They burn more calories (that's where the energy for propulsion comes from). Calories come from food. If meat is part of their diet, then yes, they eat more meat. Which has a huge CO2 footprint associated with it. Vegetables too have often very high CO2 footprints per calorie (because they have so few calories). As does anything shipped in from long distances away.

A cyclist can maintain a low CO2 footprint, but only by eating a diet that has low CO2 emissions per calorie - for example, locally grown grains, potatoes, etc.

Now, an electric bicycle is a different story; they have incredibly low CO2 footprints.

(It's not just a stereotype that athletes eat big meals after a big game or hard workout. They have to to not lose weight to the point that they lose energy and their body starts to eat itself. While a disturbing number of people seem to have this notion that exercise is "free energy", it's simply not the reality. Yes, a person being fit and thin by exercising regularly will have a somewhat lower baseline metabolism. But it's not even close to the number of calories they burn to get there.)

First off, cyclists suffer higher rates of death and injury even in areas where there is no traffic, per kilometer. Secondly, are you planning to take all goods by bicycle? No? Then there will still be vehicles on the roads no matter how aggressive you are at switching people over to bikes. My city, for example, is trying to increase cycling from about 4% of trips to about 20% of trips. That's a 5-fold increase in the number of cyclists but only about a 20% reduction in the number of cars. Aka, you're looking at a massive net increase in serious injuries.

Do you drive your SUV without eating anything?

Are we now pretending that moving by human power comes without an additional caloric cost over resting metabolism? That bicycles work by magic free energy?

Water vapor also has a mean atmospheric residence time of 2 to 20 days. You do something to completely throw water vapor levels off balance, it'll be back to where it was a few weeks later. It can only function as a feedback mechanism; water vapor is limited to fluctuating around a mean. What that mean is depends on the other driving factors in the environment. These are known as forcing. For something to act as forcing, it has to have far longer residence times.

(Note that while on human timescales carbon dioxide is forcing, on geological timescales it's mere feedback. A couple hundred years is nothing compared to, say, Milankovitch cycles)

Explain to me again why the addition of something that is " leading to global warming" and "is also a major source of ocean acidification" is not pollution?

Cobalt is a vital element to the human body, critical to health in the sort of quantities naturally consumed. That doesn't mean that it'd be good for us if someone started dumping huge amounts of cobalt in our water supply.

Concerning such pollutants, we actually don't share the same atmosphere. These sort of pollutants have short atmospheric residence periods, they're mainly problems at or near the point of emission (the particular distance that they pose a problem for depends on the type of pollutant).

It's one of the reasons that even if electric cars didn't cut down in pollution (which studies repeatedly show that they do) and simply moved the same amount of pollution from the streets to the top of power plant smokestacks, they'd still improve public health on average. Any pollutants you do emit, you want them as far as possible away from where most people are (aka, away from areas with lots of traffic, aka, lots of people), and as high up as possible.

And the several percent of non-vegans who travel by bicycle instead of cars are acting all smug thinking they're saving the planet, when their consumption of meat for the calories they burn gives them the per-kilometer carbon footprint of an SUV. Plus an order-of-magnitude higher per-kilometer risk of death or serious injury than a person in a car.

Continuing in the same article: "It is an important greenhouse gas and burning of carbon-based fuels since the industrial revolution has rapidly increased its concentration in the atmosphere, leading to global warming. It is also a major source of ocean acidification since it dissolves in water to form carbonic acid."

A lot was left out of the study. I find their methodology fishy. For example, here's their test area:

Located west of the sampling site is a set of traffic lights, which results in various driving states such as cruising, braking, idling, and acceleration. Stop-and-go traffic dominates during rush hour periods, while free flowing traffic is more typical outside of these hours, especially overnight. Given the downtown location...

Downtown... stop and go for large portions of the day... various driving states... in short, even if two people are driving the exact same car in the exact same condition in the exact same driving style on average, if one at the particular moment of passing the sensor happens to be letting off the gas, while the other just happens to be accelerating when it passes the sensor, the two cars are going to give wildly different pollution readings.

I'll also note that the paper says that it's still in review, aka it hasn't passed peer-review yet.

I'm sure the general premise is right, that small numbers of vehicles cause most pollution. But I think their experimental setup is pretty bad. The stupid thing is they're collecting the data they'd need to control for it - they're taking pictures, which would let them tie vehicle plumes to particular license plate numbers, and then only study vehicles that pass by the sensor a number of times times to that they can get a running average. Another way to control for it would be to have a dozen or so sensors spaced out down the road spaced well apart so that they can average a particular vehicle's emissions on a single drive down the road. But a single sensor, single pass way to rate a vehicle's emissions as good or bad? That's a terrible approach. And they stretch very far on their conclusions based on this approach.

Hahaha... you know, this gives the term "going postal" a new meaning. Imagine a world where an Amazon delivery center worker who can't take it anymore starts duct taping cats into the package slot... turning the drones into flying, clawing machines that chase after their horrified, fleeing targets.

Bonus points if they could get their hands on bobcats, honey badgers, etc.

It's only painful if you check the option for "Release my package at flight altitude on an intercept course to me."

You laugh, but while it's maybe a bad idea if you're ordering a cell phone, it's a heck of a lot of fun if you're ordering a football.

Huh... does that really work? What a cool lifehack! Do cars have GPS trackers and cameras like drones do?

I'd be more worried about a 10 tonne delivery truck crashing through my wall than a 10 kilogram drone crashing through my roof.

Indeed. I really don't understand why people freak out about companies making optional features that people who aren't "Google Is Plotting With The NSA To Have My Teeth Removed In My Sleep" nutters generally appreciate. Don't like it? Don't use it.

I didn't see how fast the drones fly, but if it can fly say 60mph then it can hold position in gusts up to 60mph. They generally have quite fast response times to varying windspeeds.

That said, they will have a fixed operating envelope, and if the weather is outside that envelope, just like with any other aircraft, they won't be allowed to fly. Even if Amazon wanted them too, the FAA would never permit that.

As for "leaving it outside", I imagine the drone would follow whatever delivery instructions you gave it.

Really? We in countries with single payer are clamouring for a system more like America's? That's fresh. America's healthcare system is a boogieman concept here, the sort of thing that one scares voters with - "my opponent's policies will make out healthcare system end up like America's!" Even conservative Americaphiles are usually scared of it.