11 posts tagged “global warming”

Time for another pop quiz, this time on climate change. Here are the questions; the answers are given below [1]:

Q1: When was the last time that the average temperature was as high as it is now?

A) Never; this is the hottest it has ever been, thanks to climate change
B) Never; this is the hottest it has ever been, but climate change has nothing to do with it
C) About  5,000 years ago
D) About 3,000,000 years ago

Q2: CO₂ is at 382 PPM. What is the highest level it has ever been?

A) 382 PPM; we have set a new record
B) 3,000 PPM
C) 900,000 PPM

Q3: Polar bears are in danger because the Arctic ice is melting.

A) True, they've never had to face this before
B) False, they are in trouble because their habitat is being encroached by man
C) False, they are in no trouble

Q4: CO₂ is the only greenhouse gas

A) True
B) Not true, but the other gases are insignificant compared to the effects of CO₂
C) Not true, the effects of other gases are about equal to that of CO₂
D) Not true, but we aren't sure what the relationship between the various gases and climate change is

Let's start off with the question of temperature. Today, the average temperature [3] of the globe is about 0.5 C above "normal". However, during the Holocene (5,000-9,000 years ago), the average global temperature was even higher than it is now. The temperature during the late Pliocene (~3,000,000 years ago) was also higher than it is today. We know this from a variety of sources, the best known of which are the oxygen isotope ratios.  The change in temperature comes from a variety of factors, including changes in the Earth's orbit (Milankovitch cycles), changes in the amount of energy the Sun emits, changes in the location of the continents [4], changes in vegetation [5], and (of course) changes in the Earth's atmospheric chemistry. Of these factors, we have had the most influence on the last two.

We have changed the vegetation in ways both large (e.g., the Colorado River) and small (e.g., Roundup). But it could be argued that we have had an even larger impact on the chemistry of the atmosphere. We have added radioactive materials [6], we have added complex chemicals [7], and most notably we have added CO₂. The Keeling curve is the best known record of the level of CO₂ in the atmosphere, but it is not the only one. This is good, because Keeling didn't start his work until 1958! In addition, we have ice cores that contain records of both CO2 (from air bubbles trapped in the ice) and temperature [8] (from the oxygen isotope ratio in the water of the ice) extending back nearly 800,000 years.  Before that, we have a series of proxies for both temperature and CO₂.

What they show is that the temperature has often been much higher than it is now, and that the CO₂ level has increased when the temperature has gone up. During the Cretaceous (145.4 - 65.5 million years ago {MYA}), temperatures were about 4 C higher than now on average, and the CO₂ level was about six  times higher than it is now. More recently, during the Holocene Climatic Optimum [9] about 5,000 years ago, temperatures were about 2.5 C higher than they are now and CO₂ levels were similarly increased. Thus, the Earth has been hotter than it is right now; it has even been hotter in historical times than it is right now. Similarly, the Earth has had higher levels of CO₂ than those we see today; it has even had higher levels of CO₂ than we expect to see in the next century.

So why all the fuss? If this has happened before, then we don't need to worry about it, right? Wrong. The problem is that the last time an organism had this strong an influence on the Earth's atmosphere, it significantly changed the makeup of life on Earth [10]. We already see some evidence of this change happening now. However, not every extinction we see is caused by climate change -  not even every anthropogenic extinction.

Take, for example, the poor polar bear. Right now, it is the poster child for endangerment due to climate change. However, polar bears have been around for about 200,000 years which means that they were here during the Holocene Climatic Optimum. So they've seen temperatures even higher and ice levels even lower than what we see today. So why are they endangered? Simply because the last time this happened, there weren't many other competitors for their niche and the polar bear was able to adapt. Today, the polar bear competes for land and food with the most vicious predator on the planet - man. Thus, the polar bear cannot retreat onto the land when the ice melts because we've taken all of the good spots. And it can't hunt moose instead of seals, because we've taken all the good ones. And so on. Unfortunately, those who would rescue it hurt their cause by oversimplifying and saying that the polar bear is threatened due to climate change. As a result, folks who would deny that climate change will change life on Earth [11] can seize on the motes in our eye while ignoring the beams in theirs.

