There are few topics with a wider disconnect between what scientists know to be true and what the general public thinks than global warming. Based on the most recent Gallup poll numbers (which were from 2013 when this post was written), only 54% of Americans think that climate change is already happening, 39% think that its natural rather than anthropogenic, and only 62% think that there is a scientific consensus about it. In reality, roughly 97% of climatologists agree that the planet is currently warming and we are causing it. This disparity is largely attributable to a great deal of misinformation about climate change. The internet is full of nauseatingly horrible arguments like, “well it changed naturally in the past, so it must be natural now” or the erroneous claim that “in the 70s all the scientists were predicting global cooling” and the misconception that “climate change has paused during the past 15 years.” Therefore, I am going to try to briefly explain how climate change actually works, and present a logical proof that we are causing it. According to the rules of logic, the inane dribble of the internet will then be meaningless, as we have no choice but to accept the conclusion of a logical proof.
Premise 1: CO2 traps heat and is largely responsible for the earth’s climate.
This is a simple scientific fact. Not even the 3% of scientists who disagree with climate change disagree with this premise. CO2 traps IR radiation, preventing it from leaving the earth. Without it, earth would be much colder. That is an irrefutable scientific fact.
Premise 2: We have greatly increased the CO2 in the atmosphere.
Again, this is an irrefutable scientific fact. We can measure past CO2 levels in the environment using ice cores. In certain parts of the world, ice forms annual layers, and air bubbles containing CO2 get trapped as those layers form. So we can drill into those bubbles Jurassic Park style and measure the past CO2 levels. Further, we can confirm that ice layers form annually by checking them against known volcanic events (ash from the volcanoes gets trapped in the ice layers, so we can check the date based on counting layers to the known dates of eruptions like Pompeii, and see that the dating method does work). So, using these data, we can tell that there is more CO2 in the atmosphere now than at any point in roughly the past 800,000 years.
Image from the Scripps Institution of Oceanography
Further, we know that this increase is from us because of the Carbon-13/Carbon-12 ratio. Carbon exists in three different isotopes (i.e., they have different numbers of neutrons), but Carbon-13 and Carbon-12 are the most abundant (Carbon-14 is unstable). The Carbon-13/Carbon-12 ratio that is naturally in the atmosphere is different from the ratio in our fossil fuels. So, if the in the increase in CO2 is from our fossil fuels, we expect the Carbon-13/Carbon-12 ratio in the atmosphere to shift to be closer the ratio in fossil fuels. Guess what, the ratio has shifted significantly, clearly demonstrating that we have altered the atmosphere and increased the CO2 concentrations (Bohm et al. 2002; Ghosh and Brand 2003;Wei et al. 2009). These isotope data are unambiguous. They are like fingerprints, and they trace back to us.
These data come from Wei et al. 2009, but the legend of this figure was modified for readability by skepticalscience.com (the data themselves were in no way manipulated as you can see in Figure 4 of Wei et al 2009.)
Premise 3: When you increase something that traps heat, you trap more heat.
This is thermodynamics 101 and should be intuitively obvious to everyone. If you didn’t accept this premise, you wouldn’t wear a thicker coat in January than you wear in April. Further, we have demonstrated many times in the laboratory that if you increase the CO2 concentrations, you will trap more heat.
Conclusion: Therefore, we are causing the climate to change.
This conclusion follows necessarily from the premises. CO2 traps heat, more CO2 traps more heat, we have greatly increased the CO2 in the atmosphere, therefore the earth is trapping more heat. This is irrefutable. It’s not opinion, it’s fact. Unless you can discredit one of these premises or show that a logical fallacy has been committed, you MUST accept the conclusion.
Finally, just in case someone isn’t convinced, I will offer one more piece of evidence. Energy from the sun enters the earth as high energy, short wavelength light. It leaves the earth as longer wavelength IR radiation, some of which gets trapped by CO2. So, if our increase in CO2 levels is causing the planet to warm, we would expect the input from the sun to remain constant, but the amount of IR leaving the earth should decrease. Note: this is an exclusive prediction. In other words, the ONLY way that you would get constant input but decreasing output is if greenhouse gasses like CO2 are trapping more heat. So, in the 70s we launched satellites to measure energy going in and leaving, and, lo and behold, the input from the sun has remained essentially unchanged, but the IR leaving the earth has decreased significantly (Harries et al. 2001; Chen et al. 2007; Griggs and Harries. 2007). Importantly, this decrease has been at the wavelength that CO2 absorbs, and the decrease correlates nicely with increasing CO2 levels. The only reasonable explanation for those data is that our CO2 is trapping more energy. This is a close to proving something as science ever comes. It is an incontrovertible fact that we are causing this planet to warm.
