Why are the models suddenly so high?
From Real Climate:
The US federal government goes to quite a lot of effort to (mostly successfully) keep sensitive but unclassified (SBU) information (like personal data) out of the hands of people who would abuse it. But when it comes to the latest climate models, quite a few are SBU as well.
The results from climate models that are being run for CMIP6 have been talked about for a few months as the papers describing them have made it in to the literature, and the first assessments of the multi-model ensemble have been done. For those of you not familiar with the CMIP process, it is a periodic exercise for any climate model groups who want to have their results compared with other models and observations in a consistent manner. CMIP6 is the 5th iteration of this exercise (we skipped CMIP4 for reasons that remain a little obscure) that has been going since the 1990s.
The main focus has been on the climate sensitivity of these models - not necessarily because it’s the most important diagnostic, but it is an easily calculated short-hand to encapsulate the total feedbacks that occur as you increase CO2.
The first public hint of something strange going on, was at the Barcelona CMIP6 meeting in March earlier this year where this graphic showing Equilibrium Climate Sensitivity (ECS) for the models was prepared:
This showed that quite a few of the models were possibly coming in with sensitivities above 5ºC (grey bars were self-reported, green bars were calculated coherently from the archive). At about the same time, developers at the Hadley Centre and IPSL, wrote about their preliminary results. This was news because the previous IPCC report (and most assessments) have found the likely range of climate sensitivity is roughly 2 to 4.5ºC. For contrast the range in CMIP5 models was 2.1 to 4.6ºC.
Sensitive-But-Unlassified: What is going on?
The US federal government goes to quite a lot of effort to (mostly successfully) keep sensitive but unclassified (SBU) information (like personal data) out of the hands of people who would abuse it. But when it comes to the latest climate models, quite a few are SBU as well.
The results from climate models that are being run for CMIP6 have been talked about for a few months as the papers describing them have made it in to the literature, and the first assessments of the multi-model ensemble have been done. For those of you not familiar with the CMIP process, it is a periodic exercise for any climate model groups who want to have their results compared with other models and observations in a consistent manner. CMIP6 is the 5th iteration of this exercise (we skipped CMIP4 for reasons that remain a little obscure) that has been going since the 1990s.
The main focus has been on the climate sensitivity of these models - not necessarily because it’s the most important diagnostic, but it is an easily calculated short-hand to encapsulate the total feedbacks that occur as you increase CO2.
The first public hint of something strange going on, was at the Barcelona CMIP6 meeting in March earlier this year where this graphic showing Equilibrium Climate Sensitivity (ECS) for the models was prepared:
This showed that quite a few of the models were possibly coming in with sensitivities above 5ºC (grey bars were self-reported, green bars were calculated coherently from the archive). At about the same time, developers at the Hadley Centre and IPSL, wrote about their preliminary results. This was news because the previous IPCC report (and most assessments) have found the likely range of climate sensitivity is roughly 2 to 4.5ºC. For contrast the range in CMIP5 models was 2.1 to 4.6ºC.
Sensitive-But-Unlassified: What is going on?