And there are plenty of motes to seize on. For example, the focus on CO₂ as a greenhouse gas [12]. Though it is the most prevalent greenhouse gas, and the one that is most intrinsically linked to mankind's efforts, there are others. And some of the others are even more effective at increasing the greenhouse effect. There is methane (CH₄, which is a natural byproduct of digestion for critters from no legs (phytoplankton) to four legs (cattle) to n legs (creepy-crawlies). It is 20 times more effective at trapping heat than CO₂; fortunately it decays rapidly in the atmosphere into CO₂. Unfortunately, there are great stores of methane locked in clathrates  (aka "gas hydrates") just offshore and locked in the tundra. If temperatures increase enough, this methane may be "burped" into the atmosphere rapidly, leading to an increase in greenhouse conditions [13].  Another greenhouse gas is water vapor, which acts both as greenhouse gas and (when it condenses into high-level clouds) as a cooling agent. The sheer volume of water in the atmosphere gives it a larger contribution toward warming than CO₂ has. And, in one of those funny practical jokes that Mother Nature likes to play on us, increased temperatures can increase the ability of the atmosphere to hold water which then leads to an even stronger greenhouse effect and even higher temperatures.

Another favorite is the instability of climate models. Even today, we still don't know what happens to about 1/3 of the atmospheric CO₂. We know it goes somewhere, because the amount isn't building up as quickly as it should. But where does it go? Favorite candidates are peat bogs, northern forests, and "missing" primary productivity. With a hole this big in the model inputs, you can imagine what skeptics have to say about the outputs [14].

Which brings us back to the point of this pop quiz. Quizzes should be a measure of the student's learning. But they are also a measure of the quality of the teaching. And thus far, the quality of education on climate change has been dreadful (in both senses of the word). By making the overly simplistic statements and by covering up the good that will come from climate change along with the bad, those who would "educate" others on climate change do themselves and their cause a disservice. And that is never a good thing.

John

[1] But try to give your answer before reading the actual ones, OK?

[2] The math starts at tensor calculus and works its way up from there.

[3] We pass over the problem of deriving an average temperature for something that varies widely in heat input and output. In truth, most climatologists use heat (a measure of the energy in a system) rather than temperature (a measure of how that energy has excited a particular part of the system) and only convert to temperature at the last step. By watching how the heat flows in a climate model, they are better able to understand the system. For analogy's sake, consider traffic on the highway. You and I measure traffic in speed; when we get stuck in a jam, we slow down and so think the two are synonymous. However, civil engineers measure traffic in the number of vehicles (and have even found that decreasing the average speed can increase the amount of traffic that flows through, thus shortening a trip!).  From their calculations, civil engineers can take the more fundamental measurement (number of vehicles) and convert it into a more mundane one (speed). Climatologists do the same with heat and temperature.

[4] High latitude continents tend to accumulate snow, which has a high albedo, which reflects more energy back into space, thus cooling the earth.

[5] Ignoring the obvious, there is also the shift from dark-leaved vegetation to light-leaved varieties famously modeled in Daisyworld and seen in the change from tropical forests to grasslands.

[6] Which have proven to be a boon to anthropologists, as they allow a more precise dating of recent artifacts.  

[7] Such as the CFCs that were widely hailed as a godsend in the 1930's (because they replaced even more dangerous chemicals in refrigeration units and made home fridges possible). After discovery of the ozone holes and banning of CFC’s, their concentration in the atmosphere has begun to drop off and is projected to return to 1980 levels by 2060. This quick turnaround unfortunately makes some people think that we can have the same effect on CO₂; nothing could be further from the truth. CFCs are naturally unstable in the atmosphere (which was the problem - they reacted with something we wanted to keep!), whereas CO₂ is naturally stable. So the CFCs go away quickly and the CO₂ is here to stay.

[8] Yes, I know I said that they use heat and not temperature [3]. But here the proxy records temperature (because the oxygen isotope ratio changes with temperature) and has to be translated into heat. This is typically done with modern analogs to provide a baseline for the relationship. Hey, nobody ever said this would be easy!

[9] Which, translated from the science-ese, means "Recent freakin' hot time". Honestly.

[10] Not that I'm complaining! I happen to enjoy breathing, thank you very much, and am grateful to those little slime-buckets that make it all possible. (It is a common mis-perception that trees provide all of the oxygen to the atmosphere. Actually, they provide only about 15%; more than half of the Earth's atmospheric oxygen comes from the ocean's phytoplankton. Were every tree to die, we would still breathe quite happily, thank you.)

[11] Believe it or not, there are those who do so. They run the gamut from denying that CO2 is even a greenhouse gas (Hello! Venus, anyone?) to denying that the temperature has changed at all to denying that there will be effects from the change in temperature.  