The Logic of Science 
A very useful post. But just writing to note that I do actually wear a thicker coat in April than in January, given that I live in the south of the southern hemisphere…
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So, what happened to the mile thick sheet of ice that once covered North America?
As soon as you say “In reality, over 97% of climatologists agree that the planet is currently warming and we are causing it” you are repeating the grand lie from the IPCC which is but a quasi-religious belief.
Doesn’t the FACT that our “climate scientists” have been changing temperature values for the past to make the present seem warmer concern you at all or are you afraid for being hounded for stepping out of line with some sort of intellectually dishonest “consensus?”
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By “mile thick ice sheet” I presume that you are referring to one of the previous ice ages. In which case, the answer is quite simple: the climate does change naturally; however,the fact that it has changed naturally in the past does not in anyway shape or form indicate that it is changing naturally now, and (as explained in this post) we can clearly demonstrate that we are the ones currently changing the climate. Also, CO2 was one of the key drivers that caused the ice ages to end. Importantly, that CO2 was released naturally, but (as explained in this post) we know that the current CO2 entering the atmosphere is from us because of the isotope ratios.
Regarding 97%, good job fact checking since that claim doesn’t come from the IPCC. Rather, it comes from numerous surveys and reviews of the literature. You would know this if you had bothered to click the link in the sentence that you quoted rather than simply plowing forward with your biases and misconceptions. This is what frustrates me, I made it really, really easy for you to fact check. I gave you my source, yet you assumed that I was wrong without even bothering to check my source. That is not the action of someone who is actually interested in facts. So, since you missed it before, here is the systematic review of the literature on climate change which shows a 97% agreement:
http://iopscience.iop.org/1748-9326/8/2/024024/article
There are also several other papers which have arrived at roughly the same numbers, for example: http://www.pnas.org/content/107/27/12107.full.pdf%29
Regarding climategate, absolutely nothing dishonest happened there. A handful of emails were cherry picked and misconstrued to give the false appearance of deception, but those emails have been thoroughly reviewed, over and over again, and the notion that the scientists were being disingenuous has been thoroughly debunked. Skeptical Science has good explanations of the climategate nonsense, so I encourage you to read them. https://www.skepticalscience.com/Climategate-CRU-emails-hacked.htm
Although you reference climategate, your comment of falsifying past data sounds far more inline with the more recent (and equally flawed conspiracy) about the GHCN data. I’ve already debunked that one, so I will simply refer you to that post:
https://thelogicofscience.wordpress.com/2015/02/09/the-ghcn-temperature-adjustment-myth/
Finally, and most importantly, I presented you with a logical proof that we are causing the planet to warm. You responded by completely ignoring my proof and falling back and well worn and thoroughly debunked conspiracy theorist arguments. That is a logically invalid tactic known as red herring. According to the rules of logic, you must either show that one of my premises is false or that I have committed a logical fallacy. If you cannot do one of those two things, then you must accept my conclusion. That is what the rules of logic dictate.
So, I have one simple question for you: can you either disprove one of my premises or show that I have committed a logical fallacy?
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You are amazing. You have my utmost respect for not just your intelligence and the time you have put into this, but also your polite yet stern demeanor.
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I don’t doubt that we are changing climate or the fact that it is our use of fossile energy buried in the ground that is in fact causing it.
What I wonder is if the cost of controlling these fuels in this moment makes it worth the effort. The temperature cycle of the planet will eventually reach a point where we are heading anyway (we are just shortening the cycle). All the carbons that are now buried in the earth has at one point been in circulation in the eco system at the surface and it didn’t bring the end of time at that period.
Absolutely no one (I hope) believes in the sustainability of fossile energy because it is not endless (ok, neither is the sun, but in the grand scheme of things… it is). I do however believe that to reach a stable society wherein you can do research on good and sustainable ways to obtain energy, we need this energy for the time being. We wouldn’t have all these energy consuming research centers with all those white coated people finding important things out if it wasn’t for the stable energy supply. Research is hard when you have to combine it with fighting off mr sabre tooth or hunt deer in the woods (or try to grow crops in my case since I am a vegetarian).
