Equilibrium Climate Sensitivity (ECS) is the claimed increase in the global average temperature following a doubling of the carbon dioxide concentration in the atmosphere.
Note: The climate has actually never been in equilibrium.
Climate modelers ignore data showing troposphere temperature, measured from weather satellites.
Those measurements show the actual temperature effect of greenhouse gases exactly where the greenhouse effect occurs -- in the troposphere.
Those measurements can't differentiate between the many greenhouse gases -- water vapor, CO2, methane, etc. --- but they provide the total greenhouse effect from all of them combined.
For the latest climate computer models (CMIP6), the modelers have added clouds to the mix.
That sounds like an improvement ... but it actually permits even more assumptions, many never thoroughly tested.
Untested assumptions could be wrong.
Many CMIP6 models that have high ECS values (CO2 causes lots of global warming) are manipulated using the cooling effect of aerosols (think of aerosols as air pollution that block some sunlight).
The aerosol cooling effect is used to offset some of the warming effect of carbon dioxide (CO2).
That offset is needed to make the model output (hindcasts) match actual surface temperature measurements in the past.
Aerosols are fine solid particles or liquid droplets suspended in the atmosphere that may be natural or human caused (anthropogenic).
Examples of natural aerosols are volcanic emissions, fog, mist, dust, organic compounds released by vegetation, smoke form wildfires, etc.
Examples of anthropogenic aerosols are particulate air pollutants, smoke from power plants and industrial processes.
In the United States and Western Europe, anthropogenic aerosols have been largely eliminated.
In Asia and other developing regions, they (air pollution) are still a problem.
None of the climate models would match the change in the average global temperature over the past century without assuming some cooling from aerosols (blocking sunlight).
ECS numbers generated by climate models, therefore, are artifacts of the assumed aerosol effects used by the models.
For many decades, global climate modelers have manipulated data to promote a high ECS (high sensitivity of surface temperatures to changing atmospheric carbon dioxide).
But they need model output to match actual so they have to assume aerosol air pollution was blocking some sunlight.
All the key components of ECS are in the atmosphere -- CO2, aerosols, and the greenhouse effect.
Yet the modelers completely ignore temperature measurements in the atmosphere, using weather satellites.
They ignore reality.
In plain English, climate models predict whatever the modelers who programmed them want to predict.
With climate models, accurate predictions have never been a goal.
And their accuracy has not improved in the past 30 years.
Nature does not obey climate models ... which, on average, have been predicting more than double the global warming that actually happened for over three decades!
The three decades of very wrong global average temperature predictions, with no improvement over time, are why I call climate models "computer games".