I get a lot of questions about the connection between heatwaves and climate change these days. Particularly about the heatwave that has affected northern Europe this summer. If you live in Japan, South Korea, California, Spain, or Canada, you may have asked the same question.
The raindrop analogy
However, the question is inaccurate and I will try to explain this through an analogy. Let’s say I go for a walk with a friend and my friend feels a few drops of water that fall on her. She asks me if it’s raining. But as long as there was only few drops of water, it could also be something else.
I tell her that we can get some more relevant information in order to get a more reliable answer. Look at the sky. Are there dark clouds on the sky above? And what does the weather forecast say?
If there are dark clouds above and the weather forecast suggests showers, it’s a safe bet to say it is the start of the rain. The rain always start with a few drops, just the way a climate change starts with a few events.
In the same way as with the observation of the first drops of of water, you could not be sure whether the heatwave is a freak event or the emerging pattern of climate change, if you don’t include other relevant information.
There is a range of different pieces of information which are relevant when it comes to the question about weather events and climate change: (a) statistical evidence, (b) physical processes connecting different aspects, and (c) attribution work.
(a) Statistical evidence
Heatwaves are becoming more widespread, last longer, and are getting more extreme (e.g. Keellings and Waylen, 2014). This trend has been predicted and reported in multiple reports, such as the IPCC SREX (2013), the Proceedings of National Academy of Sciences (e.g. Palmer, 2009), and European Academy Science Advisory Council (EASAC, 2013).
Climate change is equivalent to changing weather statistics, and one line of evidence includes the nature of record-breaking events. We can find evidence in both the number[a] and the magnitude of new record-breaking values.
Coumou et al., (2013) observed an increase in the global number of monthly heat records that corresponded to what one should expect if the temperatures increased everywhere by the same rate as the global mean. They also found that local monthly records are on average five times as frequent as they would be in a stationary climate. In other words, four out of five new heat records would not have occurred without global warming.
Other types of evidence includes how often the events (e.g hurricanes) take place, their duration and intensity. Standard statistical tests can also indicate whether a particular event fits in with the expected range of outcomes.
(b) Physical processes
Physical conditions and processes play a role both for the emerging pattern of precipitation, the evolution of weather, and their statistical characteristics. Indeed, we expect the statistics of rainfall and temperature to respond to an altered physical situation.
Earth’s climate has always changed, and there have always been physical causes for the changes. This means that the climate is sensitive to altered conditions, such as greenhouse gases.
It would be difficult to explain why increased concentrations of greenhouse gases had no effect on the global mean temperature or on the statistics of extreme weather conditions while other types of forcing clearly have an effect.
There is no shortage on explanations for why changes in the physical environment should cause more extreme events. Some of these are:
I have also reviewed the greenhouse effect and described how convection can be altered by higher concentration of greenhouse gases. This link with the hydrological cycle may explain why the rains seem to be concentrated over small area of Earth’s surface (Benestad, 2018).
Diminished area of precipitation explains both more frequent flooding and more droughts, and dry conditions exacerbate the heat, as moisture restrain temperatures during evaporation.
We also expect more extreme rainfall in some locations, as higher surface temperatures boost the evaporation and increase the turn-around rate of the hydrological cycle. There are also indications of higher cloud tops (Witze, 2016) which allow the rain drops to grow further than before.
(c) Attribution
It is possible to reproduce extreme weather episodes in computer models, such as those used for weather forecasting. We can conduct experiments to see which effects greenhouse gases have for the outcome. In other words, the models can be used to simulate the same event with and without the present levels (Schiermeier ,2018).
The World Weather Attribution (WWA) has carried out such experiments, and their efforts suggest that recent extreme events have become more likely with an increased greenhouse effect.
Individual cases and emergent behaviour of many events
The planetary system is extremely complex, with interactions between atmosphere, oceans, ice and land, and taking place over a vast range of temporal and spatial scales.
It is hard to say that one aspect is directly connected to another, when there are so many interacting parts and such rich level of complexity. Understanding the difference between individual versus collective events is key to making sense of the situation.
Nevertheless, complex systems tend to give rise to emergent behaviour (explained in Gavin’s TED-talk). And the statistical characteristics of a large number of outcomes is often predictable. In fact, statistics is remarkably predictable, and we can often attribute some probability to the causes of some event through standard statistical tests.
What is causing what?
On another level, there is also the more philosophical question of whether rain drops are caused by the rain or the rain is a result of many rain drops. Rain is a phenomenon that includes many collective events in the clouds.
The same way that extra information such as cloud observation and weather forecast give confidence in our interpretation of the first drops being the start of the rain, the statistical evidence and our understanding of the atmospheric physics provide relevant information for judging the connection between heatwaves and climate change.
A more relevant question
I think it makes sense to rephrase the usual question of whether climate change causes a particular event, since climate and weather are different aspects of the same earth system.
The bottom line is whether we now are observing the first glimpse of a new normal, or if the world will return to its old state. In other words, the question should be whether the recent heatwave is a signs of a new type of weather patterns we can expect for the future. I think the answer to this question is “yes”, based on current information and knowledge.
Footnotes
[a] If data is independent and identically distributed (iid), then the probability of a new record-breaking event diminishes with the number of measurements (
) ![P(X > [x_1, x_2, ... x_{n-1}]) = 1/n](https://www.realclimate.org/wp-content/ql-cache/quicklatex.com-63def0dac8a5a1b1f89ce7ff0f456cd9_l3.png "Rendered by QuickLaTeX.com")
. In this case, the expected number of records is 
. On the other hand, if you count many more records than 
, then that is a sign that upper tail of the statistical distribution is stretching towards higher levels. In other words, it indicates that extremes are becoming more frequent.
Update
Both the World Meteorological Organisation (WMO) and Copernicus have posted some comments and analysis of the recent heatwaves.
