Global monthly temperature anomalies have exceeded 1.5°C above pre-industrial levels nine times or so in individual months in the HadCRUTv5 series since 2016. I’ve adjusted the baseline of the chart above by the LTALTA Long Term Average. This is usually defined as a 30 year period by the WMO. for the 1850-1900 period to calculate the increase in temperature since the start of the pre-industrial age. Some global series don’t extend as far back as 1850, GISTempGISTemp v4 The GISS Surface Temperature Analysis version 4 is an estimate of global surface temperature change using data from NOAA GHCN v4 (land stations) and ERSST v5 (ocean areas). 4 for example, so I imagine they can’t use this value and the LTA must be reduced to 20 years. I’ve added a 3 year linear trend (warming at the rate of +1.094°C/decade) to the chart above, and extrapolated it forward to find when 12 month average global anomalies will reach +1.5°C if temperatures remain at their record levels for the next nine months or so. The 12 month moving average could achieves this by November 2024, until six months ago I wouldn’t have believed this were possible, but with six consecutive record warmth months, I now beleive it’s perfectly possible.
If you take a more measured approach, and use a linear trend over the last 30 years (warming at the rate of +0.213°C/decade), then the 1.5°C won’t be reached for another 10 years, that’s in January 2034. So when will it be? My money’s on 2024, but I could be wrong. 😉