[12] We'll pass over the "volcanoes make more CO₂ than man" bit, as that is just silly. A quick check of the numbers shows it to be false. But then, these folks use numbers the way Humpty-Dumpty used words.  

[13] I.e., the entire Earth will begin to feel like a fraternity on the afternoon that the A/C quits working.
 
[14] "Garbage in, garbage out" is about the kindest thing they say.

Shaw once wrote that “England and America are two countries separated by a common language.”. To a lesser extent, scientists and lay people are two similarly separated groups. The problem is that often the word one uses doesn’t mean what the other person thinks it means [1].

Take, for example, the word “theory”. To a lay person, the word “theory” is roughly equivalent to guess, idea, hunch, or glimmering. Thus, calling something a theory means that you aren’t sure what really happened, but this explanation is as good as any. To a scientist, the word “theory” means that an idea has been sharpened using multiple tests and developed until it offers the best possible explanation of the observations. Thus, when a scientist says that evolution is a theory, she means that evolution is the best explanation for the diversity and variation of the natural world, just as saying that relativity is a theory means that it best explains the way that matter behaves at very high speeds [2].

Another good example is the word “model”. To a lay person, a scientist’s model is just a crude approximation and shouldn’t be used until it can provide “perfect predictability”. For example, take these comments on the use of models in climate change research:

But when I requested facts, again, I didn't mean to put you on the spot. I only wanted to demonstrate that to my knowledge, no one can point to a single fact regarding man-made warming. It's all speculation no matter how "close" they get with their statistics and modeling.

It's only a model and models cannot account for everything, which actually causes whatever warming or cooling takes place in our atmosphere. Then there is the bias of the creator of the models and the motives behind their results

But just getting one to mimic the past would be a good start, but here's the problem even with that - it would have to track actual past events -perfectly- to even have a remote chance for predicting the future, and even if one did, it shouldn't be taken as... um... gospel, as members of the religion no doubt will.

To a scientist, models allow us to predict how things will behave. Thus, everything is a model, from the laws to the theories to the hypotheses to the very measurements that we make. A necessary result of this is that we must use the best models we have, but be aware of their limitations.

The first limitation of models is that they need measurements. This is a limitation because every measurement is a model, too! For example, take out your ruler and measure a sheet of paper. What were the dimensions? Did you get 8.5” x 11” x .004”? Or did you get 8.51” x 10.58” x .003”? Or some other number? Try measuring another sheet of paper. Do you get the same dimensions? Or different ones? Now ask someone else to measure those same two sheets of paper –I’ll bet that they get different results.

The reason is  that all measurements have two characteristics: accuracy and precision. An accurate measurement is one that comes close to the true value. For ordinary note paper, that’s 8.5” x 11” x .004” on average. But not everything is as easy to measure as paper! Scientists typically use different types of measurement to determine how accurate their measurements are. If all of the measurements give the same result (within the margins of error), then they know that the results are good enough to test their ideas with. If you have gotten a value of 6” x 13” x .1” when measuring the paper, then odds are your measurement wouldn’t have been very accurate.

Similarly, measurements of something are precise when they all cluster around the same value. If you have gotten a value of 6” x 13” x .1” when measuring the paper then 8.51” x 10.58” x .003” when you repeated the measurement, your measurements wouldn’t have been very precise. Precision is important because it allows us to lower the error bars on our measurements and know that we are truly measuring what we think we are measuring.

A classic example of this is the neutrino deficit problem in solar physics. According to the theory for our Sun’s fusion reaction, it should be producing more neutrinos than we detect. One of three things could be the answer:

I)       Our measurements could be inaccurate

II)     Our measurements could be imprecise

III)    Our theory could be wrong

Scientists tested the measurements several ways and determined that they were precise. And they tested the theory using other data and decided that it was probably right. The only thing left was that the neutrino measurements weren’t accurate for some reason. So they shot a beam of neutrinos at a detector from various particle accelerators and have discovered that neutrinos change “flavor”. Because the detectors can only “see” one type of neutrino, they were missing the others, leading to the apparent deficit[3].

Why are accuracy and precision important to models? Because models are like viaducts – what you get out of them depends on what you put into them [4]. Let’s take a simple model with a linear function:

Y=X

This is what happens when measurement error is introduced:

Model1

The true answer lies somewhere inside the yellow zone. But all we can say from the model is that, for X=15, the result( Y) is somewhere between 13.5 and 15.5. This is part of why scientists spend so much time concentrating on reducing measurement errors; buy doing so, we can reduce the uncertainty zones.

