What really matters is not when we get to 'net-zero', but the path we take to get there
1.5°C: science says no. The amount of emissions from now until 'net-zero' will determine exactly how f*cked we are and the magnitude of the mess we need to clean up
What is often lost in the net-zero commitments being announced on a near daily basis is the emission journey we will take to reach that point. This is especially concerning with 2040, 2050 and 2060 goals which, for all intents and purposes, abdicates responsibility to someone else in the future and speaks nothing to what we are going to do in the short-term. This conversation however cannot be had without first understanding the concept of a carbon budget.
A carbon budget is the cumulative amount of carbon dioxide (CO2) emissions permitted over a period of time to keep within a certain temperature threshold. Scientists have found a remarkable correlation between temperature and the concentration of carbon dioxide in the atmosphere. That’s to say, when carbon dioxide concentration goes up, temperature does too. The concentration of carbon dioxide in the atmopshere - 417.5 parts of CO2 per million (ppm) and rising - is at its highest point for 800,000 years (or something more relateable, all of human history). Yes, you read that right.
Now contrary to the magic money tree (developed world) governments have found with their recent budgets, the carbon budget is finite. No extensions. No bailout (at least not a cheap one but we’ll get to that). The Intergovernmental Panel on Climate Change’s (IPCC’s) Special Report on global warming of 1.5°C essentially concluded that we’re flirting with humanitarian and ecological disaster with temperatures above 1.5°C, so that’s where we will focus our carbon budgetary attention. The IPCC calculated that as of 01/01/2018, the remaining carbon budget to give us a likely chance of limiting warming to 1.5°C above pre-industrial levels was 420 billion tonnes of CO2 (GtCO2). At a carbon emissions run rate of 36.6 GtCO2 in 2018, 36.8 GtCO2 in 2019 and 34.1 GtCO2 in 2020, our global carbon budget has dwindled to 312.5 GtCO2 as of the start of 2021.
Now that’s not to say the world ends after we cross this threshold - which we probably will some time between 2030-2035, but it certainly doesn’t get better. So why does this dwindling carbon budget matter. Imagine a paddling pool with 312.5 litres of water. Every purchasing or investment decision we make from today will impact the volume of water left in our pool. The recent furor over a new Cumbrian coal mine in north-west England is a perfect example. The UK government has issued a license for the mine to operate until 2049, giving it a whole year to clean up the 30 years of emissions it leaves behind before the UK’s 2050 net-zero commitment. The magnitude of the mess it’s producing in the meantime? Just another 250 million tonnes of CO2, or 0.25 litres of water thrown out of our global carbon budget paddling pool.
This is why the arbitrary technicality of net-zero by X date is redundant while we neglect the science of cumulative emissions and don’t live with a spirit consistent with a net-zero world. We can’t just turn off the taps in 2050 and expect the emissions we produced up to that point to no longer count. The climate unfortunately doesn’t work like that. For those wondering where the ‘net-zero by 2050’ sentiment even arose, it’s founded in not science but rather political comprimise.
Climate negotiations over the last three decades have been characterised by what one can only describe as kicking the can down the road. This has led to the necessity for climate scientists to rewrite and extend their models to delay and deliver future emission mitigation. For example, the fourth assessment of the IPCC published in 2007 stated that emissions must peak by 2015 to stay within 2°C of warming; yet the fifth IPCC report from 2014 referred to 2030 emissions levels higher than in 2015 that were still compatible with a 2°C limit, albeit with annual emissions-reduction rates of 6%. This isn’t so much the climate science being wrong but more a wholesale shifting of the climate goal posts.
And welcome to our present reality. The IPCC today speaks in terms of a ‘temporary temperature overshoot’ before temperatures return to ‘safe levels’ through the monumental project which will be ‘negative emissions’ or carbon dioxide removal (CDR). Here we arrive at the carbon budget bailout to repay our carbon debt. This hosepipe to refill the paddling pool will definitely not come cheap - we will need to build industries on the scale of those which got us in this mess in the first place.
Exactly how big will depend on the global emissions we produce up to the point we reach ‘net-zero’. Every additional internal-combustion engine vehicle, coal mine, gas boiler system and steel plant will need to be compensated by increased carbon stored in soils, direct air capture facilities, trees and enhanced rock weathering infrastructure. It is nowhere near sufficient to just turn off the emission taps at the last minute and pretend job done. Cumulative emissions matter. The sooner governments, businesses and humanity start operating in the spirit of net-zero, the more chance we have of actually achieving it with a hope of averting climate catastrophe.
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