References
- D. Keellings, and P. Waylen, "Increased risk of heat waves in Florida: Characterizing changes in bivariate heat wave risk using extreme value analysis", Applied Geography, vol. 46, pp. 90-97, 2014. http://dx.doi.org/10.1016/j.apgeog.2013.11.008
- T.N. Palmer, "Climate extremes and the role of dynamics", Proceedings of the National Academy of Sciences, vol. 110, pp. 5281-5282, 2013. http://dx.doi.org/10.1073/pnas.1303295110
- J.A. Francis, and S.J. Vavrus, "Evidence linking Arctic amplification to extreme weather in mid‐latitudes", Geophysical Research Letters, vol. 39, 2012. http://dx.doi.org/10.1029/2012GL051000
- V. Petoukhov, S. Rahmstorf, S. Petri, and H.J. Schellnhuber, "Quasiresonant amplification of planetary waves and recent Northern Hemisphere weather extremes", Proceedings of the National Academy of Sciences, vol. 110, pp. 5336-5341, 2013. http://dx.doi.org/10.1073/pnas.1222000110
- M.E. Mann, S. Rahmstorf, K. Kornhuber, B.A. Steinman, S.K. Miller, and D. Coumou, "Influence of Anthropogenic Climate Change on Planetary Wave Resonance and Extreme Weather Events", Scientific Reports, vol. 7, 2017. http://dx.doi.org/10.1038/srep45242
- R.E. Benestad, "Implications of a decrease in the precipitation area for the past and the future", Environmental Research Letters, vol. 13, pp. 044022, 2018. http://dx.doi.org/10.1088/1748-9326/aab375
- A. Witze, "Clouds get high on climate change", Nature, 2016. http://dx.doi.org/10.1038/nature.2016.20230
- Q. Schiermeier, "Droughts, heatwaves and floods: How to tell when climate change is to blame", Nature, vol. 560, pp. 20-22, 2018. http://dx.doi.org/10.1038/d41586-018-05849-9
@92
“So when we see NO evidence whatsoever of a correlation between CO2 emissions and global temperatures over an 80 year period…”
But we DO objectively measure a high correlation over the past 80 years. You are falsified.
The facts that you are both too ignorant to know what correlation actually means, and that you don’t know how to calculate a correlation or discuss its significance are your own problems.
CALIFORNIA’S FOURTH CLIMATE CHANGE ASSESSMENT
http://www.climateassessment.ca.gov/state/docs/20180827-StatewideSummary.pdf
One Region’s insights
Fourth Climate Change Assessment
Statewide Summary Report
| 10
People: Public Health
Impact
: Climate change poses direct and indirect risks to public health, as people will experience earlier death and
worsening illnesses. However, deep greenhouse gas emission (GHG) reductions (80% below 1990 levels) in California
could significantly improve health outcomes, and costs avoided would be comparable to the cost of achieving 80%
GHG reductions by 2050. This would occur because technology with no or very low GHG emissions is associated
with a reduction of conventional air pollutants that are damaging to human health.
Nineteen heat-related events occurred from 1999 to 2009 that had significant impacts on human health, resulting
in about 11,000 excess hospitalizations. However, the National Weather Service issued Heat Advisories for only six
of the events. Heat-Health Events (HHEs), which better predict risk to populations vulnerable to heat, will worsen
drastically throughout the state: by midcentury, the Central Valley is projected to experience average Heat-Health
Events that are two weeks longer, and HHEs could occur four to ten times more often in the Northern Sierra region.
Action:
The Fourth Assessment led to the development of a prototype warning system known as the California Heat
Assessment Tool (CHAT). It will support public health departments taking action to reduce heat-related morbidity
and mortality outcomes. It is designed to provide information about heat events most likely to result in adverse
health outcomes.
Projections: Wildfire
Impact
: Climate change will make forests more susceptible to extreme wildfires. By 2100, if greenhouse gas emissions
continue to rise, one study found that the frequency of extreme wildfires burning over approximately 25,000 acres
would increase by nearly 50 percent, and that average area burned statewide would increase by 77 percent by the
end of the century. In the areas that have the highest fire risk, wildfire insurance is estimated to see costs rise by 18
percent by 2055 and the fraction of property insured would decrease.
Action
: An extensive scientific review supported by the Fourth Assessment found that reducing tree density and
restoring beneficial fire can improve long-term resilience to California’s forests. Simulations of large-scale fuels
treatments in Sierra Nevada forests substantially reduce increases in burned area. Improving forest health by
removing fuels can have important impacts to reduce rising wildfire insurance costs. Increasing understanding of
megafires remains a critical research need for California.
I should add that the correlation between the Mauna Loa annual data and GISS annual values from 1959-2017 is .95 which means they share over 90% common variance.
While this is not experimental design, any “theory” demanding that they not be correlated–or any ignorant statement that there is “NO correlation” is not at all supported.
V 92: we see NO evidence whatsoever of a correlation between CO2 emissions and global temperatures over an 80 year period
BPL: That this is false has been demonstrated to you, over and over again. Your repitition of it has passed the point of being a mistake and entered the realm of being a God-damned lie. Quit posting stuff that isn’t true, Victor.
Victor, #92–
‘”We,” Kimo Sabe?’
*You* see no correlation. I’ve graphed the numbers previously, and I do see such a correlation.
More importantly, standard-issue statistical measures show a correlation.
I would suggest that the difference is in what you are prepared to see–or not see, as the case may be.
Here’s the comparison, for 1929 to 2008 (chosen because the copy of the Law Dome data I have ends in that year, and because 80 years was specified.)
http://i1108.photobucket.com/albums/h402/brassdoc/Law%20Dome%20CO2%20%20GISTEMP%20J-D%20anomaly.png
Note that that’s a naive graph; the CO2 data are as reported, except for a baseline offset setting the 1929 value to 0. GISTEMP anomalies are similarly baselined. This is not the correct way to do it; you’d want to baseline by mean value over some reasonable reference span, but hey, this is just a blog comment. (In addition, the GISTEMP data are scaled by a factor of 2/3.) This ignores a bunch of issues, like relative variability in the two data sets, and the non-linear forcing effect of CO2, just for starters. But it’s a reasonable BOTE effort, I think.
Certainly one may wonder why the deviations early in the record, and one would conclude that CO2 can’t be the only thing influencing temperature. But I think it would also be quite silly to claim ‘no influence’ on the basis of this comparison, much less to wax dogmatic about it.
Al Bundy: Hey Vic! When playing darts and you get a double-bull, do you whine that the dart is .02964319mm from the exact center?
V: No. But when pondering the future of sea level rise I learn that past sea level rise has been estimated at anywhere from 1.5 to 3mm per year, I wonder how the “experts” are predicting rises of several feet over the next 50 years, as opposed to, say, 50 x 3mm = 150mm = 0.492126ft.
#100 Ray Ladbury.
“The null hypothesis, H0 is the commonly accepted fact; it is the opposite of the alternate hypothesis. Researchers work to reject, nullify or disprove the null hypothesis. Researchers come up with an alternate hypothesis, one that they think explains a phenomenon, and then work to reject the null hypothesis.”
“Example
Not so long ago, people believed that the world was flat. Null hypothesis, H0: The world is flat. Alternate hypothesis: The world is round. Several scientists, including Copernicus, set out to disprove the null hypothesis. This eventually led to the rejection of the null and the acceptance of the alternate.” http://www.statisticshowto.com/probability-and-statistics/null-hypothesis/
Now Ray, you can object to this definition until you’re blue in the face, but you are not the only scientist in the world and this person, with an advanced degree in math, obviously sees things differently from you. Live with it.
