@NathanpmYoung would be interested if you're willing to share your reasoning for ~doubling the percent this market was at

Can you expand a bit on which resource you are likely going to be using to resolve this? NASA? IPCC? Our World In Data?

Lots of nuance in the definition of "2 degrees". Baseline, method, averaging out period, overshoot included or not...

The biggest uncertainty around all of this is currently your definition, that is even more core to resolving this than the uncertainty on reality.

You might find this article useful. It is likely to be a close call given the question posed:

https://www.carbonbrief.org/analysis-when-might-the-world-exceed-1-5c-and-2c-of-global-warming/

Analysis: When might the world exceed 1.5C and 2C of global warming? - Carbon Brief

Nations pledged to limit global warming to “well below” 2C above pre-industrial levels and also to “pursue” efforts to cap warming at 1.5C under the Paris Agreement.

Does this mean that there will be an invented 2 degree change by 2045, or that a student amount of carbon will have been emitted that 2 degrees is "locked in"?

@jonsimon I’m sorry I don’t understand

@humblestumble Normally, when reports talk about "2 degrees warming", they're talking about what the new stable climate would be if future emissions followed a specific pattern. We are currently at around 1.1C above pre-industrial levels, but even if we stopped all emissions now then in a century we would likely be around 1.8C above pre-industrial levels.

It is reasonably likely that by 2045, there is nothing we can do to prevent the temperature in 2145 from being less than 2C above the pre-industrial level (barring something truly transformative like grey goo or nuclear winter). However, it is reasonably unlikely that in 2045 global temperatures will be more than 2C above the pre-industrial level.

"successfully limiting climate change to under 2C" seems to indicate an expectation in 2045 that climate change will not surpass 2C.

"global warming is under 2C at the end of 2045" seems to indicate that global temperatures haven't surpassed 2C by 2045, even though it will in the future.

@dph121 Not sure where you're getting your numbers from. We're currently around 1.2-1.3C above preindustrial, although @humblestumble should specify what sort of measurement is being used https://www.igcc.earth/ . If all emissions stopped in a realistic way, we'd probably still be ~1.5C, you don't lose all of the aerosol cooling effect because some is natural (and besides some will persist in a human-existant net zero) (https://climate.nasa.gov/explore/ask-nasa-climate/3271/aerosols-small-particles-with-big-climate-effects/#:~:text=Aerosol%20air%20pollution%20has%20made,1.5%C2%B0C)%20of%20warming). The best estimates of locked-in warming from greenhouse gases is ~0C https://bg.copernicus.org/articles/17/2987/2020/.

Is this compared to preindustrial levels?

@JosephNoonan Yes

I think this isn't a good throshold, even pessimistic forecasts don't predict we'll pass 2 degrees by 2045 I think

@YoavTzfati Free mana then i suppose

@YoavTzfati But if new technologies come out that pushes it back below 2C, does it resolve YES or NO?

@ShadowyZephyr It resolves YES

I would clarify with “at the end of 2045” then instead of using “by” which is more ambiguous