This is too good not to archive. I got into an argument about climate change with a stranger on Facebook today. I spit out a 15 page rebuttal to his "take down" of climate science in just about two hours. There's some good basic climate science here, as well as rebuttals to some of the stock talking points that skeptics use. YMMV.
Here's the original post (he had it numbered at one point, but eliminated those on an edit):
You are correct, it is a matter of evolving understanding; and the evolution has come full circle. As of Halloween of 2014- the climate change trend has lasted 18 years and one month. So there was thirty years of cooling followed by 20 years of warming and almost 18 years of cooling…and that’s what the global warming scare is all about. Antarctic Sea Ice is at record levels and the Arctic ice cap has seen record growth. Global sea ice area has been averaging above normal for the past two years.
Carbon Dioxide (CO2) is not a pollutant it’s what you exhale and it is what “feeds” plants. Without CO2 there would not be a single blade of grass or a redwood tree, nor would there be the animal life that depends on vegetation; wheat and rice, for example, as food.
There is not ONE climate computer model that has accurately connected CO2 to climate change. In fact CO2 is at its highest levels in 13,000 years and the earth hasn’t warmed in almost 18 years.
The fact that CO2 is the least most common gas in the atmosphere seems to be a moot point to global climate change propoents...
If you believe AL Gores model, all Polar Ice caps should have melted by last year and most costal cities should be underwater. The Earth’s climate is a very complicated system and the scientists haven’t been able to account for all the components to create an accurate model.
It is misleading and just plain incorrect to claim that disasters associated with hurricanes, tornadoes, floods or droughts have increased on climate timescales either in the United States or globally.
A study published in the July 2012 Journal of the American Meteorological Society concluded unequivocally there is no trend of stronger or more frequent storms, asserting:
"We have identified considerable inter-annual variability in the frequency of global hurricane landfalls, but within the resolution of the available data, our evidence does not support the presence of significant long-period global or individual basin linear trends for minor, major, or total hurricanes within the period(s) covered by the available quality data."
The only thing “man-made” about global warming, is the argument that we should all stop thinking because there is a scientific consensus about global warming. There are too many questions still open.
And here's my response.
I'm writing this from my office in the earth sciences department at USC, where I work as a postdoctoral researcher on climate modeling and geoengineering. I have a PhD, and I work on this stuff for a living. I say this not as an appeal to authority (I'm going to back up what I say), but to establish that I very much know what I'm talking about here. I'm not a layperson; this is my job, and I've been researching it for the better part of a decade. Let's go through this point by point.
1. The sea ice extent is a complicated case. The argument is not that global warming causes global cooling. That's obviously idiotic, though due to changes in atmospheric and oceanic circulation patterns, some areas can indeed expect to see record low temperatures. The increase in the ice caps has more to do with slightly elevated temperatures being more conducive to snow accumulation. This sounds just as paradoxical, but it isn't really. The water vapor capacity of air is partially a function of temperature, and (all other things being equal) warmer air is better at holding moisture. The polar regions are cold--really, really cold. In the polar winters, they're generally so cold that they don't hold much moisture at all. This is particularly true in Antarctica, which is significantly colder than the Arctic. It seems strange, but most of the ice shelf in Antarctica has historically been due to accumulated ice rather than snowfall. The ice extent in Antarctica has indeed expanded in recent years, but that's because the slightly warmer temperatures around the southern pole have slightly increased, which has allowed the air to take up far more water vapor than it could before, and winter snowfall has increased. This isn't paradoxical because the Antarctic is still far, far, far below the freezing point of water during the winter months, but the slight increase in temperature has allowed more snow (rather than just ice) to fall and accumulate down there. Moreover, the increase in surface ice
is precisely what we'd expect to see if deep water ocean currents were warming, slowly melting ice underwater and bringing very cold water to the surface. The Earth's oceans are very dynamically active, with currents moving not just horizontally but vertically as well. The vertical circulation currents are called the thermohaline, and their stability is integral to aquatic ecosystems. The thermohaline helps "recycle" ocean water, bringing more nutrient rich water up from the deep oceans so life closer to the surface can survive. The disruption of the thermohaline, which is primarily driven by temperature differences, is one of the biggest concerns that many climate scientists have. It's a fairly delicate system, and it's the kind of thing that will not gradually shift, but rather will work well until it suddenly collapses. If that happens, it's going to spell big trouble for everyone.