Ray: “One thing your null hypothesis cannot be is unphysical–and positing that an entire planet can just heat up all by itself with no external source of energy is unphysical. You denialist imbeciles remind me of a teenager explaining how they got into an accident, “It just happened, OK!”
V: My oh my. Get a grip, Ray. Looks to me like you need a remedial reading class. Since when are natural variations unphysical? Just what do you think the term means anyhow? Natural variations in this context are simply all the sources of energy that affected the climate of the Earth prior to the influence of humans. Natural vs. human. Get it?
Victor @98
My way of thinking? All I asked was for you to explain your so called *null hypothesis* for climate change. *Natural Variation* in itself is not a theory nor is it an explanation of any physical phenomena. The fact that you cannot explain what your null hypothesis actually is shows the silliness of your *null hypothesis* claim. I have not made any statements as to what your claim and inability to explain it means for the science behind AGW other than your claims of *natural variation* as a *null hypothesis* for the current warming is pure bunk. *Natural Variation* is not a *null hypothesis* because it is not an explanation of anything. So I will ask it again, what is your *null hypothesis*? What is the science? When you have explained exactly what your *null hypothesis* actually is, we can discuss its usefulness in the determination of the strength of the evidence for AGW theory. Until then, your so called *Natural Variation* default hypothesis is meaningless prevarication that serves no purpose in discussing the voracity of the science.
Furthermore, your discussion on UFOs etc. and peer review is just more garbage. My questioning your *null hypothesis* in no way means any of what you state.
Victor says “V: No. But when pondering the future of sea level rise I learn that past sea level rise has been estimated at anywhere from 1.5 to 3mm per year, I wonder how the “experts” are predicting rises of several feet over the next 50 years, as opposed to, say, 50 x 3mm = 150mm = 0.492126ft.”
Things accelerate. Sea level rise has already shown an acceleration over the last couple of decades which would lead to more than two feet of sea level rise by 2100 according to this study (it quotes 2100, not 2050).
https://www.nasa.gov/feature/goddard/2018/new-study-finds-sea-level-rise-accelerating
If this acceleration itself ‘accelerates’, which is expected based on the modelling, sea level rise will be over 3 feet by 2100. Past climates with similar CO2 levels to currently had eventual sea level rise over 30 feet.
Victor wouldn’t notice if his own hair was on fire.
Let’s look a little more at Victor’s claims as to the *null hypothesis*
Victor seems to think that a new theory is what falsifies an old theory. This just isn’t true. It is the evidence that falsifies a theory or hypothesis, not alternatives. A theory clearly can be falsified with no alternative hypothesis. Anyone the least bit knowledgable of science knows this.
Take his earth-centric hypothesis claim. Once actual measurements of the planets location in the sky became moire precise, it was shown that the earth-centric models could not accurately predict the future locations of the planets. In addition, observations of the phases of Venus were not consistent with the theory. This evidence is what falsified the theory and made a new theory necessary. The ultimate new theory of planets revolving around the sun did nothing to falsify the old theory, it simply replaced it due to better conforming to the observations and evidence. However, any lack of evidence for the solar centric model still would not have made the earth-centric hypothesis correct. Once falsified, the earth-centric model could no longer be the accepted default regardless of acceptable alternatives.
Same for Einstein’s work. His theories did not falsify Newtons’s laws of motion, it was the inability of Newton’s theory to explain what happens when objects in motion approach the speed of light. The theory was inadequate. This is what drove Einstein to develop relativity. Relativity in itself did not falsify Newtonian physics, the evidence did.
This is why Victor’s claim that *natural variation* must be the default hypothesis until AGW is established beyond some unknown evidential bar of Victor’s is complete bunk. No known natural causes can explain the warming nor do any of the known natural causes conform to the observed evidence. Natural causes have for the most part been falsified, not by AGW theory, but by the evidence.
Fake naivete again?
Well, I understand all science, everything known and more, completely. But I’m not going to explain it to you… :)
V @108 Since when are natural variations unphysical? Just what do you think the term means anyhow? Natural variations in this context are simply all the sources of energy that affected the climate of the Earth prior to the influence of humans. Natural vs. human.
So are you imputing these natural physical variations are un-quantifiable? Let’s think what sources of energy there are. The sun, radioactive decay of rocks in the earth’s interior and maybe a bit of tidal drag from the moon?. That’s it. There aren’t any other. So we ask has the sun’s energy changed – well we know it does, but we also know how much by and it doesn’t explain the temperature changes we observe. Maybe radioactive decay rates are changing? Physically impossible, but I guess you could release more heat through changes in volcanism – but we can quantify that and again doesn’t explain the temperature changes we observe.
So we aren’t changing energy inputs – maybe we are changing the rate at which energy is radiated back into space? That implies a change in atmospheric gases. We can look at what has changed in the atmospher, and, lo and behold, changes that we observe in CO2 and CH4 are of the right magnitude to explain the changes we are seeing.
But perhaps there is some kind of magic, unknowable, source of energy that we have missed. If there is it will have to be balanced by another magic, unknowable, source of cooling, otherwise how do we explain why, with the CO2 and the magic energy, temperatures are not rising twice as fast as observed.
In the context of climate change Victor is the the one arguing the earth is flat, against science’s Copernicus approach of observe – hypothesise – test – repeat.
Victor: “The null hypothesis, H0 is the commonly accepted fact; it is the opposite of the alternate hypothesis.”
Absolute bullshit! Whoever said this is a historically and mathematically illiterate moron! In many cases, the null hypothesis is known a priori to be false!
To understand the null hypothesis, you have to go back to its introduction in the work of Fisher, Neyman and Egon Pearson. Its sole reason for existence is that the “goodness” metrics we have are not absolute, but rather comparative. Look, the null hypothesis is one of the most commonly misunderstood constructs in probability. Even a lot of so-called experts don’t understand it because they haven’t looked at its history or why it is needed in frequentist statistical theory. Such ignorance might be forgivable if all one is doing is workaday hypothesis testing.
However, if one’s ignorance is leading one to state absolute bullshit like “H0 is commonly accepted fact,” or that H0 is true if the test isn’t statistically significant, that is not just wrong, it’s “not even wrong.” Statistics is a complicated field. Much of the conventional methodology is merely a series of “recipes” handed down by the pioneers of the field. The thing is that when they developed these recipes, they had a particular goal in mind. You have to understand at least a little bit of its history to understand what is fundamental and what is merely convention left over from the methods introduced by the pioneers. Especially when it comes to probability and statistics, “some guy on the internet” is not an adequate authority.
