In the previous postings, the computers predicting global temperatures were shown to be much higher than the actual measured temperatures and that you are not being told that the actual measured global temperatures are currently falling and do not seem to have a link with the rising CO2 accumulating in the atmosphere. This posting looks at the future predictions of global temperatures and how they are biased to make you think they are going to be rising quickly.
To have some understanding how the computers are programed one needs to be acquainted with Equilibrium Climate Sensitivity (ECS) and Representative Concentration Pathways (RCP).
Firstly, an examination of ECS. The 1979 Charney Report, named for the Chairman of an Ad Hoc group stated:
“We believe, therefore, that the equilibrium surface global warming due to doubled CO2 will be in the range IC to 4C, with the most probable value near 3°C”.
That means, for a doubling of atmospheric CO2, global temperature will rise approximately 1C due to CO2, and the CO2 induced increase in temperature will result in more water vapor. Water vapor is a powerful greenhouse gas. That and some other minor changes in atmospheric gases will result in an additional rise of 2C. Thus, CO2 doubling does not just create 1C rise but rather a 3C rise. They acknowledged that there was a lot of uncertainty about this number. How water vapor and clouds interact are not yet known with any certainty.
Climate sensitivity is expressed two ways. Transient Climate Sensitivity (TCS) is the initial effect of the change in CO2 concentration. ECS does not happen until the oceans heat come into equilibrium with atmospheric heat, for example.
ECS is controversial. There are those that do not believe in the CO2 effect at all. They may not appreciate this postings discussion of ECS and RCP but the posting is addressing what the Alarmists believe. Also, many others buy into the concept but conclude that the effect is much lower than the 3C rise due to a doubling of atmospheric CO2. Down as low as 1C. As well, there are alarmists that use ECS in the 4C range.
As can be seen in the Part 1 posting, the ECS being used has yielded too high of global temperatures.
Tests of the new CMIP-6 climate computer programs conducted by McKitrick and Christy reported: Pervasive Warming Bias in CMIP6 Tropospheric Layers – McKitrick – 2020 – Earth and Space Science – Wiley Online Library
It has long been known that previous generations of climate models exhibit excessive warming rates in the tropical troposphere. With the release of the CMIP6 (Coupled Model Intercomparison Project Version 6) climate model archive we can now update the comparison. We examined historical (hindcast) runs from 38 CMIP6 models in which the models were run using historically observed forcings. We focus on the 1979–2014 interval, the maximum for which all models and observational data are available and for which the models were run with historical forcings. What was previously a tropical bias is now global. All model runs warmed faster than observations in the lower troposphere and midtroposphere, in the tropics, and globally. On average, and in most individual cases, the trend difference is significant. Warming trends in models tend to rise with the model Equilibrium Climate Sensitivity (ECS), and we present evidence that the distribution of ECS values across the model is unrealistically high.”
If you are a climate computer programmer, you can increase the ECS, and it will result in an increase in forecast temperature.
Representative Concentration Pathway (RCP) is an estimate of the amount of CO2 in the atmosphere at any given time. After studying numerous scenarios, more than the available computer time would allow, they settled on just 5 RCPs.
It is my understanding that the upcoming IPCC’s 6th Assessment Report will use somewhat revised versions of the original 5 pathways. These revisions are to accommodate current thinking about the options and potential pathways. Only RCP 8.5 remains as orginally conceived. At least one of the pathways will meet Paris Agreement goal of of keeping global temperature rise below 1.5C . In between 1.5 and 8.5are three others that do not meet the objective but are considered potential outcomes depending on mitigation policies. The pathways keep track of the forecast fossil fuel emissions of CO2” versus “years” beginning at the current time continuing out to the year 2100.