The 2C temperature limit: A "defense line," not a "guard rail"

Just in case you were wondering, a key “Structured Expert Dialogue” between IPCC scientists and UNFCCC negotiators has just released its technical summary.  And, happily, it has been digested by the Climate Analytics team into this short, clear overview.

This SED is news because it essentially confirms the arguments that the Small Island Developing States and the Least Developed Countries have been making for years, that 2°C warming limit is too high.  And that it must not be crossed.  To wit:

“We are therefore of the view that Parties would profit from restating the long-term global goal as a ‘defence line’ or ‘buffer zone’, instead of a ‘guardrail’ up to which all would be safe. This new understanding would then probably favor emission pathways that will limit warming to a range of temperatures below 2 °C. In the very near term, such aspirations would keep open as long as possible the option of a warming limit of 1.5°C, and would avoid embarking on a pathway that unnecessarily excludes a warming limit below 2°C.”

This clear statement is hugely relevant to the ongoing negotiations, which are stretching towards a possible breakthrough in Paris later this year.  The problem is that, while Paris is likely to be an official success, it’s not at all clear that it’s going to set us up for the extremely challenging transition that will be necessary if we’re going to successfully “defend” the 2°C line. The good news is that the assembled experts also concluded that the stricter 1.5°C temperature goal is still within reach, just.  It’s going to take everything to reach it.


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