#97 Victor,
As illustrated by other comments, the definitions and rules I have given are consistent with how scientists in general (in all fields, not just Climate Science) understand the terms. Anyone who has done science at any level has applied them that way.
Science is all about “nitpicking”, or precision of language and consistent application of rules. My point was that if you want to take issue with the established “Philosophy of Science” that tells us how to do science, then make your case at that level.
Here’s an easy beginning: Explain why “null hypothesis” is called “null” instead of “currently accepted” hypothesis.
Interesting discussion guys,
It echoes a long discussion I had with zebra (and Ray a little) a while ago, about the question “is there a precedent to the present global warming?”
This is very related to the discussion of this thread. Because if you admit there could have been precedents, then you can say that the actual warming is indistinguishable from the natural variations, i.e. the background noise, i.e. the null hypothesis. Hence the data are compatible with the null hypothesis, and the null hypothesis cannot be rejected. No alternative theory to the AGW one is required.
Victor, you are not helping with your wrong analogies involving Copernic, Newton or Einstein. This is irrelevant and people rightly told you so. There is no null hypothesis in these cases, just alternative theories. This is different.
More adequate analogies are to be found in drug testing, maybe.
One of the issue here is quantifying the null hypothesis, i.e. estimating the amplitudes and slopes of the past natural variations.
People here seem to be sure than they are necessarily small, based on physics (“where such energy, capable of warming and cooling the planet in such small time scale would come from?”). The null hypothesis is then rejected, because the present warming is incompatible with it.
Other people are not so sure…
CCHolley: “*Natural Variation* in itself is not a theory nor is it an explanation of any physical phenomena. The fact that you cannot explain what your null hypothesis actually is shows the silliness of your *null hypothesis* claim.”
Natural variation is the sum of all factors that have influenced Earth’s climate other than those produced by humans (e.g., CO2 emissions due to the burning of fossil fuels). Why is that so hard for you to understand? I see no reason why it can’t be characterized as a null hypothesis since it represents the default state of things prior to the industrial revolution and the introduction of fossil fuels. If “null hypothesis” is a problem for you that’s fine with me since the terminology doesn’t really matter all that much. What matters is the basic scientific principle that any hypothesis seeking to overturn a long established interpretation bears the burden of proof.
“When two parties are in a discussion and one makes a claim that the other disputes, the one who makes the claim typically has a burden of proof to justify or substantiate that claim especially when it challenges a perceived status quo.” https://en.wikipedia.org/wiki/Burden_of_proof_(philosophy)#Holder_of_the_burden
In this case the perceived status quo is the notion that climate is and always has been largely determined by natural forces. The burden of proof is on anyone who claims otherwise.
From the same source: “One way in which one would attempt to shift the burden of proof is by committing a logical fallacy known as the argument from ignorance. It occurs when either a proposition is assumed to be true because it has not yet been proved false or a proposition is assumed to be false because it has not yet been proved true.”
To expect skeptics to provide you with a better explanation for the temperature variations we’ve seen since the industrial revolution is an argument from ignorance. Just because you can’t come up with a better explanation than the one provided by your pet theory is no reason to demand that your critics do so, as the burden of proof is on YOU, not them.
Weaktor,
OK. Just to assess whether you still maintain even a nodding acquaintance with relaity: Would you agree that a hypothesis that does not conserve energy is unphysical?
The energy in Earth’s climate system is increasing at a rate of ~25 exajoules per day. Do you at least agree that energy must come from somewhere? If so, where do you propose? Here’s a hint. It is NOT the Sun.
Gavin, you are letting Victor take the discussion down the rabbit hole. Instead, you should be sending him to the bore hole. A couple of examples:
First, Victor insists that there is no evidence of correlation between carbon dioxide concentrations and surface temperature. Numerous people have pointed out to him that this is not the case, yet he continues. The Mauna Loa CO2 data set starts in 1959. On 1959-2017 data, an analysis gives the following:
a. A initial visual check of the two time series indicate that both have similar upward trends.
b. Scatterplots of CO2 concentration vs. temperature have clear linear upward sloping patterns on both monthly and annual data. This is strong evidence of correlation.
c. Correlation coefficients strongly support correlation:
i) Pearson’s correlation coefficient is 0.948 for annual data and 0.890 for monthly data.
ii) Spearman’s correlation coefficient is 0.933 for annual data and 0.888 for monthly data.
iii) Kendall’s correlation coefficient is 0.776 for annual data and 0.695 for monthly data.
Even if you disagree that a final judgment of correlation is justified, you cannot deny that these factors are all evidence of correlation. Victor denies this. You should not let him torture the language, the science or the data this way.
Second, Victor talks about the pre-Copernican “null hypothesis” being that the earth is the center of the Universe. A null hypothesis is a hypothesis about the value of a parameter of a probability distribution. While Victor’s statement is sort of kind of something that might be like a null hypothesis, it is not one and he has managed to drag the conversation into a completely silly cul-de-sac – talking about non-statistics as if they were statistics. Victor’s aggressive and persistent ignorance on statistical issues basically allows him to take arguments way outside of their context. You shouldn’t let him do that.
Here’s the deal. It would take Victor 2 semesters to get a fairly thorough basic understanding of statistics at his local university. Until he does that, or until he proves himself self-educated enough to converse in statistical language, you should bore-hole him whenever he pipes up, especially about correlation or null hypotheses.
V 97: If CO2 emissions do not affect global warming, then the only alternative is natural variation
BPL: Fallacy of bifurcation.
V 108: Not so long ago, people believed that the world was flat. Null hypothesis, H0: The world is flat. Alternate hypothesis: The world is round. Several scientists, including Copernicus, set out to disprove the null hypothesis. This eventually led to the rejection of the null and the acceptance of the alternate.”
BPL: The educated community has accepted that the world is round since Eratosthenes measured its circumference in the 3rd century BC. Copernicus had nothing to do with it.
nigelj @ 100,
The study stated that if acceleration were to continue at this rate, sea level would rise 26 inches (not more that three feet). Their acceleration is a 37% increase in the rise rate every two decades, resulting in a 12mm annual rise by 2100.
120 jb says:
“First, Victor insists that there is no evidence of correlation between carbon dioxide concentrations and surface temperature.”
I did not “insist” on anything. I provided a link to a graph that clearly demonstrates lack of correlation. You are the one who is insisting, jb.
jb: “Numerous people have pointed out to him that this is not the case, yet he continues. The Mauna Loa CO2 data set starts in 1959. On 1959-2017 data, an analysis gives the following:”
V: Yes, you can get any trend you like by cherry picking the end points. The period I referenced covers the entirety of the 20th century. The lack of correlation during the first 80 years should be obvious to any objective observer. And yes, there have been attempts to account for this lack of correlation by invoking all sorts of natural variations that supposedly distort the “underlying trend.” But before you can posit an “underlying trend” you need to provide evidence that it exists. Excuses for why such evidence is lacking do not constitute evidence, sorry.
jb: “Second, Victor talks about the pre-Copernican “null hypothesis” being that the earth is the center of the Universe. A null hypothesis is a hypothesis about the value of a parameter of a probability distribution.”
