Climate History
Climate changes in the deep past of Earth provides strong evidence that we
​are in a committed global warming planetary emergency.

2009 research found that atmospheric CO2 is now the highest
​in at least 15 million years ​​

Scientists can ​tell the state of past climates by examining ice cores, animal
​and plant fossils, preserved pollens and tree rings.

​​Global temperatures and atmospheric CO2 concentrations have been
​much higher in the deep past. However the rate of global warming is
​extremely high and the rate of increase ​in atmospheric CO2
​(and presumably methane and nitrous oxide) is ​unprecedented (IPCC).

Allianz (Insurance) Climate timeline - A short history of the Earth's climate
The deepest ice core from Antarctica goes back 800,000 years
Climate swings between ice ages and warm interglacial ages.  Atmospheric GHGs increase with warming which tends to be rapid and decrease with cooling which is  much slower. The increase in GHGs occurs as a feedback response to a tiny increase in the sun's warmth. The changes in methane are most closely tied to the temperature change. The most recent research finds that the feedback response is very rapid for methane and CO2.  
Over millions of years the climate is controlled by the sinking of carbon from atmospheric CO2.
What we call fossil fuels are the land fossil carbon sinks that has allowed live oxygen dependent life to evolve  ​to the great biodiversity of today. Most of the Earth coal deposits are 250 million years old or more.  

The land carbon sink of fossil carbon has been reversed by industrialized civilization burning coal oil and gas.
The only carbon sink now is the ocean that sinks carbon as carbonate rock- limestone and dolomite, over 10,000s to 100,000s of years.​  

 The health and human rights approach to climate change​