When Will We Cross IPCC Targets?

Recently NOAA released v. 5.1 of their global GMST dataset and, aside from adding full global coverage, it extended the dataset back to 1850. This gives us a third GMST dataset that goes back to 1850. Since the IPCC uses the 1850-1900 mean as a baseline to represent "preindustrial" temperatures, this gives us three datasets to use to calculate the amount of warming we've experienced above preindustrial levels. The IPCC has set a target of +1.5°C above preindustrial temperatures, where +1.5°C is a 30-year average above the 1850-1900 mean. The IPCC estimates that 2011-2020 averaged +1.1°C above preindustrial levels. But the question I have is, where are we now, and when will we cross the +1.5°C and +2.0°C targets if we continue warming at current rates?

To answer this question, I took the data I've already downloaded from NOAA (monthly), HadCRUT5 (monthly) and Berkeley Earth (annual). The NOAA dataset is current through January 2023 and the other two are current through the end of 2022. I plotted centered 30-year means for each dataset, and then I calculated the most recent 30-year trend and projected warming from the center of the last 30 year mean to present. Here's what I came up with.
Then using the current projected 30-year anomaly and 30-year trend, I projected when we would cross the +1.5°C and +2.0°C targets if we continue warming at current rates. In the following table, I show the calculated anomalies above the 1850-1900 mean, the current trend, and projections for when we would cross the +1.5°C and +2.0°C targets if we continue warming at current rates, along with averages for all three. According to these data, We are currently at +1.24°C above preindustrial levels with warming occurring at +0.21°C/decade. We would cross the +1.5°C target in ~2034 and the +2.0°C target in ~2058.


As best I can tell, the differences between the anomalies of the three datasets are mostly due to uncertainties between 1850 and 1900, but there is remarkable agreement on the current warming trend. Obviously a lot could happen to change these projections. A major El Niño event might push this a little close to present, while persistent La Niña conditions may delay them. I consider the +1.5°C target all but lost to us and the +2.0°C target almost so. Rapid mitigation efforts may delay us crossing these targets, but at this point it would take pretty drastic measures to avoid them.




Comments

  1. FizzyMarch 29, 2023 at 2:41 PM

    Just discovered your blog(s). Good stuff, well-written. How do I subscribe to receive notices of new posts?

    ReplyDelete
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    1. Scott SimmonsMarch 30, 2023 at 1:08 PM

      Thanks for asking. I just added a "followers" widget that should allow you to subscribe to the blog. I'm glad you like the content!

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