Just a quick post to highlight that – according to the UK Met Office – 2015 is likely to be 1oC above pre-industrial – well, 1oC above the 1850 to 1900 average. If you think that we should have a target of staying below 2oC, then this is something of a milestone; we’re halfway there. Or, are we?
Well, it depends on how you consider this. It’s taken us about 160 years to warm by about 1oC. This is associated with emissions of about 550GtC (550 billion tonnes of carbon, or ~2000 billion tonnes of CO2). Current emissions are around 10GtC/year. If we continue emitting as we are, we will double our cumulative emissions in about 50 years. If we continue to increase our emissions, it will be even sooner (H/T Aaron on Twitter). If we want to have a >66% chance of staying below 2oC, then we have a carbon budget of only about 250GtC (850GtCO2) from 2015, which we could reach in only 25 years at current emissions.
So, we might be halfway to 2oC in terms of temperature, but we’re much more than halfway there in terms of time. Of course, whether or not we should actually have a 2oC target, and an associated carbon budget, is a complex issue, but that doesn’t change that if we carry on as we are, the second 1oC will probably happen much faster the first.
[Update: Here’s the Met Office press release which I tried, and failed, to find before writing this – mainly because I looked at their blog, and didn’t think of looking for a press release.]