The linked article is entitled: "Climate inertia".
https://ourchangingclimate.wordpress.com/2016/08/09/climate-inertia/
Extract: "The climate system also has a tremendous amount of inertia built in. And like with the supertanker, this means that early action is required if we want to change the climate’s course. This inertia is a crucial aspect of the climate system, both scientifically but also societally – but in the latter realm it’s a very underappreciated aspect. Just do a mental check: when did you last hear or read about the climate’s inertia in mainstream media or from politicians?"
As a follow-up on the article about Climate Inertia, decision makers are also using the logarithmic nature of climate sensitivity to CO2 concentrations (see attached plot) to hide the fact that even when making the conservative assumption that ECS = 3C (it may be as high as 4.6C), that CO2 is the only GHG worth talking about (it is not), and that we are currently only at a GMSTA of 1.0C (rather than the 1.25C that we actually are at) we are already more than committed to passing a Global Mean Surface Temperature Anomaly increase of 1.5C.
http://www.bitsofscience.org/do-the-math-climate-sensitivity-logarithmic-1-5-degrees-400-ppm-7237/Extract: "According to ‘conventional climate science’ the currently already emitted amount of CO2 (404 ppm) leads to a committed warming of 1.56 degrees Celsius. To keep ‘the promise of Paris’ – the CO2 concentration must go down, down to below 400 ppm on the decades timescale, and (yes, Hansen was right there too) closer to 350 ppm to also prevent ‘the slow climate catastrophe’.
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Let’s call this piece a short supplement on our ‘Real’ Global Temperature Trend series. Because it’s too important – and everyone seems to have overlooked something that is politically quite relevant: if you assume Equilibrium Climate Sensitivity is 3 degrees (which is IPCC’s median value – and seems a good yet slightly conservative number judging by our expert survey) at the current CO2 concentration of 404 ppm we already have a committed warming (‘Real’ Global Temperature) of 1.56 degrees Celsius.
The reason is a rather odd characteristic of greenhouse gases: they warm the climate logarithmically. That means linear growth of temperature is reached after exponential growth of the concentration of heat-absorbing gases in the atmosphere. Therefore climate sensitivity is expressed as a certain amount of warming (probably close to/somewhat above 3 degrees [second link to our expert survey – give it a read]) for every doubling of the CO2 concentration. You get that amount of warming from 280 (pre-industrial CO2) to 560 – and again from 560 to 1120 ppm of CO2.
We actually knew this (no proof but our word) when we made our special climate inertia global temperature graph (that we think still offers a nice visualisation and proper indication of committed warming (at different climate inertia time scales) at various CO2 levels/year!), but chose to ignore it – and drew a linear line instead, between 280 and (3 degrees warming at) 560 ppm. ‘Because how big can the difference be,’ if you zoom out a bit.
Well, that was a bit silly of us. We had a little chat with atmospheric scientist Bart Verheggen (please also read his special blog post about climate inertia!), who pointed out that –because at 400 ppm we are close to the middle between 280 and 560!– the difference between a logarithmic line and a linear one is now relatively large: not 43% of climate sensitivity, but 51% – a difference between 1.29 and 1.53 degrees.
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Shown above is a basic graph – to help you get an understanding of a logarithmic connection. On x=1, you could visualise preindustrial CO2 (280 ppm). x=2 would be 560 ppm and 3 degrees warming. We’re somewhere in the middle between those two dots, which is why a linear line between x=1 and x=2 would now lead to underestimation of warming (and why 400 ppm equals a 1.5 degrees temperature rise). But if you would look beyond 560 ppm, the fact that there’s a logarithmic connection is actually good news, wouldn’t you say? You’d have to keep doubling the CO2 concentration for every 3 degrees of further temperature rise (please let’s not)."
