Unless emissions decline rapidly in coming years, the world is on track to soon pass 1.5C above preindustrial levels. In a new analysis we use the latest climate models (CMIP6) to determine when the world will likely exceed 1.5C and 2C warming: https://www.carbonbrief.org/analysis-when-might-the-world-exceed-1-5c-and-2c-of-global-warming 1/10

In order to do this we need to answer a few questions, including:
- When is "pre-industrial" in reference to
- How do you determine when 1.5C/2C is crossed
- How do you match up future model projections with observations to-date
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For preindustrial we adopted a pretty standard convention of showing warming relative to the 1850-1899 period, though we acknowledge that earlier temperatures may have been a bit cooler: https://www.carbonbrief.org/challenge-defining-pre-industrial-era 3/10

To determine when 1.5C and 2C are passed, we smooth observations and climate model output using a localized regression method (LOWESS) over 25-year window to remove short term variability driven by El Nino and similar factors. This gives us an estimate of longer-term warming 4/10

We then match up the smoothed observational and climate model records in the year 2020, using the Global Warming Index value to estimate the human-induced warming in 2020 (though it turns out this is also pretty close to the obs smoothed average). https://www.globalwarmingindex.org/  5/10

Now we can determine the range of years in which warming will exceed various targets relative to today across CMIP6 models: 6/10

In the SSP1-2.6 scenario we exceed 1.5C b/w 2026 and 2057 with a median estimate of 2033. For SSP2-4.5 its 2032 (2026-2042). For SSP3-7.0 its 2032 (2026-2038). For SSP5-8.5 its 2030 (2026-2039).

Note that SSP2-4.5 is the scenario consistent with current/stated policies. 7/10

Exceeding 2C warming will occur between 2038 and 2072 in SSP2-4.5 with a median year of 2052. In SSP3-7.0 its 2048 (2035-2058). For SSP5-8.5 its 2043 (2034-2052). 8/x

Whether we exceed these targets is still up to us. We have some future emissions scenarios (SSP1-1.9) where warming stays below 1.5C, at least in some models. Similarly, 2C is avoided in all SSP1-1.9 model runs and most SSP2-2.6 model runs. 9/10

But without rapid emissions cuts, the world will soon pass 1.5C, and may pass 2C not too long after that in scenarios where emissions continue to increase. 10/10