If you want to argue for 'playing things safe' that's exactly my point. With what we currently don't know, we could spend billions on reducing CO2 emissions, and make little noticeable difference to future conditions. We could spend those same billions on dykes, irrigation and water management to deal with the warming that we DO know is coming. You seem to think we should gamble on being able to make a difference with reducing our CO2 emissions, I'm saying let's have some better info before risking wasting dollars we could really use to deal with changes.
Do you seriously expect future conditions to remain the same if CO2 in the atmosphere continues to rise and oceans continue to acidify? We may not know exactly what's going to happen but it will be very different than the relatively stable climate we've built our civilization on over the last 6,000+ years. Are you willing to bet the farm it won't be that bad?
You need to read more closely, the numbers for total radiation coming into the atmosphere and leaving are in the hundreds, and the net difference is near zero.
Yes, the insolation at the top of atmosphere (where they measure the imbalance) is around 1360 W/m^2. With a 0.58 W/m^2 energy imbalance the energy exiting the Earth is 1359.42 W/m^2. Doesn't sound like much but the area of the disk of the Earth facing the Sun is 128 trillion m^2 so the total imbalance is about 74 Terawatts (or 74 million Megawatts). A Watt is defined as 1 joule/second so that's 74 Terajoules/second. And that continues 24/7/365, it's going to add up.
That is meaning without the 2.9W/m^2 from our human emissions we'd be facing a much bigger imbalance, but in the opposite direction around -2.5W/m^2.
If that 2.9 W/m^2 dropped to zero then the energy imbalance would also drop to zero once the Earth was again in energy balance. It wouldn't go negative. If we just held the additional forcing at 2.9 W/m^2 instead of increasing it by adding more CO2 the Earth would eventually reach a new equilibrium (at a higher temperature) and the imbalance would drop to zero again.
Reality would appear to dictate that our actual influence on the energy budget isn't nearly that extreme, as I've pointed out twice already. The entire time our contribution (forcing from human GHGs) has been rising steadily, the energy imbalance has remained oblivious to that, or at least hasn't changed to an extent that we have the precision to measure yet
As long as the energy imbalance is greater than zero temperatures will continue to rise.