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