Electric cars are coming. The question is how soon.

According to a new report by the UN International Panel on Climate Change earlier in October, coastal cities and coral reefs will begin experiencing "devastating effects" by 2040 from climate change if emissions of global-warming carbon-dioxide continue.

Estimates on electric-car adoption range from 50 percent of new cars sold by 2030 to about 25 percent by 2050.

DON'T MISS: Catastrophic climate effects could hit by 2040, UN report says

Several cities and countries, including China, Israel, Los Angeles, and Britain have adopted requirements to end sales of non-electric cars in the coming decades.

All that begs the question, how soon is it realistic to expect sales of new combustion-engine cars to be phased out?

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Last week, we decided to put the question to our Twitter followers.

Bearing in mind the optimistic crowd of electric-car early adopters among our readers and Twitter followers, it's worth mentioning that for all new-car sales to be electric, automakers would have to sell electric versions of all kinds of cars, including pickups and SUVs. And while two expensive electric luxury SUVs are now available (the Tesla Model X and Jaguar I-Pace) production versions of a few electric pickups on the drawing boards are still at least a few years off.

Specifically, our Twitter poll last week asked followers: "How soon can all new car sales realistically be electric?" 

Almost half of our respondents (48 percent) chose the most aggressive yet possible timeline: 2030.

Another 28 percent said by 2040, which coincides with Britain's target.

READ THIS: Electric cars will exceed half the market and displace 7 percent of gasoline consumption by 2040: report

Only 6 percent thought all new cars should be electric by 2020, which is essentially next year when it comes to car models.

Another 20 percent were far less optimistic, saying the day of all-electric new-car sales wouldn't arrive "for a long time."

Overall, if this poll is any indication, our readers are a realistic bunch of optimists.

As always, remember that our Twitter polls are unscientific because our respondents are self-selected and because our sample size is not nationally representative.