V: In a narrowly technical sense, as applied to statistical analysis, yes, this is true. But the term also has a more general meaning, which can be applied when evaluating any scientific hypothesis. To wit: “The null hypothesis is generally assumed to be true until evidence indicates otherwise.” https://en.wikipedia.org/wiki/Null_hypothesis
From the same source: “Testing (accepting, approving, rejecting, or disproving) the null hypothesis—and thus concluding that there are or are not grounds for believing that there is a relationship between two phenomena (e.g. that a potential treatment has a measurable effect)—is a central task in the modern practice of science; the field of statistics gives precise criteria for rejecting a null hypothesis.” But statistics is only one of many tools employed by scientists to evaluate any hypothesis.
From a different source: “The null hypothesis (H0) is a hypothesis which the researcher tries to disprove, reject or nullify. The ‘null’ often refers to the common view of something, while the alternative hypothesis is what the researcher really thinks is the cause of a phenomenon.” https://explorable.com/null-hypothesis
From the same source:
“Development of the Null
The Flat Earth model was common in ancient times, such as in the civilizations of the Bronze Age or Iron Age. This may be thought of as the null hypothesis, H0, at the time.
H0: World is Flat
Many of the Ancient Greek philosophers assumed that the sun, moon and other objects in the universe circled around the Earth. Hellenistic astronomy established the spherical shape of the earth around 300 BC.
H0: The Geocentric Model: Earth is the centre of the Universe and it is Spherical
Copernicus had an alternative hypothesis, H1 that the world actually circled around the sun, thus being the center of the universe. Eventually, people got convinced and accepted it as the null, H0.”
#117 Romain,
I vaguely recall the conversation, but let’s address what you say here.
First, yes, thanks, a hypothesis and its test, and the process of replacing the foundational physics Theories, are completely different. But I doubt one more voice, even from a skeptic, is going to get him to stop conflating them.
However, you may be making a similar mistake. We have concluded, by working with known physics (GHG effect, the thermodynamics, fluid dynamics, and all the other stuff) that the energy in the climate system should be increasing because of increase in CO2. If we never could take any measurements of that energy, it would still be what the existing physics and climate Theory concludes.
So, it is not the case that we have suddenly observed an increase in the climate system energy, and someone then came up with a causal “hypothesis” that can be tested or falsified in the sense you are talking about. Rather, you are proposing an alternative Theory in which increasing CO2 would not result in an increasing system energy.
So, as long as our observations– of GMST, OHC, and changes in events like heat waves and downpours and melting ice, and so on– are consistent with the existing theoretical framework, the existing Theory is considered valid, regardless of the precision/accuracy of one prediction or another.
You have not provided any kind of theoretical framework for what you are saying, so even if we had data that demonstrated similar changes in the past, Anthropogenic climate system energy increase through CO2 emissions would still be the correct scientific conclusion.
Victor @118
Oh I understand all right. The problem is your generalization and lumping all these causes into one and calling that a default cause. Science does not work that way. Science is about looking at all of the evidence including how what has happened in the past can apply to the present and future state. You, in your ultimate ignorance and desire to create doubt, see no reason why the past can’t be characterized as a null hypothesis. But you are wrong. Dead wrong. And nothing you write will change that. Your position is just rhetorical tripe.
BTW, *natural* releases of CO2 are known to have caused warming in the past (see PETM for example), and that fact would be part of your silly *null hypothesis*. So your *null hypothesis* actually supports the contention that the current warming is caused by mankind since it is easily shown that the current rise is anthropogenic. However, you may respond to this fact by saying, but we know CO2 levels have not changed naturally since the last ice age. Which would support the argument for the scientific case that there is no default cause, each possible natural or other cause must be looked at individually, which is what good scientists have done.
Yes, exactly. The scientific status quo is that the current warming trend is cause by mankind’s release of greenhouse gases into the atmosphere. You have the burden of proof to show otherwise and after several years of attempts have given us nothing.
Perceived status quo by Victor. Burden of proof as perceived by Victor. Science as perceived by Victor.
Ironic. Seems to me it is Victor that argues from ignorance. Sigh.
Nigelj seems to be having a bad hair on fire day. What he says of the year 2100 too much resembles what some predicted for 2020 four decades ago. and others have opined for 2030 and 2050.
An oracular chorus has chanted the mantra of meter per century sea level rise for over a generation, but the rate has failed to accelerate by as much as a milimeter a year.
It takes inflection points to get to tipping points. In which decade of this century does Nigel expect to see modelers flocking to bet their pension funds on a rise of one centimeter a year ten years after the bet ?
vic–“…Natural variation is the sum of all factors that have influenced Earth’s climate other than those produced by humans (e.g., CO2 emissions due to the burning of fossil fuels). Why is that so hard for you to understand? I see no reason why it can’t be characterized as a null hypothesis…”
All you’ve done here is prove you know nothing about inferential stats.
First, there is no experimental manipulation, therefore there is no null hypothesis. Period. The null hypothesis applies to experimental situations. What we are performing, and what physicists are studying, is a quasi-experiment–specifically a variant of the interrupted time series design where CO2 introduction (over time) is the interrupting agent. Essentially one studies the situation before and after the introduction of the interrupter and sees if the situation changes. Turns out that after the introduction of CO2, the situation changes quote measurably. You are falsified insofar as this quasi-experimental design can do so.
Second, if there were an experimental manipulation, the experimenter would take, say, 100 identical 280ppm Earths uninhabited by mankind but with all other pre-existing life and all sinks exactly the same and pick 50 at random to add enough CO2 to take the concentrations from 280ppm to over 400ppm and leave the 50 others untouched at 280ppm. Then one would take measurements. This in no way has any relation to your idiosyncratic definition of the concept. There is also no way one would not observe a clear experimental effect were one to do this experiment based on thousands upon thousands of laboratory studies where experimental controls were possible.
Third, a more correct procedure–the one scientists actually use–is to model natural variation and model natural variation plus CO2 additions. Turns out that modeling natural variation leads to no trend. Adding CO2 to the models shows a warming trend. While not experimental and therefore less definitive in and of itself standing alone, natural variation simply does not describe the observed evidence unless, as others have pointed out, one posits some sort of magic force that has yet to be observed together with a second magic force which counteracts the effects of the first magical force.
