in monitoring systems
but don't forget their original point that low confidence doesn't exclude an effect. And then:
Increasing exposure of people and economic assets has been the major cause of the longterm increases in economic losses from weather- and climate-related disasters (high confidence). Long-term trends in economic disaster losses adjusted for wealth and population increases have not been attributed to climate change, but a role for climate change has not been excluded (medium evidence, high agreement)
Attribution:
There is evidence that some extremes have changed as a result of anthropogenic influences... It is likely that anthropogenic influences have led to warming of extreme daily minimum and maximum temperatures on the global scale. There is medium confidence that anthropogenic influences have contributed to intensification of extreme precipitation on the global scale... The uncertainties in the historical tropical cyclone records, the incomplete understanding of the physical mechanisms linking tropical cyclone metrics to climate change, and the degree of tropical cyclone variability provide only low confidence for the attribution of any detectable changes in tropical cyclone activity to anthropogenic influences.
Yup, that's right: its got warmer, as wedunnit. We knew that already. But the cyclones are too wobbly to say much about them. And dealing with it? Deep insights such as
Developed countries are often better equipped financially and institutionally to adopt explicit measures to effectively respond and adapt to projected changes in exposure, vulnerability, and climate extremes than developing countries
So all in all, nothing exciting or surprising. RP Jr is happy with it, no surprise, and Romm is well pissed off, ditto. As usual, Pielke wipes the floor with Romm. Revkin appears to be sane but dull.
I seem to have forgotten what my second point was. Never mind. I didn't quite get to the end of the SPM. Hopefully that isn't too obvious.
Refs
* Nurture - boring
* RC is mostly interested in the cyclones
* JF has the right idea
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More like this
[ Begging for Life] Complaint about IBM China CSR on Centennial
Please Google:
IBM detained mother of ex-employee on the day of centennial
or
How Much IBM Can Get Away with is the Responsibility of the Media
or
Tragedy of Labor Rights Repression in IBM China
or
IBM Advised to Treat its People with Humanism in China
[without the reference to 'prior']
Useful link. I haven't looked yet and am no expert.
Perhaps you are complaining that you agree with it too much?
Following your example, I might say that I agree with your remark
but don't find it (i.e. your remark) very thrilling either, because I thought from the title that it was going to be about "...managing risks and climate adaptation" which could include a related but less boring question i.e. "assuming global warming (GW) as given, how do the risks of floods in Pakistan compare to a world without GW? Miles Allen * was on BBC2 the other night and was optimistic that progress would (has been?) be made in this area.
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* Possible litigation would not be so dull.
William --- Thanks. This subject isn't stiff & cold anyway.
Summary of the summary: "we haven't seen much so far, and we don't expect to see much in the next two-three decades, but by the end of the 21st the fan will definitely be hit".
(Right?)
[But we knew that already :-) -W]
Useful link. I haven't looked yet and am no expert.
But as I see it you are complaining that you agree with it too much.
Following your example, I might say that I agree with your remark
but don't find it (i.e. your remark) very thrilling either, because I thought from the title that it was going to be about "...managing risks and climate adaptation" which could include solving a different inference problem i.e. "given global warming (GW) as a prior how do the risks of floods in Pakistan compare to one without the GW? Miles Allen * was on BBC2 the other night and was optimistic that progress would (has been?) be made in this area.
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* Possible litigation would not be so dull.
[But we knew that already :-) -W]
Scientifically, nobody can say 'we know that already' -- right? Because it hasn't happened yet.
Are you sure this isn't a handbasket we're in?
It looks like WG1 of AR5 is going to come out some months before WG2 and 3? Isn't that something you've suggested? Though I'm not sure it's enough of a lead to make any difference.
[Yes, it would need to be a year or two to be useful -W]
"And of course, floods in Pakistan don't have any effect on me".
[I wasn't being entirely serious at that point -W]
The floods in Thailand however have caused a global shortage of computer harddrives. I've already seen the price of hard drives double and there are concerns that manufacturers will not be able to meet the demand for computers.
Forget about the many brands you see in the shops for computers, televisions, refrigerators as many depend on components that are only made in a few factories worldwide.
Has this been accounted for in the economic projections?
[If you mean the IPCC-type ones, no, I doubt it, they are too broad-brush for that kind of detail. That kind of fluctuation will smooth itself out on the large scale -W]
I left a thoughtful comment on Dot Earth about this, probably too intellectually demanding for the crowd there. Anyway, I'll not repeat it.
