Black Carbon – a glimmer of hope?

Like most people, you’ve probably heard about it, but are not entirely sure what it is. You are not alone.

While eminent scientists have been sounding the alarm over Black Carbon as a powerful climate-forcing emission for more than a decade, only recently has the world woken up to the scale of its devastating impacts, backed up by an increasing scientific consensus that Black Carbon is the emission with the second highest contribution to global warming after CO2. It was discussed in the International Panel on Climate Change’s (IPCC) fourth Assessment Report for its damaging effects as a powerful climate forcer. Since then, the most recent studies suggest that Black Carbon, in isolation from other components of ‘soot’, may well be responsible for up to 40% of the net warming the planet is experiencing.

So what it is Black Carbon? The first thing to realise is that it is not a greenhouse gas. It is an aerosol particle released during the combustion of fossil fuels and biomass, a component of particulate matter (colloquially known as ‘soot’).

We are all weather-makers: aside from our CO2 footprint, if we burn wood, organic waste or fossil fuel in our home or garden, chances are we will be emitting Black Carbon. The climate-forcing effects of this are two-fold: the particles absorb heat while airborne, and also significantly reduce albedo (reflectivity) when landing on snow or other light-reflecting surfaces.

There are also significant health benefits of controlling Black Carbon – the smallest particles, including those emitted from diesel exhaust, are capable of entering the human respiratory system.

There may well be a need to address Black Carbon specifically rather than merely relying on existing laws that control particulate matter in general. While Black Carbon is a subset of particulate matter, (which includes things like soot and dust) the need to target it directly for purposes of monitoring, and possibly control, includes such factors as the severity of Black Carbon as a climate forcer, the fact that different sources of particulate will emit different proportions of black carbon in different-sized particles, and the fact that other components of particulate emissions can have cooling effects of scattering radiation, thereby ‘masking’ some of the warming caused by Black Carbon and greenhouse gases. ClientEarth has begun to track the latest Black Carbon science and will be examining its regulatory implications within the context of the matrix of EU laws.

We are excited by Black Carbon. It offers a glimmer of hope for two reasons. Firstly, unlike CO2, Black Carbon only remains in the atmosphere for a matter of weeks, meaning that any reductions can make an immediate dent in climate forcing, buying the planet more time before the passing of potentially irreversible tipping points in the earth’s thermostat. Secondly, also unlike CO2, many technologies and techniques already exist to eliminate or reduce Black Carbon. These include fitting diesel particulate filters to all on- and off-road engines, improved particulate filters on stationary installations to ensure that fine and ultra-fine Black Carbon particles are captured, reducing land burning, reducing the use of certain fuel types and establishing alternative designs for cooking and heating stoves. ClientEarth understands that technology for monitoring Black Carbon emissions is already commercially available  in Europe.

Globally, the regions of the world that emit the largest amounts of Black Carbon include South East Asia and the Americas, where domestic sources such as burning wood and other biomass as well as highly inefficient fossil fuel power generation contribute large quantities.

And while European emissions of Black Carbon have been reduced over the last 50 years, there is more that Europe can and must do to control its Black Carbon emissions.

Black Carbon can travel for very long distances  and has regional as well as global climate impacts – including the acceleration of the melting of the arctic and alteration of rain cycles. The proximity of European nations to the arctic region adds weight to our responsibility to urgently adopt effective strategies to eliminate remaining sources of Black Carbon.

Regulation of Black Carbon is now at its launching point. Last year the proposed US climate legislation (Waxman Markey Bill) contained measures to monitor and reduce Black Carbon. Black Carbon also appears in the Senate version of the Bill, (Kerry-Boxer Bill) and it is therefore likely that any climate legislation passed by Congress will give rise to monitoring and regulation of Black Carbon.

My personal reaction to Black Carbon is mixed.  It certainly offers a very real glimmer of hope, yet the lesson of the Black Carbon story is also sobering – science continues to catch up to the full scale, gravity, and complexities of anthropogenic climate change. This underscores yet again the inadequacy, and the arrogance, of climate policies predicated upon dicey odds for limiting the damage to 2 degrees of warming.

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