Absolutely true. Also, the isotope ratio of C12/C14 tells us that the increasing CO2 is from burning fossil carbon, the effect of doubling CO2 is an extra 3.7 W/m[sup]2[/sup], and a simple grey-body calculation implies that extra 3.7 W should result in an extra 1.5 deg. C average temperature. This response to a CO2 doubling is frequently reported as the “climate sensitivity”. However, most climate models add amplifying feedbacks to calculate climate sensitivities of 2-4 deg. C per doubling, with a few going even higher than that.
Well this is a matter of language use. Let’s be clear, if you cherry-pick any two dates on the temperature record and do a least-squares straight-line fit to the data over that period, the trend this gives you over that period is perfectly correct. So it IS correct to say there has technically, factually been cooling since 1998, but it’s a real reach to claim that the long term trend has changed on the basis of this. That is in essence what Waldo Pepper has been asking in this thread - what would we have to see in the temperature record before we COULD conclude that the long term trend had altered? Unfortunately the answer is basically “flat or declining temperatures for several decades”* if all we’re looking at is surface temperature*. Something that would be clearly be unprecedented in the existing temperature record, which itself contains notable flat spots and periods of decline.
Water vapour is certainly a greenhouse gas and it’s entirely reasonable to predict that a raised air temperature and sea surface temperature will increase the concentration of water in the atmosphere. There is a question of how much water vapour will increase - most models have assumed the relative humidity will stay constant and then worked off the temperature increase. IIRC the actual measurements show a reduction in relative humidity, which implies the water vapour feedback has probably been overestimated, but the measurements are pretty tentative anyway at the moment. Neverthess, personally I’d be surprised if there isn’t a substantial positive water vapour feedback.
Rather more uncertainty IMO lies with clouds and this is acknowledged in the IPCC reports. Clouds increase albedo, but they also reflect heat back to Earth. Cloud altitude has an effect and also cloud distribution. Even if clouds technically have a warming effect and cloudiness increases, if the distribution changes in favour of high latitudes as well it would result in a negative feedback, and the same is true if everything reverses. At the moment we don’t really know the sign or magnitude of cloud effects.
The prediction is basically a long-term warming trend, about 0.2 deg C per decade on average. I’m fairly sure this prediction will turn out to be pessimistic but that won’t disprove global warming - it would only show that the IPCC has overestimated climate sensitivity, which I personally believe is the case.
My take on the whole thing is that the majority of the economic activity on face of the planet - the mining and logging and drilling and mechanised agriculture and fishing and transport and building and the rest of it - is mostly for the benefit of a billion-odd people in the developed world. Us and our underappreciated lives of relative opulent luxury. We’re looking at another 2.5 billion Chinese and Indians aspiring to enjoy the same standard of living in a few dacades, and another 3.5 billion in the rest of the world some time after that, and who can blame them? The thing is, their path to prosperity can’t be the same as our path. Not without cutting the last tree down and trawling the last bluefin tuna out of the sea, which nobody wants to see happen. So figuring out how to do economic activity sustainably, wasting as little resources as possible, using renewable/nuclear/ low carbon fossil fuel energy, is vitally important whether climate sensitivity is high or low. Even if it’s low, I don’t care to run the experiment of tripling CO2, or quadrupling it, and just seeing what happens. I have no patience for impractical Greens who feel the rightness of their cause justifies overstating the certainty and exaggerating the danger in order to effect policy. I also have no patience for unrealistic free marketeers thinking we’re not facing any kind of problem here.
I would be surprised. Feel free to make arguments to the contrary, but I’m pretty confident that you take a complex system which has been reasonably stable for a long time and push on it, the smart money is that it will push back.
I would say that for all practical purposes, “global warming” – as the phrase is commonly understood – will have been disproved. Keep in mind the fundamental issue is whether mankind needs to go through the trouble of dramatically cutting CO2 emissions.