Romain @117
“Because if you admit there could have been precedents, then you can say that the actual warming is indistinguishable from the natural variations, i.e. the background noise, i.e. the null hypothesis. ”
1) The null hypothesis is not strictly speaking background noise or natural variation.
Natural variation is one possible explanation for recent warming, but it doesn’t explain it. The earth currently has a build up of heat energy according to satellite data. There are only limited sources of heat energy, geothermal, the sun and these don’t explain the recent build up of heat energy and the related warming period.
We have at least 10 reasons that this recent warming period is related to greenhouse gases generated by fossil fuel burning, and can be distinguished from natural variation as below:
https://www.skepticalscience.com/10-Indicators-of-a-Human-Fingerprint-on-Climate-Change.html
So I suggest stop wasting your time going over old ground, again, and again, and again.
https://www.metoffice.gov.uk/news/releases/2018/end-of-summer-stats
“With one day to go, it is clear that 2018 has been one of the hottest summers on record for the UK, however, the margin between the mean temperatures at the top of the league tables (records dating back to 1910) is so small that at this point it is impossible to say if 2018 will be an outright winner. It is very close to the record-breaking summers of 2006 (15.78C), 2003 (15.77C), and 1976 (15.77C) all of which are within 0.01C of each other.”
“To get an even longer-term perspective our multi-century Central England Temperature* (CET) series dates back to 1659. In this dataset summer 2018 looks likely to slip behind the summers of 1976 and 1826. If we look back through the CET series only 10 summers recorded an average temperature above 17C. Six of those have occurred since 1976, and only two (1826, 1846) were pre 20th Century, which is consistent with the general picture of our warming climate globally and here in the UK.”
Zebra writes:
“#42 Dan Miller, Wrong.”
Nothing that Dan Miller wrote is wrong. Certainly Zebra does not identify any such thing.
“This is another example of saying that climate change is caused by climate change.”
That’s not at all true of what Dan actually wrote.
Victor: “Now why didn’t I think of that?”
There’s a simple, obvious explanation for why you don’t think of things.
“I wonder how the “experts” are predicting rises of several feet over the next 50 years, as opposed to, say, 50 x 3mm = 150mm = 0.492126ft.”
The same way that an intelligent person could predict a large future increase in the water level of a swimming pool if King Kong is teetering precariously on a roof above the pool.
BTW, if you had any credibility at all, you would have lost it by putting scare quotes around a word referring to people who know stuff and aren’t stupid.
Victor @118
makes the claim typically has a burden of proof to justify or substantiate that claim especially when it challenges a perceived status quo.” ….
In this case the perceived status quo is the notion that climate is and always has been largely determined by natural forces. The burden of proof is on anyone who claims otherwise.
Totally agree, except for one small point. The perceived status quo is that current climate change has a strong anthropogenic component. So the burden of proof is on you.
‘Discussions’ have to start from a position of parity of expertise, or they just get silly. I could postulate that the moon is made of blue cheese. But that wouldn’t mean that NASA would have to bother responding. Now if I postulated it and came up with a creditable testable hypothesis, maybe a discussion could start.
Re the reference given by Victor #123,
The quick Linkedin profile for this “expert” lists employment history as
“Assistant Manager at Superdrug, Supervisor at Robert Dyas, Stock Controller at Tesco PLC, Store Supervisor at Blockbuster Video, Telesales..”
Anyone who is signed up for Linkedin can perhaps get some more details about this blockbuster expert on Philosophy of Science.
127 jgnfld says:
vic–“…Natural variation is the sum of all factors that have influenced Earth’s climate other than those produced by humans (e.g., CO2 emissions due to the burning of fossil fuels). Why is that so hard for you to understand? I see no reason why it can’t be characterized as a null hypothesis…”
j: All you’ve done here is prove you know nothing about inferential stats.
First, there is no experimental manipulation, therefore there is no null hypothesis. Period. The null hypothesis applies to experimental situations.
V: Strictly speaking yes, the null hypothesis is usually defined in the context of inferential statistics as applied to specific experiments. But the term has also been used in a more general sense, as I’ve demonstrated above (see #123). Regardless of whether or not you are willing to accept this more general usage, the basic principle remains: any hypothesis proposing a new interpretation of a generally accepted view carries the burden of proof. If you prefer not to characterize the generally accepted view as a “null hypothesis” that is your prerogative — but the basic principle remains the same. The generally accepted view of climate, prior to the development of the AGW hypothesis, was that it was driven by natural forces (aka “natural variation”). There is no need to “prove” this as the long history of the Earth’s climate is clearly consistent with this notion, once we rule out the possible influence of “the Gods” or “God” or spirits or aliens from outer space, etc.
There is, therefor, no need to defend this generally accepted view, as it has already been established beyond doubt. The notion that the Earth’s climate is now, after billions of years, controlled largely by something new (i.e., CO2 emissions) is an alternative hypothesis that requires supporting evidence. The influence of natural variation requires no supporting evidence as it has been long established. It has, in fact, been frequently invoked by AGW supporters in their own attempts to justify their theory.
To put it more generally, a peer reviewer evaluating a paper submitted for publication is never expected to defend any skepticism by producing evidence of his own to support an alternative view. All he need do is point to weaknesses in the argument presented by the author of the submitted paper.
J: Turns out that modeling natural variation leads to no trend. Adding CO2 to the models shows a warming trend.
V: Come again? Earth’s history reveals a number of trends, both warming and cooling, with no assistance from anything that could have been caused by human activity. What is it that produced the Ice Ages, the Medieval Warm Period, the Little Ice Age, etc.? The considerable warming trend we see in the early 20th century was primarily the result of natural forces, as CO2 levels during that period were too low to be more than a minor influence. That was followed by a 40 year period when temperatures either cooled or leveled off. There is in fact only ONE period where we see a distinct warming trend: 1979-1998. It is the effect of only these 20 years that we are really talking about when we reference “global warming.” If CO2 were a factor we’d have seen temperatures increasingly rising over the last 120 years or so, but that is clearly NOT the case.
In order to be taken seriously, Victor (his latest comment is here) needs to supply references to the peer-reviewed scientific literature that
1. Global warming isn’t happening; or
2. It’s happening but CO2 emissions aren’t the major contributor.
He hasn’t.
@134
zebra…Yes. That page is simply an astoundingly bad description of what a null hypothesis is at anything even remotely approaching a professional level.
The wiki page is much better. But note how vic quotes the true factoid from it–“The null hypothesis is generally assumed to be true until evidence indicates otherwise”–apparently without understanding that the article does NOT define accepting the null hypothesis as accepting “natural variation causes X”. This peculiar definition only occurs in vic’s mind and nowhere else.
