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Suppose you take a trip with a gas-guzzling car on a Sunday. Will your action increase the global temperature by an infinitesimal amount?

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  • $\begingroup$ What's an "infinitesimal amount"? $\endgroup$ – valerio Feb 22 '18 at 14:37
  • $\begingroup$ @valerio infinitely small, but not zero $\endgroup$ – Mark Feb 24 '18 at 18:36
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    $\begingroup$ What I mean is that I don't think the concept of "infinitesimal" has any real meaning here...Will your car trip have an effect on Earth's atmosphere? Yes, it will. Will the effect of this single car trip be detectable? No, it won't. "Infinitesimal" means nothing here really. An effect can be detectable or not detectable, that's all. $\endgroup$ – valerio Feb 24 '18 at 19:29
  • $\begingroup$ @valerio An effect can still exist and not be detectable. The question is not if it is possible to detect, but rather if such an increase exists. Also note the threshold problem mentioned below: small quantities of GHG do not alter the global temperature, there is a certain threshold that triggers global warming. $\endgroup$ – Mark Feb 24 '18 at 19:58
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    $\begingroup$ When does sand become a pile? en.wikipedia.org/wiki/Sorites_paradox $\endgroup$ – Rococo Feb 27 '18 at 16:33
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Green house gases, of which the main contributor is H20, water,maintain the temperature of earth at temperatures friendly to the appearance of life.

Water vapor is the most abundant greenhouse gas in the atmosphere. Human activities have only a small direct influence on atmospheric concentrations of water vapor, primarily through irrigation and deforestation, so it is not included in this indicator.4 The surface warming caused by human production of other greenhouse gases, however, leads to an increase in atmospheric water vapor because warmer temperatures make it easier for water to evaporate and stay in the air in vapor form. This creates a positive “feedback loop” in which warming leads to more warming.

As CO2 is a greenhouse gas, it will contribute in the total amount in the atmosphere, and will affect to that tiny percentage global warming. Note that the same can be said about cows, which emit methane, a gas more potent in shielding radiation and contributing to warming than CO2 . If you are worrying about your car emissions you should also start worrying about eating beef.

A car emits about 2.6 kg CO2 per litre of gas, a cow 110 kg methane per year. Methane is 21 percent more potent as a green house gas than CO2:

Methane has a GWP of 21, which means it's 21 times more effective at preventing infrared radiation from escaping the planet.

It needs some algebra to see how many cows are equivalent to the usual car exhausts, but it is not trivial.

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  • $\begingroup$ That is not really to where my question is aiming: I know that a lot of cars contribute to global warming, but can we really say that ONE car rises the global temperature? $\endgroup$ – Mark Feb 24 '18 at 18:34
  • $\begingroup$ Temperature is a statistical variable, an intensive thermodynamic variable. Yes, one car or one cow will raise the global temperature by a very very small not measurable amount. (divide one car by the total number of cars to get an estimate of the importance of one car). $\endgroup$ – anna v Feb 24 '18 at 18:51
  • $\begingroup$ If you want to get to numbers see here co2.earth/global-co2-emissions, it is over 30 gigatons of emmisions per year , and one car even burning 10.000 litres is only 26 tons a year , order of magnitude. $\endgroup$ – anna v Feb 24 '18 at 19:01
  • $\begingroup$ Still this assumes that gobal warming is a linear process in which every car contributes evenly. (See the objection of Oбжорoв) $\endgroup$ – Mark Feb 24 '18 at 19:05
  • $\begingroup$ @Mark Polutants and exhaust gases are distributed and diluted over large volumes of the atmosphere. So every car indeed contributes evenly to the traffic portion of global warming. $\endgroup$ – Aziraphale Feb 24 '18 at 20:35
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Yes. If the effect were zero, you could have a million cars with a total effect of zero. I guess you could even calculate the exact amount using some assumptions. Say, 1000000 cars cause 0.2 Degrees increase in one year, your trip causes 0.2*10^-6 / 365 degrees Celsius increase in global temperature. Is your question aiming in this direction?

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    $\begingroup$ This is a highly non-linear process. There is no way you can establish that link for a single car. For all you know the inverse might occur. $\endgroup$ – Oбжорoв Feb 22 '18 at 15:30
  • $\begingroup$ Driving a car emits a fraction of the total amount of CO2 which in turn causes warming of the atmosphere. It does not matter whether the temperature/CO2 relation is linear or not. Each source contributes to the total effect. Why would one car cause warming and the other one cause cooling? $\endgroup$ – Aziraphale Feb 22 '18 at 20:18
  • $\begingroup$ A single car may or may not increase temperature. I am not answering that question. I am just pointing out that your reasoning is flawed. Are you familiar with non-linear phenomena at all? Your last sentence is clearly besides the point I am making. $\endgroup$ – Oбжорoв Feb 22 '18 at 20:48
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    $\begingroup$ You speculated that "the inverse might occur", so I picked that up in my comment. I am familiar with non-linearity. Do we agree that a Million cars have some effect? Then each car contributes. Of course, no one can measure what the exact effect of a particular Pickup truck in Oklahoma on the temperature in Quebec is, but that was not the OP's question anyway. All I am saying is that each CO2 source contributes to the total effect. There is no reason to believe that one particular source (see OP) does not contribute. $\endgroup$ – Aziraphale Feb 23 '18 at 6:39
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    $\begingroup$ @Mark The question here is not "Does my car trigger global warming?" Of course it does not. Likewise, you cannot prevent global warming if you decide to walk to the office. But traffic does have a positive effect on air temperature. If you are part of the traffic, you are a tiny, tiny part of the increase. $\endgroup$ – Aziraphale Feb 24 '18 at 20:27
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Your trip with a gas guzzling car contributes $CO_2$ to atmosphere. $CO_2$ has greenhouse effect.

The thing is that we need greenhouse gas to maintain the temperature of the earth temperature. In ice age, where greenhouse gas was little, the global temperature was extremely low. By the end of ice age when the greenhouse gas increased, the global temperate rose and there was flooding.

We also don't want too much greenhouse gas, where the global temperature would be too high and there would be too many consequences for human beings to comfortably live on earth.

Greenhouse gas cycles; it is produced somewhere and is absorbed somewhere else. Over millions of years, the greenhouse gas reaches to an equilibrium point where we are now, which is not bad so far. We need cows to produce greenhouse gas because we know the gas is absorbed somehow that the greenhouse gas concentration in atmosphere is maintained.

However, human beings interferences to environment, such as using cars, trucks, furnaces and farms, change the equation such that we gradually increase greenhouse gas without enough measure to remove them from the atmosphere to maintain that favorable level. Even though the extra greenhouse gas produced is only a very small fraction of the total greenhouse gas produced on earth, the fact that we change the balancing equation is of concern; the global temperature will gradually increase to a level which we don't like!

So to answer your question, if you think we are close to ice age where we need more greenhouse gas, please drive out you gas guzzling car as much as possible. That would prevent the global temperature from decreasing too much or maintain the temperature or increase the temperature.

If you think we have too much greenhouse gas, please design a $CO_2$ extracting machine to take some of greenhouse gas off the equation. And please park your car in your garage:).

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  • $\begingroup$ It still does not really answer my question. $\endgroup$ – Mark Feb 24 '18 at 21:49
  • $\begingroup$ Your question doesn't have answer :) It is not yes or no style question. $\endgroup$ – user115350 Feb 25 '18 at 0:22

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