Why do economists tend to support a carbon tax instead of cap and trade? To my understanding, the main difference is that with a carbon tax, the regulatory authority has to pick the optimal price of carbon while with cap and trade, it has to pick the optimal quantity of carbon. Either option runs into a Hayekian knowledge problem. And I can't imagine that transaction costs would be a significant problem for cap and trade to reach an optimal allocation if carbon rights are traded like other securities.

That said, I know very little about environmental economics.