[supercow12]

There are predictions based on various scenarios.

you can see them in more detail here: https://science2017.globalchange.gov/chapter/4/

And the various probabilities that we will stay below X degrees under the various scenarios can be found in figure 14.3 here: https://science2017.globalchange.gov/chapter/14/

I think you are seeing an artifact of how difficult it is to explain things to non-scientists (and non-scientists misinterpreting the claims).

It also tends to be difficult to find these kinds of good sources with a generic google search and no prior knowledge of the appropriate search terms. Using google scholar instead can be helpful sometimes in weeding out non-science answers for science questions.

[tunesmith]

It's too bad, because I think people need to be able to make at least a simple version of the argument for themselves, from premises, rather than simply relying on "Scientists say..."

Edit: Another example. The source you listed says the world is emitting just under 10 GtC/year. Another source I've recently seen said we are emitting 37.1 GtC/year. I've also heard 54/year but don't remember where. I mean, these numbers aren't even close.

[skybrian]

Hmm, I didn't see where it says 10 GtC/year, but perhaps I missed it. Could you be more specific?

Looking at Figure 2.7 [1] they have "Fossil fuels and industry" at what looks like about 37, which agrees with your other source?

The discrepancy in numbers might just be from measuring different things.

[1] https://science2017.globalchange.gov/chapter/2/

[tunesmith]

Key finding #4 in your first link: "The present-day emissions rate of nearly 10 GtC per year suggests that..."

[skybrian]

It seems to be the difference between carbon emissions and carbon dioxide emissions. From a different web page:

"Global carbon (C) emissions from fossil fuel use were 9.795 gigatonnes (Gt) in 2014 (or 35.9 GtCO2 of carbon dioxide)."

https://www.co2.earth/global-co2-emissions

Carbon's atomic mass is about 12 and oxygen about 16. CO2 is about 27% carbon by weight.

[tunesmith]

Oy. Thanks. I'm really getting a lesson on reading these things more closely.