How do Climate Models Work?

Climate Models are based on two main components:

a) the concentration and emission rates of atmospheric chemicals.

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Cross-Chapter Box 1.4, Figure 2 from IPCC 6th Assessment Report WG1 showing potential future Shared Socio-economic Pathways (SSP) scenarios and the Representative Concentration Pathways (RCP).

b) the underlying physics of the model.

Some Questions

Below is Figure 1.9 from the IPCC 6th Assessment Report WG1 that shows how well some climate models have done in predicting global temperature change. These models have done incredible well.

But...

Q1) Are we only comparing 10 models? How many models went into each of these papers cited in Figure 1.9 in the IPCC 6th Assessment Report WG1?

Q2) Are there any climate models that showed different results that were not included?

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Q1) Model Number Summaries

Papers that use a single model

Papers that comparing multiple models or a model ran multiple times with different inputs

IPCC Reports and their Energy Balance Model (EBM)

IPCC Reports compile, compare, conduct, and validate many climate models - there a lot to dig into here

Q2) Model Selection

This IPCC reports Figure 1.9 does not include every climate model ever. This figure includes models whose fundamental physics were deemed accurate by Hausfather et al., 2020 who investigated how previous models did in modeling the underlying physics of radiative forcing.

<aside> ⚠️ Radiative forcing (or climate forcing): is the change in energy flux in the atmosphere caused by natural or anthropogenic factors of climate change.

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Figure 1 from Hausfather et al., 2020 showing model performance which highlights models that did strongly and poorly.

Bonus: Where do we need more research?

Conclusions

There is a long history of climate science and climate change modeling. Many researchers have contributed many hours to understand, advancing, and scrutinizing the atmospheric climate science field through the scientific collaborative process. A quick search on google scholar for “climate change” pulls nearly 4.5 million peer reviewed publications (meaning usually 3 experts reviewed and approved your work for publication) . Assuming it takes 177 hours to publish a paper, this is over 90,000 years of work. If you do just a few hours of work learning about atmosphere science basics like the greenhouse effect, radiative forcings, and feedback cycles, you will likely come to the same scientific conclusion that human caused climate change is real.

<aside> ⚠️ We can tell by our earth vital signs that climate is changing

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Figure 1.4 from IPCC 6th Assessment Report WG1 showing main realms of the climate system: atmosphere, biosphere, cryosphere and ocean and their climate change responses

<aside> ⚠️ There is scientific consensus on what is causing the changing the climate.

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<aside> ⚠️ We know the science but there is still a lot of uncertainty. What we do or dont do now will shape the future.

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Figure 1.11 from IPCC 6th Assessment Report WG1 showing global mean surface air temperature anomalies(grey) from a range of CMIP6 historical simulations (1850–2014; 25 models).