Now let’s try it for something a bit more challenging – the non-linear function Y=X*X:

Model2

The error range has increased significantly. Now when we “know” X=15, we can only say that Y is somewhere between 182.25 and 272.25.

Let’s examine one more example of how measurement errors can make models more challenging. This time, we’ll use a simple trigonometric function:

Y=tan(X) 

Model3

Notice that this time the errors make it very difficult to tell what the true value of Y should be. This function is what scientists call “chaotic” – a very small change in the inputs can cause a large change in the outputs. If we knew what the true value of X was, then it would simplify to this:

Model3a

Or would it? You see, there’s another bias that’s been built into the measurements – how often do we make them? The graph above shows what we get if we measure X only for the integers. This is what we get when we measure it twice as often (every 0.5):

Model3b

And this is what we get when we measure it every 0.1:

Model3c

Notice that the patterns are starting to resemble each other. That’s when we know that we are close to the best measurement interval for a particular phenomenon. If adding more measurements doesn’t make the pattern change significantly (i.e., doesn’t mean that you would predict something else based on the results), then you have enough measurements..

But even with enough measurements taken with enough precision and enough accuracy, can you achieve perfect predictability using a model? No.

The reason is that those limits pass through the model and create a level of blurriness that limits what can and cannot be said. That’s why scientists use multiple models run multiple ways and feed them with multiple measurements from multiple sources. Only when the majority of the models agree can we say that what is predicted is likely to happen [5]. The most that we can say about a model’s output is called its resolution. That tells us the dimensions that we can predict, including volume, time period, and outputs.

It isn’t just climate modeling that is subject to these problems with modeling resolution. It is seen in cosmology, seismology, biology, chemistry, and every other field of quantitative science.

Does this therefore mean that we can’t use the predictions of climate change models to decide what is happening now and what might happen later? Not unless you are also willing to refuse to use the medical models that tell us how to use vaccines, and the chemical models that formulate your vitamins, and the physics models that power your lights.

Does it mean that we should blindly accept what the models say? Heck no – no more than you would blindly accept the advice of a doctor. Instead, you should check, and be skeptical. Just don’t expose your ignorance and ask for impossible things.

John

[1] This is not the Humpty-Dumptyism of groups such as politicians. Nor is it the simple erroneous usage of the well-meaning but ill-read that give use such egregious boo-boos as “octopi” [a] and “enervatingly strong” [b]. Rather, it is in the Vizzini-inspired sense.

[2] Amusingly, the word “hypothesis” has almost exactly opposite meanings in the two groups as well. To a scientist, a hypothesis is just a working idea that has some support but really, really needs to be tested to get the bugs out. To a lay person, calling something a hypothesis frequently elevates it to near “law” status.

[3] The good news about this is, as one physics wag put it, “Now we know the Sun isn’t going to go out any time soon.”

[4] Geek points for the reference!

[5] This is another one of those words that means different things to lay people and scientists. To lay people “likely” typically means better than even odds that something will occur. To a scientist, “likely” means that there is a 95% probability that something will happen (unless they state lower likelihood, such as the 90% probability that is common in climate modeling or the 80% that is seen in many education works).

[a] As any good linguist will tell you, the proper plural of “octopus” is either “octopodes” or “octopuses”. The word “octopus” comes from the Latin “octo” for eight and the Greek “pus” for foot. Greeks do not conjugate their nouns the way the Latins did; thus, using “octopi” for the plural of “octopus” is as erroneous as using “womans” for the plural of “woman”.

[b] “Enervatingly” means lacking in strength; however, a surprising number of erstwhile scholars use it to mean the exact opposite.

Today was a good day for climate wonks. Several news stories [1] came out. The most interesting, IMHO?

A) Coral reefs decline faster than thought

In a report published in Plos One, Bruno et al. noted that the amount of live coral found on reefs had declined significantly; today, fewer than 2% of the extant reefs are more than 50% covered with live coral. They also found that reef interventions seem to have had little effect.

based on ice cores with data stretching back to 1788, McConnel et al. found that industrialization was responsible for significant changes in the Arctic climate.

The ice cover in the Arctic has decreased further and faster than ever before in recorded history. At this rate, Denmark, Russia, and the others will be able to use that Northwest Passage to get at the oil and minerals in the Arctic sooner rather than later...

John

[1] Which mostly got the facts right, for a change.

[2] Whihc geeks have been calling for for years, and have been ignored about for almost as long.

