Sequester – it means to hold back. As in all the carbon based fossil fuel that has been stored in Mother Earth for hundreds of millions of years. We call it coal or oil, as appropriate, and it it is the remains of plants that grew in swampy areas and then died and decomposed there. Turned into coal. And it had been “held back.” It has not been burned and turned into CO2.
What this really means is that while ‘X’ amount of carbon based material each year (or century) was created, a percent of that carbon based material was locked up in the earth. And, as I’ve already said, that went on for hundreds of centuries.
Now we are releasing far too much of it at one time. As CO2 goes into our oceans, the oceans are acidifying. The temperature of the oceans drives the weather we all must put up with.