In an addendum to yesterdays blog “Is it 1°C higher or not?“, I can now say yes, recent global temperature were 1°C higher than pre-industrial levels for the best part of two years or more, but in the latter part of 2017 monthly temperatures dropped below the magic +1°C, and that’s why the press releases seem to suggest things haven’t changed. In fact they have gone up and crashed back down again in that period.
Perhaps if they had used a more detailed and larger graph of changes in global temperatures in the latest news release that might have helped. And so to clarify what’s actually going on in more detail I decided to create my own graph based on the CRUTEM4 monthly data that you can freely download (fig 1).
I can now also understand why professor Stephen Belcher the Met Office chief scientist is saying that global surface temperature anomalies could reach 1.5°C above pre-industrial levels in the next 5 years. Already monthly values in the last El Niño event in early 2016 got close to 1.5°C (fig 1). He is obviously banking on the current La Niña fizzling out and a return to the strong warming we saw in 2015.
There is a natural seasonality to the monthly values and that’s why I’ve added a 12 month moving average to the graph. That 12 month moving averaged peaked at +1.25°C in early 2016 and by December 2017 it’s fallen back to +1.05°C. The linear trend for the last five years does indicate that there’s been a decadal increase of 0.547°C, which would be enough to take temperatures above 1.5°C, possibly in the next ten years rather than the five suggested by Stephen Belcher.