It's easier to avoid future emissions than reduce current emissions

Here's a bold statement: In the future, we will travel. We will travel either more, less or the same amount as we do now. How our future travel will change depends on economics, technologies, accessibility and opportunities.
To reduce carbon emissions and mitigate climate change, many people want to reduce auto travel and plane travel in the future. These folks support transit including high speed rail, biking and land use mixing to lower carbon emissions. Yet new construction for infrastructure emits carbon, too, offsetting some potential reductions. It is also hard to get people to change their behavior (drive less) without credible price signals and incentives. Maybe we will get such signals in time.
But the efforts to reduce future emissions are fraught with uncertainty. However, if we can avoid massive carbon emissions from new transportation technologies by, say, not letting people rocket off into space for pleasure, we are all better off. I, for one, think the burgeoning space tourism industry should be halted before it really gets started, and I suspected that launching lots of rockets into the delicate stratosphere would be especially bad for emissions. According to a new study discussed in Nature, my suspicions were right:

Climate change caused by black carbon, also known as soot, emitted during a decade of commercial space flight would be comparable to that from current global aviation, researchers estimate.

The findings, reported in a paper in press in Geophysical Research Letters1, suggest that emissions from 1,000 private rocket launches a year would persist high in the stratosphere, potentially altering global atmospheric circulation and distributions of ozone. The simulations show that the changes to Earth's climate could increase polar surface temperatures by 1 °C, and reduce polar sea ice by 5–15%.

"There are fundamental limits to how much material human beings can put into orbit without having a significant impact," says Martin Ross, an atmospheric scientist at the Aerospace Corporation in Los Angeles, California and an author of the study.

Private space flight is a rapidly maturing industry. Spaceport America, a launch site in Las Cruces, New Mexico, opened its first runway on 22 October. During the next three years, companies such as Virgin Galactic, headquartered at Spaceport America, expect to make up to two launches per day for space tourists. Meanwhile, the NASA Authorization Act passed by US Congress in September provides US$1.6 billion in private space-flight investments to develop vehicles to take astronauts and cargo into orbit.

I guess I think the industry is "growing," not "maturing," but that doesn't change the calculus here. This industry is promising Sunday drives to orbit, and while the cost per traveler are high (over $100,000 currently), the social costs of this travel are enormous when climate change is factored in. If this industry "takes off" then all of the efforts to reduce carbon emissions by us lowly surface transportation planners will be for naught. This is a case where we should avoid a new source of emissions as a method of reducing overall carbon in the atmosphere.