Well, not much change there, but it is hopeful to see examples elsewhere of skeptics that do learn that mankind needs to go through that inconvenience to prevent real trouble later.
Among climate feedbacks which are known, some are positive feedbacks. Among these the most famous is glacier albedo: ice forms on a cool Earth, reflecting sunlight and thus making it even cooler. How does today’s ice cover compare with that of earlier interglacials? If it soon will indeed be the least ice-cover in almost a million years, would that be a significant fact?
And if examining the glaciation cycles of the last million years does not put to rest the claim that “smart money” is on stability, I’d ask Dopers to examine a larger period: the past billion years or more. “Stability” is not the word that comes to mind when contemplating Earth’s climate history at any time scale.
One fact arguing against optimism is that the heat input from the Sun has never been higher than it is during our own era. Despite this, the Earth is much cooler today than it was at some points in the long-distant past. Viewed differently this means that the present life-friendly temperatures are not a “stable” outcome despite the Sun’s own warming, but rather may be the fortunate outcome of the positive cooling feedbacks in the Quaternary Age of Glaciation (whose onset is, AFAIK, unexplained).
BTW, brazil84, I noticed no response from you (besides an ambiguous claim of confusion) about increasing ocean acidity. Too inconvenient of a fact?
First, can you show me solid evidence that this (alleged) positive feedback actually takes place in the Earth’s climate system? And if the evidence is a computer simulation, I would need solid evidence that the computer simulation has been tested and validated. i.e. proof that the computer simulation has made actual predictions which later turned out to be accurate and were very unlikely to have been the result of chance.
Second, are you saying that positive feedbacks are somewhat common compared to negative feedbacks? Again I would want evidence.
I don’t know.
To me it would, in terms of the global warming debate.
Well according the commonly cited graph here, global surface temperatures have stayed within a ten degree range over the last 500 million years. Agreed?
Here’s what I said in response:
It doesn’t seem to me to be a claim of confusion so much as a request for the evidence underlying this “fact.”
Personally, I find understanding science to be an interesting pastime regardless of conclusions. Without mentioning names, others seem agenda-driven, happy to pick and choose which areas of science are interesting and which they prefer to pretend not to understand.
All the claims I have seen about the supposed dangers of increased CO2 levels have not stood up to scrutiny. So I don’t usually bother to go out looking for more claims.
If you want to defend the ocean acidification hypothesis with cites, links, and quotes, I am happy to consider it.
Then I imagine will enjoy finding, summarizing, citing, linking, and quoting the evidence to support your claims about ice-driven positive feedback and positive feedbacks in general.
Why, what as-yet-hypothetical evidence would the UN need to say there’s no warming trend? Would the same evidence convince you?
I realize what they have isn’t yet enough for them, and haven’t said otherwise. But until they spell out what would be enough for them, they’re not making a meaningful prediction; we can’t know if they’re right unless they tell us what it would mean to be wrong.
As this will be ignored also, the reality is that models are not the only way scientists found out we have a problem with the oceans too.
Modelling studies based on what are essentially simple geochemical processes** have matched the observed decline in ocean pH. ** Essentially, while we are there is still much to learn about how the ocean works, there are many empirical studies that show that ocean pH is changing rapidly. An excellent description of this work can be found in Doney et al. (2009). Ocean acidification is occurring at rates which dwarf anything seen over the recent past.
Does anybody *NOT *see how Gigobuster is squirming around trying to avoid simple questions? He makes a lot of broad declarations about what is and is not correct. And he pastes a lot of links. But when it comes to actually explaining what the facts are in his own words, for some reason he is forced to weasel out of answering simple questions for 3 pages and 4 days.
Of course where real science is involved, weaseling is never necessary. Real science is base don hard fact and figures and doesn’t require or even permit weaseling.
It’s only alarmist psuedoscience that requires such weasel tactics.
You pointed at them for the support of your claim, and that is what I wanted to show, you have no support from them to base your overall point.