However, attempting to set the return period for the reference flood is very important to the plannng and financing of civil structures; siting of buildings, flood protection, etc. (The reference flood is the maximum flood engineers aim to protect against. The return period is the inversse of the expected frequency; a typical return period used is 100 years but sometimes longer is thought best.)
With climate changes an already almost impossible task becomes actually impossible; one is forced to guess, in effect. I know of cases of civil engineers tasked with setting the return period at a certain elevation near a river delta arbitraily changing the formerly 100 year contour to the 30 year contour after a rather dramatic flooding which destroyed many houses (and other structures).
The matter is made even more difficult for the insurance actuaries, for reasons which don't seem to directly relate to the (unknown) physics but rather the so-called economic development.
All told, I fail to see what this particular IPCC report adds beyond retelling, rather turgidly, that "stationarity is dead" (even if it actually was ever alive with regard to extreme rainfall events).
"Extreme events don't have stable statistics, because they are extreme, so concluding anything from them is much harder than concluding things from averages."
So the rate of warm or cold extremes varies? Seems counter intuative to me. I'd guess (and only that) that over time the rate of comparable extreme events would be stable in a stable climate. But, maybe I'm wrong about that - I really don't know.
[What I'm trying to say is this: that if you want to know the average value of some quantity - like the global temperature - then you'll have a pretty good idea of it within 10 years, and a very good idea within 30 - assuming that the climate is reasonably stable. If you want to know whether a given flood surpasses the expected 100-year flood, then you need a far longer series, of the order of 100 years. Extreme event statistics will be well-defined (for a stable climate) over a very long time period; but not for a much shorter one. If, now, you're thinking about a changing climate, and wondering if the 100-year flood level has changed, things get very difficult. But if you just want to know of the global temperature is increasing, it is much easier -W]
So, if the average warms does that mean it's really the case the number of comparible warmth extremes might not change? Or, rather, that for such a change in warm extremes in a warming climate to be undetectable, they actually fall? Or, perhaps to finally get the question out of myself, just how much do extremes have to change (in this case more comparible warm extremes in a warming climate?) for that change to be confidently detectable? And its really the case we can be confident we *know* the climate has warmed by now but we wont know anything about warmth extremes for another thirty years of warming? Seems odd to me.
David #6,
"All told, I fail to see what this particular IPCC report adds beyond retelling [..]"
Well, isn't that precisely IPCC's job? To gather the current state of scientific knowledge and present it to the public and politicians?
[Yes, quite right -W]
Maybe we need to remember, when assessing if the future is likely to be better or worse than we thought, that there may be unknown unknowns in climate science - the calculated uncertainties do not, by definition, take these into account.
For certain, we know that the planet is accumulating heat and has not reached equilibrium. In the distant past there have been dramatic climate shifts which caused major rapid onset problems for the existing life. Current posited explanations of the forcings that caused these may be wrong or incomplete and, correct me if I am wrong, the evidence for the magnitude of the forcings and consequent feedbacks is not rock solid beyond all reasonable doubt. An "unknown unknown" aspect to feedbacks may be out there and, if there is, there is no way we can easily predict when it may kick in, how fast and how far it may take us.
Climate scientists are used to the "sceptic" element pooh-poohing any problems they outline but just because the sceptic arguments are at best weak, at worst mendacious, does not mean that the science itself has definitively got how reality will react accurately in the crosshairs.
Whatever happens we have to remember that we are conducting an unprecedented experiment with the atmospheric composition of Earth. Short of using a time machine to make repeated journeys back to the past so we could pursue different emissions strategies to nail the sensitivity(ies) experimentally, we cannot be certain what it is or if there are as yet unknown step changes in the changing dynamics of the complex systems. The existing figure and error bars may be close. We surely wish they are, but they may not be so. The hubris of scientists that their scenarios can be used to accurately assess the full risks to our civilisation probably needs to come down a peg or two.
Sceptics are dangerously complacent compared with how they should be, based on current knowledge. The pronouncements from climate science, and this IPCC report in particular, are complacent too because of their confidence that they have got it right enough to be virtually sure of the uncertainties.
Whatever happens will happen exactly according to the laws of physics, biology and chemistry and the multitude of interactions between them. We only get to run this big experiment once. Remember, we are in the test tube and we can't get out.
Nicely put, Nick.
While we seem to have a pretty good handle on Earth system sensitivity and the associated equilibrium climate states, albeit that figuring out the timing remains difficult, "unknown unknowns" seem very much a possibilty due to the fact that we are pushing the system faster than it has been in the past. There is also the wrinkle of non-climate forcings on biological systems.
