When will global temperature anomalies be 1.5°C higher than those of 1850?

The IPCC seem to be fixated on when global temperatures will be 1.5°C higher than those in pre-industrial times, no doubt naturally thinking, that there was time left to do something about it. This is what the IPCC report says about when they expect this to happen.

Global warming will likely rise to 1.5 °C above pre-industrial levels between 2030 and 2052

The missing graph

The isn’t a single graph of forecast global temperatures in the IPCC report of 2018 illustrating just how world temperatures are forecast to rise in the coming years to achieve the magic value of 1.5°C warmer than those in pre-industrial times. So to remedy that situation I have produced my own best guess graph of when this magic +1.5°C year will occur based on the latest global temperature data in the CRUTEM series, and it doesn’t make use of any sophisticated climate model either!

AGW,1.5 degrees, IPCC

As you can see all that I’ve done in the above graph is to overlay two simple linear trends, one for the last 30 years (blue dash) and one for the last 10 years (red dash) on top of a 12 month moving average of CRUTEM values (black) from the Met Office. For the purpose of this article I have taken pre-industrial times to be the year 1850, which is convenient because that’s when the CRUTEM global temperature series began. The two trends that I use indicate that the 1.5°C mark occur between the years 2034 and 2044, which is broadly in line with what the IPCC are suggesting. Here’s a much more detailed look at the last 30 years of global temperatures.

A closer look at the detail

Global Warming,1.5 degrees,IPCC

The 10 year trend is obviously heavily influenced by the spike in global temperatures that occurred around 2016 linked which was linked to the major El Niño event that was happening at the time. The thirty year trend handles the 2016 spike more easily, but you can see that the globe has cooled by over 0.25°C since the hiatus of 2016.

Conclusion

The 12 month moving average shows just how volatile global temperatures are, and if the globe experienced warming at the same rate as it did between 2013 and 2016 (of around 0.35°C), the +1.5°C could easily occur in the next decade. A betting man might tend favour 2044 rather than 2034 as the year when the magic +1.5°C is finally reached, but either is equally possible.

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