136 Steven Emmerson says:
“In order to be taken seriously, Victor (his latest comment is here) needs to supply references to the peer-reviewed scientific literature that
1. Global warming isn’t happening; or
2. It’s happening but CO2 emissions aren’t the major contributor.
He hasn’t.”
V: 1. Global warming has happened many times in the past, so whether or not it’s happening now means little.
2. If you believe CO2 emissions are the major contributor then the burden of proof is on YOU to supply sufficient evidence to that effect. Moreover, when graphs of temperature and CO2 levels from respected sources reveal NO correlation between CO2 and temperature for the first 80 years of the 20th century, and NO correlation for the first 15 years of the 21st, then references to peer reviewed papers should not be necessary. In any case there are a great many peer reviewed papers that cast serious doubt on AGW as you very well know.
137 jgnfld says:
3 Sep 2018 at 11:28 AM
“@134 zebra…Yes. That page is simply an astoundingly bad description of what a null hypothesis is at anything even remotely approaching a professional level.
The wiki page is much better. But note how vic quotes the true factoid from it–“The null hypothesis is generally assumed to be true until evidence indicates otherwise”–apparently without understanding that the article does NOT define accepting the null hypothesis as accepting “natural variation causes X”. This peculiar definition only occurs in vic’s mind and nowhere else.”
As I said before, the notion of a null hypothesis can be generalized to include many cases where statistics is not applicable, such as the instances referred to on that website regarding the Copernican view of the planetary system. One could thus rewrite the above quote to read as follows: “A null hypothesis is any hypothesis generally assumed to be true until evidence indicates otherwise.” The key phrase is “until evidence indicates otherwise.” The nature of that evidence, whether it be statistical or otherwise, doesn’t really matter, so long as it’s gathered according to generally accepted scientific principles.
Victor, #–
A serious misframing, since natural variations in CO2 have been a major control on climate over “billions of years.” In fact, that hypothesis is at least as old as the idea that human influence could affect CO2 and hence climate. (The climate efficacy of natural variations in CO2 was Arrhenius’s major research question in 1896, and the possibility that human influence might eventually also prove significant a mere ‘throwaway’ speculation mentioned, in passing, in his conclusion.)
But the priority of those two notions scarcely matters, given that the potential of CO2 and other greenhouse gases to affect climate had already been demonstrated in the lab in 1859-60.
https://hubpages.com/education/Global-Warming-Science-In-The-Age-Of-Queen-Victoria
Victor, #135–
OK, which is it? Was CO2 ‘too low to have an effect’ in the early 20th century? Or do we have to look for ‘increasingly rising’ temperatures ever since 1899, which would be the requisite 120 years? One can’t have it both ways.
And it the former is supposed to be true, then I think the burden falls on Victor to specify just when the burden was no longer ‘too low.’
Very strange that the period of ‘indistinct warming’ since 1998 actually shows a stronger trend than the period of ‘distinct warming’ from 1979-1998!
http://woodfortrees.org/data/wti/plot/wti/from:1979/to:1998/trend/plot/wti/from:1998/trend
’97-’98: “#Least squares trend line; slope = 0.011312 per year”
”98-present: “#Least squares trend line; slope = 0.0137834 per year“
Oh, and the 1998-present trend is *much* greater than ’79-’98 if you look at GISTEMP, rather than the WTI data I used in my first graph:
http://woodfortrees.org/plot/gistemp/from:1979/plot/gistemp/from:1979/to:1998/trend/plot/gistemp/from:1998/trend
Just sayin’.
Victor @135
Wrong.
There was no accepted view of climate change prior to the development of the AGW hypothesis by Arrhenius. It was; however, well accepted before then from the work of Tyndall that CO2 contributes to the temperature of the planet system. Since that time it can be said that CO2 is the scientific status quo understanding of what keeps the planet warmer than what it should theoretically be based on the laws of heat transfer. There is no alternative hypothesis for this discrepancy.
Ice ages and the possibility that climate had ever changed were first hypothesized in 1834. However, the theory was met with heavy skepticism and was not widely accepted until the late 1870s. Hence, no one up until that time really gave much thought about what could influence climate and cause it to change whether natural or by man. Regardless, such a choice would be a false dichotomy. Ice ages stimulated interest in climate. Arrhenius first hypothesized that ice ages were the result of changes in CO2 levels as changes in CO2 levels were the first recognized driver of temperatures and climate….that the sources of the CO2 was natural or manmade was not a consideration or even relevant to the science. In other words, CO2’s role in climate is not an alternative view, it is the default view. Furthermore, AGW theory was not developed to explain the current warming, it was predictive of the warming. Arrhenius’ work stimulated more interest in climate. Other drivers beyond CO2 were identified as climate drivers including changes in solar irradiation which had been thought constant.
Changes in natural drivers may not always be predictable, but they are observable, especially in the modern satellite era. And their resulting effect on climate is predictable based on physics. Which one of these drivers would be the real default when looking at the current warming trend? None, as each driver can change in its influence over time and has to stand on its own evidence because each and every one contributes varying amounts. Like the inability of the earth centric model to accurately predict the position of the planets, natural climate drivers cannot account for all of the observed warming.
Contrary to Victor’s false claims, there is significant evidence for CO2’s role in driving climate. That is why it is the consensus view. Victor just pretends the evidence does not exist. His whole *null hypothesis* meme is just one big stinking red herring.
In Victor’s mind, natural causes are the default explanation, but when warming does not follow CO2 rise precisely then natural causes must not have had any influence in that variation. Apparently, Victor wants people to believe that CO2 theory states that CO2 warming is so powerful as to make other temperature drivers disappear…it is either/or, which of course is absurd.
Victor just makes stuff up. No correlation. No evidence. No warming trend beyond 1998. Null hypothesis. blah blah blah. Sad really.
Select a temperature series and compute the forward moving average of the yearly differences, starting from the first year n the series. (I chose GISS; the satellite series are too short for this exercise.) Look at the longest runs during which the moving average is positive. Until 1948, the longest run is 15 years. From 1948 onward, every 30-year moving average is positive until you run out of 30-year forward series–and the average remains positive if you look at the subsequent 29-year, then 28-year…moving averages. The current warming epoch is unprecedented in the instrumental record, and indeed it is unprecedented in how well we know the possible causes. We know what volcanoes do. We know about the influence of ENSO. We know the energy isn’t being borrowed from the ocean depths, because they are warming, too.
Natural variation is an unphysical “null hypothesis”. It is also falsified at a very high level of significance.
Finally, a simple look at the correlation coefficients between global temperature and CO2 shows >0.9 over the full interval, and for no interval does the correlation fall below 0.68, and that is when you have only 14 years. Weaktor, your Eyeball Mark II calibration is haywire. If you don’t even know how to determine correlation, why should we listen to anything you have to say?
