Climate Science Glossary

Term Lookup

Enter a term in the search box to find its definition.


Use the controls in the far right panel to increase or decrease the number of terms automatically displayed (or to completely turn that feature off).

Term Lookup


All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Home Arguments Software Resources Comments The Consensus Project Translations About Support

Bluesky Facebook LinkedIn Mastodon MeWe

Twitter YouTube RSS Posts RSS Comments Email Subscribe

Climate's changed before
It's the sun
It's not bad
There is no consensus
It's cooling
Models are unreliable
Temp record is unreliable
Animals and plants can adapt
It hasn't warmed since 1998
Antarctica is gaining ice
View All Arguments...

New? Register here
Forgot your password?

Latest Posts


SkS Analogy 2 - Ferrari Without Gas

Posted on 24 April 2017 by Evan, jg

Tag Line

A Ferrari without gasoline goes nowhere.
Greenhouse gases (GHGs) without infrared (IR) radiation cause no warming.

Elevator Statement

  • The concentration of GHGs is like the size of a car engine: higher greenhouse gas concentration is like a bigger engine. IR radiation is like the gasoline in the tank of a car.
  • Just as gasoline is the fuel that drives an engine, infrared radiation is the fuel that drives the greenhouse effect.

Climate Science

Global warming occurs because IR radiation emitted from the surface of the Earth is captured by GHGs in the atmosphere, increasing the temperature of the atmosphere and of the Earth. Increased GHGs in an atmosphere with constant background IR radiation will absorb an increasing fraction of the emitted IR radiation, causing warming. Increased GHGs in the atmosphere combined with increased IR radiation causes even faster warming. Warming melts snow and ice, replacing it with dark oceans that absorb Ultraviolet (UV) radiation instead of reflecting it back out to space, causing more warming. The warming oceans emit IR radiation. The combination of the sun warming oceans that were once covered in ice, combined with increased emissions of IR radiation from the warm oceans, is causing the Arctic to warm faster than anywhere else on Earth.

Snowball and Dirtball Earth Radiation Balances

Snowball Earth is a period about 650 million years ago when CO2 concentrations were much higher than today, but when the entire Earth was covered in ice. Some people claim that the existence of an ice age when CO2 concentrations were higher than today proves that CO2 does not cause warming. Part of what allowed Snowball Earth to occur was because solar radiation was about 4% lower than today. But a major reason that Snowball Earth persisted for so long is that snow and ice reflect 90% of incoming solar radiation, reducing the generation of IR radiation to the point that the greenhouse effect was severely reduced. Even with high concentrations of CO2, without IR radiation the greenhouse effect was much weaker than it is today, and the ice persisted.

To power a Ferrari, one needs a big engine and plenty of gasoline. To power the greenhouse effect, one needs lots of GHGs and IR radiation.

Additional Reading

For additional reading see a study published in Nature Communications and summarized in this SkS posting.

0 0

Printable Version  |  Link to this page


Comments 1 to 20:

  1. In the 1930s my father-in-law escaped Depression-era Seattle for Alaska to pan for gold (his father had made quite a bit of money that way).  He and his friends hooked up with an old prospector who was certain that up a particular river they would find El Dorado.  After much trial and tribulation, they ended up-river with no gold, winter approaching, and then the prospector died.  They quickly did an about-face, the river froze, it became perilous.  Worst of all, my father-in-law had drawn the short straw, and had to sleep with the old man's body in his tent (the ground was too frozen to bury him properly).  One night he woke up, and the old man was staring at him, and he swore at the old man that if he ever haunted him, he would find a worthy adversary as they fought their way down to hell.

    This is a long-winded, more macabre way of saying that another way of making your analogy is to note that you can throw a blanket (of CO2) on a freezing human being, and they will warm up.  But, if you throw a blanket on a freezing corpse, they just stay frozen.

    0 0
  2. Macabre, but effective analogy. We need lots of variations on the same theme to reach the broadest audience, and your's works. Thanks. Perhaps we can publish this as Analogy 2B.

    0 0
  3. The solution may be at hand.  We are in a horse race to see whether sudden climate change or economic collapse will come first.  If Economic collapse knocks us back into a dark ages or even into a stone age, our carbon output will crash and huge areas of the world will go back to forest.  Imagine the legends that the remaining survivors will tell of this "Atlantis" and the deniers that will maintain that it could never have been.  For that matter, sudden climate change will precipitate an economic collapse so pretty soon we will stop straining our poor old earth whichever wins the race.

