Zero emissions would quickly stabilise climate

 It had been thought that the lags in climate change were decades long, so that even if we reached zero emissions, global temperatures would keep on rising for decades afterwards.  New research suggests that may not be true. 

From  CleanTechnica

Rising seas, ocean acidification, melting ice caps, raging forest fires, melting tundra — everywhere you look, the news about climate change and the effects of a warming planet is bad. The world’s nations are continuing to spew billions of tons of carbon dioxide and methane into the atmosphere despite all their happy talk about meeting the “spirit” of the accords they signed in Paris in 2015. Is there no respite from the dire news, no relief from the constant drumbeat of bad news and apocalyptic projections?

The conventional wisdom among climate scientists has long been that if we stopped all carbon emissions today, the climate would continue to warm for decades or even centuries. Think of climate change as a really big oil tanker. Even after the engines are shut down, its forward progress continues for miles and miles. That has led many people to throw up their hands in despair and choosing to continue doing what they have always done because if we are doomed, at least let’s have some fun while we still can. It’s like the band playing Nearer My God To Thee on the fantail of the Titanic as it slipped beneath the waves but if the message is that there is no hope, why not?

Writing for Inside Climate News, Bob Berwyn reports on a recent conversation he had with Joeri Rogelj of Imperial College London. Rogelj is not some crackpot on the lunatic fringe of climate science. He is the lead author of the next major climate assessment by the Intergovernmental Panel on Climate Change.

“It is our best understanding that, if we bring down CO2 to net zero, the warming will level off. The climate will stabilize within a decade or two,” Rogelj told Berwyn. “There will be very little to no additional warming. Our best estimate is zero.” He adds the notion that decades or even centuries of additional warming are already baked into the system as suggested by previous IPCC reports was based on an “unfortunate misunderstanding of experiments done with climate models that never assumed zero emissions.”

Those models assumed that concentrations of greenhouse gases in the atmosphere would remain constant and it would take centuries before they decline, Penn State climate scientist Michael Mann told 60 Minutes last October. At the time, Covering Climate Now reported the idea that global warming could stop relatively quickly after emissions go to zero was a “game-changing new scientific understanding.”

Mann told Scott Pelley of 60 Minutes, “This really is true. It’s a dramatic change in the paradigm that has been lost on many who cover this issue, perhaps because it hasn’t been well explained by the scientific community. It’s an important development that is still under-appreciated. It’s definitely the scientific consensus now that warming stabilizes quickly, within 10 years, of emissions going to zero,” he said.

He explained that climate research over the past decade has led scientists to revise their vision of the climate system. Previously, they treated “carbon dioxide in the atmosphere as if it was a simple control knob that you turn up” and temperatures climb accordingly, “but in the real world we now know that’s not what happens.” Instead, if humans “stop emitting carbon right now … the oceans start to take up carbon more rapidly.” The actual lag between halting CO2 emissions and halting temperature rise will not be 25 to 30 years as previously thought but “more like three to five years.”

Global CO2 emissions by sector, 2020.  Source: Statista

This is good news.  Let's suppose we actually manage to cut emissions by 50% by ~2030.  Not impossible: electricity generation and transportation are 57% of total CO2 emissions.  We could switch generation to renewables, and it would pay us to do it, because they're cheaper than coal and gas.  EVs, PHEVs and hybrids could plausibly reach 90% of sales by 2035.  If vehicles have an average life of 15 years, that means by ~2030, at least one third of the vehicle fleet will have an electric motor.  Aircraft and sea transport could use synthetic jetfuel/diesel.  That would increase the emissions reduction to 44%.  Add in green steel, made using green hydrogen instead of coal, and we should be close to a 50% cut (the next 50% will be much harder).

Since the decadal rise in temperature is linearly related to the level of emissions, halving emissions would halve the decadal rise in temperatures from 0.2 degrees C to 0.1 C.  And instead of having to wait 20 or 30 years for this to happen, it will happen in the 40s.  If we halve emissions again in the 40s, the rise in the 50s could be down to 0.05 degrees C.   From then on, we could continue to cut emissions while also starting to remove CO2 from the atmosphere via tree-planting, etc.  This would mean that the total rise in temperatures from now to 2050 would be 0.35 C.  As temps are up roughly 1.2 C since pre-industrial times, that would mean we will have almost limited the rise to 1.5 degrees C.

That's the optimistic outlook.  The pessimistic outlook is that everybody pays lip service to the net-zero 2050 goal, but doesn't do enough to achieve it; fossil fuel interests continue to pervert and subvert politics; and inertia not urgency continue to rule the roost.