Pious hopes

 It's grand that 84% of  CO2 emissions are covered by net-zero commitments.   But we all know about pious hopes for the future.  Yes, I am going to lose weight over the next year.  Yes, I am going to pay down my credit card.  Or perhaps the most famous, by St Augustine: Give me virtue but not yet.  For net-zero targets by 2050 to be credible, we need to see the steps to getting there.  Because the politicians and CEOs who make these grand gestures and pious pronouncements won't be around in 2050 to explain their negligence to angry electorates.  We require annual targets and quarterly emissions reports, just like we have for GDP.

To halve emissions by 2035, which is halfway to 2050, we must cut them by roughly 4.8% per year relative to the previous year.  So how easy is that to do?  

Well, in most countries, unless they have lots of hydro, emissions from electricity generation are ± 25 - 35% of total emissions.  If we replaced our coal power stations by wind, solar and storage over the next 14 years, that would reduce emissions by 2.1% a year. 

But is replacing our entire grid by 2035 feasible?  

New-build wind and solar are much cheaper than new-build coal.  Lazard estimates the cost of  new-build utility-scale solar at US$32.50/MWh, and of new-build wind at $38/MWh, which compares with the cost of new-build coal at $108.50/MWh and even the marginal cost of coal (= operating cost, i.e., excluding the cost of depreciation and interest payments) at $42/MWh.  On my calculations, a grid with 50% wind and 50% solar, plus 4 hrs of lithium-ion storage would produce electricity at $38/MWh which is comparable to the marginal cost of coal.  Is 4 hours of storage enough?  Research using actual weather data and demand (see 96% renewables possible;  A vexed question; and How much storage) suggests that a grid with 50% wind and solar can reliably supply 90% of demand with 4 hours of storage.  This is called "near firm" in the industry.  The remaining 10% will need to be supplied by hydro/gas peaking/power-to-gas.  And by 2035, power-to-gas (no net emissions) will be cost-effective, especially with a price on carbon, which is essential to push the transition and is also certain to occur.

EVs still remain pricey, but their costs continue to decline rapidly, and are likely to reach cost parity within a couple of years.  However, even if we ignore EVs, hybrids deliver a 40-45% cut in emissions, and now cost only a couple of thousand dollars more than old-fashioned petrol/diesel vehicles (ICEVs).  With an incentive of, say, $3000 for all cars with an electric motor (hybrids, PHEVs & EVs) new sales will rapidly transition away from ICEVs.   It will take another 10-15 years for the whole vehicle fleet to switch.   But by 2025 or so, it will be mostly EVs, because they'll have reached price parity then.  So we could reduce emissions from land transport by 90% by 2035.  This would reduce emissions by another 0.6% a year.

Iron and Steel makes up 7% of emissions, and in this sector we have already started to replace coal with hydrogen.  This process should be complete by 2035,  This would cut emissions by another 0.5% a year.   Agriculture contributes 18%, and it is plausible to argue that emissions here could be halved by 2035,  another 0.6% per annum.  Fugitive emissions (gas leaks)  contribute (at least) 5.8% to emissions; they can be eliminated by 2035 -- another 0.4% per annum. 

Together these add up to 4.4% a year, which will cut emissions by 47% by 2035.  

You can see from my back of the envelope analysis that many policies will have to be initiated to achieve a 50% cut by 2035.  Just promising net-zero by 2050 is not enough.  What will be the road map?  How fast will we drive?  How rapidly will emissions decline each year?  Without these details, net-zero proclamations are just greenwashing.   And as long as countries continue to subsidise fossil fuels and refuse to impose a price on carbon, their pious statements of future virtue have no credibility.

Note that gas is twice as expensive outside the USA, making it as expensive as coal.