How much global warming will I save with my Electic Nissan Leaf ?

A few months ago, I bought a Nissan Leaf, full electric car.  Very nice car, fun to drive, fun not to go to gas station.  Faster acceleration than my Jetta TDI.  Nice equipment, GPS, Carwings, remote control and others.

So, I was interested to see how much "global warming" I would save with my Nissan Leaf.

I knew from intuition that it would be a very small number of °C.  So I did the calculation to see how many cars would be needed to "remove" 1 ppmv of CO2 from the atmosphere.

And from this 1 ppmv, I could calculate the number of °C I would save by using the "climate sensitivity" of a doubling of CO2.

So... here's the basic information I needed.

1. How much kg of CO2 is "saved" with my Leaf.

This is approximated with the Carwings Nissan application.  So after 4179 km, I saved 761 kg.  Extrapolating this to 24,000 km per year (lease contract), I can calculate I will save 4370 kg

2. Now I need to know how much kg of CO2 is equal to 1 ppmv of atmosphere. 
For this, I used this information:

Using 5.137 x 1018 kg as the mass of the atmosphere (Trenberth, 1981 JGR 86:5238-46), 1 ppmv of CO2= 2.13 Gt of carbon.

So from there, I calculated that 1.93E12 kg of CO2 = 1ppmv

3. How much CO2 is really saved compared to gas cars ?
It's not because you can save x amount of kg with an electric car that you saved it compared to a gas car.  For starters, it is more complex to build a Leaf compared to a simple gas car.... there's a good discussion of this topic here:

http://www.greencarcongress.com/2011/06/lowcvp-20110608.html

To make a long story short... we save around 20% of CO2 compared to a gas car...
So the above figure of 4370 kg for 24,000 km (1 year) comes down to : 874 kg.

4. How many Leaf is needed to "reduce" the CO2 content of the atmosphere by 1 ppmv ?
Ok now we can simply take the number from 2: 1.93E12 kg of CO2 = 1ppmv and divide by 3: 874 kg
=== > we would need 2,210,735,217 Nissan Leaf on the road per year to cut 1 ppmv of CO2!

Wow, that's a lot of electric cars!  Not sure if we have enough resources, like Lithium, to build all that!

5. How many °C did we save with all those Leaf on the road ?
To calculate this, we need to know the "climate sensitivity"... this is the number of °C increase for a doubling of CO2.  Here's one source of many for informations on this...

http://www.scientificamerican.com/article/ipcc-revises-climate-sensitivity/

Number from latest IPCC AR5 report is 1.5°C.  Ranges are from 1.5 to 4.5... So I will take the latest number from IPCC AR5... 1.5 °C.  This is for a doubling of CO2 from pre industrial level of 280 ppmv.... so... we have a double of 280 ppmv... will give 1.5 °C.  So this is:
1.5 °C / 280 ppmv = 0.005 °C per ppmv of CO2.

CONCLUSION:
We would need 2.2 billions Nissan Leaf to cut 1 ppmv that would reduce global warming by 0.005 °C .... This is for 1 year of all Leaf doing 24,000 km compared to gas cars.

If we where able to build those 2.2 billions cars NOW and use them for 8 years... we would save 8x0.005 or 0.04 °C total global warming.

So my Leaf, leased for 4 years, by itself, would save:
0.000000000009 °C of global warming!

That's why I bought it, not to save the environment, but other reasons... but that would be for another time!

Comments ?