The IPCC, NOAA, NASA, the EPA and other agencies promoting catastrophic global warming hope politicians and the public don't realize the significance of the fundamental physics.
Simply stated, the more CO2 increases in the atmosphere, the less influence CO2 has on global temperatures - it's a logarithmic thing.
All climate scientists know this. It's the actual hard physics. (Btw, that "positive" feedback thingy about CO2's "tipping point" impact? That's actually soft science - quasi-speculative, not hard physics.)
The adjacent chart though depicts the factual reality about the ever smaller impact of growing levels of CO2.
The reddish columns represent a plot of global temperature sensitivity to CO2. Specifically, they represent 60-year changes in global temperature divided by the corresponding 60-year change in atmospheric CO2 levels (ppm) - a ratio.
The bright red curve is a simple 20-period average of that ratio, which has been declining since the 1950's. Recall that it is the IPCC that states categorically that modern "dangerous" warming started in the 1950s with the growth of industrial/consumer CO2 emissions.
Finally, the rapid growth of total atmospheric CO2 levels is shown by the black dots.
When it's all put together, per the IPCC, the red columns should be gaining in height as the years pass due to the accumulation of CO2 emissions in the atmosphere grows. Taller columns means that the ever increasing amounts of emissions are causing an even greater temperature change.
Clearly, the empirical evidence reveals that as atmospheric CO2 levels have grown, the impact on 60-year temperature changes has shrunk. From a high in the 1950s, to a very low impact as of 2012 (see blue column).
In summary, it's these stubborn climate facts that expose the invalidity/weakness of the AGW alarmist hypothesis. Sure, CO2 has an impact on temperatures but its maximum impact was decades ago and it is shrinking.
As human CO2 emissions continue to increase in the future, the resultant global warming will be smaller and smaller, and will continue to be overwhelmed by natural climate variation.
Note: Excel used to plot datasets. Ratio is simply the 60-year change in annual HadCRUT4 temperatures divided by the 60-year change in annual atomspheric CO2 levels. Dataset sources.