Zebra, 125,
Thanks for your reply, but I fail to see the mistake you are talking about.
At the beginning of your message you agree that this is a bad idea to conflate theories with hypothesis testing. And in the same message you do just that, by putting an alternative theory in my mouth…
You:”So, it is not the case that we have suddenly observed an increase in the climate system energy, and someone then came up with a causal “hypothesis” that can be tested or falsified in the sense you are talking about.”
Me: No it is not the case. And that’s good. When you want to test a hypothesis, the hypothesis comes first, and the test comes second. It’s all fine.
Hypothesis: human induced atmospheric CO2 increase brings Earth global temperature up (one formulation among many).
Test: the present increase in atmospheric CO2, and the resulting global temperature measurement.
You: “Rather, you are proposing an alternative Theory in which increasing CO2 would not result in an increasing system energy.”
Me: No I’m not. This is not a theory, this is a possible formulation of a null hypothesis to test the CO2 hypothesis above.
I would prefer this formulation: Earth global temperature is independent of human induced atmospheric CO2 increase.
Of course the problem is that the test is far from perfect because:
1. We cannot repeat it
2. Difficult to be sure that everything but CO2 is constant
3. The temperature (or energy?) measurement are complicated
4. It is even harder to estimate the background noise (the fluctuations of the temperature with constant CO2), as we have to rely on sparse proxys
5. The test is still on-going!
So this is all a very theoretical (if not rhetorical!) discussion. But interesting. At least to me. :-)
More thoughts re the null hypothesis — ala Kenneth Trenberth. From “What if climatologists reversed the null hypothesis?”, by James Hrynyshyn (http://scienceblogs.com/classm/2011/11/14/what-if-climatologists-reverse/):
“So far in climate science, the null hypothesis is that humans are not to blame for climate change. Climate research is designed to test that idea. If it finds evidence that contradicts the hypothesis that humans aren’t to blame, then it’s falsified, leaving the alternative that humans are to blame. This sort of conclusion is accompanied by a degree of confidence. In most cases, the hull hypothesis is rejected if the results shown there is less than a 5% chance that it’s correct.
But, says Trenberth, science has been pretty clear for a while now that humans are to blame, in general terms, for the global average temperature rise since the advent of the industrial revolution.
“Given that global warming is ‘unequivocal’, and is ‘very likely’ due to human activities, to quote the 2007 IPCC report, should not the null hypothesis now be reversed? Should not the burden of proof be on showing that there is no human influence?””
#144 Romain,
You are ignoring the important thing I said:
Again, you are exhibiting this conflation of hypothesis and a scientific Theory.
What you call a “hypothesis” is in fact a challenge to the Theory, because it must be the case, if anthropogenic CO2 is not causing an increase in climate system energy, that there is some error in the physics that leads us to conclude that it is. You are required then to propose an alternative that corrects the supposed error in the physics.
The only requirement for the validity of the existing Theory is that our observations are consistent with it (rather than contradictory), which they are, both qualitatively and quantitatively, for different effects to differing degrees.
There is no magic threshold of the data that is needed to make the Theory valid.
A Theory is not “proved” or “disproved”; we use its theoretical foundations, as I have described earlier, until it is replaced by a different Theory.
Victor@138 wrote:
First off, scientists don’t “believe” a hypothesis or theory, they provisionally accept one until evidence shows otherwise. This is one of the differences between religion and science.
Secondly, given that volume 1 of the IPCC report reflects the scientific consensus that AGW is real, the burden of proof lies with Victor. And because he’s admitted that he “can’t to the math”, his only hope to be taken seriously is to provide references to the peer-reviewed scientific literature supporting his assertions. He hasn’t.
Ah, it would appear that Victor wants to start a new dance craze by dancing all around the issues without ever landing on one and making a point. I call his dance the “Obtusi,” because it relies on his being astoundingly obtuse in response to the substantive points others are raising.
Yes, Weaktor, it is true that “natural variation” has been invoked to explain (some, not all) past warming epochs. However, “natural variation” is not a synonym for “shit happens”. If a system is warming, energy is flowing into it. If that system is a frigging planet, then a buttload of energy is flowing into it. Energy must come from somewhere.
In the case of the ice ages and the interglacials, we understand where the energy is coming from–a combination of Milankovitch Cycles and the way the continents were arranged, particularly in the Northern Hemisphere. The changes were small, but they persisted a LONG time. Now, the theory of Earth’s climate has no problem explaining these cycles. It’s not just a matter of “shit happens”. So, guess what, Vic, in your attempt to cast doubt on our understanding of Earth’s climate, you’ve inadvertently cited evidence that we do understand it pretty well. In other words “Own Gooooooooooooooooaaaaaaaaaaaaaaalllllllllllllllll!!!!”
As to the MWP and the LIA, uh, dude, you do realize that 1)the MWP wasn’t a global phenomenon and 2)the temperature changes over these periods were less than half what we’ve observed in the current warming epoch? The MWP may have merely been a fluctuation in the Gulf Stream. The LIA…well, there were changes in solar output and volcanism, none of which are occurring now
So, in other words, we understand much of the energy sources that played a role in past climatic changes. Again “Own Gooooooooooooooooooaaaaaaaaaaaaaalllllllllllll!!!!”
Finally, you really don’t understand where the idea of global warming came from. It was a prediction, based on a theory of Earth’s climate, made long before we saw that warming. And NOW, we do have measurements of the energy flows into and out of the climate. We know what the Sun is doing. We know what the oceans are doing. We know what clouds are doing. And guess what, Victor, nothing explains the warming seen except anthropogenic greenhouse gasses.
Please sweep up the ashes of your credibility on your way out the door.
Nobody but Victor uses his “eyeball” method of assessing statistical significance.
Alan Lomax must be spinning in his grave.
Nigelj, @129.
First, the article behind your link do not present “10 reasons that this recent warming period is related to greenhouse gases generated by fossil fuel burning”
The four first “reasons” are about evidences of human induced carbon in the atmosphere. No attribution.
5 and 6 ok. There are the two direct evidences that there is a CO2 green house effect.
7 to 10 are evidences that the recent warming is due to green house effect. Big deal! The Earth climate is dominated by H2O greenhouse effect.
So from 10 you go to 2 indicators.
But fair enough, there is a measurable CO2 effect. No doubt about that. That is just an experimental confirmation of basic radiation physics. That is good to have. The discussion here is more about the quantifiable impact on Earth climate. And if it makes the global temperature go off the rails compared to the previous natural variations. Which I still think we can assimilate to the background noise of the null hypothesis. And I fail to understand why people have difficulties with this. After all this is what the hockey stick is about. Attempting to show that the previous natural variation are so small that the current warming is off the rails.