The 2°C Target

In a report by the Guardian in July 2013, Swedish scientists have asserted that limiting carbon emissions to achieve no more than 2 °C rise in global temperature, would not be enough to stop potential problems such as biodiversity impacts, sea-level rise, or halt the acidification of the oceans.

Some of us may also be familiar with the 2 °C target that has often been cited by governments in UNFCCC negotiations. This leads one to wonder why 2 °C? 

Building on the work of the German Advisory Council on Global Change (WBGU) in 1995, Bruckner and Schellnhuber (1999) suggested that to prevent shut-down of the North Atlantic thermohaline circulation (which plays an important role in bringing heat to the polar regions), global mean temperature change should be kept to less than 2 °C relative to the pre-industrial level. 

Illustration by Wikipedia

In light of this background, there may be some basis to the scientists claim that more ambitious targets may be needed, since there are many potential impacts apart from polar ice melt that could arise due to global warming. 

This thus leads us to the next question. How far down are we in terms of mankind's fossil fuel emissions with respect to the 2°C Target ? 

The 5th assessment report (AR5) of the IPCC calculated that the combustion of fossil fuels (coal, gas, oil, and gas flaring) and the production of cement have resulted in 365 GtC being released to the atmosphere between the period of 1750 to 2011. Cement production constitutes about 8 GtC to this value. 

The other major contribution comes form land use change activities, mainly deforestation, which released an additional 180GtC . 

The combined fossil fuel and land use change emissions make up the bulk of anthropogenic carbon emissions. 531 GtC of anthropogenic carbon was emitted by 2011.

For a more than 50% probability of limiting warming to less than 2°C (since the period of 1861–1880), IPCC thinks that CO2 emissions from all anthropogenic sources will need to be limited to 840 GtC. 

The video below from "Shrink that footprint" provides a simple illustration of what this may all mean. 

We are indeed nearing the upper limits of the 2 °C guard-rail. Fossil fuel use, being the major contributor, would be a key area that would deserve our attention in our bid to better understand how measures can be taken to minimise its impact on global warming.