2. The supposed global warming pause you're alluding to is a myth. The flattened curve that often gets passed around in these discussions is usually a depiction not of temperature, but rather of the first derivative of temperature: the last few years have showed a slowdown in the rate
of warming, but average temperatures have continued to increase. Exactly what caused the slowdown isn't completely understood yet (science is hard!), but there are a few things to say. First, remember that climate fluctuations are very long-term movements. The climate changes at the very fastest
on an order of decades, not months or even years. Climatology is a study of long-term trends, and we expect to see some fluctuation on a year-by-year basis, even with the very strong change in radiative forcing caused by anthropogenic greenhouse gas emissions (more on that in a moment). In the same way that a freak snowstorm in July (or an unseasonably warm day in February) doesn't signal the onset of a season change, a few years with a warming rate slowdown doesn't signal the end of a decades-long trend. Rather than attending to small fluctuations, we look at the overall trajectory of the system across a relatively long time. There are a lot of neat mathematical tricks that we can use to extract signals like this from the data that don't rely on "well, this graph looks a little flatter to me" style evidence, and the data are unequivocal that warming is not pausing or decreasing.
The second major point that needs to be made in this discussion is that air surface temperature data only give us a small slice of the entire picture of what's going on with our climate. Part of why climate science is difficult to a degree that (I would argue) is unrivaled in either contemporary or historical science--with the possible exception of cognitive neuroscience--is that a complete understanding of the state of the global climate requires collaboration between experts in what would have previously been considered disparate fields. Oceanography and atmospheric physics, for instance, both require highly specialized knowledge and very different training; they are sciences in their own right. Understanding the climate as whole, though, means that we have to understand what's going on deep underwater, as well as what's going on in the upper atmosphere (and those are just two examples). Water makes a significantly better reservoir for heat than does air (see 1), and there's a lot
of water in the oceans. One of the ocean's biggest influences on the global climate comes from its ability to act as a heat reservoir for the atmosphere. This also explains why coastal regions tend to be more temperate than regions of the same latitude, but further inland. When the air is cold, the ocean radiates heat to keep it warm. When the air is warm, the ocean absorbs heat to cool it down. This is why, for instance, Santa Monica and Irvine, CA can have such wildly different temperatures on the same day, despite being only a few dozen miles apart: the ocean acts to moderate the temperatures in Santa Monica. On a global scale, this is important for a few different reasons. First, since the vast majority of the Earth's surface is covered by the oceans, and because ocean water has a relatively low albedo--it absorbs far more sunlight than it reflects--much of the incoming solar energy gets absorbed by the oceans. As the air has warmed up, the oceans have absorbed more of this heat energy, where it is sequestered in the deeper waters via the thermohaline (again, see 1). The reason why warmer temperatures make the oceans absorb more heat is complicated, but it's not terribly important for our purposes here: it's enough to understand that we don't have a complete picture of warming just by considering atmospheric temperatures. All of the evidence indicates that deep water temperatures are rising, and this helps explain the nature of the atmospheric temperature slowdown; the Earth isn't warming less, it's simply warming in different places. As I said before, there's reason to think that this is even more worrying than mere atmospheric warming, since the oceans are in some ways far more delicate than the atmosphere.
3. This is just silly. The worry is not that CO2 is a pollutant in the standard sense (i.e. that it's going to decrease air quality, cause asthma, or suffocate people). The CO2 concentration in the atmosphere is on the order of hundreds of parts per million, which is very, very well within breathable range for humans. Things have to get Apollo 11 levels of bad before we worry about not being able to breathe, and that's not going to happen. The concern is that CO2 is a greenhouse gas. Here's how the greenhouse effect works.
