Certainly the climate has a memory. It won't let us forget. We have altered the composition of the atmosphere by our introduction of greenhouse gases to levels that we haven't seen for close to a million years. We know what effect greenhouse gases have on the climate, and therefore it is very solid physics. We know that we can expect impacts as a result of what we've already done.
As the IPCC says in its report, some of those, regardless of what we do in the short term to reduce emissions.... That doesn't mean we shouldn't do everything we can to set ourselves on a path to reduce emissions.