We have a fighting chance

Emissions have probably peaked, or will soon, but that still means that the level of CO2 in the atmosphere continues to rise, because we are still adding to it faster than natural processes can remove it. To stop the level in parts per million of CO2 in the atmosphere from rising, we have to reduce emissions by at least 80%.  Maybe more, because the natural "sinks" which absorb CO2 are full--the world's seas, for example are already turning more acidic.

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The good news is that emissions are about to start falling.

Renewables are getting progressively cheaper, and are steadily replacing coal.  The total costs of new renewables (without "firming") are now at or below the total cost of new coal and gas. Over the next 10 or so years, BNEF reckons that the total cost of new renewables will fall below the operating cost (mostly fuel and maintenance) of existing coal and gas power plants.  At that point, coal and gas power station shut-downs will be limited only by the cost of "firming", i.e, the costs of making variable wind and solar as "firm" as supply from baseload power stations which burn coal, gas or uranium.  And the costs of batteries, concentrated solar power (CSP) are falling fast, and there is always the 100 year old technology of pumped hydro storage.  Some estimates show that the cost of pumped hydro is as low $20/MWh.  CSP is coming at at $60-$70/MWh for power plus storage: "firm" (i.e. baseload) plus dispatchable capacity.  And you don't need 100% backup for variable renewables.  In most places 25% will do, so you will be able to combine cheap wind and solar with some storage and get baseload output more cheaply than from coal and gas.  At that point, existing coal and gas power stations will be rapidly and completely replaced with renewables.

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For the first time, mid-priced electric cars are available, and China (responsible for 1/3rd of global CO2 emissions) has tough new standards to reduce the sale of petrol/diesel vehicles (ICEVs). France, UK, Holland, Austria and now California are contemplating or planning a ban on petrol/diesel car sales from 2030 onward.  By 2022 or so, EVs will have the same "sticker price" as ICEVs, but they are far cheaper to drive.  By 2030, or before, 100% of car and light van sales will be electric.

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There remain some hurdles--agriculture, burning forests/scrubland, cement and iron and steel production, jet travel. But even together, these are smaller than transport and electricity generation combined. If we can convert electricity production to renewables/nuclear and can electrify our car/truck fleet, we have a fighting chance.

But there is a race between de-carbonising our economy and the rise in world temperatures.  As long as atmospheric CO2 keeps on rising, so will average world temperatures.  And CO2 will only stop rising when CO2 emissions have fallen at least 80%.

Global temperatures are rising by 0.2 degrees C per decade. The rise may be accelerating--let's hope that it's not.

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Let's say it takes us 20 years to move to 100% renewable electricity. Hydro+renewables are now 22% of world electricity supply, which means we need to target a 4% per annum switch, but it will likely be slower in earlier years and much faster towards the end.  That means that global temperatures will rise by another 0.4 degrees.

Cars will take longer. As I said, we'll prolly get to 100% electric sales by 2030, maybe earlier, but cars last a long time (I've seen data varying between 11 and 20 years, depending on the country) If it's 20 years, we won't have a 100% car fleet till 2050. That means temps will rise another 0.2 degrees. So by 2050 we will end up 0.6 degrees above 2016, 1.8 degrees (?) above the pre-industrial average. Plus there are built in lags in the system's response to forcing which will cause temperatures to go on rising for a few decades even with zero emissions.

Hence the "fighting chance" in my title: we have started the switch to a carbon-free economy, but we have left it so late we may not avoid catastrophe.  We have a "fighting chance".

But I suspect the screws will tighten every year. Despite Donald Trump, Tony Abbott and other gibbering imbeciles on the right. What will it take to make the Republicans sensible about global warming? How many more hurricanes, heatwaves, floods? Miami constantly under water from "nuisance" or "sunny day" flooding?

The world is going to commit itself ever more urgently and with ever greater force to reducing CO2 emissions as the evidence of global warming becomes ever more obvious and the cost of de-carbonising continues to fall.  And that improves the odds of our "fighting chance".