I and I think many others are most worried about the "known unknown" East Siberian Shelf-area methane deposits, noting that they're very recent (mostly Pleistocene), seem to be unique during the Phanerozoic, and are large enough to push us into another PETM.
Then there's this new result, which appears to have captured increasingly extreme climate behavior that's not currently modeled:
'The first climate study to focus on variations in daily weather conditions has found that day-to-day weather has grown increasingly erratic and extreme, with significant fluctuations in sunshine and rainfall affecting more than a third of the planet.
'Princeton University researchers recently reported in the Journal of Climate that extremely sunny or cloudy days are more common than in the early 1980s, and that swings from thunderstorms to dry days rose considerably since the late 1990s. These swings could have consequences for ecosystem stability and the control of pests and diseases, as well as for industries such as agriculture and solar-energy production, all of which are vulnerable to inconsistent and extreme weather, the researchers noted.
'The day-to-day variations also could affect what scientists can expect to see as Earth's climate changes, according to the researchers and other scientists familiar with the work. Constant fluctuations in severe conditions could alter how the atmosphere distributes heat and rainfall, as well as inhibit the ability of plants to remove carbon dioxide from the atmosphere, possibly leading to higher levels of the greenhouse gas than currently accounted for.
'Existing climate-change models have historically been evaluated against the average weather per month, an approach that hides variability, explained lead author David Medvigy, an assistant professor in the Department of Geosciences at Princeton. To conduct their analysis, he and co-author Claudie Beaulieu, a postdoctoral research fellow in Princeton's Program in Atmospheric and Oceanic Sciences, used a recently developed computer program that has allowed climatologists to examine weather data on a daily level for the first time, Medvigy said.
'"Monthly averages reflect a misty world that is a little rainy and cloudy every day. That is very different from the weather of our actual world, where some days are very sunny and dry," Medvigy said.
'"Our work adds to what we know about climate change in the real world and places the whole problem of climate change in a new light," he said. "Nobody has looked for these daily changes on a global scale. We usually think of climate change as an increase in mean global temperature and potentially more extreme conditions -- there's practically no discussion of day-to-day variability."
'The Princeton findings stress that analysis of erratic daily conditions such as frequent thunderstorms may in fact be crucial to truly understanding the factors shaping the climate and affecting the atmosphere, said William Rossow, a professor of earth system science and environmental engineering at the City College of New York.
'"It's important to know what the daily extremes might do because we might care about that sooner," said Rossow, who also has studied weather variability. He had no role in the Princeton research but is familiar with it.
'Rossow said existing climate-change models show light rain more frequently than they should and don't show extreme precipitation. "If it rains a little bit every day, the atmosphere may respond differently than if there's a really big rainstorm once every week. One of the things you find about rainstorms is that the really extreme ones are at a scale the atmosphere responds to," he said.
'Although climate-change models predict future changes in weather as the planet warms, those calculations are hindered by a lack of representation of day-to-day patterns, Rossow said.
'"If you don't know what role variability is playing now, you're not in a very strong position for making remarks about how it might change in the future," he said. "We're at a stage where we had better take a look at what this research is pointing out."'
(article continues)
[Yes. The thought is good: after all, if Cambridge becomes warmer in winter that might be good, but if it ends up shrouded in cloud that would be bad. However, I'm dubious they have the data to do this. Notice the huge areas of less-variable at the poles - are those real, or dataset artifacts? Notice also that the more-var areas are concentrated in a few tropical regions -W]
Yup, I saw that science Daily article.
FWIW I have been hang gliding for 35 years and I swear that winds where I live (English Channel) have changed since the mid 70's/early 80s. I would say that nowadays we get more frequent episodes of either light (Force 3 or less) or strong (Force 6 or more) winds but most obviously the length of time that any wind stays from the same direction is much less than it used to be. Looking at my logbook over the period shows that soarable conditions for hang gliders (directionally stable Force 4-5s) seem nowhere near as frequent as they used to be.
Well, yes, it's the proverbial first paper, but OTOH Rossow isn't chopped liver on this stuff. Wouldn't we expect to see the major effect in the tropics?
[I don't see why. You tend to see the largest changes in, say, absolute ppn in the tropics, just because it is largest there. But this is effectively a relative change, so no reason to expect the largest value in the tropics -W]
And Cambridge has what to do with all of this?
[Nothing, just an illustration -W]
They say in the article that the effect is greatest in convective clouds, so why wouldn't we expect it to be preferential to the tropics?
But that's the article, not the paper, which I suppose I should acquire and read.
[Ah yes, I thought the pattern looked a bit like the ITCZ, so that would indeed fit -W]