First, it's important to understand that the term “greenhouse effect” is somewhat misleading: the mechanics of the effect bear only a passing resemblance to the mechanics of man-made greenhouses. Artificial greenhouses are kept warmer than the ambient environment primarily through a suppression of convection: that is, the glass in the greenhouse prevents warm air—which is less dense than cold air, and so will tend to rise above it—from rising away from ground level, and thus keeps conditions warmer than they would be otherwise. A similar mechanism is at work when you leave your car parked in the sun on a warm day: the interior heats up, but because the cabin is air-tight (at least on the timescales of interest to you during your trip to the shopping mall or grocery store), the warmer air inside the car and the cooler air outside the car cannot circulate, so the temperature increase can build up over time. The planetary greenhouse effect operates very differently. The layers of the Earth’s atmosphere are not closed systems in this sense, and while convection impediment can play a role in increasing radiative forcing felt on the ground—the fact that cloudy nights are generally warmer than clear nights is partially explained by this effect—it is not the driving factor in keeping the surface of the Earth warm. It has to do with the absorption and emission of radiation.
Different gases have different absorption properties, and so interact differently with various wavelengths of radiation. Radiation of a given wavelength may pass almost unimpeded through relatively thick layers of one gas, but be almost totally absorbed by even small amounts of another gas. This is the source of the greenhouse effect: the composition of the atmosphere directly affects how much radiation (and of which wavelengths) is able to escape to space. The wavelength of the energy radiated by an object depends on its absolute temperature, and that this means that the temperature of the Earth depends on the composition of the atmosphere.
Molecules of different gases have different molecular structures, which (among other things) affects their size and chemical properties. As incoming radiation passes through the atmosphere, it strikes a (quite large) number of different molecules. In some cases, the molecule will absorb a few of the photons (quanta of energy for electromagnetic radiation) as the radiation passes through, which can push some of the electrons in the molecule into an “excited” state. This can be thought of as the electron moving into an orbit at a greater distance from the nucleus, though it is more accurate to simply say that the electron is more energetic. This new excited state is unstable, though, which means that the electron will (eventually) “calm down,” returning to its previous ground state. Because energy is conserved throughout this process, the molecule must re-emit the energy it absorbed during the excitation, which it does in the form of more E/M radiation, which might be of different wavelengths than the energy originally absorbed. Effectively, the gas molecule has “stored” some of the radiation’s incoming energy for a time, only to re-radiate it later. Because the incoming solar radiation and the outgoing radiation leaving the Earth are of very different wavelengths, they interact with the gasses in the atmosphere very differently. Most saliently, the atmosphere is nearly transparent with respect to the peak wavelengths of incoming radiation, and nearly opaque (with some exceptions) with respect to the peak wavelengths of outgoing radiation.
The physics behind this is very well understood, and not at all controversial. The deeper explanation appeals to quantum mechanical features of gas molecules, and I can say more about that if you like, but that's not necessary to get the idea. Again, this is not at all controversial. It's basic physics.
4. Much of this is just misinformation--it's simply factually wrong. I'll say more about the points having to do with modeling in a moment. The only thing I'll say here is that while CO2 levels contribute to warming, they're not the only thing that does so. Demonstrating that CO2 levels were different in the past and that temperatures were different doesn't show anything interesting at all, as there are many factors (the scientists call them "forcings") that contribute to global temperature. CO2, as you likely know, isn't even the strongest greenhouse gas. It simply makes a convenient standardized measurement.
5. CO2 is not the least abundant gas in the atmosphere. Not even close. Other than that, I'm not sure what your point is here.
6. This is the most interesting point in this whole discussion, in my opinion. The reliability of computer modeling in complex systems is my specialty, and what you're saying is (at best) a half truth. Here are the senses in which what you said is true: no single computer model gets everything right, the global climate is a monstrously complex system, and we're still working on improving our models.