I understand that it is fashion these days to go to our last untouched patches of nature in mega cruise liners that burn fossile fuel, board RIB boats that burn more fossile fuel and sit in expensive winter clothes manufactured with plastics from fossile oils and sob over the dying polar bears while dropping candy wraps on the ground. I believe, however, that even if we stop society tomorrow, the earth will eventually warm to the point where the polar bear will decrease in population significantly (or even die out) anyway due to the natural hot and cold cycles of the earth. I’d be happy to be proven wrong though!
I should add that I work in the oil industry so I do have bias towards it of course… but when I look at our energy supply and the methods we use to obtain energy I do wonder what is going on in the name of green energy. Most things considered environmentally friendly like solar power and hybrid or electric cars have dark backsides that isn’t seen by most (like environmental impact of manufacturing + installation, life cycle energy costs, energy production vs energy cost of manufacture + installation and maintenance + life expectancy etc etc). Water dams destroy vast areas of nature and disrupt the eco systems in rivers. Wind turbines require vast amounts of energy for manufacture, transport and installation in relation to what they produce (plus the fact that you ruin large portions of nature with maintenance roads, installation etc etc) and they also have a relatively short life expectancy. It is the same story with solar panels; the manufacturing process is energy costly in relation to production and again we have the issue of land use and destroying large areas or relatively untouched nature.
As a side note, I am a great believer in the energy of the earth’s core… it is a vast untapped heat source that currently only Iceland is using via it’s geysers and I can not understand why more nations don’t look at this source of energy!
For the time being though, until we have researched proper ways to obtain sustainable energy, I do believe we need fossile fuels and nuclear power.
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That’s not correct. New Zealand uses a lot of geothermal energy. The geothermal fields around Rotorua were tapped so long and so effectively that they started to fail.
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Is it possible that Geothermal fields can really “fail” or go cold due to human activity? Are they sure it wasn’t for geological reasons? It is after all the earths core as heat source we are talking about here. Gazillions upon gazillions of liters or hot flowing mush reaching several thousand degrees… and thermal travel should ensure a steady flow of temperature. Spontaneously it sounds to me like plate tectonics could have shifted and distanced the thermal source further from the core or something like that. Tiny puny humans should not in my mind be able to affect such a vast system.
Also… I mean, for the sake of gold we can dig 4 km into the ground and use vast complex air conditioning plants to keep our gold mines cool and nice, but somehow we can not drill into the ground and insert some large thermal pickup device? I don’t believe that for one second!
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Some of your points are correct. Alternatives do often have drawbacks, but the technologies are constantly improving, and some of them are better than others. For example, hydroelectric tends to be very detrimental, but geothermal tends to have fairly low impacts. So, I agree that we cannot switch away from fossil fuels overnight, but I think that it is important to start making the switch while we still have time because if left unchecked the effects of climate change will be very detrimental for both humans and the environment.
Regarding natural cycles, yes, the earth will eventually balance itself out…in a few thousand years. The earth’s natural cycles take about 10,000 years. Importantly, this happens very slowly so plants and animals have time to adapt. The current rate of change is much faster than the natural change so most species don’t have time to adapt.
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Please explain your comment that C-13/C-12 ratios are different in fossil fuels than in the current atmosphere. As both are stable isotopes, it cannot be due to decay. Is it due to the warmer ocean temps which would cause water to be depleted of C-13 relative to C-12 (similar to O-16/O-18 ratio changes due to changes in water temps) and this affects the carbon isotope ratios in corals?
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It’s because of the carbon cycle. Plants incorporate carbon via photosynthesis, and animals obtain carbon by eating plants or other animals (with a few exceptions, like corals), but when plants perform photosynthesis, they tend to use C12 more than C13. As a result, the ratio of C13/C12 in living organisms tends to have relatively more C12 than the ratio in the atmosphere. Our fossil fuels are simply the remains of dead plants (coal) and marine organisms (oil) that were deposited during the carboniferous period. So, since living things have different C13/C12 ratios than the atmosphere, and fossil fuels formed from living things, they also have different C13/C12 ratios than the atmosphere.
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