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The first half of 2016 has seen astonishing growth in global average temperatures, building on similar growth in 2015, meaning the full year is heading for a record, fifth, successive annual increase.
El Nino events typically occur every few years, and contribute much to the natural variability of the Earth’s climate. The latest cycle peaked in November last year, but its effects have lingered. As well as contributing to regional weather effects, it is associated with higher global average temperatures.
The chart below takes the latest global temperature data to June 2016, from Britain’s Hadley Centre/ Climatic Research Unit (CRU). The dataset is the longest available, starting in 1850. It shows an unmistakable warming trend which extends well beyond the occasional El Nino like the one we’ve just seen.
I have switched the baseline for the temperature data from the usual 1961-1990 to 1850-1900, so that we can see the warming effect compared with “pre-industrial” levels.
A pre-industrial reference is more relevant, given that scientists measure climate threats in terms of global average warming above pre-industrial levels, with 2 degrees Celsius warming often viewed as a safety “guardrail”. Similarly, world leaders last December agreed targets to limit climate change, with a long-term goal to limit warming to “well below 2C”, and to try for 1.5C, above pre-industrial levels.
The chart below puts those targets in perspective. It shows that, so far, 2016 has seen an average 1.21C warming above 1850-1900 levels, a big increase on the 1.06C warming last year, in turn a big increase on 0.88C warming the year before.
Regarding the underlying monthly data, not shown in this chart of annual rises, March 2016 was an all-time record month, 1.46C warmer than pre-industrial levels, already near the 1.5C target set eight months ago. Since March, global average temperatures have fallen, but monthly averages have remained more than 1C above the 1850-1900 baseline through the first six months of the year.
What the chart shows is an aggressive warming trend, in almost a straight line since the mid-1970s, after removing annual natural variation due to events like El Nino. It shows the continued warming impact of greenhouse gases already in the atmosphere, and the impact of adding record amounts of additional carbon dioxide and other GHGs to the atmosphere each year. It puts into perspective recently stalled growth in annual emissions – a great achievement in itself, but only a first step in addressing the climate change problem.
Chart. Global average warming 1850-2016 (YTD), degrees Celsius, compared with 1850-1900 baseline