Thursday, April 22, 2021

If we halve emissions we halve warming

 I had a Twitter exchange with Michael E Mann, the climatologist, about whether if we (the world) cut emissions by half over the next decade, whether the global temperature increase, currently 0.2 degrees C per decade, would fall. 

Me: Hi. A quick question. If we cut emissions by 50% by 2030, will the rate of increase in global temps start to fall, so the decadal increase in the 2030s is 0.1 degrees C as opposed to the current 0.2? And if we halve emissions again, will the increase fall again?

Michael E Mann: Roughly yes. The transient warming response is roughly linear in the incremental emissions, so cut emissions in half, you cut the warming in half.

Me:Thank you. That is excellent news. It's better than I've been thinking (I thought temps would go on rising at 0.2 degrees until emissions cease). It implies that we should front-load emissions cuts, doesn't it?

Michael E Mann: Yes.

If we cut emissions by half, the transient rise (i.e., on a decade-by-decade basis, as opposed to the longer-term rise over centuries) will also halve. In other words, the temperature rise in the 2030s could fall to 0.1 degree if we halved emissions. And if we halve emissions again, the decade-by-decade temperature increases will halve again, getting close to zero.

This is incredibly good news. We are not helpless to avert disastrous climate change. Because together, globally, emissions from electricity generation and land transport make up ~50% of total emissions, and renewables are cheaper than coal in electricity generation, while battery pack costs will reach $100 by late 2022, allowing EVs to have the same 'sticker price' as petrol/diesel cars. Indeed, The Driven has a report that BYD, China's largest EV manufacturer, will start selling an EV in Australia with a drive-away price of A$35,000 as of next year.

And a national fleet of EVs will be very useful for stabilising the grid, because even small ones store about 2 days of an average household's electricity use, while the grander EVs store 4 days. Since 'near firm' electricity generation requires just four hours of storage, an electric fleet attached to the grid will provide more than enough backup to stabilise the grid in all but the most extreme circumstances. EVs can be used to stabilise the grid either passively or actively. Passive stabilisation is where EVs don't charge when demand on the grid is high, but do when demand is low. Active stabilisation is when EVs put some of their stored power back into the grid when demand is high/supply low. Of course, charging pricing regimes will have to be revised, to reward owners for allowing some of their stored electricity to be used by the grid.

There are still ill-informed (or venal) troglodytes out there who oppose these shifts. But they are inevitable, because of the technological advances and cost declines in renewables and batteries. Inevitable. And the spread of carbon prices as the EU insists its trading partners introduce their own or face carbon tariffs on their exports to the EU will only accelerate these inexorable and unavoidable trends.

Source: NOAA

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