That said, none of this implies that the models don't do well, or that we're ignorant. It's true that individual models have variable degrees of success in predicting the evolution of the global climate. However, we don't make predictions based on the output of single models for this very reason--hell, individual models can differ in their predictions from model run to model run. Rather, we use a technique called "statistical ensemble modeling" that takes this variability into account, and even capitalizes it. Rather than looking at the output of a single model run (or family of model runs), we look at the output of a wide variety of different models parameterized with different initial conditions and assumptions about how things work. The output of these different models is then "averaged" (it's a little more complicated than regular averaging, but that's basically what's going on) to provide a meta-model prediction. These ensembles of models do extraordinarily well in predicting how things are going to change, and are almost mind-bogglingly computationally complex. They're also built from very uncontroversial equations of motion drawn from radiative physics and fluid mechanics. The best contemporary models--coupled global circulation models (CGCMs)--are literally simulations of the world's climate. CGCMs break the planet down into a three dimensional grid composed of cells, each of which is (in the best CGCMs) a few kilometers on a side. The computer runs some physics equations that describe what's going on with each cell, and then step the time forward a few seconds, use the last state of the cell, and run the equations again. The output is marvelously precise, and reproduces past climate changes perfectly. Are there still improvements to be made? Absolutely. Shrinking the grid size to below 1 KM is a big goal, because that will give us the kind of resolution that will allow us to model even individual clouds accurately. Science is a work in progress, but our models are remarkably reliable, and comparing the observed data to the ensemble prediction results in a very, very good match.
7. The trick going on here is that claims about a great scientific controversy survey anyone
working in any
science (and often engineering). Those aren't the people worth paying attention to: scientists specializing in climate science
are. The opinion of someone working outside the field is worth little more than the opinion of an educated layperson.
The most recent example of this kind of sleight of hand that comes to mind was the recent article in Forbes claiming that peer reviewed survey found that the majority of scientists were skeptics about global warming (http://www.forbes.com/sites/jamestaylor/2013/02/13/peer-reviewed-survey-finds-majority-of-scientists-skeptical-of-global-warming-crisis/
). The catch is that if you read the actual study, their definition of "scientist" includes anyone with a PhD or master's degree in "geosciences or geoengineering" working in any field of science or engineering, and living in Alberta, Canada. Why does that matter? Well, because (as the paper itself notes):
"And the petroleum industry – through oil and gas companies, related industrial services, and consulting services – is the largest employer, either directly or indirectly, of professional engineers and geoscientists in Alberta." The vast majority of those surveyed were petroleum engineers employed by oil companies, not climate scientists doing peer reviewed research. My point is not that there's some kind of conspiracy going on, but just that it's very easy to manipulate data by this kind of study design. You need to be careful and dig deeply when looking at this stuff.
The meta-studies you described are actually far more reliable than simple surveys, as they let us look at what research is actually being published in reputable journals by specialists. All those meta-studies support the position that there's a strong consensus about anthropogenic causes of global warming.
8. Moore is simply wrong about the lack of evidence. Also, his full claim was that humans are not solely
responsible for global warming, and he suggested that increased solar activity was a more likely culprit. Even he has had to back off this claim, though, as solar activity has been far below average during the period when warming has been sharpest.
How do we know that humans are contributing to global warming? There are lots of ways. For example, not all CO2 is created equal. The process of combusting fossil fuels that's characteristic of most anthropogenic CO2 release results in a chemically distinctive CO2 molecule that looks different from those released by other causes. We can measure the CO2 content of the atmosphere, and then look at what percentage of the CO2 increase is accounted for by the anthropogenic CO2. When we make this measurement, it turns out that the vast majority of CO2 increase is coming from people, which means that we are significant drivers of the greenhouse effect. If you're skeptical about the greenhouse effect, refer to (3).
