Global emissions: what fractions capture our attention?

The causes of climate change are often solely attributed to the combustion of fossil fuels and the release of carbon dioxide (CO2) in the atmosphere. Countries’ pledges to mitigate climate change often focus on the energy sector and how to reduce the use of fossil fuels. Within the energy sector, most of the focus is put on the power sector (electricity and heat generation). As a result, wind turbines and solar panels are very popular symbols of the action against climate change.

But what fraction of the problem can they truly help to solve?

To “quantify” the problem, it is essential to make sure that all anthropogenic emissions that contribute to warming the Earth are taken into account. In that respect, the so-called greenhouse gases (GHG) are all the by-products from our activities (not only CO2) that contribute to climate change (e.g. methane or nitrous oxide). These chemicals have the same ability to absorb and remits radiant energy from the Earth or also commonly known as the greenhouse effect [1].

However, depending on their chemical and physical properties and their atmospheric lifetime, each greenhouse gas will produce a different warming effect over a certain period. That is why a unified metric called the Global Warming Potential (GWP) has been proposed and calculated for each greenhouse gas with CO2 as a reference. In some ways, the GWP of a greenhouse gas can be viewed as its warming strength compared to CO2. For instance, methane (CH4) has a GWP of 28 over a period of 100 years [2]. It means that one tonne of CH4 released in the atmosphere has the same warming effect (or is equivalent) as 28 tonnes of CO2 over 100 years. A more formal way to write it is 1 tCH4= 28 tCO2e, e standing for “equivalent” and t for “tonne”.

The following table summarises the properties of the six greenhouse gases (or families of gases) resulting from anthropogenic emissions covered under the 1997 Kyoto Protocol [1]:

Once all the greenhouse gases are aggregated and counted with their respective warming potential, global anthropogenic emissions are estimated at approximately 50 GtCO2e per year [9] (“Gigatonnes of CO2 equivalent per year”). These emissions can be broken down by gas or by economic sector as per the two figures below (GHG emissions for the year 2014 [9]):

Note on the economic sectors:

·  Power Sector: emissions from electricity and heat generation (predominantly coal and gas).

·  Transportation: emissions from domestic travels within countries with cars, trucks, ships and planes.

·  Manufacturing/Construction: fossil fuels burn on site at facilities for energy.

·  Other Fuel Combustion: energy use in buildings (e.g. gas combustion for cooking or heating) and other sources of energy use.

·  Fugitive Emissions: mostly occur during fossil fuel extraction and processing.

·  Industrial Processes: emissions not associated with energy use (e.g. lime calcination for cement production).

·  Agriculture: mostly result from livestock farming, rice paddies, application of fertilisers and manure on soils (predominantly non-CO2 gases).

·  Waste: emissions from landfills, wastewater handling, waste incineration and other waste handling.

·  Land-Use Change and Forestry: emissions from conversion of forest, cropland, grassland and burning biomass for agriculture or other uses.

·  Bunker fuels: international transports (ships and planes) for which the emissions cannot be attributed to one specific country.

Since wind turbines and solar panels only produce electricity, they can only be potential solutions to one third of the problem. If transportation is included in the action, about half of the problem is still not addressed. Therefore, even though it is essential, action against climate should not be limited to the decarbonisation of the power sector and transportation, but it should also encompass two other large sectors that represent almost half of global GHG emissions: agriculture (associated with land-use change and forestry) and industry. These sectors cannot be overlooked if we want to have the best chances of success against climate change.

Action in these two sectors cannot be embodied by a technicist vision unlike in the power sector because, so far, no proven technologies deployable at a large-scale can significantly reduce these emissions. Given that the emissions from these sectors are closely linked to our meat consumption and our consumption of industrial products (e.g. cars, laptops, appliances, buildings), they can hardly be reduced in the time frame of the Paris Agreement if we do not accept to reduce our consumption. What a queasy feeling.

Elliot MARI

Energy Researcher at Sustainable Energy Network Solutions