But let’s stick to the Montreal spirit and call it a challenge instead of a problem.

First of all it is thanks to the Montreal Protocol that well into the 21^st century we can still enjoy life on a green planet, including the benefits of cropland agriculture and outdoor walks in that now fast-approaching spring sunshine. Without doubt it has been the most successful environmental treaty and an important showcase that the geopolitical route can work.

Secondly the Montreal Protocol has not only helped preserve the ozone layer, it has also helped the climate. Under the ozone treaty the production of CFC gases has been strongly diminished – and these CFCs happen to also be (very powerful) greenhouse gases.

Less CFC therefore means less climate forcing – unless of course the substitute would be worse…

A ‘new’ GHG – in sheep’s clothing

As cooling agents [guess why we will be needing these] CFCs are currently replaced by HFCs, hydrofluorocarbons, which contain hydrogen instead of chlorine. For the ozone layer that makes the big difference. To assess the potential as a greenhouse gas however it is not so much the chemical building blocks, but rather the size and shape of a molecule, that determine its climate warming potential.

And that means CFCs, HCFCs and HFCs are all about equally bad*. Fortunately though the Montreal Protocol has not simply led to a transition from the one polluting fluorocarbon to the other. Compared to the 70s and 80s mainly the combined fluorocarbon emissions have sharply declined – and the world is now at a point where we emit only comparatively small amounts of any of the harmful gases.

[*) Yes, but no. HFCs are a group of different gases. These all warm, but have greatly differing atmospheric lifetimes. Some stay up for 15 years, others for less than two months, having a far smaller cumulative warming effect. That’s were the actual HFC policy focus should lie – a new Science publication states.]

HFC emission trajectory

But while CFC and HCFC emissions are still declining, HFCs are on the rise. And that rise is troublesome – an international research group led by the Dutch National Institute for Public Health and the Environment (RIVM) writes in Science – especially since the projected HFC increase is allowed by the UN’s ozone protection treaty.

HFCs are recognised as greenhouse gases by the Kyoto Protocol, but thus far this climate treaty has no successor – which means there are only a handful of hardly-ambitious emission targets reaching no further than the current year of 2012 – and only for a set of industrialised countries.

Saving stratosphere worked well – why no include troposphere while at it

The Science authors therefore suggest a pragmatic approach: including HFC control under future updates of the Montreal Protocol. This has been suggested before – and could according to some calculations save the atmosphere up to 100 gigatonnes worth of CO2 equivalents up to the year 2050 [educated guesswork, as no one is really sure just how much we would want to emit these gases in the first place – see different trajectories in above graph].

As HFC mitigation does nothing to further speed up ozone recovery, including it under the Montreal Protocol officially makes little sense – but at least it could work. And unfortunately thus far general success is the main shortcoming of the alternative, the UNFCCC route – the one that was actually designed to save the (tropospheric) climate.

Meanwhile though the ozone crisis is far from over. And in part that could actually be due to tropospheric warming. So in the end it does make sense – let the Montreal Protocol save the climate, in order to save the ozone layer. Everyone happy.

© Rolf Schuttenhelm | www.bitsofscience.org