If internal combustion engines were replaced by steam...

If internal combustion-engined cars were replaced by steam engines, or if steam engines had become the industry standard from the very beginning, would there be climate problems as a result of so much water vapor being released into the atmosphere?

No there would be a massive climate problem because you have to heat the water somehow.

No. The absolute amount of water vapor in the atmosphere is largely a function of temperature. If more water is added to the atmosphere it just precipitates out as rain because the relative humidity remains fairly constant. So adding more water would make no difference, but by the same token, raising the air temperature via CO2 and other GHGs does make a difference to the absolute amount of water vapor. That’s why water vapor is considered an important climate feedback that amplifies the effect of CO2, but not an independent greenhouse gas even though it has significant radiative transfer properties, even more than CO2.

It also wouldn’t be too terribly difficult to recover the exhaust steam instead of venting it. The pre-electrification London Underground locomotives did, as did other steam locomotives that operated in arid conditions where water was hard to come by.

Also consider that combustion itself (be it internal or external) produces significant amounts of water vapor on its own. With gasoline, it makes about five gallons of water per gallon of gasoline. I don’t know much the fuel versus water consumption is on an oil-fired locomotive, but it might be that the water vapor from the combustion is much more significant than the water vapor from steam exhaust.

Later steamers did have condensers to recover the steam, which made a big difference. Wiki says of the Type B Doble prototype:

We could use gasoline and diesel powered water heaters and be exactly where we are today. Or perhaps the proverbial golf ball sized chunk of plutonium? I look forward to my healthy green glow!

The “ideal” steam engine doesn’t vent steam at all – it’s working fluid, not “fuel”. It seems like if steam engines had become the standard, technology would have progressed to the point where very little of the working fluid was actually released.

The waste products from external combustion would still be there, though.

The climate problem would come from all the extra fuel we burn to produce steam.

Climate change would be arguably worse than it is today; steam engines are considerably less efficient than internal combustion engines, so for the same amount of “effort”, we’d end up burning more fuel to accomplish the same task.

Steam engines (reciprocating or turbine) are pretty mature technologies, and have been for a long, long time- something like 130 years or so.

There’s a good reason that pretty much everything that can switch away from steam power is doing so; the alternatives are more efficient. Small vehicles like cars never even used steam, railroads switched some 60-70 years ago, and marine propulsion is doing so/has done so somewhat more recently, with most large container ships and tankers using huge marine diesels instead of oil fired steam turbines. Even power stations, some of the last holdouts, are tending to go with natural gas, instead of coal, albeit as much for environmental as cost/efficiency reasons.

I have a suspicion that as steam powerplants grow larger, their relative efficiency to internal combustion increases, and that’s why you see the pattern I showed above- the smallest engines never were steam, and the smaller ones were quickly replaced, while the largest ones have been phased out more gradually.

The primary reason railroads never really got into locomotives that condensed their steam and reused it is twofold. First, railroads were developed before that technology was available, so the infrastructure for taking on coal and water every 50-100 miles was in place very early on. Second, the way that steam locomotives are designed, the “exhaust” steam is vented through the stack in such a way that it draws air into the firebox, and hot gas through the boiler better than natural flow would. It’s sort of analogous to a turbocharger, in a very broad sense.

Condenser engines have to be designed in such a way that the blastpipe effect isn’t available, which tends to reduce power, and whatever mechanism to condense the steam adds weight. They have been used in the past, but weren’t common. Marine steam engines typically did condense their steam, with distillation apparatus to make up for any losses.

TL, DR: Steam engines have been mature technology for a long time, and were superseded by internal combustion engines due to greater efficiency. Therefore, if we’d stayed with steam engines, we’d likely have burned MORE fossil fuels, not less.

This. The oceans already provide almost 200 million square miles of surface area for evaporation; on a global scale, the atmosphere is already just about as damp as it can possibly be.

The wide adoption of non-condensing steam engines for cars wouldn’t cause global climate change (at least not due to steam emissions), but they might increase local humidity by a notable amount. For a modern gasoline-powered IC-engine car, roughly 1/3 of the fuel’s energy leaves as heat via the tailpipe, 1/3 leaves as mechanical energy delivered to the driveline, and 1/3 leaves as heat rejected by the radiator. Imagine that last third - the heat normally rejected by the radiator - is instead rejected as steam. If I’ve done my math right, you’d have about 3.9 gallons of liquid water turned to steam for every gallon of gasoline burned (this does not include the water vapor present in the combustion exhaust stream):

120,176 KJ of energy released per gallon of gasoline burned
1/3 of that goes to turning 0C liquid water into 100C steam
a kg of water need 418.4 KJ to go from 0-100C, then another 2287 KJ to convert to steam

120,176/3/(418.4+2287)= 14.8 kg of water = 3.9 gallons

Add this to the five gallons of water directly created by burning a gallon of gasoline, and you’ve nearly doubled the steam output of the car.

As yabob notes, you wouldn’t run a steam-engine vehicle like this; you’d try to condense most/all of the steam coming out of the steam engine to minimize the need for water refills. IOW, you’re back to not emitting any/much more water than a modern IC-engine powered car.

How quickly we forget! Remember the Stanley Steamer?

But, the wiki article supports your broader point: the Stanley Steamer Company was founded in 1902, defunct by 1924:

The Doble was probably the pinnacle of steam car development before the company went bust in 1931. For the later models, supposedly Abner Doble used do public demonstrations of his automobile in which he challenged anybody to see a single whiff of steam escaping from the vehicle due to his superior condenser. He had cold startup down to under a minute.

And yes, the electric starter was a big killer of the steamer. When you had to crank your ICE auto and risk getting your arm broken if you you did it wrong, having to wait for a boiler to warm up didn’t seem so bad.

The White Steamer was another popular model. White also made gas powered models.

The steamers were the muscle cars of their day. In some early auto races, they banned steamers, because the gas cars didn’t stand a chance against them.

Aside from cost (of fuel and emissions controls), one big advantage of a gas-turbine generator is it’s quick start-up time, compared to a steam boiler (powered either by gas or coal). That’s a factor that hasn’t really been mentioned, but ‘getting up steam’ takes longer than cranking an internal-combustion engine (I assume a turbine is in between, closer to an internal combustion).

No, because the energy doesn’t come from steam. The energy comes from fossil fuels, just like in gasoline engines. Burn coal or gas, either way the climate changes.

Much electricity is generated by steam heated from a variety of means (coal, nuclear, even solar from mirrors).

Some of that electricity makes its way into electric cars.

Is there an alternative to internal combustion that would produce minimal pollution that would be economically feasible?

Pick any two of the three for now. Since you didn’t mention “safe” we could put something together this afternoon.

However, the future is wide open.

Vehicles that derive their motive power from the electrical grid are pretty much it. This includes electric trains and battery-powered cars. The energy source is then either renewable (solar/hydro/wind), nuclear, or fossil fuel combustion. For the latter, once you put the combustion in a stationary location you have a lot more aftertreatment options to deal with the noxious components of the exhaust (particulates, NOx, heavy metals, etc.). A large-scale power plant operating at/near its design capacity is going to be much more efficient than an automotive IC engine running at a tiny fraction of its peak power, so this is also likely to generate less CO2 per mile.

Trains that are packed with passengers tend to have the lowest CO2 emissions per passenger mile.