Decarbonizing the global economy – our finite carbon budget
Our atmosphere has a finite volume with an ‘effective thickness’ (sometimes referred to as the ‘pressure scale height’) of less than 10km, equivalent to a mere 0.15% of the radius of the earth. And into this we emit a net 20 Gigatonnes (20 Billion metric tons) of greenhouse gases (CO2, Methane, NOx, SOx etc.) each year, the balance absorbed by various carbon sinks such as vegetation, soils and the ocean. This growing amount of heat trapping gases in our finite atmosphere will continue to warm the planet [1].
In their ‘IPCC SR1.5’ report [1] issued in October 2018 the Intergovernmental Panel on Climate Change described in alarming detail what this means. Simplistically put, as we move towards a global average temperature increase of 1.5 deg C (compared with the consensus pre-industrial global average) we will witness increasing intensity of extreme events from storms to flooding, to drought and heatwave, resulting in human distress and economic hardship that may result in mass migration of climate refugees. As we approach 2 deg C of average warming, the effects will likely become disproportionately greater due to ‘impact cascades’ – events triggered by a combination of factors. Overshooting 2 deg C will propel us into uncharted territory, triggering tipping points that will unleash new levels of planetary distress. The IPCC’s ‘Summary for Policymakers’ gives an ominous overview and, complementing this, Carbon Brief has prepared an excellent – and equally alarming - interactive graphical summary [2].
Science indicates that if we are to avoid surging past the mark of 1.5 deg C above pre-industrial temperatures, we can emit no more than around 500 Gt CO2eq (gross) of additional heat trapping gases. This is our carbon budget [3,4} for 1.5 deg C and at present rates, we have little more than ten years until we reach that value. Each subsequent temperature threshold has a corresponding volume of CO2eq gases that we can emit into our atmosphere.
This is the driver of our urgent quest to decarbonize our global economy and why we must introduce low and zero carbon sources of power in all the sectors of our economy from power generation to mobility to industrial production. Many governments and corporations have committed to achieving ‘net-zero’ in economies and operations. Essentially this means that current GHG emissions from combustion of hydrocarbons must be eliminated by introducing technologies that do not rely on carbon intensive fuels.
[1] IPCC - Special Report on Global Warming of 1.5 C
[2] Carbon Brief - Interactive Report on IPCC SR 1.5
[3]] Carbon Tracker - Explaining the Carbon Budget. See also Carbon Tracker’s detailed Infographic resource page
[4] Why the IPCC [SR] 1.5 C Report Expanded the Carbon Budget - Zeke Hausfather - article in Carbon Brief