    0 0
  4. The blanket / body analogy is excellent, and will bring a wry smile to people, but I do think most people probably accept the greenhouse effect. The small number who don't might be the very stubborn types who will be hard to convert.

    The problem is people query whether the CO2 is coming from fossil fuels or the oceans or volcanoes, or whether natural causes for warming dominate, etc,etc, ad infinitum. I suppose all we can do is combat these fallacies, and this website is a good resource for this.

    Combatting climate change is more of a political / psychological / economic /social /vested interests  problem.

    It's tempting to be pessimistic about the whole climate thing at times, with the slow progress, complacency, and astoundingly ignorant and self interested positions of people like Donald Trump, but things in life often reach tipping points, where the public and even most politicians suddenly change their positions, and progress starts to happen rapidly. It's like there is a silent gestation period, and then everyone reaches a silent consensus, and change their mind or want action almost in unison. You see it in politics sometimes.

    People can be fixed and partisan, yet they "do" eventually change positions on at least some things. I think this may happen over climate, and full commitment to renewable energy. The question is whether it's soon enough to be of any use.

    However it may take longer in America given the deep divisions, and powerful influence of lobby groups and various other factors.

    0 0
  5. William @3, yes very bad scenarios are certainly possible.

    Also have a look at "The Revenge of Gaia" on wikipedia.

    0 0
  6. Just related to snowball earth, I had to read up on wikipedia, I confess. It appears solar radiation was very significantly less when earth first formed, and has been gradually increasing over the millenia, at an incredibly slow pace according to well understood astronomical evidence.

    Whats interesting is that prior to snowball earth there was a period of liquid water  that coincided with a weak sun. It's called  "the faint sun paradox" given solar output suggests everything should have been frozen.  It's thought that greenhouse gas concentrations were extremely high, enough to keep the planet above freezing point. Some think alternatively that given oceans were larger in extent, this affected the heat balance.

    It's thought the greenhouse gas balance eventually fell leading to snowball earth. Snowball earth was a period of low solar radiation, and quite high greenhouse gases, but not high enough to overcome the weak sun. Eventually the sun strengthened enough to warm things up.

    Now the suns energy output is essentially falling very slightly, and we are adding greenhouse gases, so this is the dominant factor affecting climate.

    This is my understanding. From snowball earth and related links on wikipedia.

    0 0
  7. NigelJ: point out to them that all the volcanoes on Earth provide only 1% of the CO2 we are emitting, sometimes less. Note that there are more vents, geysers, fumerols, mud pools and other geothermal outlets in Yellowstone Park than the rest of the world combined but there are more "fumerols" (exhaust pipes) on the LA Freeways alone, let alone the rest of the planet.True, big volcanic eruptions release a lot of gas, but they are all over in a few days or weeks, with decades/centuries until the next time. Exhaust pipes are 24/7/365.25.

    0 0
  8. ? looking for help here. The article says:

    "... infrared radiation ... captured by greenhouse gases in the atmosphere, increasing the temperature of the atmosphere. ... absorb an increasing fraction of the emitted infrared radiation, causing warming."   

    captured?  absorbed?

    I thought that the CO2 reemitted the IR, causing the surface to warm. 

    The surface then warmed the lower atmosphere.

    Is that a more accurate desciption?


    0 0
  9. This analogy does not claim to be a definitive thesis on snowball earth. But here are a couple of points I think worth pondering. Related to the comment

    "Eventually the sun strengthened enough to warm things up."

    The sun strengthens over geologic times due to changing fusion reactions in the core of the sun. These change are on the order of 100' millions of years, far too slow to bring the earth out of snowball earth. Earth's orbit changes, causing a small amount of warming. One theory of what brought us out of snowball earth is plate tectonics, which caused increased vulcanism, which increased the CO2 in the atmosphere to the point that at the equator the ice melted just enough to expose dark oceans underneath. This increased warming, which melted more ice, exposing more dark oceans, etc. Very quickly we came out of snowball earth and, because of all the CO2 that built up during snowball earth, we entered a hothouse.

