The parameterizations in climate models are done to cover things that don't fit well with the scale* the models have to run on or things that are not well enough understood to put into code in the model. The parameterizations just basically emulate things we know about that can't be directly included in the code. Even though they are derived from measurements that have error it makes no sense to carry that error into the models because the parameters are only an emulation of reality. It would make more sense to just vary the parameters based on the measurement error for different model runs to see how that affects the output.

* By scale I mean the grid size and time divisions they have to use due to the limitations of computer power.

I think we're using two different definitions for forcing and researching the matter doesn't really clear it up very well. I was using forcing in the sense that the 280 ppm of CO2 that was in the atmosphere before the recent rise is a forcing and by adding more CO2 we've increase the forcing. A quote from a 2005 paper "Earth's Energy Imbalance: Confirmation and Implications". by James Hansen, et. al. supports this:

Notice the paper says "2.75 W/m^2 in 2003 relative to the 1880 value" which implies they're taking existing natural forcing into account. But I can see where you might consider forcing to mean just that part that's over and above the exiting natural forcing that preexisted anthropogenic climate change.

Also I don't think your math of subtracting the current anthropogenic forcing of 2.9 W/m^2 from the energy imbalance in valid. In the first place if the 2.9 W/m^2 forcing is relative to sometime in the 1800's then we've already realized a fair amount of the warming it caused so the energy imbalance is from only the part of that forcing that hasn't been realized yet, not the whole 2.9 W/m^2. To me that implies if the energy imbalance continues to remain the same over time then the forcing must be increasing to keep the imbalance going. Otherwise the energy imbalance would cause temperatures to eventually catch up to the existing forcing (natural and anthropogenic) reducing the imbalance to zero.

The only way we could reduce the anthropogenic forcing of 2.9 W/m^2 is by reducing the concentration of CO2 in the atmosphere. If all we did was stop emitting CO2 the excess that we've added would remain and the anthropogenic forcing would still exist.

As the GP said it's more about the rate of change than the absolute number. If the increase in CO2 we are seeing took place over 2,000 years rather than 200 years it wouldn't be nearly as big a deal as natural (and human) systems would have more time to adapt.

Speaking of low-flow toilets I installed a high quality (recommended by Consumer Reports) low flow dual flush mode toilet two years ago and it's only plugged once in all that time. The older normal toilet it replaced used to plug weekly. So the problem with most low flow toilets is a matter of design, not the concept.

I think it is you who doesn't understand how physics works. The energy imbalance is a function of the change in forcing over time (dF/dT), not the forcing itself. If forcing didn't change the energy imbalance would be zero. That the energy imbalance isn't changing is just evidence that forcing continues to increase due to the anthropogenic rise in greenhouse gases in the atmosphere.

What are these measurements you think are inputs to climate models? It's certainly not temperature measurements or precipitation measurements or wind measurements.

It sounds to me like you badly misunderstand how climate models work. As much as possible they are physical models. That is they model the actual physics that combine to produce our climate. Measurements of the actual climate are only useful as something to compare model output against.

What you call error bars on climate model projections are more properly called confidence intervals, that is the range within which 95% of the weather is expected to vary. Since measurements are not used as inputs to climate models any measurement error is immaterial to them.

Perhaps rolling dice would have been a better example than coin flips. A single flip or roll of dice is equivalent to weather, the average of many flips or rolls of the dice is equivalent to climate.

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?

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.

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.

As long as the energy imbalance is greater than zero temperatures will continue to rise.

Too bad the Supreme Court said the Clean Air Act authorizes the EPA to regulate CO2.

The difference between weather model and climate model prediction is like the difference between predicting one flip of a coin and the average of 1000 flips of a coin. You can't predict the results of the 1000th flip any better than you can predict the first but you can predict that the split between heads and tails will be right around 50%.

A recent study by the University of Minnesota and Woods Hole Oceanographic Institute found that while the amount of precipitation wasn't unusually low for a drought the intense heat was. That causes increased soil and plant evapotranspiration leaving the soil dryer making the the worst drought in the past 1,200 years. The intense heat is easier to connect to AGW.

You're right, climate change doesn't cause wildfires. But it does exacerbate conditions that lead to larger and more intense fires.

Perhaps the problem is the hyperbolic overstatement of predictions by climate science denial leaders or even unscientific people on the alarmist side rather than the actual predictions of scientists. I find most of the actual scientific predictions to be on the conservative side.

Sure. If you know what the danger is you can figure out what to do to prepare for it. If you don't know what the danger is you have no idea how to prepare for it and it's probably better to avoid it. Simply assuming that if you don't know how bad something may be that it won't be that bad is like an ostrich sticking its head in the sand.

It sounds to me what you're talking about is the total forcing from CO2, not the energy imbalance. Your number for energy imbalance is about right, what I get from a 2012 paper by James Hansen, et. al is 0.58 W/m^2. But the the total additional forcing from human added greenhouse gases is about 2.9 W/m^2.

As long as the energy imbalance is greater than zero the Earth will continue to heat up. If the energy imbalance remains the same while CO2 increases that just means the temperature the Earth has to reach to again have energy balance is higher still. If the Earth is getting closer to energy balance the number would be going down, not remaining the same.

I think it's your expectation of what agreeing with each other means that needs adjustment. Based on my understanding of the limitations and expectations of climate models they agree with each other and with observations pretty well over the long run.