We can be very sure a heat wave is not going to hit 500 degrees Farenheit, on Earth as we know it. We can also be sure that heat waves are going to continue to extend their RANGE of possible states in direct correlation with global climate energy increasing. And we are seeing exactly this.
We will also see that as the energy in the climate increases, our ability to predict into the future gets worse rather than better. Not because we got dumber, but because the chaotic system is becoming more chaotic as energy is added. The more extreme it gets, the more capacity it develops to confound projected outcomes due to chaos's sensitivity to initial conditions.
If you wanted the ability to predict more accurately, the only way to get that is to cool off the globe and take energy out of the system. It's the energy that's driving the chaotic behavior.
Consider the concept of 'period three implies chaos': we do indeed understand chaos, but its sensitivity to initial conditions means we can't make deterministic projections of its future state, only projections of the range of possible future states (and a good solid notion of how deterministic it's gonna be based on how much energy is in the system: period three is arrived at from deterministic oscillations through INCREASING energy, and we know exactly what happens to the unpredictability as we continue to add energy)
Climate is a giant chaotic system of atmosphere energy.
We absolutely understand what, in a general sense, happens when we alter the amount of energy in the system.