This is by far the best depiction I have yet seen as to what has actually been occurring with regard to global warming over the last 160 years or so. It is perfectly and undeniably clear that global temperatures have overall been rising consistently but at varying rates, in bands of time, over that period.
The colour scale on the right, marked off in 20 year blocks of linear time, intentionally has no scalar relation to the graph. That much should be obvious. It is there purely so that we can view bands of time by their colour. The colour is meaningless but it is clear that there are bands of colour (even though the colours change gradually over time) in Mauves, Blue-Greens and Yellows.
Note that these are monthly global average temperatures and the zero line represents the baseline pre-industrial level. It is not 0°C. It is whatever the calculated global average temperature was prior to the start of the industrial revolution. The scale on the left then shows temperatures in °C above or below that baseline. Actual temperatures are immaterial. It is the deviation from the ‘normal’ baseline, the zero baseline, that we are interested in.
Note also, that this is a time-series graph, a continuous line, starting from some undecipherable (to my aging eyes) point in 1850 right through to March 2016. For convenience of viewing, the line goes from left to right (Jan to Dec), exits at the right hand side in mid-Dec and wraps around back to the left hand side still in mid-Dec (as you would expect).
There, that’s all of the mystery taken out of the thing now. Everybody should be able to understand what is going on (even those dim climate deniers). Now, let’s take a look at what it is telling us.
The sections of the line (remember it is continuous and the colour of the line changes, as time goes on, in accordance with the colour/time scale on the right) that are coloured in Mauves, indicate the temperature movements during the earlier part of the period from 1850 to around 1900. It shows that there was considerable variation in temperature back then with some of the readings indicating that there were times when a drop in temperature to as low as -0.5°C below pre-industrial levels. A careful look however, will reveal that there are about as many monthly readings above the baseline (zero level) as below it. Indeed there are some readings from these years that are as high as 0.7°C above baseline. I would suggest that this is the sort of variation that could be expected to be seen in the second half of the nineteenth century because the large scale industrial activity of the twentieth century had not yet begun and the global population was still at ‘normal’ levels ie. below 2 billion.
The line colour variations from blues to greens cover a longer 80 year period between 1900 and 1980 and it is obvious that the readings are still quite variable but there are many more of them above the baseline than below it and the blue-green band does generally appear to sit above the mauve band. This indicates a slight rise in average temperatures during this period over the previous one.
The yellow coloured portions of the line cover a much smaller timeframe of just 35 years from 1980 to today. There is a much wider spread of these fewer readings (which is remarkable in itself, because it shows that something is happening, relatively quickly), pretty much all of them being both above the baseline and also above the blue-green band. This indicates a much more volatile period of temperature change where the majority of the readings are higher than either of the two earlier colour bands. What is more, the latest readings (the last few years) appear to be breaking away to form a new band by themselves that is way above the average for even the short yellow period …and that is very worrying (not that there is anything we can do about it).
I think we are entering a new period of runaway global temperature rises that could well mark the end of our journey on Earth. And it is all our own fault.
I am equally sure that there will be those who say “Ah yes, but there has always been variation in global climate. It naturally goes up and down”.
True, but those natural variations are gradual. Any movement upward or downward taking place over centuries or millennia, not 30-50 years. Believe me, this is something different.
Oh, and by the way, remember the COP21 Paris agreement with its (what did they call it? Aspirational?) level of 1.5°C? Well take a look at the chart. We have already as good as reached that, unless my spectacles are a little misted up. And their 2°C ceiling? Give it another five years and even that will be history. Then sit back and watch the fireworks show begin.
Added after publishing.
If straight lines aren’t your thing, try this alternative .gif of the same data The ending is quite striking. Thanks to foodnstuff for the link.