    But my point is primarily this. The greenhouse effect requires both the engine (CO2, CH4, etc.) and the fuel (infrared radiation). Once the world got locked into a snowball earth, for whatever reason, for a very long time, high CO2 levels were insufficient on their own to bring the earth out of its deep freeze. This is partly because the snow and ice reflected most of the incident radiation back to space. Eventually a combination of plate tectonics, vulcanism, orbital alignment all happening together increased CO2 and temperatures to the point that we did come out of snowball earth, but for a very long time CO2 was at a level which, under non-snowball earth conditions, would have caused significant heating. The proof is just how hot it got immediately after snowball earth. Really hot, because all of the CO2 built up during snowball earth, combined with all of the radiation present after snowball earth, meant extreme heating.

    No analogy is perfect, but this analogy is trying to make the point that when skeptics/deniers point to periods such as snowball earth as proof that CO2 does not cause warming and that high levels of CO2 are not dangerous, we simply want to remind them that warming requires both the engine and the fuel, and not just the engine. During snowball earth we had a big engine (CO2) and little fuel. Today we have both the engine and the fuel, both in plenty of supply.

    0 0
  10. "The proof is just how hot it got immediately after snowball earth"

    A second "proof" are the cap carbonate layers that follow every snowball excusion, caused by the sudden increase in rock weathering after the land ice melts, exposing freshly ground rock to the high-CO2 atmosphere and acidic rainfall.

    0 0
  11. Thanks Jim for this insight.

    0 0
  12. "The concentration of greenhouse gases is like the size of a car engine: higher greenhouse gas concentration is like a bigger engine."

    But greenhouse gases is the waste from the engine of a car. Or rather, the combustion product left after thermal energy is released. Making it low in internal energy and a potent absorber. First it is included in high energy hydrocarbon molecules, prone to release it´s internal energy. When energy is released it is in the opposite state, prone to absorb energy.

    "Infrared radiation is like the gasoline in the tank of a car."

    No, it is like the heat leaving the radiating body, cooling it. Exactly that. Infrared radiation is energy leaving the engine, the sun is like the gasoline in the tank of the car.

    "Just as gasoline is the fuel that drives an engine, infrared radiation is the fuel that drives the greenhouse effect."

    No, heat from the sun is the fuel that drives the engine. What you refer to as infrared radiation I suppose is the thermal emission from the surface or atmosphere. That is exactly equal to the infrared radiation leaving the cooler of the engine when water circulate in contact with a high flow of air molecules across the surface. Like wind across the earth surface.

    "Global warming occurs because infrared radiation emitted from the surface of the Earth is captured by greenhouse gases in the atmosphere, increasing the temperature of the atmosphere."

    But I thought greenhouse gases increased absorption, isn´t that confirmed by decreasing emission from the atmosphere? How can the atmosphere increase absorption and temperature at the same time as it decrease it´s emission?

    0 0
  13. nigelj 

    "The blanket / body analogy is excellent, and will bring a wry smile to people, but I do think most people probably accept the greenhouse effect."

    How do you explain the greenhouse effect with the blanket/body analogy then? Is the blanket the crust and the body is the hot interior? A blanket reduce the amount of heat absorbed by the surroundings from the hotter body, by being a poor conductor and a poor absorber. If you put something on your body increasing the amount of body heat that is absorbed, what you do is changing the surroundings of your body to suck more heat out of your body.

    0 0
  14. vatmark@13

    The blanket is the greenhouse gases in the atmosphere & the body is the earth's surface*.

    Suppose my skin temperature is 80 F, the air and walls of my bedroom are at 60 F, the lower surface of the blanket is at 75 F and the upper surface of the blanket is at 65 F. The blanket *has* absorbed some heat— if it weren't for my body, the blanket would be at 60 F.

    Likewise the atmosphere and clouds absorb some heat. See

    and especially the NASA chart they give at

    *(I'm no expert. Maybe, more technically, the body is 'a "surface" in the mid-troposphere'. See

    "The atmosphere near the surface is largely opaque to thermal radiation (with important exceptions for "window" bands), and most heat loss from the surface is by sensible heat and latent heat transport. Radiative energy losses become increasingly important higher in the atmosphere, largely because of the decreasing concentration of water vapor, an important greenhouse gas. It is more realistic to think of the greenhouse effect as applying to a "surface" in the mid-troposphere, which is effectively coupled to the surface by a lapse rate."

