"Do your homework!" is what I would say to the Chicago Tribune editorial writer who claims that it is time to build the Keystone XL pipeline (Short Takes, Feb. 13.)

1) Claim: That the tar sands oil in Alberta, Canada, will be extracted anyway. Fact: We face a staggering problem. Burning fossil fuels (oil, natural gas and coal) is creating climate havoc. Leaving tar sands, the dirtiest oil, in the ground would be one step in the right direction. We could take that step.

2) Claim: That the only question is whether the tar sands oil goes to U.S. refineries, or to markets in China and elsewhere. Fact: If the pipeline is built, oil sent down it will be headed for the international market. It will not provide a politically friendly source of oil and gasoline for us. It will cross our land; we will suffer from oil spills, and we will get little of the oil.

3) Claim: Transporting the oil to refineries by rail or tanker truck would create more greenhouse gas emissions than sending the oil by pipeline; therefore, we should build the pipeline. Fact: The amount of greenhouse gas released by moving the oil around is a drop in the bucket compared with the amount released by extracting and burning the tar sands oil. We simply shouldn't do it.

MARY JEAN PORT, Minneapolis