a) Pre-industrial was like windows fully open .. 200ppm CO2
b) Burning coal ……………..1/5th closed …………… 250ppm
c) Burning oil …………………2/5th closed ………….. 300ppm
d) Burning nat.gas……….. 3/5th closed ………….. 350ppm
e) more of the above ….. 4/5th closed ………….. 400ppm (in 2014)
We have burned massive amounts of fossil fuels, doubling atmospheric CO2 levels from pre-industrial levels. This has raised global temperatures 1.8degF, like a car with the windows 4/5th up. If the windows keep going up, the car will heat up faster. As long as we keep burning more coal, oil, and gas, we keep closing the windows.
Scientists are saying that we must keep the temperature below a 3.6degF increase and that could occur in just 15 years. After we exceed that temperature, feedback loops will begin to make the windows go up on their own and humans will lose control. If that occurs, temperatures will increase 5-20 degF, over the coming centuries… just like a car on a sunny day. Allowing global warming to continue is like leaving our children in a car with the windows rolled up. We must keep the window open, by reducing fossil fuel usage, and that will only occur with a Carbon Pollution Tax, to keep fossil fuels in the ground.
Please sign this petition. https://www.change.org/p/u-s-house-of-representatives-pass-a-carbon-tax-to-stop-global-warming-and-protect-earth
The Middle Way 
A global agreement to curb greenhouse gas emissions would prevent nearly 70,000 premature American deaths annually by the end of the century while sparing the country hundreds of billions of dollars’ worth of economic losses, according to a major government study on the cost of climate change. http://www.washingtonpost.com/news/energy-environment/wp/2015/06/22/inaction-on-climate-change-would-cost-billions-in-economic-losses-major-epa-sponsored-study-finds/