    0 0
    Moderator Response:

    [PS] Fixed links. Please learn how to do this yourself with link button in the comment editor.

  15. vatmark@12

    An analogy is just a comparison in which some aspects of situation A correspond in some ways to some aspects of situation B.

    You're constructing a different analogy between a Ferrari and the greenhouse effect than the one Evan had in mind, i.e. using a different set of correspondences.

    I kind of like his analogy, but I think it's actually pretty crude, i.e. it doesn't hold up well under close examination:

    concentration of greenhouse gases size of car engine

    infrared radiation emitted by Earth's surface gasoline

    warming due to greenhouse effect What? Speed of car? Distance a car can travel?

    The speed of a car doesn't depend on the amount of gas; as long as you've got one gallon (one quart? one cup?) the Ferrari can go top speed, albeit briefly.

    The distance a car can go depends on how much fuel is in the tank, but it's approximately *inversely* related to the size of the engine. (Someone correct me if I'm wrong?)

    0 0
  16. vatmark @3

    All Evan's analogy is saying is that it takes a combination of two things to get a result.

    It takes both water and dirt to make mud. It takes both bread and a filling to make a sandwich. It takes water and light (along with other things) for a houseplant to grow. It takes both gasoline and an engine (along with other things, e.g. wheels) for car motion to happen. It takes longwave energy leaving the surface of a planet, along with gases in the atmosphere that absorb and re-emit much of that energy, for the  greenhouse effect to happen.

    Some of the things you point out (greenhouse gases in a car' exhaust, car's engine radiating heat, gasoline being the source of that heat) are certainly true, but aren't relevant to his analogy.

    As to the actual greenhouse effect, you say one thing I think isn't true: "decreasing emission from the atmosphere". At equilibrium, the total radiation energy leaving the Earth and its atmosphere is equal to the total radiation energy entering.

    0 0
  17. gnmw #14, in your last paragraph you say:
    "…and most heat loss from the surface is by sensible heat and latent heat transport."

    According to NASAs energy budget chart, 79% of the heat loss from the surface is actually by radiation, but most of that is absorbed by the atmosphere. Convection/advection and latent heat is then responsible for most of the heat transport within the atmosphere. Maybe you were referring to net heat loss defined as surface radiation minus back radiation? In that case, sensible heat and latent heat account for about 1.8 more surface heat loss than radiation does.

    Regarding the blanket analogy, I would say the outside of the blanket corresponds to the average altitude of heat loss to space (about 5 km), while your skin is the Earths surface. The average temperature (-18°C) at that altitude is sufficient for the heat loss there to balance the 240 w/m² of incoming radiation from the sun. The lapse rate then sets the temperature difference between that altitude and the surface.

    If the amount of greenhouse gases increased enough to raise the heat loss altitude from 5 to 6 km, the surface temperature would increase by about 6.5°C if the lapse rate and the Earth’s albedo remained unchanged. In reality, both would decrease somewhat and produce a negative and positive feedback to the initial warming, respectively.

    0 0
  18. For those brave souls who have made it this far down the comment list, one more comment. Yes, the analogy may be interpreted as crude and does not hold up under all considerations of the actual greenhouse effects. The purpose was to draw attention to the fact that it takes more than just CO2 to cause warming. It also takes infrared radiation. If we try to draw too much from an analogy it can become confusing, and the purpose of these analogies is not to educate the well-educated commenters, but to educate people who may be new to the science of global warming.

    That said, I am always open to modifying and improving these analogies, so thanks all for the many constructive comments. I will consider them all and will consider how we can improve this analogy and make it more effective.

    0 0
  19. HK— Why would the lapse rate decrease?

    0 0
  20. gnmw:

    The lapse rate is expected to decrease somewhat because surface warming leads to increased evaporation of water. When this water vapour condenses in the middle and upper troposphere it dumps its content of latent heat and causes extra warming there. This impact is expected to be strongest in the tropics and give rise to the so-called tropospheric hot spot.
    Read more about that topic here.

    0 0

You need to be logged in to post a comment. Login via the left margin or if you're new, register here.

The Consensus Project Website


(free to republish)

© Copyright 2024 John Cook
Home | Translations | About Us | Privacy | Contact Us