There has been a lot of discussion over the role of the Sun in global warming. Many skeptics have been pointing to Sol as a possible culprit, with the hope of exculpating the hominids. Their rationale goes like this:

A) The Sun is responsible for the vast majority of the heat on the Earth's surface [1]
B) If the amount of light from the sun (the solar luminosity in geek speak) increases, the amount that hits the Earth (the solar irradiance in geek speak) increases
C) This then implies that the Earth's temperature should increase as well

However, a recent study indicates that Sol is not responsible for this latest change in temperature. It shows that solar luminosity has decreased over the past two decades while temperatures have increased. Thus, the anthropogenic forcing appears to have been larger than expected, rather than smaller.

Is this the end of the matter? No. The data needs to be verified by independent researchers, and the conclusions need to be tested as well [4]. But it certainly indicates that we can no longer blame stellar influence for our troubles. As Shakespeare would say:

"The fault, dear Brutus, is not in our stars,
But in ourselves, that we are underlings."
--From Julius Caesar (I, ii, 140-141)

[1] Approximately 1000 W/m^2, compared with the approximately  0.075 W/m^2 from the Earth's interior heat (radioactivity, crystallization of the inner core, and "fossil heat" from the Earth's formation).

[2] Thereby answering the question of "Why do we spend so much money on abstract research?" Because, in the long run, it isn't abstract - it makes a practical difference and lets us know where we can save money. NASA is one of the greatest money-makers for the United States as a whole; it's research underlies most of the major advances made in air travel [a].

[3] During the first hundred million years or so, Sol was much more variable as it went through the T-Tauri phase that blew away the Earth's early atmosphere and made life possible.

[4] That's how science goes. An interesting result is just that; it isn't proof. Actually, you can't prove something true in science (except in mathematics), what you have to do is try to prove it false by testing its predictions. If its predictions are not verified, then the hypothesis was false. If its predictions are verified, then the hypothesis might be correct or it may have been chance - so we can never prove it, but merely accept it as a working hypothesis.

[a] No, not the hub-and-spoke model for airlines or the best way to sell overpriced, undercooked food at 30,000 ft. The other advances, such as how to get from point A to point B in the shortest, safest time.

A friend sent me the link to this post, which has a picture of a letter to the editor. The Arkansas Democrat Gazette does exist, so there is a good chance that this is actually a real letter, and not a spoof.

In which case, all I can say is "Wow." I sure hope she was kidding, but I'm really, really afraid that she wasn't.

John

[1] Geek points for the reference!

Right now, it is the fashion to protest for higher MPG on cars (typically after driving to the rally in an SUV that gets 5 mpg [1]), and to call for greenhouse emissions curbs (while burning our leaders in effigy [1]).

Me, I've decided to put my muscles where my mouth is. I am fortunate enough to live  near enough to my work that I can drive, bike, or take mass transit. So I've decided to bike to work as often as possible, and to drive only when absolutely necessary [2]. Having timed the drive and the bike, I know that it takes only five minutes longer to ride my bike than to drive [3].

So I've done a stupid thing and bought myself a bike [4]. A nice bike. A really, really nice bike - a Sun EZ Rider AX that cost me more than my last three bikes put together [5]. Based on my car's gas mileage, local gas prices, and the distance to work, I figure that riding it to work every day for nine months will pay it off. And, as a nice bonus, it will improve my health [6], decrease this blubber gut of mine, and reduce the CO2 emissions that I am responsible for.

Bike1

All told, a win-win-win situation.

Now if I can just get my legs to quit aching [7].

John

[1] Hyperbole and urban legend, but you get the point.

[2] I.e., when I have to be there before 8 AM or after 7 PM [a], or when I have a load of heavy stuff to take to work, or have to run an errand that is more than five miles away during lunch.

[3] Have I mentioned that Miami traffic is terrible?

[4] My friends are now panicking, as the only times I've seriously hurt myself (other than the blood poisoning incident which wasn't my fault) have been when riding a bike. Actually, immediately after the riding stopped and the hitting the ground at too high a rate of speed began. But the bones always healed and they never kept me in the hospital more than two days, so what's the big deal?

[5] Of course, part of that is because I've always bought my bikes at Target and the like. Perhaps that is part of why my bikes had a habit of coming apart just when I needed them the most?

[6] Barring the ever-present possibility of yet another wreck...

[7] Ow. Ow. Ow.

[a] Miami traffic is insane to start with, and I don't want to add low lighting to the hazards.

