Something I always ask deniers. What is the safe level of CO2 that would not cause climate change? I have never received an answer.
History of climate change science
The history of the scientific discovery of climate change began in the early 19th century when ice ages and other natural changes in paleoclimate were first suspected and the natural greenhouse effect first identified. In the late 19th century, scientists first argued that human emissions of greenhouse gases could change the climate, but the calculations were disputed.
From that you could extrapolate that levels should be at pre-industrial levels (say 1850).
All we've got to do to achieve this goal is:
Get rid of technology that is run by fossil fuel based power.
Plant a load of trees that we've destroyed to make room for housing and farming.
Reduce the
World's population from 7,000,000,000 to about 1,250,000,000
Achieve this and we'd be laughing.
Any ideas how we can cull 5,750,000,000 of our fellow human beings?
World War 1 casualties:
10,000,000 military deaths
7,000,000 civilian deaths
World War 2 casualties:
50,000,000 - 80,000,000
Epidemics / Pandemics:
Black Death (bubonic plague), Europe & Asia (1338–1351) - 100,000,000
Influenza, Worldwide (1918–1920) - 75,000,000
Since we're rather attached to peace and pretty good at controlling disease these days the above reductions in the World's population are probably not going to repeat any time soon.