According to Kevin Anderson, emissions per adult in the UK are at 7 tonnes of CO2 per year (2019). Around 4.5 tonnes (~60%) of energy emissions arose from the direct use of energy by individuals:

• 2 tonnes for private car travel
• 1.5 tonnes domestic heating (including hot water and cooking)
• 0.5 tonnes non-business aviation
• 0.5 tonnes domestic electricity use.

What would it look like for the average UK citizen to decarbonize by 2040? First, you'd want to identify the low-hanging fruit. There is likely a "floor" to emissions reductions, beyond which would be very challenging.

Let's assume that the 0.5 tonnes from flying is immediately eliminated. No more airline industry, starting today. What would further reductions look like?

2 tonnes of CO2 for car travel, if driven in a car that achieves 30 miles/gallon, equals 6,750miles per year. Right off the bat, understand that the average person will not be able to drive more than that, per year, in an internal combustion vehicle, ever again. In fact, the reduction in auto use has to decrease much quicker, because we can reasonably assume that, given the choice between driving and heating/cooking, people will give up the car before giving up the kettle. That means that your 30 mile/gallon car has to be scrapped by around the year 2024. There's no room in the budget to keep driving four years from today. Perhaps you can replace it with a new electric car, but if we account for the embodied energy in the manufacture of the car (contributing around 4 tonnes of CO2), then simply owning the car will have blown your per-capita budget going out to 2040...

Once the car is gone in 2024, it's difficult to see how to reduce emissions further, in the home. If you can cut the heating and cooking energy in half (for instance, by installing massive amounts of insulation, being stingy with the thermostat, living with more friends, or downsizing your house), then that only buys you another year in the budget.

If, by some miracle, the entire electric grid in the UK were decarbonized by 2030, it still wouldn't be enough to stay within the budget, as long as heating and cooking are not also electrified by then. And, given the enormous task of replacing all of the existing fossil-fuel-powered infrastructure with electric equivalents, the replacement alone would likely bust the carbon budget for 2040.

Jean-Marc Jancovici has very comprehensively outlined the energy trap that we're in, and the specific challenges of decarbonizing the entire world while also trying to grow the economy, and deal with declining energy density.

Something in the system has to give. At the moment, when the IEA anticipates no actual emission reductions this decade, it's absurd to think that the 2040 target will be met. Even if an individual wanted to voluntarily decarbonize, it's plain to see how difficult the task would be, as long as the grid depends on carbon-emitting sources.

Unfortunately, we've waited too long, and there's too much inertia in the system to avoid breaching +2ºC of warming. There's likely already at least 2.3º-2.8º baked into the system. We're at the point now where we need to make drastic, immediate reductions, even as we fail to adhere to the Paris Agreement.

If we take the carbon budget and 2040 target seriously, then we're all looking at very difficult choices affecting quality of life -- starting today and continuing through the next several decades.

If we don't take the budget seriously, and believe we can kick the can down the road, to 2039 or 2050, then we'd better start thinking about what 3º-5º or warming looks like.

January 11, 2021