Vostok ice core data
Over the last sixty years, atmospheric CO2 has risen almost 50% higher than at any other time during the last 400,000 years. Temperatures at Vostok during that time have been flat to down.
The implication is that climate sensitivity is zero, and that past (lagging) changes in CO2 are are due to outgassing and absorption of CO2 by the oceans.
Why is this obvious fact being ignored by climate scientists?