Humans were not around the last time earth saw a tipping point. That is how scientists know that heat from the sun and the earth's orbit/inclination are the primary driving forces. The ice data also shows that relatively small factors (meteor impact, volcanic eruption, etc.) can measurably affect climate. Some things increase warming and others increase cooling.

            An ice age will not cause the end of the world but will end the world as you/we know it. The ice data shows that one tipping point occurred over a period of 3 years or less. If you want to think about this issue, read about the year of 1816, the year without a summer, to get a feel for the havoc an ice age would bring. This is the scenario that has governments spooked.

            An analysis of cycles says that the earth should not reach the tipping point for >10k years. But analysis of global temperatures (and CO2 levels) says that it is around the corner. What no one knows is whether CO2 is a cause of or the result of climate change. The hope is that it is the cause and that by reducing (or at least reducing the rate of increase), humans can prolong the time to the next tipping point.