The Albanese government, in line with the UN agreements on climate change, aims to reduce greenhouse gas emissions by 43% from 2005 levels by 2030. Without judging or questioning, this post just aims to determine the impact this can have on global warming by itself.
According to the Australian Bureau of Statistics, Australia’s net greenhouse gas emissions in 2005 were 559.1 Mt CO2e (million tonnes CO2 equivalent). So, by 2030 we have to reduce emissions to 318.7 Mt.
By 2019, emissions fell by 26.6Mt to 532.5 Mt Co2e, leaving a 214 Mt CO2e gap to fill.
We took three approaches: First, using two models that are the products of computer simulations and PhDs and lots of government-funded research; Second, a rough estimate based on an IPCC chart; and Third, by calculating the impact based on “known” variables.
We’ll start with the summarized results:
43% reduction in emissions could reduce global warming by 0.008°C over 70 years
And let’s not forget, 0.008 degrees isn’t nothing. That’s how much the temperature changes every 35 seconds in Melbourne on average (10 degrees per day).
It sounds minuscule and irrelevant, but it should stave off this climate emergency.
Here’s the summary:
If you weren’t aware we are in a climate emergency, I suggest you enrol in the Oxford Climate Emergency Programme for a six-week £1900 education.
The rest is just details on methodology so you know we’re not making this up.
Results from climate models
We looked at two models:
1. UCAR, funded by the (US) National Center for Climate Research, Simple Model
We compared the base case of 10.4 Gt Carbon (approx 50,000 MtCo2e) to the case with a 0.2 Gt Carbon (approx 1,000 MtCo2e) permanent emissions reduction from 2015 and used 20% of the difference to simulate a 214 Mt Co2e reduction, and 50% of the difference to simulate net zero (from 2015).
The results indicate that Australia could reduce global warming by 0.006°C by 2100 with a 43% reduction, or 0.01°C with net zero, by 2100 if we started immediately.
2. En-Roads, in conjunction with MIT, Climate Simulator
This simulator has a built-in base case, so we just adjusted the coal usage to reduce 2040 emissions by 240MT CO2e to simulate the 214Mt reduction by 2030 and adjusted the coal usage further to reduce 2040 emissions by 540 Mt CO2e to simulate the 532.5Mt reduction required for Net Zero by 2040. The caveat here is that the model assumes that these reductions continue to grow and eventually achieve a 1000MtCO2e reduction by 2100. So the results will slightly exaggerate the real impact of these greenhouse gas emissions policies.
The results indicate that Australia could reduce global warming by 0.01°C by 2100 with a 43% reduction, and by 0.02°C by achieving Net Zero by 2040, with the caveat explained above.
Estimates based on predicted outcomes
This is probably the roughest “calculation” we use. Just going from a simple chart from the IPCC we can see that there are differences in 2050, 2075, and 2100 of 0.4°C, 1.0°C, and 2.2°C respectively. in the two scenarios: Not cuts and substantial cuts in CO2 emissions.
Global greenhouse gas emissions in 2019 were 52.4 Gt Co2e, making Australia’s 0.532 contributions 1% of global emissions.
Assuming substantial cuts are net zero by 2050, a 1% reduction (i.e. Australia achieving net zero by 2050) would be a 0.02°C difference in global warming by 2100. A 43% reduction by 2030 would have a .01°C impact over 70 years. For 2050 and 2075, these would be 0.002 and 0.005 for the net zero scenario.
Calculation based on estimated variables
When facing a challenge such as calculating the impact of Australia’s climate policies on global warming, the best approach is to ask someone who knows what they are talking about. Here’s a response to my question on Quora asking how much a 1000Mt CO2e reduction would have on global warming:
The observations by Feldman et al (2015) show that CO2 has a forcing of about 0.01 W/m² per 1ppmv which is a very small quantity indeed and which Feldman acknowledges is only 10% of the trend in radiative forcing at the surface. The result I got was 0.00034°C of global warming per Gt (i.e. ‘billion tons’). Assuming the observations by Feldman are correct, we obtain the following logical result:
- Relationship between CO2’s forcing and its ppmv = 0.01 W/m² per 1ppmv
- Relationship between CO2 in ppmv and Gts = 1ppmv per 7.8 Gts
- Thus relationship between CO2’s forcing and its Gts = 0.01 W/m² per 7.8 Gts
- Thus the amount of forcing per Gt from CO2 = 0.00128 W/m² (i.e. 0.01/7.8)
- Thus amount of global warming from 0.00128 W/m² using S-B law = 0.00034°C
Based on this calculation, a 214Mt CO2e reduction from 2030 (the 43% target) would reduce global warming by 0.005°C and a 532 Mt CO2e reduction from 2040 (“Net Zero”) would reduce global warming by 0.011°C.