NOAA has just released their beta-version of what they are calling Carbon Tracker. Using the interface, you can make maps of the estimated CO2 flux in various regions over various periods of time, ranging form a week to a year. The annual global map for 2005 is shown below.

Annualfluxmap_glb_2005.large

The tool is nice, but it is a work in progress. Right now, there are very few sites giving the data (e.g., only 10 in North America); most of the points are extrapolated via terrestrial process models. The data can be accessed directly as well as in map form, and includes uncertainty measures; however, the level of uncertainty in the uncertainty is pretty high (i.e., "I'm pretty sure that we're within 10% of the right answer"). And, IMHO, the most serious problem is that currently the terrestrial processes are modeled but not the anthropogenic ones (i.e., fossil fuel use). Given that these are the most significant contributors on short time scales, adding them as soon as possible is essential to getting a quality product.

Nevertheless, it is a great tool that holds promise of getting better. But don't take my word for it - go, play!

John

A few days ago, I asked "What is proof?  What evidence would the doubters consider sufficient to demonstrate (A) that the climate is currently changing, (B) that it is headed toward the warmer end of the scale, and (C) that the root cause of these changes is anthropogenic?"

Dox^2 replied with a nicely reasoned exploration of the IPCC's report, concluding that two unresolved issues are what cause him to be somewhat skeptical of climate change science:

A) The net effect is still uncertain
B) The level of uncertainty is not well expressed in the popular literature [2]

A) Global temperatures will increase over the next century
B) Polar ice levels will decrease
C) The increase in energy will allow stronger extremes in weather - more and deeper droughts, more and fiercer hurricanes, more and snowier blizzards [4]
D) There will be destruction of existing beach-front property, offset partially by the creation of new beach-front property
E) Some crops will decrease in productivity, whereas others will increase; the exact level of productivity change depends on the temperature effect and the CO2 change [5]
F) There will be more invasive species and shifts in the ranges of infectious diseases [5]
G) There will be decreases in the supplies of potable water [5]

ASAT

Temp

Sealevel

Looking over the various posts on global warming/climate change [2], something jumps out at me. Many of the detractors of the state of climatological science appear to hold the position that there is no evidence for a change in the climate. Which begs the question - what is proof? What evidence would the doubters consider sufficient to demonstrate (A) that the climate is currently changing, (B) that it is headed toward the warmer end of the scale, and (C) that the root cause of these changes is anthropogenic?

What level of accuracy and precision [3] on the measurements is needed to convince them that a valid measurement has been made [4]? What length of baseline is needed [5]? Which measurements are needed [6]? What proxies are acceptable?

Until these questions are answered, those who hold that the average temperature is increasing leading to climatological changes (regardless of root cause) will probably have the same effect on doubters as evolutionary biologists would have in explaining their science to Pat Robertson. And if the detractors are incapable of expressing the level of evidence that would be needed to convince them[7] , then they should be as ignored by climatologists and politicians as those who would replace evolutionary theory with "creation science" are.

John

[1] With apologies to St. John

[2] Though the two are not synonymous, they are often used interchangeably. Just another example of synecdoche, I guess.

[3] Not the same thing!

[4] Note that I do not write "to convince them that climate change/global warming has occurred"; after all, a negative result is still a valid result in an experiment provided that it was properly constructed. What I meant (and wrote) is that the evidence should be collected in a fashion that will convince all parties that the experiment itself was valid [a].

[5] Given that climate is a decadal process, it seems unlikely to me that anything shorter than 150 years would be accepted. But then, I've been wrong before...

[6] Is just temperature/temperature proxy sufficient? Or are other metrics needed? If so, which ones?

[7] In other words, their incredulity springs not from science but from belief.

[a] For example, take the case of Fleischmann and Pons announcement of cold fusion. The skeptics clearly stated what evidence would convince them, and when it wasn't found decided that no cold fusion had occurred.

The letters to the editor in today's issue of the Oklahoman are just too damn funny! The editors must have selected them for maximum silliness, as there is a consistent lack of basic science knowledge. For example, P. Jan Cannon says:

Carbon dioxide is not a greenhouse gas. Proof of this is demonstrated by the fact that the atmosphere of Mars is 95 percent carbon dioxide and that planet has no greenhouse gas.
...
Satellite imagery indicates the Antarctic ice pack is growing, not shrinking. Working in the Arctic over the past 32 years, I've observed no changes in the variations of winter and summer temperatures. No new shipping lanes have opened in the Arctic. If they had, cruise lines would be running trips through them.

Meananomalies

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