If we assume that human civilization will continue for at least another 1000 years, then we will eventually arrive at a 100 percent renewable energy system. Whatever you believe about the existing reserves and undiscovered sources of fossil fuels and other combustible or radioactive minerals, they will eventually be exhausted or too expensive to extract.
Policymakers often act as if we had that kind of time. Unfortunately, we don't.
As the science clearly shows, CO2 and other greenhouse gas (GHG) emissions must peak and begin to decline in less than a decade if we are to meet the target of staying below 2¬∞C of global mean temperature rise -- the target to which the 192 member governments of the United Nations Framework Convention on Climate Change (UNFCCC) have committed themselves.