Again the point was to press you into finding other evidence that the UN was not overweeningly talking about a warming trend. The evidence that would convince me that there is no warming trend would be an independent group of statisticians looking at the data from NASA, HadCRUT or NOAA and come with a different conclusion as the UN. And we already know what did say about it.
The sad part is that you have not noticed yet that the UN also relies on the data from NASA, HadCRUT or NOAA, so that is why it has been really silly to avoid dealing with what the independent statisticians are saying.
And so, we come to this, for all what you said you only ended going back to the same point, but at least with the acknowledgment that the UN is not supporting it.
So you’re interested in science but too lazy to click those links. And pretend that you’d be more interested in my summary than the writings of scientists. Got it.
And, either you’re unaware of the ice-driven positive feedback mentioned in any junior-high-school summary of global warming or, more likely, are so intent on finding fault that you’ve not bothered to understand my sentences. Got it.
This isn’t BBQ Pit, which is why I didn’t “mention names” but now we’re seeing the sort of Know-Nothing non sequiturs which make clear who is who in this thread.
No, everyone can see that I explained twice why, the fact that you want to ignore the clear evidence that simple answers only generate myths that are never corrected or acknowledged by the groups I deal with is your problem, as it is your baseless accusation here.
So far the pseudoscience is the one coming from deniers, the “just asking questions” groups, and people accusing others of being alarmists when at the same time they ignore the scientists being cited.
I pointed at them in reply to a specific question about '98 and '05 and '10. I’d previously mentioned them and made specific mention that I know it’s not good enough for you, and so would like to know what would be.
I’ll admit that’s a baby step forward for you, but it’s still the same type of evasion. It’d be obviously inadequate for you to state no falsification criteria, and it’d be obviously inadequate if the folks you’re talking about state no falsification criteria – and so switching from I Won’t Name Such A Criterion all the way over to My Criterion Is The Criterion They Won’t Name is still a bit lacking.
You’re saying no change in temperature over any span of years could falsify it for you in its own right; it’s someone else’s conclusion that will win you over, not their facts. That’s, like, the opposite of science.
(Unless, again, they’ve stated falsification criteria you’re endorsing by proxy? If so, name 'em and end my objection.)
And so we come to this: for all you’ve said, you acknowledge that no amount of hypothetical evidence could sway you so long as folks you trust keep telling you the evidence isn’t good enough – without them ever telling you what evidence would be good enough. You’re not the one who refrains from making falsifiable predictions; you’re the one who refrains from asking for them.
“The evidence that would convince would be an independent group of statisticians looking at the data from NASA, HadCRUT or NOAA and come with a different conclusion as the UN.”
We know what did they said, so the evidence is already in favor of the warming trend, anyone saying that that is not so has to point at the evidence from experts that it is not, as it is clear that you are not an expert on this. And the UN and the other climate research centers still report a warming trend that continues after the CO2 forcing began to overwhelm the solar one.
If the independent statisticians and other experts would come up with evidence that your opinion is a valid one, then that would already had made a blow to the idea that there is no warming trend and the results reported in scientific journals.
The fact that you had to go for an out of context quote from the UN for support and that the context shows that they continue to report a warming trend is enough for me to say that your points can be ignored until better support is found.
A little ways back, I didn’t know what you were using as falsification criteria and I also didn’t know what they were using as falsification criteria. Telling me that whatever criteria they’re using would be good enough for you – look, that’s admittedly something, you’ve now taken two vague claims and unified 'em into one, but there’s still no there there. So long as I don’t know what they want, I still don’t know what you want.
Absent a stated falsification criterion, they can always say such points can be ignored until better support is found. So long as they never specify what facts would add up to a big enough context, they can always brand any given facts as out-of-context items that fall short of a trend.
How much “better” does the support need to get? I don’t know. What amount passes the “trend” threshold? I don’t know. Would any hypothetical evidence make their claim subject to revision? Or can they reassuringly placate you by just repeating a context-free We Haven’t Yet Seen Enough again and again, forever and ever, amen?