Does this prove that we're the sole cause? Of course not. The climate is (again) very complex, and there are lots of factors at play. The fact that we may not bear sole responsibility for warming, though, doesn't exonerate from being responsible for the role we are playing, and if there are non-anthropogenic forces at work in warming the climate, that's only more reason for us to be cautious: it suggests that even if we stop contributing, warming might continue (albeit at a much slower rate) anyway. This should make us more concerned, not less concerned.
Another good indicator comes from the computer models, which can (and have) been run to generate predictions about what the climate would look like without anthropogenic forcings. The projections don't match observed data at all, whereas predictions that include anthropogenic forcings match observation quite well.
9. There was some talk in the mid-20th century about global cooling. Most of it had to do with concern over the increasing release of sulfur dioxide into the atmosphere; Carl Sagan was a notable figure who worried about this. SO2 is a naturally-occurring (though tiny) constituent of the atmosphere--and also the byproduct of a number of important industrial processes. It’s also released in very large quantities during volcanic eruptions.
SO2 is what climate scientists call an aerosol; soot is another prominent aerosol. Contrary to many other cases, the technical use of this word isn’t significantly different from the colloquial use: aerosols are small particulates that get suspended in the air (think of everyday aerosols, like spray paint or nasal spray, which propel tiny particles of liquid suspended in a gas). Aerosols are significant for the global climate because when they’re present in significant amounts, they exert a quite strong cooling influence on the global temperature. They do this in two distinct but related ways. The first is by modifying the amount of incoming light that simply “bounces off” the atmosphere without ever having a chance to make it very far in (climate scientists call the amount of light that bounces off in this way the albedo of the planet). The tiny particles in aerosols act as what we might think of as “microshades,” helping to shield the planet from sunlight. Aerosol particles also act as nuclei for water vapor to collect around, thus contributing to the formation of cloud cover, similarly cooling the planet. These effects are why, for instance, large volcanic eruptions can drop the average global temperature by significant (in the scheme of things) amounts. Anthropogenic emissions of aerosols skyrocketed (so to speak) in the mid-20th century:
While the concerns about global cooling--both from aerosols and from nuclear winter--were quickly eclipsed by other concerns (and never really represented a scientific consensus in the first place), they represent an important milestone for this discussion: the very public discussion surrounding nuclear war and SO2’s effect on climate was, for many average citizens, the first time they were exposed to the idea that human behavior might shape climate trends in a significant, long-term, irreversible way. It represented one of the first instances of a dawning realization that would come to dominate much of the public discussion of climate for the next decades: human civilization has gotten so big that we’re now acting on a global scale.
Overall, though, the idea that there was a scientific consensus about global cooling in the 70s is largely a myth. There were a small number of studies that considered the possibility, but we quickly realized that the greenhouse effect was a more dominant feature in the Earth's climate. There's some talk these days about utilizing aerosols as a geoengineering solution to slow warming down by injecting certain aerosols into the atmosphere, but that's another discussion.
10. The key phrase there is "on climate timescales." Remember, climate change operates on a scale of decades. We simply don't have the data yet to be able to differentiate a signal from noise--to be able to tell climate change caused shifts in droughts from the background noise of normal climate fluctuation (see 2). It's clear that some areas of the world are experiencing unusual droughts, but we just can't tell yet if that's part of the normal variability. The model predictions aren't good, though.
It's also worth pointing out that some areas may see an increase in rainfall as a result of climate change, while others may see a decrease. This isn't paradoxical, but it could be a big problem. Some major agricultural powerhouses (especially in Africa) operate on a very thin margin of rain, and even a very small change could be disastrous. Similarly, a small increase in annual rainfall in other areas could have significant consequences for human life, as things like levees and dikes are overwhelmed by the increase.
11. I can't speak to this one. I'm not a biologist or an ecologist.
12. It's true that no change in hurricane intensity has been detected, but (to my knowledge) there was never a suggestion in the scientific literature that it would be.